岩澤 康裕

燃料電池・水素イノベーション研究センター特任教授
基盤理工学専攻特任教授
Ⅲ類(理工系)特任教授
  • プロフィール:
    昭和47年4月1日 横浜国立大学工学部(応用化学科)助手
    昭和52年4月1日 横浜国立大学工学部(応用化学科)講師
    昭和56年4月1日 横浜国立大学工学部(応用化学科)助教授
    昭和59年4月1日 東京大学理学部(化学科)助教授
    昭和61年1月16日 東京大学理学部(化学科)教授
      (平成5年4月1日 東京大学大学院理学系研究科(化学専攻)に組織変更)
    平成13年4月1日 東京大学評議員(平成16年3月31日まで)
    平成16年10月1日 日本学術会議会員(内閣府)
       (日本学術会議化学委員会委員長)
    平成17年4月1日 東京大学理学系研究科長・理学部長(平成19年3月31日まで)
    平成19年4月1日 東京大学理学系研究科スペクトル化学研究センター長
    平成20年6月1日 電気通信大学教授(併任)
    平成20年10月1日 日本学術会議第三部(理学・工学)部長(内閣府)
    平成21年3月31日 東京大学定年退職(6月1日 東京大学名誉教授)
    平成21年4月1日 電気通信大学電気通信学部(量子・物質工学科)教授
    平成22年4月1日 電気通信大学院情報理工学研究科(先進理工学専攻)教授
    (組織名称変更)
    平成22年5月28日 電気通信大学燃料電池イノベーション研究センター長
    平成23年3月31日 電気通信大学定年退職
    平成23年4月1日 電気通信大学燃料電池イノベーション研究センター長・特任教授
              (兼)大学院情報理工学研究科(基盤理工学専攻)特任教授
    令和4年10月1日 燃料電池・水素イノベーション研究センターに名称変更(センター長・特任教授)
    現在に至る

学位

  • 理学博士, 東京大学
  • Doctor of Science, The University of Tokyo
  • 理学修士, 東京大学
  • Ms of Science, The University of Tokyo

研究キーワード

  • 触媒のin situ/operandoキャラクタリゼーション
  • 原子分子レベル触媒反応機構
  • 燃料電池触媒開発
  • オペランド燃料電池解析
  • 時空間分解XAFS
  • 放射光X線発光分光
  • 触媒表面の化学設計
  • 触媒化学
  • 表面・界面科学
  • Catalytic reaction mechanisms
  • Operando fuel cell analysis
  • Fuel cell catalyst development
  • Time-resolved & spatial imaging XAFS
  • Surface and interface science
  • Catalyst surface design

研究分野

  • ナノテク・材料, 基礎物理化学
  • ものづくり技術(機械・電気電子・化学工学), 触媒プロセス、資源化学プロセス
  • エネルギー, 量子ビーム科学
  • ナノテク・材料, 機能物性化学
  • ナノテク・材料, グリーンサステイナブルケミストリー、環境化学
  • ナノテク・材料, エネルギー化学

経歴

  • 2011年04月 - 2025年03月
    電気通信大学, 燃料電池・水素イノベーション研究センター, センター長・特任教授
  • 2011年04月 - 2025年03月
    電気通信大学, 大学院情報理工学研究科 基盤理工学専攻, 特任教授
  • 2009年04月01日 - 2011年03月31日
    電気通信大学, 大学院情報理工学研究科, 教授
  • 2008年04月01日 - 2009年03月31日
    東京大学, 理学系研究科スペクトル化学研究センター, センター長
  • 1986年01月16日 - 2009年03月31日
    東京大学, 大学院理学系研究科, 教授
  • 2005年04月01日 - 2007年03月31日
    東京大学, 理学系研究科・理学部, 理学系研究科長・理学部長
  • 2001年04月01日 - 2004年03月31日
    東京大学, 理学系研究科・理学部, 評議員
  • 1984年04月 - 1986年01月
    東京大学, 大学院理学系研究科, 准教授, 日本国
  • 1981年04月 - 1984年03月
    横浜国立大学, 工学部応用化学科, 准教授, 日本国

学歴

  • 1970年04月 - 1972年03月
    東京大学, 大学院理学系研究科博士課程, 化学専攻
  • 1968年04月 - 1970年03月
    東京大学, 大学院理学系研究科修士課程, 化学専攻
  • 1964年04月 - 1968年03月
    東京大学, 理学部, 化学科
  • 1961年04月01日 - 1964年03月
    県立浦和高校

委員歴

  • 2022年04月 - 現在
    委員, 北陸先端科学技術大学院大学経営評議会
  • 2022年04月 - 現在
    委員長, 北陸先端科学技術大学院大学学長選考・監察会議, その他
  • 2020年04月 - 現在
    委員, 北陸先端科学技術大学院大学アカデミックアドバイザー会議, その他
  • 2018年06月 - 現在
    会長, 日本化学連合, 学協会
  • 2007年04月 - 現在
    委員長, 野口研究所研究助成選考委員会
  • 2006年04月 - 現在
    委員長, PCCP賞選考委員会, 学協会, 英国王立化学会の委託を受け日本化学会が賞を選考する。PCCPがカバーする研究分野における35歳以下の優れた若手研究者に授与。
  • 2014年04月 - 2022年03月
    委員, 北陸先端科学技術大学院大学経営評議会, その他
  • 2010年01月 - 2019年09月30日
    委員, 厦門大学化学研究院評価委員会
  • 2012年04月 - 2018年03月31日
    プログラムオフィサー, 大学院博士課程リーディングプログラム, その他
  • 2012年01月 - 2017年09月30日
    委員長, 日本学術会議東日本大震災調査検討委員会
  • 2010年04月 - 2015年03月31日
    委員長, 北海道大学触媒化学研究センター運営委員会
  • 2010年04月 - 2014年03月
    アカデミックアドバイザー, 北陸先端科学技術大学院大学アカデミックアドバイザー会議
  • 2012年08月 - 2012年12月
    委員, 文科省文化審議会文化功労者分科会, 政府
  • 2010年07月 - 2012年06月
    理事, 化学技術戦略推進機構理事会
  • 2010年03月 - 2012年05月
    会長, 日本化学会, 学協会
  • 2009年04月 - 2011年09月
    委員長, 日本学術会議・大型研究計画検討分科会
  • 2008年10月 - 2011年09月
    副委員長, 日本学術会議会員選考委員会
  • 2008年10月 - 2011年09月
    幹事, 日本学術会議幹事会
  • 2008年10月 - 2011年09月
    第三部(理学・工学)部長, 日本学術会議, 学協会
  • 2010年05月 - 2011年03月
    委員, 最先端研究基盤事業選定検討会
  • 2005年01月 - 2006年02月
    会長, 触媒学会, 学協会
  • 2004年 - 2006年
    会長, 日本表面科学会, 学協会

受賞

  • 受賞日 2024年03月
    触媒学会
    触媒学会教育賞, 福井賢一;吉信淳;中村潤児;岩澤康裕
  • 受賞日 2019年05月
    内閣総理大臣、天皇, 瑞宝中綬章を受章し皇居にて拝謁
    叙勲(瑞宝中綬章), 岩澤康裕
    その他の賞, 日本国
  • 受賞日 2016年05月
    日本表面科学会
    Japan
    日本表面科学会名誉会員称号, 岩澤康裕
    その他の賞, 日本国
  • 受賞日 2015年11月
    アジア化学連合, アジア化学連合では2年毎に分野を指定してFACS Foundation Lectureship Awardを授賞
    FACS創立レクチュアシップ賞2015, 岩澤康裕
    国内外の国際的学術賞
  • 受賞日 2013年03月
    日本化学会
    日本化学会名誉会員称号
  • 受賞日 2012年12月
    Chinese Chemical Society
    China
    Honorary Fellow of Chinese Chemical Society
    中華人民共和国
  • 受賞日 2010年05月
    UOP/Honeywell
    USA
    UOP/Honeywell レクチュアシップ
    アメリカ合衆国
  • 受賞日 2009年06月
    東京応用科学技術財団
    向井賞
  • 受賞日 2009年02月
    Materials Research Society of India
    India
    Honorary Member of Materials Research Society of India
    インド
  • 受賞日 2004年12月
    厦門(アモイ)大学
    China
    南強レクチュアシップ
    中華人民共和国
  • 受賞日 2004年03月
    日本化学会
    日本化学会賞
  • 受賞日 2003年11月
    内閣総理大臣、天皇
    紫綬褒章
  • 受賞日 2000年12月
    日本表面科学会
    日本表面科学会学会賞
  • 受賞日 1999年03月
    触媒学会
    触媒学会学会賞
  • 受賞日 1995年06月
    UOP、米国
    USA
    UOPレクチュアシップ
    アメリカ合衆国
  • 受賞日 1995年05月
    オランダ触媒研究機構
    The Netherlands
    NIOKレクチュアシップ
    オランダ王国
  • 受賞日 1995年02月
    井上科学財団
    井上学術賞
  • 受賞日 1990年12月
    日本IBM
    日本IBM科学賞
  • 受賞日 1990年07月
    西ヨーロッパ触媒学会
    フランソア・ゴー レクチュアシップ
  • 受賞日 1976年03月
    日本化学会
    日本化学会進歩賞

論文

  • Subnanometric Osmium Clusters Confined on Palladium Metallenes for Enhanced Hydrogen Evolution and Oxygen Reduction Catalysis
    P Prabhu; Viet-Hung Do; Takefumi Yoshida; Yingtang Zhou; Hiroko Ariga-Miwa; Takuma Kaneko; Tomoya Uruga; Yasuhiro Iwasawa; Jong-Min Lee
    ACS Nano, American Chemical Society (ACS), 出版日 2024年03月29日
    研究論文(学術雑誌)
  • In situ Study on Structure of a Diluted Pt/HOPG Model Catalyst System Prepared by the Two-phase Liquid Reduction Method Using a Novel BCLA/HERFD+BI-XAFS Method
    Kaiyue Dong; Bing Hu; Md Harun Al Rashid; Bang Lu; Keiko Miyabayashi; Kotaro Higashi; Tomoya Uruga; Yasuhiro Iwasawa; Daiki Kido; Satoru Takakusagi; Kiyotaka Asakura
    e-Journal of Surface Science and Nanotechnology, Surface Science Society Japan, 出版日 2024年02月15日, 査読付
    研究論文(学術雑誌), 英語
  • Elucidation of Active Sites and Mechanistic Pathways of a Heteropolyacid/Cu-Metal–Organic Framework Catalyst for Selective Oxidation of 5-Hydroxymethylfurfural via Ex Situ X-ray Absorption Spectroscopy and In Situ Attenuated Total Reflection-Infrared Studies
    Paramita Koley; Subhash Chandra Shit; Takefumi Yoshida; Hiroko Ariga-Miwa; Tomoya Uruga; Tayebeh Hosseinnejad; Selvakannan Periasamy; Su-Il In; Dharmendra D. Mandaliya; Ravindra D. Gudi; Yasuhiro Iwasawa; Suresh K. Bhargava
    責任著者, ACS Catalysis, American Chemical Society (ACS), 13巻, 9号, 掲載ページ 6076-6092, 出版日 2023年04月18日, 査読付
    研究論文(学術雑誌)
  • Roles of structural defects in polycrystalline platinum nanowires for enhanced Oxygen Reduction Activity
    X. Zhao, S. Takao, Y. Yoshida, T. Kaneko, T. Gunji, K. Higashi, T. Uruga, and Y. Iwasawa
    責任著者, Appl. Catal. B: Environmental, Elsevier, 324巻, 掲載ページ 122268, 出版日 2023年02月, 査読付, 国際誌, Roles of structural defects in polycrystalline platinum nanowires for enhanced Oxygen Reduction Activity
    研究論文(学術雑誌), 英語
  • Pd‐PdO Nanodomains on Amorphous Ru Metallene Oxide for High‐Performance Multifunctional Electrocatalysis
    Viet‐Hung Do; P Prabhu; Vishal Jose; Takefumi Yoshida; Yingtang Zhou; Hiroko Miwa; Takuma Kaneko; Tomoya Uruga; Yasuhiro Iwasawa; Jong‐Min Lee
    責任著者, Advanced Materials, Wiley, 5巻, 掲載ページ 2208860, 出版日 2023年01月, 査読付, Developing highly efficient multifunctional electrocatalysts is crucial for future sustainable energy pursuits, but remains a great challenge. Herein, a facile synthetic strategy is used to confine atomically thin Pd-PdO nanodomains to amorphous Ru metallene oxide (RuO2). The as-synthesized electrocatalyst (Pd(2)RuOx-0.5 h) exhibits excellent catalytic activity toward the pH-universal hydrogen evolution reaction (eta(10) = 14 mV in 1 m KOH, eta(10) = 12 mV in 0.5 m H2SO4, and eta(10) = 22 mV in 1 m PBS), alkaline oxygen evolution reaction (eta(10) = 225 mV), and overall water splitting (E-10 = 1.49 V) with high mass activity and operational stability. Further reduction endows the material (Pd(2)RuOx-2 h) with a promising alkaline oxygen reduction activity, evidenced by high halfway potential, four-electron selectivity, and excellent poison tolerance. The enhanced catalytic activity is attributed to the rational integration of favorable nanostructures, including 1) the atomically thin nanosheet morphology, 2) the coexisting amorphous and defective crystalline phases, and 3) the multi-component heterostructural features. These structural factors effectively regulate the material's electronic configuration and the adsorption of intermediates at the active sites for favorable reaction energetics.
    研究論文(学術雑誌), 英語
  • Non-Traditional Aldol Condensation Performance of Highly Efficient and Reusable Cs+ Single Sites in β-Zeolite Channels
    S. Ghosh; S. S. Acharyya; Y. Yoshida; T. Kaneko; Y. Iwasawa; T. Sasaki
    責任著者, ACS Appl. Mater. Interfaces, ACS, 14巻, 出版日 2022年04月, 査読付
    研究論文(学術雑誌), 英語
  • Surfaces and interfaces
    朝倉清髙; 近藤寛; 唯美津木; 岩澤康裕
    International Tables for Crystallography, International Union of Crystallography, I巻, 出版日 2022年03月11日, 査読付, 招待
    研究論文(その他学術会議資料等)
  • Operando Imaging of Ce Radical Scavenger in a Practical Polymer Electrolyte Fuel Cell by 3D Fluorescence CT–XAFS and Depth-Profiling Nano-XAFS–SEM/EDS Techniques
    H. Matsui; S. Takao; K. Higashi; T. Kaneko; G. Samjeské; T. Uruga; M. Tada; Y. Iwasawa
    責任著者, ACS Appl. Mater. Interfaces, ACS, 14巻, 掲載ページ 6762-6776, 出版日 2022年03月, 査読付, There is little information on the spatial distribution, migration, and valence of Ce species doped as an efficient radical scavenger in a practical polymer electrolyte fuel cell (PEFC) for commercial fuel cell vehicles (FCVs) closely related to a severe reliability issue for long-term PEFC operation. An in situ three-dimensional fluorescence computed tomography-X-ray absorption fine structure (CT-XAFS) imaging technique and an in situ same-view nano-XAFS-scanning electron microscopy (SEM)/energy-dispersive spectrometry (EDS) combination technique were applied for the first time to perform operando spatial visualization and depth-profiling analysis of Ce radical scavengers in a practical PEFC of Toyota MIRAI FCV under PEFC operating conditions. Using these in situ techniques, we successfully visualized and analyzed the domain, density, valence, and migration of Ce scavengers that were heterogeneously distributed in the components of PEFC, such as anode microporous layer, anode catalyst layer, polymer electrolyte membrane (PEM), cathode catalyst layer, and cathode microporous layer. The average Ce valence states in the whole PEFC and PEM were 3.9(+) and 3.4(+), respectively, and the Ce3+/Ce4+ ratios in the PEM under H-2 (anode)-N-2 (cathode) at an open-circuit voltage (OCV), H-2-air at 0.2 A cm(-2), and H-2-air at 0.0 A cm(-2) were 70 +/- 5:30 +/- 5%, as estimated by both in situ fluorescence CT-X-ray absorption near-edge spectroscopy (XANES) and nano-XANES-SEM/EDS techniques. The Ce3+ migration rates in the electrolyte membrane toward the anode and cathode electrodes ranged from 0.3 to 3.8 mu m h(-1), depending on the PEFC operating conditions. Faster Ce3+ migration was not observed with voltage transient response processes by highly time-resolved (100 ms) and spatially resolved (200 nm) nano-XANES imaging. Ce3+ ions were suggested to be coordinated with both Nafion sulfonate (Nf(sul)) groups and water to form [Ce(Nfsul)(x)(H2O)(y)](3+). The Ce migration behavior may also be affected by the spatial density of Ce, interactions of Ce with Nafion, thickness and states of the PEM, and H2O convection, in addition to the PEFC operating conditions. The unprecedented operando imaging of Ce radical scavengers in the practical PEFCs by both in situ three-dimensional (3D) fluorescence CT-XAFS imaging and in situ depth-profiling nano-XAFS-SEM/EDS techniques yields intriguing insights into the spatial distribution, chemical states, and behavior of Ce scavengers under the working conditions for the development of next-generation PEFCs with high long-term reliability and durability.
    研究論文(学術雑誌), 英語
  • Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: In Situ Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition
    Bing Hu; Bapurao Bharate; Juan D. Jimenez; Jochen Lauterbach; Naoto Todoroki; Toshimasa Wadayama; Kotaro Higashi; Tomoya Uruga; Yasuhiro Iwasawa; Hiroko Ariga-Miwa; Satoru Takakusagi; Kiyotaka Asakura
    The Journal of Physical Chemistry C, American Chemical Society (ACS), 126巻, 2号, 掲載ページ 1006-1016, 出版日 2022年01月20日, 査読付, To reveal the origin of the difference between the Pt-Pt bond distance in Au(core)-Pt(shell)-type (PtAu) nanoparticles and that in a Pt overlayer on Au(111), alloy-type PtAu nanoparticles were prepared on a highly oriented pyrolytic graphite (HOPG) surface by arc plasma deposition and their structure was investigated under various electrochemical conditions by bent-crystal Laue analyzer (BCLA)-empowered back-illuminated X-ray absorption fine structure (BCLA + BI-XAFS) and high-energy-resolution fluorescence detection (HERFD)-empowered back-illuminated X-ray absorption near-edge structure (HERFD + BI-XANES) methods. On the basis of the XAFS analysis at both edges, we proposed the formation of a PtAu alloy core covered with a Pt-rich shell at 0.4 VRHE, where the Pt-Pt, Pt-Au, and Au-Au bond lengths were all found to be ∼2.76 Å. The Au-Au bond length was abnormally shorter than that for bulk Au. The Pt shell was dissolved under applied potentials greater than 0.8 VRHE with the aid of the high-intensity X-rays, and the Au-Au distance increased. We concluded that the abnormal bond lengths were due to the strong surface tension from the Pt-rich shell and the relaxation of the lattice distortion. The Pt-Pt bond length in the PtAu nanoparticles decreases as a result of the surface tension of the nanoparticles; this surface tension does not exist on flat Au surfaces, where the lattice distortion between the Pt overlayer and the substrate is the main driving force for the expansion of the Pt-Pt bond length.
    研究論文(学術雑誌), 英語
  • Hidden Heterometallic Interaction Emerging from Resonant Inelastic X-ray Scattering in Luminescent Tb-Pt Molecules
    Takefumi Yoshida; Ahmed Shabana; David Chukwuma Izuogu; Kentaro Fuku; Tetsu Sato; Haitao Zhang; Yukina Yamamoto; Jun Kamata; Hitomi Ohmagari; Miki Hasegawa; Goulven Cosquer; Shinya Takaishi; Takuma Kaneko; Tomoya Uruga; Yasuhiro Iwasawa; Masahiro Yamashita
    Journal of Physical Chemistry C, 出版日 2022年, 査読付, Theoretical calculations are typically utilized for examining intermetallic interactions. However, to validate the theory, experimental confirmation of the existence of these interactions is necessary. We synthesized new heterometallic Ln-Pt complexes, NEt4{[Pt(PhSAc)4]Ln[ (PhSAc)4Pt]}·2DMF (Ln: lanthanoid = Gd (1), Tb (2), Dy (3), PhSAc = benzothioacetate, NEt4 = tetraethylammonium), in which both diamagnetic Pt(II) ions interact with the central Ln(III) ion. Typically, these interactions are not detected because the distance between Ln and Pt atoms (∼3.6 Å) is much larger than the covalent radius (∼3.3 Å) and ionic radius (∼3.10 Å). Pt-LIII resonant inelastic X-ray scattering (RIXS) analysis was conducted to experimentally confirm the unique influence of the hidden Ln-Pt interaction on the luminescence of the Tb-Pt molecule, where the interaction induced emission properties in the Tb and Pt ions, with high quantum yield (59%). Quantum theory of atoms in molecules (QTAIM) analysis was also used to confirm the experimental results. RIXS analysis allowed the identification of several distinctive characteristics of the coordination environment, including the existence of heterometallic interactions, that affected the observed luminescence.
    研究論文(学術雑誌)
  • Recent Progress in Advanced SR Characterization of Fuel Cells at SPring-8
    Y. Iwasawa
    責任著者, SPring-8/SACLA Research Frontiers 2020, 掲載ページ 8-11, 出版日 2021年08月, 査読付, 招待
  • Unprecedented Catalysis of Cs+ Single Sites Confined in Y Zeolite Pores for Selective Csp3-H Bond Ammoxidation: Transformation of Inactive Cs+ Ions with a Noble Gas Electronic Structure to Active Cs+ Single Sites
    S. S. Acharyya; S. Ghosh; Y. Yoshida; T. Kaneko; T. Sasaki; Y. Iwasawa
    責任著者, ACS Catal., アメリカ化学会, 11巻, 掲載ページ 6698-6708, 出版日 2021年06月, 査読付
    研究論文(学術雑誌), 英語
  • X-ray Absorption Fine Structure Techniques for Nano-Catalytic Materials
    N. Ichikuni; K. Okumura; Y. Iwasawa
    責任著者, Advanced Characterization of Nanostructured Materials (S. K. Sinha, M. K. Sanyal, C. K. Loong eds.), 掲載ページ Chapter 8, 出版日 2021年03月, 査読付, 招待
  • Status of Synchrotron Radiation X-ray-based Multi-analytical Beamline BL36XU for Fuel Cell Electrocatalysis Research at SPring-8
    T. Uruga; M. Tada; O. Sekizawa; Y. Takagi; T. Yokoyama; Y. Iwasawa
    責任著者, Synchrotron Radiation News, 33巻, 掲載ページ 26-28, 出版日 2021年01月, 査読付, 招待
  • In Situ X-ray Absorption Spectroscopy to Monitor the Degradation of Fe/N/C Cathode Catalyst in Proton Exchange Membrane Fuel Cells
    Y. Nabae; Q. Yuan; S. Nagata; K. Kusaba; T. Aoki; N. Takao; T. Itoh; M. Arao; H. Imai; K. Higashi; T. Sakata; T. Uruga; Y. Iwasawa
    J. Electrochem. Soc., 168巻, 1号, 掲載ページ 014513, 出版日 2021年, 査読付, Understanding the degradation mechanism of Fe/N/C cathode catalysts in proton exchange membrane fuel cells (PEMFCs) is important. We studied the degradation of an Fe/N/C catalyst prepared from polyimide nanoparticles in an in situ cell by X-ray absorption spectroscopy (XAS). This technique enables real-time monitoring of the Fe species during a fuel cell operation. The Fe K-edge absorption spectra were recorded during the continuous operation of the fuel cell. Initially during the fuel cell operation, the Fe species were atomically isolated and their valence state was found to be 3+. The spectra gradually changed during the first few hours of operation, suggesting the dissolution of the Fe species from the active sites, whereas the fuel cell performance continued to decrease during the eight hours of operation. The demetallation from the FeNx centers during the first few hours has been successfully monitored in real time, while the remaining FeNx centers seem to be stable in the following fuel cell operating condition.
    研究論文(学術雑誌), 英語
  • Synthesis of catalysts with fine platinum particles supported by high-surface-area activated carbons and optimization of their catalytic activities for polymer electrolyte fuel cells
    Md. M. Rahman; K. Inaba; G. Batnyag; M. Saikawa; Y. Kato; R. Awata; B. Delgertsetsega; Y. Kaneta; K. Higashi; T. Uruga; Y. Iwasawa; K. Ui; T. Takeguchi
    RSC Adv., 11巻, 33号, 掲載ページ 20601-20611, 出版日 2021年, 査読付, Herein, we demonstrated that carbon-supported platinum (Pt/C) is a low-cost and high-performance electrocatalyst for polymer electrolyte fuel cells (PEFCs). The ethanol reduction method was used to prepare the Pt/C catalyst, which was realized by an effective matching of the carbon support and optimization of the Pt content for preparing a membrane electrode assembly (MEA). For this, the synthesis of Pt/C catalysts with different Pt loadings was performed on two different carbons (KB1600 and KB800) as new support materials. Analysis of the XRD pattern and TEM images showed that the Pt nanoparticles (NPs) with an average diameter ofca.1.5 nm were uniformly dispersed on the carbon surface. To further confirm the size of the NPs, the coordination numbers of Pt derived from X-ray absorption fine structure (XAFS) data were used. These results suggest that the NP size is almost identical, irrespective of Pt loading. Nitrogen adsorption-desorption analysis indicated the presence of mesopores in each carbon. The BET surface area was found to increase with increasing Pt loading, and the value of the BET surface area was as high as 1286 m2gcarbon−1. However, after 40 wt% Pt loading on both carbons, the BET surface area was decreased due to pore blockage by Pt NPs. The oxidation reduction reaction (ORR) activity for Pt/KB1600, Pt/KB800 and commercial Pt/C was evaluated by Koutecky-Levich (K-L) analysis, and the results showed first-order kinetics with ORR. The favourable surface properties of carbon produced Pt NPs with increased density, uniformity and small size, which led to a higher electrochemical surface area (ECSA). The ECSA value of the 35 wt% Pt/KB1600 catalyst was 155.0 m2gpt−1higher than that of the Pt/KB800 and commercial Pt/C (36.7 wt%) catalysts. A Higher ECSA indicates more available active sites for catalyst particles. The single cell test with MEA revealed that the cell voltage in the high current density regions depends on the BET surface area, and the durability of the 35 wt% Pt/KB1600 catalyst was superior to that of the 30 wt% Pt/KB800 and commercial Pt/C (46.2 wt%) catalysts. This suggests that an optimal ratio of Pt to Pt/KB1600 catalyst provides adequate reaction sites and mass transport, which is crucial to the PEFC's high performance.
    研究論文(学術雑誌), 英語
  • Sulfur poisoning of Pt and PtCo anode and cathode catalysts in polymer electrolyte fuel cells studied by operando near ambient pressure hard X-ray photoelectron spectroscopy
    Suwilai Chaveanghong; Takahiro Nakamura; Yasumasa Takagi; Benjamin Cagnon; Tomoya Uruga; Mizuki Tada; Yasuhiro Iwasawa; Toshihiko Yokoyama
    Physical Chemistry Chemical Physics, Royal Society of Chemistry (RSC), 23巻, 6号, 掲載ページ 3866-3873, 出版日 2021年, 査読付,

    We have investigated the S adsorption behaviours on Pt and Pt3Co anode and cathode electrode catalysts in PEFC under working conditions for the fresh and degraded states, by studying near ambient pressure HAXPES.


    研究論文(学術雑誌)
  • Visualization and understanding of the degradation behaviors of a PEFC Pt/C cathode electrocatalyst using a multi-analysis system combining time-resolved quick XAFS, three-dimensional XAFS-CT, and same-view nano-XAFS/STEM-EDS techniques
    Kotaro Higashi; Shinobu Takao; Gabor Samjeske; Hirosuke Matsui; Mizuki Tada; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, Physical Chemistry Chemical Physics, ROYAL SOC CHEMISTRY, 22巻, 34号, 掲載ページ 18919-18931, 出版日 2020年09月, 査読付, We developed a multi-analysis system that can measurein situtime-resolved quick XAFS (QXAFS) andin situthree-dimensional XAFS-CT spatial imaging in the same area of a cathode electrocatalyst layer in a membrane-electrode assembly (MEA) of a polymer electrolyte fuel cell (PEFC) at the BL36XU beamline of SPring-8. The multi-analysis system also achievesex situtwo-dimensional nano-XAFS/STEM-EDS same-view measurements of a sliced MEA fabricated from a given place in the XAFS-CT imaged area at high spatial resolutions under a water-vapor saturated N(2)atmosphere using a same-view SiN membrane cell. In this study, we applied the combination method of time-resolved QXAFS/3D XAFS-CT/2D nano-XAFS/STEM-EDS for the first time for the visualization analysis of the anode-gas exchange (AGEX) (simulation of the start-up/shut-down of PEFC vehicles) degradation process of a PEFC MEA Pt/C cathode. The AGEX cycles bring about serious irreversible degradation of both Pt nanoparticles and carbon support due to a spike-like large voltage increase. We could visualize the three-dimensional distribution and two-dimensional depth map of the amount, oxidation state (valence), Pt(2+)elution, detachment, and aggregation of Pt species and the formation of carbon voids, where the change and movement of the Pt species in the cathode catalyst layer during the AGEX cycles did not proceed exceeding the 1 mu m region. It is very different from the case of an ADT (an accelerated durability test between 0.6-1.0 V-RHE)-degraded MEA. We discuss the spatiotemporal behavior of the AGEX degradation process and the degradation mechanism.
    研究論文(学術雑誌), 英語
  • Quick Operando Ambient Pressure Hard X-ray Photoelectron Spectroscopy for Reaction Kinetic Measurements of Polymer Electrolyte Fuel Cells
    Takahiro Nakamura; Yasumasa Takagi; Suwilai Chaveanghong; Tomoya Uruga; Mizuki Tada; Yasuhiro Iwasawa; Toshihiko Yokoyama
    The Journal of Physical Chemistry C, American Chemical Society (ACS), 124巻, 32号, 掲載ページ 17520-17527, 出版日 2020年08月13日, 査読付
    研究論文(学術雑誌)
  • Feed gas exchange (startup/shutdown) effects on Pt/C cathode electrocatalysis and surface Pt-oxide behavior in polymer electrolyte fuel cells as revealed using in situ real-time XAFS and high-resolution STEM measurements
    Gabor Samjeske; Takuma Kaneko; Takao Gunji; Kotaro Higashi; Tomoya Uruga; Mizuki Tada; Yasuhiro Iwasawa
    責任著者, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 22巻, 17号, 掲載ページ 9424-9437, 出版日 2020年05月, 査読付, The synchronizing measurements of both cyclic voltammograms (CVs) and real-time quick XAFSs (QXAFSs) for Pt/C cathode electrocatalysts in a membrane electrode assembly (MEA) of polymer electrolyte fuel cells (PEFCs) treated by anode-gas exchange (AGEX) and cathode-gas exchange (CGEX) cycles (startup/shutdown conditions of FC vehicles) were performed for the first time to understand the opposite effects of the AGEX and CGEX treatments on the Pt/C performance and durability and also the contradiction between the electrochemical active surface area (ECSA) decrease and the performance increase by CGEX treatment. While the AGEX treatment decreased both the ECSA and performance of MEA Pt/C due to carbon corrosion, it was found that the CGEX treatment decreased the ECSA but increased the Pt/C performance significantly due to high-index (331) facet formation (high-resolution STEM) and hence the suppression of strongly bound Pt-oxide formation at cathode Pt nanoparticle surfaces. Transient QXAFS time-profile analysis for the MEA Pt/C also revealed a direct relationship between the electrochemical performance or durability and transient kinetics of the Pt/C cathode.
    研究論文(学術雑誌), 英語
  • Electrochemical Properties and Single Cell Performance of Pd Core-Pt Shell Structured Catalyst Synthesized by a Simple Direct Displacement Reaction
    Naoya Aoki; Hideo Inoue; Reiko Yoshiura; Yuya Hasegawa; Shunya Miyazaki; Ayono Suzuki; Hideo Daimon; Takayuki Doi; Minoru Inaba; Kotaro Higashi; Tomoya Uruga; Yasuhiro Iwasawa; Hajime Tanida; Qiuyi Yuan; Naoki Takao; Hideto Imai; Takefumi Mikami; Akimasa Daimaru
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY, ELECTROCHEMICAL SOC INC, 167巻, 4号, 出版日 2020年02月, 査読付, A carbon supported Pd core-Pt shell structured catalyst (Pt/Pd/C) was synthesized by a very simple direct displacement reaction (DDR), in which Pd core nanoparticles (NPs) were directly displaced with [PtCl4](2-) on stirring in N-2 saturated H2SO4 aqueous solution at 70 degrees C instead of a modified Cu under potential deposition (Cu-UPD)/Pt displacement method. In DDR, potential difference between Pd core and [PtCl4](2-) was decreased compared with the difference between Cu shell and [PtCl4](2-) in Cu-UPD/Pt displacement method, which suppressed non-uniform Pt shell formation and increased Pt shell coverage, enhancing oxygen reduction reaction (ORR) activity. Furthermore, fine Pd core NPs were preferentially dissolved out by Cl- anions released from [PtCl4](2-) during DDR performed in acidic H2SO4 solution at 70 degrees C and mean diameter of Pd@Pt core-shell NPs increased, improving durability of Pt/Pd/C catalyst by the size effect. Large Pd particles, however, were formed in Pt/Pd/C catalyst through a disproportionation reaction of Pd2+ cations generated in DDR, which was suppressed by addition of Br- anions as complexing agent. A single cell using Pt/Pd/C cathode catalyst synthesized by DDR with Br- anions and activated by H-2-O-2 chemical pretreatment showed 2.4-fold ORR mass activity of a commercially available Pt/C catalyst at a current density of 1.0 A cm(-2). Thus, DDR was considered to be a suitable synthetic method for a mass production of highly active and durable Pt/Pd/C catalyst for ORR. (c) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
    研究論文(学術雑誌), 英語
  • Model building analysis – a novel method for statistical evaluation of Pt L3-edge EXAFS data to unravel the structure of Pt-alloy nanoparticles for the oxygen reduction reaction on highly oriented pyrolytic graphite
    Felix E. Feiten; Shuntaro Takahashi; Oki Sekizawa; Yuki Wakisaka; Tomohiro Sakata; Naoto Todoroki; Tomoya Uruga; Toshimasa Wadayama; Yasuhiro Iwasawa; Kiyotaka Asakura
    Physical Chemistry Chemical Physics, Royal Society of Chemistry (RSC), 出版日 2020年, 査読付,

    We have developed a novel analytical method combining model building and statistical evaluation to determine the structure of multimetallic nanoparticles from EXAFS of a single adsorption edge.


    研究論文(学術雑誌)
  • Atomic-Scale Structure and Catalysis on Positively Charged Bimetallic Sites for Generation of H2
    Y. Tang; S. Zhang; T. B. Rawal; L. Nguyen; Y. Iwasawa; S. R. Acharya; J. Liu; S. Hong; T. S. Rahman; F. Tao
    Nano Lett., ACS, 20巻, 掲載ページ 6255-6262, 出版日 2020年, 査読付
    研究論文(学術雑誌), 英語
  • Plasma-Devised Pt/C Model Electrodes for Understanding Doubly Beneficial Roles of Nanoneedle-Carbon Morphology and Strong Pt-Carbon Interface in Oxygen Reduction Reaction
    X. Zhao; Y. Hamamura; Y. Yoshida; T. Kaneko; T. Gunji; S. Takao; K. Higashi; T. Uruga; and Y; Iwasawa
    責任著者, ACS Appl. Energy Mater., ACS, 3巻, 6号, 掲載ページ 5542-5551, 出版日 2020年, 査読付, The doubly beneficial contribution of a nanoscale fabricated carbon surface and devised strong Pt-carbon interface to remarkable improvements of Pt/carbon fuel cell electrodes was evidenced to be a crucial clue for rational design of next-generation less-Pt/C electrodes. Real-world carbon surface morphology and metal-carbon interfaces are complex and interrelated and hard to control at a statistical level. Herein, we fabricated plasma-devised nanoneedles-glassy carbon (GC) from well-defined flat GC as model supports, on which Pt nanoparticles were anchored by arc plasma. The arc plasma deposited (APD)-Pt/flat-GC with a strong metal-support interface exhibited enhanced activity for the electrochemical oxygen reduction reaction (ORR) compared to chemically supported Pt/flat-GC and commercial Pt/C electrodes. The APD-Pt/nanoneedles-GC further promoted the ORR and showed a remarkable durability without significant deactivation after accelerated durability test cycles. The structural defects and compressive strain of Pt nanoparticles were induced by the plasma-devised metal-support contact, which may benefit the ORR activity of APDPt/nanoneedles-GC. The nanoneedles-GC support morphology may also improve oxygen gas transport at the nanoscale through modifying the hydrophobicity/hydrophilicity of the GC surface. These results on the devised Pt/C model electrodes reveal the highly enhanced activity and durability of the APD-Pt/nanoneedles-GC electrode by the doubly beneficial effects of a support nanoscale morphology and strong metal-support interface, which were characterized by the intimate combination of Pt/GC synthesis, electrochemical measurements, in situ XAFS, and HAADF-STEM. Our experimental findings provide necessary clues for the design and synthesis of active and durable fuel cell electrodes, metal-air batteries, and catalytic materials.
    研究論文(学術雑誌), 英語
  • Visualization Analysis of Pt and Co Species in Degraded Pt3Co/C Electrocatalyst Layers of a Polymer Electrolyte Fuel Cell Using a Same-View Nano-XAFS/STEM-EDS Combination Technique
    S. Takao; O. Sekizawa; K. Higashi; G. Samjeské; T. Kaneko; T. Sakata; T. Yamamoto; T. Uruga; Y. Iwasawa
    責任著者, ACS Appl. Mater. Interfaces, ACS, 12巻, 2号, 掲載ページ 2299-2312, 出版日 2020年, 査読付
    研究論文(学術雑誌), 英語
  • Emergence of Oxygen Reduction Activity in Zirconium Oxide-Based Compounds in Acidic Media: Creation of Active Sites for the Oxygen Reduction Reaction
    Akimitsu Ishihara; Takaaki Nagai; Keisuke Ukita; Masazumi Arao; Masashi Matsumoto; Liwei Yu; Takahiro Nakamura; Oki Sekizawa; Yasumasa Takagi; Koichi Matsuzawa; Teko W. Napporn; Shigenori Mitsushima; Tomoya Uruga; Toshihiko Yokoyama; Yasuhiro Iwasawa; Hideto Imai; Ken-ichiro Ota
    J. Phys. Chem. C, ACS Publications, 123巻, 30号, 掲載ページ 18150-18159, 出版日 2019年07月08日, 査読付, To develop zirconium oxide-based electrocatalysts for the oxygen reduction reaction (ORR), we attempted to clarify the factors that affect the ORR activity of oxide-based cathodes. We prepared zirconium oxide-based electrocatalysts from oxy-zirconium phthalocyanine with multiwalled carbon nanotubes as electroconductive supports via heat treatment under a low oxygen partial pressure. We evaluated the density of the active sites, i.e., oxygen vacancies, using X-ray photoelectron spectroscopy (XPS), the average particle size of the oxide particles using a transmission electron microscopy (TEM), and the surface area utilization of the oxide particles using TEM image analysis. We successfully determined that the increase in the ORR activity was due to the increase in the density of oxygen vacancies and the effective surface area and that the decrease in the effective surface area was responsible for the decrease in the ORR activity. In addition, we performed hard X-ray photoemission spectroscopy (HAXPES) analysis to understand the process by which the active sites were created. A comparison of the XPS and HAXPES results revealed that the oxygen vacancies were concentrated near the surface during heat treatment under a low oxygen partial pressure via the oxidation of the deposited carbon. The deposited carbon plays a role in creating ORR-active oxygen vacancy sites and promoting ORR by providing local nanoscale conduction paths on the relatively insulating oxide surfaces.
    研究論文(学術雑誌), 英語
  • NH3-Driven Benzene C-H Activation with O2 that Opens a New Way for Selective Phenol Synthesis
    S. S. Acharyya; S. Ghosh; Y. Yoshida; T. Kaneko; T. Sasaki; Y. Iwasawa
    責任著者, Chem. Rec., Wiley, 19巻, 掲載ページ 2069-2081, 出版日 2019年07月, 査読付, 招待
    研究論文(学術雑誌), 英語
  • “SPring‐8 BL36XU: Synchrotron Radiation X‐ray‐based Multi‐analytical Beamline for Polymer Electrolyte Fuel Cells under Operating Conditions
    T. Uruga; M. Tada; O. Sekizawa; Y. Takagi; T. Yokoyama; Y. Iwasawa
    責任著者, Chem. Rec., Wiley, 19巻, 掲載ページ 1444-1456, 出版日 2019年07月, 査読付, 招待
    研究論文(学術雑誌), 英語
  • In-situ XAFS study to monitor the degradation of an Fe/N/C cathode catalyst in PEMFC
    Y. Nabae; S. Nagata; K. Kusaba; T. Aoki; Q. Yuan; N. Takao; T. Itoh; M. Arao; H. Imai; K. Higashi; T. Sakata; T. Uruga; Y. Iwasawa
    ECS Transactions, 92巻, 8号, 掲載ページ 621-625, 出版日 2019年, Understanding the degradation mechanism of Fe/N/C cathode catalysts in proton exchange membrane fuel cells (PEMFCs) is extremely important. In this study, an Fe/N/C catalyst prepared from polyimide nano-particles was placed in an in-situ cell for X-ray absorption spectroscopy, and its Fe K-edge adsorption spectra were acquired during a continuous operation of the fuel cell. The valence of the Fe specie at the initial stage was 3+. The spectra gradually changed during the fuel cell operation, suggesting that the dissolution of the Fe species from the active sites.
    研究論文(国際会議プロシーディングス)
  • Key Factors for Simultaneous Improvements of Performance and Durability of Core-Shell Pt3Ni/Carbon Electrocatalysts Toward Superior Polymer Electrolyte Fuel Cell
    X. Zhao; S. Takao; T. Kaneko; Y. Iwasawa
    責任著者, Chem. Rec., 19巻, 掲載ページ 1337-1353, 出版日 2019年, 査読付, 招待
    研究論文(学術雑誌), 英語
  • Effective surface termination with Au on PtCo@Pt core-shell nanoparticle: Microstructural investigations and oxygen reduction reaction properties.
    S. Takahashi; N. Todoroki; R. Myochi; T. Nagao; N. Taguchi; T. Ioroi; F.E. Feiten; Y. Wakisaka; K. Asakura; O. Sekizawa; T. Sakata; K. Higashi; T. Uruga; Y. Iwasawa; T. Wadayama
    J Electroanal Chem, 842巻, 1号, 掲載ページ 1-7, 出版日 2019年, 査読付, We investigated the microstructures of Au-deposited PtCo@Pt core-shell nanoparticles (NPs) and discussed enhancement of the oxygen reduction reaction (ORR) properties by Au termination of low-coordination sites of the Pt-shell. The Au-deposited PtCo@Pt NPs showed an improved electrochemical structural stability, together with slight increment in increased initial, pristine area-specific activity relative to the non-Au-deposited PtCo@Pt NPs. Atomic-level microstructural characterization was performed by a back-side illumination fluorescence X-ray absorption fine structure (BI-FXAFS) method and scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS). The BI-FXAFS results indicated that compressive lattice strain in the Pt-shells of the PtCo@Pt NPs was almost unchanged by the subsequent Au deposition. Furthermore, STEM-EDS mapping of Pt, Co, and Au clearly showed that the deposited Au tended to localize at low-coordination sites of the Pt-shell surface, e.g., edges and corners. The atomic-level microstructural characterization conducted in this study demonstrated that effective Au surface terminations of the Pt-shell enhance the ORR durability of Pt-based core-shell type NP catalysts.
    研究論文(学術雑誌), 英語
  • Operando Observation of Sulfur Species Poisoning Polymer Electrolyte Fuel Cell Studied by Near Ambient Pressure Hard X-ray Photoelectron Spectroscopy
    Liwei Yu; Yasumasa Takagi; Takahiro Nakamura; Tomohiro Sakata; Tomoya Uruga; Mizuki Tada; Yasuhiro Iwasawa; Shigeyuki Masaoka; Toshihiko Yokoyama
    The Journal of Physical Chemistry C, American Chemical Society ({ACS}), 123巻, 掲載ページ 603-611, 出版日 2019年01月, 査読付
    研究論文(学術雑誌), 英語
  • Single rhodium atoms anchored in micropores for efficient transformation of methane under mild conditions
    Yu Tang; Yuting Li; Victor Fung; De-En Jiang; Weixin Huang; Shiran Zhang; Yasuhiro Iwasawa; Tomohiro Sakata; Luan Nguyen; Xiaoyan Zhang; Anatoly I. Frenkel; Franklin Tao
    Nature Communications, Nature Publishing Group, 9巻, 1号, 掲載ページ 1231-1-1231-11, 出版日 2018年12月01日, 査読付, Catalytic transformation of CH4 under a mild condition is significant for efficient utilization of shale gas under the circumstance of switching raw materials of chemical industries to shale gas. Here, we report the transformation of CH4 to acetic acid and methanol through coupling of CH4, CO and O2 on single-site Rh1O5 anchored in microporous aluminosilicates in solution at ≤150 °C. The activity of these singly dispersed precious metal sites for production of organic oxygenates can reach about 0.10 acetic acid molecules on a Rh1O5 site per second at 150 °C with a selectivity of ∼70% for production of acetic acid. It is higher than the activity of free Rh cations by >
    1000 times. Computational studies suggest that the first C-H bond of CH4 is activated by Rh1O5 anchored on the wall of micropores of ZSM-5
    the formed CH3 then couples with CO and OH, to produce acetic acid over a low activation barrier.
    研究論文(学術雑誌), 英語
  • Evidence for Multi-Atom Resonance X-ray Raman Spectroscopy-An in situ Low Z-element and Bond-specific X-ray Spectroscopy
    Sirisit N; Kido D; Wakisaka Y; Ariga-Miwa H; Takakusagi S; Asakura K; Sekizawa O; Sakata T; Uruga T; Iwasawa Y
    E-Journal of Surface Science and Nanotechnology, SURFACE SCI SOC JAPAN, 16巻, 掲載ページ 387-390, 出版日 2018年09月01日, 査読付, We have shown a possibility of multi-atom resonant X-ray Raman (MARX-Raman) spectroscopy by measuring the N K-edge loss spectrum of TaN at Ta L-3-edge and C K-edge loss spectrum of Er(C5H5)(3) at Er L1-edge. When the excitation X-ray energy was tuned to the Ta L-3-edge and inelastic scattering spectra were recorded around 400 eV loss corresponding to the N K-edge Raman region, we found a clear enhancement of emission spectrum. The same enhancement was observed in C K-edge Raman region in Er(C5H5)(3). These experimental results have indicated the possibility of MARX-Raman phenomenon which may lead to a new in situ and bond-specific XAFS spectroscopy for low Z elements.
    研究論文(学術雑誌), 英語
  • Premodified Surface Method to Obtain Ultra-highly Dispersed Metals and their 3D Structure Control on an Oxide Single-crystal Surface.
    S. Takakusagi; Y. Iwasawa; K. Asakura
    The Chemical Records, 出版日 2018年09月, 査読付, 招待
    研究論文(国際会議プロシーディングス), 英語
  • In-situ 3D CT-XAFS Imaging of Pt/C Cathode Catalysts in Polymer Electrolyte Fuel Cell during Degradation Processes by Anode Gas Exchange Cycles
    Kotaro Higashi; Tomohiro Sakata; Oki Sekizawa; Nozomu Ishiguro; Gabor Samjeske; Shinobu Takao; Takuma Kaneko; Tomoya Uruga; Yasuhiro Iwasawa; Mizuki Tada
    Microscopy and Microanalysis, Oxford University Press (OUP), 24巻, S2号, 掲載ページ 442-443, 出版日 2018年08月10日
    研究論文(学術雑誌)
  • Development of Surface Fluorescence X-ray Absorption Fine Structure Spectroscopy using a Laue-Type Monochromator and its Application to Structure Determination of Nanoparticles at Submonolayer Coverage under Electrochemical Conditions
    Yuki Wakisaka; Daiki Kido; Hiromitsu Uehara; Qiuyi Yuan; Felix E. Feiten; Shingo Mukai; Satoru Takakusagi; Yohei Uemura; Toshihiko Yokoyama; Takahiro Wada; Motohiro Uo; Oki Sekizawa; Tomoya Uruga; Yasuhiro Iwasawa; Kiyotaka Asakura
    The Chemical Records, 出版日 2018年08月, 査読付
  • A Demonstration of Pt L3-Edge EXAFS Free from Au L3-Edge Using Log–Spiral Bent Crystal Laue Analyzers
    Yuki Wakisaka; Daiki Kido; Hiromitsu Uehara; Qiuyi Yuan; Satoru Takakusagi; Yohei Uemura; Toshihiko Yokoyama; Takahiro Wada; Motohiro Uo; Tomohiro Sakata; Oki Sekizawa; Tomoya Uruga; Yasuhiro Iwasawa; Kiyotaka Asakura
    Catalysts, MDPI, 8巻, 5号, 掲載ページ 204, 出版日 2018年05月, 査読付
    研究論文(学術雑誌), 英語
  • Key Structural Transformations and Kinetics of Pt Nanoparticles in PEFC Pt/C Electrocatalysts by a Simultaneous Operando Time-Resolved QXAFS‒XRD Technique
    O. Sekizawa; T. Kaneko; K. Higashi; S. Takao; Y. Yoshida; T. Gunji; X. Zhao; G. Samjeské; T. Sakata; T. Uruga; Y. Iwasawa
    責任著者, Topics Catal., Nature Springer, 61巻, 9-11号, 掲載ページ 889-901, 出版日 2018年, 査読付, This account article treats with the key structural transformations and kinetics of Pt nanoparticles in Pt/C cathode catalysts under transient voltage operations (0.4 V-RHE -> 1.4 V-RHE -> 0.4 V-RHE) by simultaneous operando time-resolved QXAFS-XRD measurements, summarizing and analyzing our previous kinetic data in more detail and discussing on the key reaction steps and rate constants for the performance and durability of polymer electrolyte fuel cells (PEFC). The time-resolved QXAFS-XRD measurements were conducted at each acquisition time of 20 ms, while measuring the current/charge of the PEFC. The rate constants for the transient responses of Pt valence, CN(Pt-O) (CN: coordination number), CN(Pt-Pt), and Pt metallic-phase core size under the transient voltage operations were determined by the combined time-resolved QXAFSaEuro'XRD technique. The relationship of the structural kinetics with the performance and durability of the PEFC Pt/C was also documented as key issues for the development of next-generation PEFCs. The present account emphasizes the time-resolved QXAFS and XRD techniques to be a powerful technique to analyze directly the structural and electronic change of metal nanoparticles inside PEFC under the operating conditions.
    研究論文(学術雑誌), 英語
  • Ambient Pressure Hard X-ray Photoelectron Spectroscopy for Functional Material Systems as Fuel Cells under Working Conditions
    Y. Takagi; T. Uruga; M. Tada; Y. Iwasawa; T. Yokoyama
    Acc. Chem. Res., ACS, 51巻, 掲載ページ 719-727, 出版日 2018年, 査読付, 招待
    研究論文(学術雑誌), 英語
  • Observation of Degradation of Pt and Carbon Support in Polymer Electrolyte Fuel Cell Using Combined Nano-XAFS and TEM Techniques
    S. Takao; O. Sekizawa; G. Samjeské; T. Kaneko; K. Higashi; Y. Yoshida; X. Zhao; T. Sakata; T. Yamamoto; T. Gunji; T. Uruga; Y. Iwasawa
    責任著者, ACS Appl. Mater. Interfaces, ACS, 10巻, 33号, 掲載ページ 27734-27744, 出版日 2018年, 査読付
    研究論文(学術雑誌), 英語
  • Confined Single Alkali Metal Ion Platform in Zeolite Pore for Concerted Benzene C–H Activation-to-Phenol Catalysis
    S. Ghosh; S. S. Acharyya; T. Kaneko; K, Higashi; Y. Yoshida; T. Sasaki; Y. Iwasawa
    責任著者, ACS Catal., ACS, 8巻, 12号, 掲載ページ 11979-11986, 出版日 2018年, 査読付, The well-known cumene process via an explosive cumene hydroperoxide intermediate in liquid phase currently employed for phenol production is energy-intensive and not environmentally friendly. Therefore, there is a demand for an alternative single-step gas-phase catalysis process. According to the conventional catalysis concept, selective oxidation reactions are promoted by redox catalysts and not by acid-base catalysts. In general, alkali and alkaline earth metal ions cannot activate each of benzene, O2, and N2O when they adsorb separately. However, we observed an unprecedented catalysis of single alkali and alkaline earth metal ion sites incorporated into zeolite pores for the selective oxidation of benzene to phenol with N2O and O2 + NH3, thereby providing a single-site catalytic platform with high selectivity. Among alkali and alkaline earth metal ions, single Cs+ and Rb+ sites with ion diameters of >300 pm in the pores of β-zeolites exhibited remarkable selectivity for benzene C-H activation to phenol catalysis in a concerted reaction pathway.
    研究論文(学術雑誌), 英語
  • Non-contact electric potential measurements of electrode components in an operating polymer electrolyte fuel cell by near ambient pressure XPS
    Liwei Yu; Yasumasa Takagi; Takahiro Nakamura; Oki Sekizawa; Tomohiro Sakata; Tomoya Uruga; Mizuki Tada; Yasuhiro Iwasawa; Gabor Samjeske; Toshihiko Yokoyama
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 19巻, 45号, 掲載ページ 30798-30803, 出版日 2017年12月, 査読付, Photoelectron spectroscopy has the advantage of providing electric potentials by non-contact measurements based on the kinetic energy shift in component potential. We performed operando hard X-ray photoelectron spectroscopy (HAXPES) measurements with an 8 keV excitation source to measure the shift in electron kinetic energies as a function of the voltages of all the components at the anode and cathode electrodes of a polymer electrolyte fuel cell (PEFC). At the cathode electrode, when we increase the voltage between the cathode and anode from 0.2 to 1.2 V, the O 1s and F 1s peaks shift to a lower binding energy and the magnitude of the energy shift is equal to the voltage. The Pt 3d and C 1s peaks do not shift with the voltage since platinum nanoparticles and carbon supports at the cathode electrode have ground contact. In contrast to the cathode electrode, the peak shifts of all the components at the anode electrode show the same amount of shift as the voltages. It is clear that the change in the potential difference occurs only in an electrical double layer at the interface between the cathode electrode (Pt/C) and the electrolyte (Nafion and water), and that the anode electrode is in equilibrium as a pseudo-hydrogen electrode. Moreover, the electric potential variation of the cathode electrode in a PEFC under a power generation condition was also directly detected by operando HAXPES.
    研究論文(学術雑誌), 英語
  • The Relationship between the Active Pt Fraction in a PEFC Pt/C Catalyst and the ECSA and Mass Activity during Start-Up/Shut-Down Degradation by in Situ Time-Resolved XAFS Technique
    Kotaro Higashi; Gabor Samjeske; Shinobu Takao; Takuma Kaneko; Oki Sekizawa; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 121巻, 40号, 掲載ページ 22164-22177, 出版日 2017年10月, 査読付, Transient-response kinetics of the transformations (six elementary steps) of the Pt valence, coordination number of Pt-Pt bonds, and coordination number of Pt-O bonds of a Pt/C cathode catalyst in a polymer electrolyte fuel cell (PEFC) under cyclic voltage operations (0.4 -> 1.4 -> 0.4 V-RHE) during anode-gas exchange (AGEX) treatments (start-up/shut-down) has been studied by in situ time-resolved quick X-ray absorption fine structure (QXAFS, 100 ms/spectrum). The transient-response analysis identified the existence and fractions of three different kinds (active, less active, and inactive) of Pt nanoparticles in the Pt/C cathode. The active Pt nanoparticles degraded to less active and inactive Pt nanoparticles by the AGEX cycles. The degradation probability and mechanism were clarified by the transient-response kinetics. The electrochemical surface area (ECSA) and mass activity (MA) of the Pt/C cathode catalyst also decreased with increasing AGEX cycles. It was found that the change in the sum of the fractions of the active and less active Pt nanoparticles correlates with the change in the ECSA and MA during the AGEX treatments. The in situ time-resolved QXAFS analysis provides direct information on the dynamic behavior of the Pt/C catalyst relevant to the electrochemical performance and property under the operando conditions for thorough understanding of the degradation process toward PEFC improvement.
    研究論文(学術雑誌), 英語
  • Controlling the inhomogeneity of solid catalysts at the mesoscopic scale
    Hua Huang; Takahiro Wada; Hiroko Ariga; Satoru Takakusagi; Kiyotaka Asakura; Yasuhiro Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 683巻, 掲載ページ 18-21, 出版日 2017年09月, 査読付, High-performance catalysts are often composed of two or more active phases, which are believed to interact with each other at the mesoscopic scale structure. Unlike conventional powder catalysts flat surfaces is advantageous in that its surface structure can be precisely designed. We prepared precisely designed Sb2O4/VSbO4/Si catalysts containing Sb2O4 ribbons with finely controlled width and separation by electron lithography. We demonstrated that the acrolein generation rate on the catalysts was related to the width and separation of the Sb2O4 ribbons. This work shows the possibility to regulate catalyses by inhomogeneity of the surface structure at the mesoscopic level. (C) 2017 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • ラウエ型湾曲結晶分光器による高感度XAFS
    脇坂祐輝; 岩崎裕也; 上原広充; 向井慎吾; 城戸大貴; 高草木達; 上村洋平; 和田敬広; Qiuyi YUAN; 関澤央輝; 宇留賀朋哉; 岩澤康裕; 朝倉清高
    表面科学, 38巻, 8号, 掲載ページ 378-383, 出版日 2017年08月, 査読付
    研究論文(学術雑誌), 日本語
  • X-ray photoelectron spectroscopy under real ambient pressure conditions
    Yasumasa Takagi; Takahiro Nakamura; Liwei Yu; Suwilai Chaveanghong; Oki Sekizawa; Tomohiro Sakata; Tomoya Uruga; Mizuki Tada; Yasuhiro Iwasawa; Toshihiko Yokoyama
    APPLIED PHYSICS EXPRESS, IOP PUBLISHING LTD, 10巻, 7号, 掲載ページ 076603, 出版日 2017年07月, 査読付, We have developed an ambient pressure hard-X-ray photoelectron spectroscopic system equipped with a differential pumping system at BL36XU of SPring-8. Photoelectron spectra from a Au(111) surface were recorded using excitation light of 8 keV focused to 20 x 20 mu m(2) and adopting an aperture diameter of 30 mu m at the entrance of the electron lens and a working distance of 60 mu m. The Au 4f and 3d(5/2) spectra were measured by increasing the ambient pressure from 1 Pa to atmospheric pressure and demonstrated that the instrument is capable of measuring the photoelectron spectrum under atmospheric pressure. (C) 2017 The Japan Society of Applied Physics
    研究論文(学術雑誌), 英語
  • Simultaneous Improvements of Performance and Durability of An Octahedral PtNix/C Electrocatalyst for Next–Generation Fuel Cells by Continuous, Compressive and Concave Pt skin layers
    X. Zhao; S. Takao; K. Higashi; T. Kaneko; G. Samjeskè; O. Sekizawa; T. Sakata; Y. Yoshida; T. Uruga; Y. Iwasawa
    責任著者, ACS Catal., アメリカ化学会, 7巻, 7号, 掲載ページ 4642-4654, 出版日 2017年07月, 査読付, Simultaneous improvements in oxygen reduction reaction (ORR) activity and long-term durability of Pt-based cathode catalysts are indispensable for the development of next-generation polymer electrolyte fuel cells but are still a major dilemma. We present a robust octahedral core-shell PtNix/C electrocatalyst with high ORR performance (mass activity and surface specific activity 6.8-16.9 and 20.3-24.0 times larger than those of Pt/C, respectively) and durability (negligible loss after 10000 accelerated durability test (ADT) cycles). The key factors of the robust octahedral nanostructure (core-shell Pt73Ni27/C) responsible for the remarkable activity and durability were found to be three continuous Pt skin layers with 2.0-3.6% compressive strain, concave facet arrangements (concave defects and high coordination), a symmetric Pt/Ni distribution, and a Pt67Ni33 intermetallic core, as found by STEM-EDS, in situ XAFS, XPS, etc. The robust core-shell Pt73Ni27/C was produced by the partial release of the stress, Pt/Ni rearrangement, and dimension reduction of an as-synthesized octahedral Pt50Ni50/C with 3.6-6.7% compressive Pt skin layers by Ni leaching during the activation process. The present results on the tailored synthesis of the PtNix structure and composition and the better control of the robust catalytic architecture renew the current knowledge and viewpoint for instability of octahedral PtNix/C samples to provide a new insight into the development of next-generation PEFC cathode catalysts.
    研究論文(学術雑誌), 英語
  • Simultaneous Operando Time-Resolved XAFS-XRD Measurements of a Pt/C Cathode Catalyst in Polymer Electrolyte Fuel Cell under Transient Potential Operations
    Oki Sekizawa; Tomoya Uruga; Kotaro Higashi; Takuma Kaneko; Yusuke Yoshida; Tomohiro Sakata; Yasuhiro Iwasawa
    責任著者, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, AMER CHEMICAL SOC, 5巻, 5号, 掲載ページ 3631-3636, 出版日 2017年05月, 査読付, We have succeeded in simultaneous operando time-resolved quick X-ray absorption fine structure (QXAFS) X-ray diffraction (XRD) measurements at each acquisition time of 20 ms for a Pt/C cathode catalyst in a polymer electrolyte fuel cell (PEFC), while measuring the current/charge of the PEFC during the transient voltage cyclic processes (0.4 V-RHE -> 1.4 V-RHE -> 0.4 V-RHE) under H-2(anode) N-2(cathode). The rate constants for Pt-O bond formation/dissociation, Pt charging/discharging, Pt-Pt bond dissociation/reformation, and decrease/increase of Pt metallic phase core size under the transient potential operations were determined by the combined time-resolved QXAFS XRD technique. The present study provides a new insight into the transient-response reaction mechanism and structural transformation in the Pt surface layer and bulk, which origin of PEFC activity and durability as key issues for the development of next-generation PEFCs.
    研究論文(学術雑誌), 英語
  • In situ study of oxidation states of platinum nanoparticles on a polymer electrolyte fuel cell electrode by near ambient pressure hard X-ray photoelectron spectroscopy
    Yasumasa Takagi; Heng Wang; Yohei Uemura; Takahiro Nakamura; Liwei Yu; Oki Sekizawa; Tomoya Uruga; Mizuki Tada; Gabor Samjeske; Yasuhiro Iwasawa; Toshihiko Yokoyama
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 19巻, 8号, 掲載ページ 6013-6021, 出版日 2017年02月, 査読付, We performed in situ hard X-ray photoelectron spectroscopy (HAXPES) measurements of the electronic states of platinum nanoparticles on the cathode electrocatalyst of a polymer electrolyte fuel cell (PEFC) using a near ambient pressure (NAP) HAXPES instrument having an 8 keV excitation source. We successfully observed in situ NAP-HAXPES spectra of the Pt/C cathode catalysts of PEFCs under working conditions involving water, not only for the Pt 3d states with large photoionization cross-sections in the hard X-ray regime but also for the Pt 4f states and the valence band with small photoionization crosssections. Thus, this setup allowed in situ observation of a variety of hard PEFC systems under operating conditions. The Pt 4f spectra of the Pt/C electrocatalysts in PEFCs clearly showed peaks originating from oxidized Pt(II) at 1.4 V, which unambiguously shows that Pt(IV) species do not exist on the Pt nanoparticles even at such large positive voltages. The water oxidation reaction might take place at that potential (the standard potential of 1.23 V versus a standard hydrogen electrode) but such a reaction should not lead to a buildup of detectable Pt(IV) species. The voltage-dependent NAP-HAXPES Pt 3d spectra revealed different behaviors with increasing voltage(0.6 -> 1.0 V) compared with decreasing voltage (1.0 -> 0.6 V), showing a clear hysteresis. Moreover, quantitative peak-fitting analysis showed that the fraction of non-metallic Pt species matched the ratio of the surface to total Pt atoms in the nanoparticles, which suggests that Pt oxidation only takes place at the surface of the Pt nanoparticles on the PEFC cathode, and the inner Pt atoms do not participate in the reaction. In the valence band spectra, the density of electronic states near the Fermi edge reduces with decreasing particle size, indicating an increase in the electrocatalytic activity. Additionally, a change in the valence band structure due to the oxidation of platinum atoms was also observed at large positive voltages. The developed apparatus is a valuable in situ tool for the investigation of the electronic states of PEFC electrocatalysts under working conditions.
    研究論文(学術雑誌), 英語
  • In-situ X-ray nano-CT System for Polymer Electrolyte Fuel Cells under Operating Conditions
    O. Sekizawa; T. Uruga; N. Ishiguro; H. Matsui; K. Higashi; T. Sakata; Y. Iwasawa; M. Tada
    責任著者, J. Phys.: Conf. Series, IOP PUBLISHING LTD, 849巻, 掲載ページ 012022, 出版日 2017年, 査読付, We developed two types of in-situ three-dimensional imaging systems on the basis of full-field transmission X-ray computed tomography (XCT) methods for polymer electrolyte fuel cells (PEFCs) under operating conditions at beamline BL36XU at SPring-8. One was for a wide field of view (more than 500 mu m) to obtain the whole membrane electrode assembly (MEA) images, and the other was for nano spatial resolution (less than 100 nm) using a Fresnel zone plate as objective optics. We succeeded in in-situ three-dimensional visualization of an MEA in PEFC using both XCT measurement systems and show preliminary results.
    研究論文(国際会議プロシーディングス), 英語
  • XAFS Techniques for Catalysts, Nanomaterials, and Surfaces
    Y. Iwasawa; K. Asakura; M. Tada
    責任著者, Springer, 出版日 2016年11月, 査読付, 招待
    英語
  • Key Structural Kinetics for Carbon Effects on the Performance and Durability of Pt/Carbon Cathode Catalysts in Polymer Electrolyte Fuel Cells Characterized by In Situ Time-Resolved X-ray Absorption Fine Structure
    Takuma Kaneko; Gabor Samjeske; Shin-ichi Nagamatsu; Kotaro Higashi; Oki Sekizawa; Shinobu Takao; Takashi Yamamoto; Xiao Zhao; Tomohiro Sakata; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 120巻, 42号, 掲載ページ 24250-24264, 出版日 2016年10月, 査読付, The structural kinetics (rate constants for electronic and structural transformations) of the Pt charging/discharging, Pt Pt bond dissociation/re-formation, and Pt-O bond formation/dissociation of Pt/Ketjenblack, Pt/acetylene black, and Pt/multiwalled carbon nanotube cathode catalysts in polymer electrolyte fuel cell (PEFC) membrane electrode assemblies (MEAs) under transient potential operations (0.4 V-RHE -> 1.4 V-RHE -> 0.4 V-RHE) has been studied by in situ/operando time-resolved quick X-ray absorption fine structure (QXAFS; 100 ms/spectrum), while measuring electrochemical currents/charges in the MEAs under the potential operations. From the systematic QXAFS analysis for potential-dependent surface structures and rate constants (k and k') for the transformations of Pt nanoparticles under the operations (0.4 V-RHE -> 1.4 V-RHE and 1.4 V-RHE -> 0.4 V-RHE), respectively, we have found the structural kinetics (k(Pt-O)' and k(valence)') controlling the oxygen reduction reaction (ORR) activity and also the structural kinetics (k(pt-pt/kpt-pt)') reflecting the durability of the cathode catalysts. The relaxation time of the Pt Pt bond re-formation and Pt-O bond dissociation processes in the activated MEAs was also suggested to predict the relative durability of similar kinds of cathode catalysts. The in situ time-resolved XAFS analysis provided direct information on the key structural kinetics of the Pt/C catalysts themselves for thorough understanding of the cathode catalysis toward PEFC improvement.
    研究論文(学術雑誌), 英語
  • Spatially Non-Uniform Degradation of Pt/C Cathode Catalysts in Polymer Electrolyte Fuel Cells Imaged by Combination of Nano XAFS and STEM-EDS Techniques
    Shinobu Takao; Oki Sekizawa; Gabor Samjesk?; Shin-ichi Nagamatsu; Takuma Kaneko; Kotaro Higashi; Takashi Yamamoto; Kensaku Nagasawa; Xiao Zhao; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, Topics in Catalysis, Springer Science and Business Media LLC, Vol.59巻, No.19号, 掲載ページ 1722-1731, 出版日 2016年08月, 査読付
    研究論文(学術雑誌), 英語
  • A New Indicator for Single Metal Dispersion on a TiO2(110) Surface Premodified with a Mercapto Compound
    Satoru Takakusagi; Akitoshi Kunimoto; Natee Sirisit; Hiromitsu Uehara; Tadashi Ohba; Yohei Uemuara; Takahiro Wada; Hiroko Ariga; Wang-Jae Chun; Yasuhiro Iwasawa; Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 120巻, 29号, 掲載ページ 15785-15791, 出版日 2016年07月, 査読付, Ni and Pt structures evaporated onto a TiO2(110) surface premodified with ortho-mercaptobenzoic acid (o-MBA) were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure analysis to determine the effects of the premodification on the dispersion of the metal atoms over the TiO2(110) surface. Ni was found to be atomically dispersed with the formation of S-Ni-O bonds (where the S is provided by the o-MBA and the 0 is present in the TiO2 lattice) on the surface. In contrast, Pt underwent aggregation to form small clusters. The varying behavior of these metals on the o-MBA-modified TiO2(110) surface is discussed based on the energy difference between sulfur-metal-oxygen and metal-metal bond formations, and we propose a new indicator for single metal dispersion on the TiO2(110) surface.
    研究論文(学術雑誌), 英語
  • Structural and Electronic Transformations of Pt/C, Pd@Pt(1 ML)/C and Pd@Pt(2 ML)/C Cathode Catalysts in Polymer Electrolyte Fuel Cells during Potential-step Operating Processes Characterized by In-situ Time-resolved XAFS
    Shin-ichi Nagamatsu; Shinobu Takao; Gabor Samjeske; Kensaku Nagasawa; Oki Sekizawa; Takuma Kaneko; Kotaro Higashi; Tomoya Uruga; Sirshendu Gayen; Srihari Velaga; Milan K. Saniyal; Yasuhiro Iwasawa
    責任著者, SURFACE SCIENCE, ELSEVIER SCIENCE BV, 648巻, 掲載ページ 100-113, 出版日 2016年06月, 査読付, 招待, The dynamic structural and electronic transformations of Pt/C, Pd@Pt(1 ML)/C, Pd@Pt(2 ML)/C cathode catalysts in polymer electrolyte fuel cells (PEFCs) during the potential-step operating processes between 0.4 and 1.4 V-RHE (potential vs RHE) were characterized by in-situ (operando) time-resolved Pt L-III-edge quick-XAFS at 100 ms time-resolution. Potential-dependent surface structures and oxidation states of Pt, Pd@Pt(1 ML) and Pd@Pt(2 ML) nanoparticles on carbon at 0.4 and 1.4 V-RHE were also analyzed by in-situ Pt L-III-edge and Pd K-edge quick-XAFS. The Pt, Pd@Pt(1 ML) and Pd@Pt(2 ML) nanoparticle surfaces were restructured and disordered at 1.4 VRHE, which were induced by strong Pt-O bonds as well as alloying effects. The rate constants for the changes of Pt valence, CN(Pt-Pt), CN(Pt-Pd) and CN(Pt-O) (CN: coordination number) in the potential-step operating processes were also determined and discussed in relation to the origin of oxygen reduction reaction (ORR) activities of the Pt/C, Pd@Pt(1 ML)/C and Pd@Pt(2 ML)/C cathode catalysts. (C) 2015 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • SPring-8 BL36XU: Catalytic Reaction Dynamics for Fuel Cells
    O. Sekizawa; T. Uruga; Y. Takagi; K. Nitta; K. Kato; H. Tanida; K. Uesugi; M. Hoshino; E. Ikenaga; K. Takeshita; S. Takahashi; M. Sano; H. Aoyagi; A. Watanabe; N. Nariyama; H. Ohashi; H. Yumoto; T. Koyama; Y. Senba; T. Takeuchi; Y. Furukawa; T. Ohata; T. Matsushita; Y. Ishizawa; T. Kudo; H. Kimura; H. Yamazaki; T. Tanaka; T. Bizen; T. Seike; S. Goto; H. Ohno; M. Takata; H. Kitamura; T. Ishikawa; M. Tada; T. Yokoyama; Y. Iwasawa
    責任著者, 16TH INTERNATIONAL CONFERENCE ON X-RAY ABSORPTION FINE STRUCTURE (XAFS16), IOP PUBLISHING LTD, 712巻, 掲載ページ 012142-1-012142-4, 出版日 2016年, 査読付, A tapered undulator beamline BL36XU was constructed at SPring-8 to conduct structural and electronic analysis of dynamic events on polymer electrolyte fuel cell (PEFC) cathode catalysts for the development of next-generation PEFCs. BL36XU provides various time and spatially resolved XAFS techniques in an energy range from 4.5 to 35 keV for investigating PEFCs under the operating conditions. In addition, we developed in-situ complementary measurement systems, such as in-situ time-resolved XAFS/XRD and ambient pressure HAXPES systems. This report describes the performance and present status of the BL36XU.
    研究論文(国際会議プロシーディングス), 英語
  • Structure of the Active Platinum Cluster and Reaction Pathway of the Selective Synthesis of Phenol from Benzene and Oxygen Regulated with Ammonia on a Platinum Cluster/β-Zeolite Catalyst Studied by DFT Calculations
    Sasaki T; Tada M; Wang L; Malwadkar S; Iwasawa Y
    責任著者, Chemistry - An Asian Journal, WILEY-V C H VERLAG GMBH, 10巻, 10号, 掲載ページ 2283-2291, 出版日 2015年10月, 査読付, DFT calculations were used to investigate the structure of the active Pt cluster and the catalytic reaction pathway for the selective synthesis of phenol from benzene and molecular oxygen regulated with ammonia on a Pt cluster/beta-zeolite catalyst that was reported to be active for the selective hydroxylation of benzene only in the coexistence of ammonia. It was found that Pt-5-Pt-6 clusters were active for the direct synthesis of phenol, and they provided the reaction sites for bond rearrangements among ammonia, oxygen, and benzene; furthermore, the coexistence of ammonia was crucial for the selective oxidation of benzene to phenol, as it suppressed benzene combustion to CO2 and promoted the selective synthesis of phenol. It was further found that water coexisting in the system also played a significant role in desorbing phenol on the Pt cluster surface, which resulted in promotion of the overall selective synthesis of phenol. The energy diagram for the reaction sequences and the structures of the transition states were obtained, which indicated the origin of the Pt/b catalysis.
    研究論文(学術雑誌), 英語
  • In Situ Techniques to Study the Effects of Anode or Cathode Gas-Exchange Cycles on the Deterioration of Pt/C Cathode Catalysts in PEFCs
    Gabor Samjeske; Kotaro Higashi; Shinobu Takao; Shin-ichi Nagamatsu; Kensaku Nagasawa; Oki Sekizawa; Takuma Kaneko; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, CHEMELECTROCHEM, WILEY-V C H VERLAG GMBH, 2巻, 10号, 掲載ページ 1595-1606, 出版日 2015年10月, 査読付, Repeated, quick anode gas-exchange (AGEX) or cathode gas-exchange (CGEX) cycles were applied to polymer electrolyte fuel cell (PEFC) membrane electrode assemblies (MEAs) with Pt/C cathode catalysts to simulate start-up/shut-down conditions and to examine a possible countermeasure for their effects on MEA cathode catalyst degradation. The peak height of the white line during insitu time-resolved X-ray absorption near-edge structure (XANES) spectra at the Pt L-III-edge decreased with an increasing number of AGEX cycles and only in the top region of the MEA cathode layer (close to the gas inlet of the fuel cell), not in the whole MEA area. End-of-life analysis after AGEX by using SEM and TEM revealed isolated Pt nanoparticles in micro-cracks and voids produced in the top region of the MEA cathode layer. The nanoparticle sizes remained almost unchanged for top, middle, and bottom regions of the MEA cathode layer. In the case of CGEX, a small increase in the Pt nanoparticle sizes in the top and bottom positions of the MEA cathode layer was observed. These findings support the role of carbon corrosion, leaving isolated, electrochemically inactive Pt nanoparticles as a consequence of the harsh reaction conditions caused by the reverse current decay mechanism during the start-up/shut-down phase, as in the case of AGEX cycles, to be the main cause for the cathode catalyst deterioration close to the anode gas inlet. On the other hand, the hydrogen gas feed to both the anode and cathode during start-up and shut-down processes seems to effectively suppress carbon corrosion and prevents a decrease in the performance.
    研究論文(学術雑誌), 英語
  • Selective Phenol Synthesis from Benzene with O2 by Switchover of the Reaction Pathways from Complete Oxidation to Selective Hydroxylation by NH3 on Ir/ and Ni/ Catalysts
    L. Wang; S. Yamamoto; K. Hayashizaki; S. Nagamatsu; S. Malwadkar; T. Sasaki; Y. Iwasawa
    責任著者, ChemCatChem, Wiley, 7巻, 20号, 掲載ページ 3248-3253, 出版日 2015年10月, 査読付, Selective Phenol Synthesis from Benzene with O2 by Switchover of the Reaction Pathways from Complete Oxidation to Selective Hydroxylation by NH3 on Ir/ and Ni/ Catalysts
    研究論文(学術雑誌), 英語
  • Surface-Regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by a Selective Electrochemical Sn Deposition Method
    Kensaku Nagasawa; Shinobu Takao; Shin-ichi Nagamatsu; Gabor Samjeske; Oki Sekizawa; Takuma Kaneko; Kotaro Higashi; Takashi Yamamoto; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 137巻, 40号, 掲載ページ 12856-12864, 出版日 2015年10月, 査読付, We have achieved significant improvements for the oxygen reduction reaction activity and durability with new SnO2-nanoislands/Pt3Co/C catalysts in 0.1 M HClO4, which were regulated by a strategic fabrication using a new selective electrochemical Sn deposition method. The nano-SnO2/Pt3Co/C catalysts with Pt/Sn = 4/1, 9/1, 11/1, and 15/1 were characterized by STEM-EDS, XRD, XRF, XPS, in situ XAFS, and electrochemical measurements to have a Pt3Co core/Pt skeleton-skin structure decorated with SnO2 nanoislands at the compressive Pt surface with the defects and dislocations. The high performances of nano-SnO2/Pt3Co/C originate from efficient electronic modification of the Pt skin surface (site 1) by both the Co of the Pt3Co core and surface nano-SnO2 and and more from the unique property of the periphery sites of the SnO2 nanoislands at the compressive Pt skeleton-skin surface (more active site 2), which were much more active than expected from the d-band center values. The white line peak intensity of the nano-SnO2/Pt3Co/C revealed no hysteresis in the potential up down operations between 0.4 and 1.0 V versus RHE, unlike the cases of Pt/C and Pt3Co/C, resulting in the high ORR performance. Here we report development of a new class of cathode catalysts with two different active sites for next-generation polymer electrolyte fuel cells.
    研究論文(学術雑誌), 英語
  • Same-View Nano-XAFS/STEM-EDS Imagings of Pt Chemical Species in Pt/C Cathode Catalyst Layers of a Polymer Electrolyte Fuel Cell
    Shinobu Takao; Oki Sekizawa; Gabor Samjeske; Shin-ichi Nagamatsu; Takuma Kaneko; Takashi Yamamoto; Kotaro Higashi; Kensaku Nagasawa; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, AMER CHEMICAL SOC, 6巻, 11号, 掲載ページ 2121-2126, 出版日 2015年06月, 査読付, We have made the first success in the same-view imagings of 2D nano-XAFS and TEM/STEM-EDS under a humid N-2 atmosphere for Pt/C cathode catalyst layers in membrane electrode assemblies (MEAs) of polymer electrolyte fuel cells (PEFCs) with Nafion membrane to examine the degradation of Pt/C cathodes by anode gas exchange cycles (start-up/shut-down simulations of PEFC vehicles). The same-view imaging under the humid N2 atmosphere provided unprecedented spatial information on the distribution of Pt nanoparticles and oxidation states in the Pt/C cathode catalyst layer as well as Nafion ionomer-filled nanoholes of carbon support in the wet MEA, which evidence the origin of the formation of Pt oxidation species and isolated Pt nanoparticles in the nanohole areas of the cathode layer with different Pt/ionomer ratios, relevant to the degradation of PEFC catalysts.
    研究論文(学術雑誌), 英語
  • Effects of repeated feed-gas exchange processes on degradation processes of Pt-based PEFC cathode catalysts studied by in-situ XAFS, STEM-EDS and electrochemical methods
    Gabor Samjeské; Kotaro Higashi; Shinobu Takao; Oki Sekizawa; Takuma Kaneko; Shinichi Nagamatsu; Kensaku Nagasawa; Tomoya Uruga; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, ECS Transactions, 69巻, 17号, 掲載ページ 1039-1045, 出版日 2015年01月, 査読付, Repeated anode gas exchange (AGEX) cycles and cathode gas exchange (CGEX) cycles were applied to MEAs with Pt3Co/C cathode catalysts to investigate the degradation processes and to compare with the case of Pt/C. The structural and electronic changes of the catalysts during the feed gas-exchange cycles were examined at the top position area of the MEAs by in-situ XAFS and at the top and bottom positions by STEM-EDS. The ORR performance decreased steadily by the AGEX cycles though STEM revealed neither large cracks nor voids nor detached particles in the top position area of the MEA by the AGEX cycles where the electrochemical surface area (ECSA) remained unchanged. On the other hand, neither ORR performance nor ECSA decreased by the CGEX cycles though the particle size only in the bottom position area increased a little after the CGEX treatment. In-situ time-resolved XAFS spectra at Pt LIII-edge showed a decrease of the XANES white line peak height in case of the AGEX, which is not due to particle growth.
    研究論文(国際会議プロシーディングス), 英語
  • Key Factors Affecting the Performance and Durability of Cathode Electrocatalysts in Polymer Electrolyte Fuel Cells Characterized by In Situ Real Time and Spatially Resolved XAFS Techniques
    Mizuki Tada; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, CATALYSIS LETTERS, SPRINGER, 145巻, 1号, 掲載ページ 58-70, 出版日 2015年01月, 査読付, 招待, The account article treats with the characterizations of the structural and electronic transformations of Pt/C, Pt3Co/C, and Pt3Ni/C cathode electrocatalysts in polymer electrolyte fuel cells (PEFCs) involving Pt charging/discharging, Pt-O bond formation/breaking, and Pt-Pt bond breaking/reformation in cathode potential-jump processes and the rate constants of those transformations in the surface reaction sequences on the cathode electrocatalysts by in situ time-resolved X-ray absorption fine structure (XAFS) method. Spatially heterogeneous issue and mechanism for the Pt oxidation and degradation of Pt/C cathode electrocatalyst layers in PEFCs under the operating conditions, which should be uncovered for development of next-generation PEFCs, were also characterized by a scanning nano-XAFS mapping method and a laminography-XAFS method, respectively for 2D and 3D visualizations of Pt chemical species in Pt/C cathode electrocatalyst layers. These XAFS techniques provided new insights into critical issues affecting the performance and property of practical PEFCs under the operating conditions.
    研究論文(学術雑誌), 英語
  • Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques
    Shinobu Takao; Oki Sekizawa; Shin-ichi Nagamatsu; Takuma Kaneko; Takashi Yamamoto; Gabor Samjeske; Kotaro Higashi; Kensaku Nagasawa; Takuya Tsuji; Motohiro Suzuki; Naomi Kawamura; Masaichiro Mizumaki; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 53巻, 51号, 掲載ページ 14110-14114, 出版日 2014年12月, 査読付, There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next-generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X-ray absorption fine structure) method and by a quick-XAFS(QXAFS) method. Information on the site-preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro-crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation.
    研究論文(学術雑誌), 英語
  • Acid-Base Cooperative Catalysis for Organic Reactions by Designed Solid Surfaces with Organofunctional Groups
    Ken Motokura; Toshihide Baba; Yasuhiro Iwasawa
    責任著者, Bridging Heterogeneous and Homogeneous Catalysis: Concepts, Strategies, and Applications, Wiley Blackwell, 掲載ページ 1-20, 出版日 2014年06月09日, 査読付, This chapter deals with acid-base bifunctional heterogeneous catalyst surfaces with organofunctional groups. Immobilization of acidic and basic species nearby on a same solid surface can create a bifunctional catalytic surface possessing acidic and basic species that are able to participate in a single reaction step, resulting in significant acceleration of the catalytic reaction. In this chapter, (i) bifunctional catalysts possessing both acidic and basic organic groups and (ii) bifunctional catalysts possessing basic organic groups and acid sites derived from their support surface are introduced and their catalytic performances are discussed.
    論文集(書籍)内論文, 英語
  • Zinc-Accelerated Cycloaddition of Carbon Dioxide to Styrene Oxide Catalyzed by Pyrrolidinopyridinium Iodides
    Ken Motokura; Shintaro Itagaki; Yasuhiro Iwasawa; Akimitsu Miyaji; Toshihide Baba
    TOPICS IN CATALYSIS, SPRINGER/PLENUM PUBLISHERS, 57巻, 10-13号, 掲載ページ 953-959, 出版日 2014年06月, 査読付, The addition of ZnI2 drastically accelerated the cycloaddition of carbon dioxide to styrene oxide catalyzed by pyrrolidinopyridinium iodides. In the presence of ZnI2, the styrene carbonate yield reached up to 89 % in 7 h at 100 degrees C under 1 atm of CO2. The rate constant increased by greater than three-fold by the addition of ZnI2. Studies of reaction kinetics in addition to high resolution mass and NMR analysis demonstrated that the primary active species consists of two or more pyrrolidinopyridinium cations combined with ZnI42- anion.
    研究論文(学術雑誌), 英語
  • Structure and Photo-Induced Charge Transfer of Pyridine Molecules Adsorbed on TiO2(110): A NEXAFS and Core-Hole-Clock Study
    Hiroshi Kondoh; Yuki Higashi; Masaaki Yoshida; Yuji Monya; Ryo Toyoshima; Kazuhiko Mase; Kenta Amemiya; Fukashi Tsukioka; Masanari Nagasaka; Yasuhiro Iwasawa; Hideo Orita; Kozo Mukai; Jun Yoshinobu
    ELECTROCHEMISTRY, ELECTROCHEMICAL SOC JAPAN, 82巻, 5号, 掲載ページ 341-345, 出版日 2014年05月, 査読付, The structure and photo-induced charge transfer time of pyridine molecules adsorbed on a rutile TiO2(110) surface have been studied by near-edge x-ray absorption fine structure (NEXAFS) spectroscopy, density functional theory (DFT) calculations and core-hole-clock (CHC) spectroscopy. Polarization dependence of NEXAFS spectra and geometrical optimization by the DFT calculations revealed that the pyridine molecules are bound to the TiO2 surface with an upright configuration where the N atom binds to a surface Ti atom. The CHC results indicate that the charge transfer from the LUMO+2 orbital of pyridine with a pi symmetry to the conduction band of TiO2 is quite fast, where the timescale is less than 3 fs. (C) The Electrochemical Society of Japan, All rights reserved.
    研究論文(学術雑誌), 英語
  • “Fabrication of PtCu and PtNiCu Multi-nanorods with Enhanced Catalytic Oxygen Reduction Activities”
    L. Liu; G. Samjeské; S. Takao; K. Nagasawa; Y. Iwasawa
    責任著者, J. Power Sources, ELSEVIER SCIENCE BV, 253巻, 掲載ページ 1-8, 出版日 2014年05月, 査読付, 1-D metallic nanomaterials have received much attention from the viewpoints of material functions of shape-controlled nanocrystals and applications to a variety of technologies. Metallic PtCu and PtNiCu multi-nanorods with diameter of about 5 nm and average length of around 10 nm were fabricated by polyol reduction method and characterized by TEM/EDS, XRD, XRF and electrochemical techniques. The multi-nanorods were successfully synthesized with CuCl2, Cu(CH3COO)(2) and CuSO4 as Cu precursors but not with Cu(NO3)(2), showing precursor dependency on the nanorod fabrication. The fcc alloy-crystal structures were observed with these multi-nanorods, which showed much more enhanced electrocatalytic activities with good stability for oxygen reduction reaction (ORR) than a conventional Pt/C catalyst. The results demonstrate that Pt-based multimetallic nanocrystals are promising candidates for cathode catalysts to develop next-generation polymer electrolyte fuel cells. (C) 2013 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Dependences of the Oxygen Reduction Reaction Activity of Pd-Co/C and Pd-Ni/C Alloy Electrocatalysts on the Nanoparticle Size and Lattice Constant
    Licheng Liu; Gabor Samjeske; Shin-ichi Nagamatsu; Oki Sekizawa; Kensaku Nagasawa; Shinobu Takao; Yoshiaki Imaizumi; Takashi Yamamoto; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, TOPICS IN CATALYSIS, SPRINGER/PLENUM PUBLISHERS, 57巻, 6-9号, 掲載ページ 595-606, 出版日 2014年04月, 査読付, Carbon-supported Pd-based binary alloy electrocatalysts (Pd-Co and Pd-Ni) with different particle sizes for polymer electrolyte fuel cells were prepared by a NaBH4 reduction method and investigated to examine effects of the size and lattice constant of the Pd alloy nanoparticles on the oxygen reduction reaction (ORR) activity. The particle size and lattice constant were controlled in the wide ranges 4.2-12.1 and 0.3802-0.3948 nm, respectively by heating the catalysts in specific atmospheres. The alloy structures were characterized by X-ray diffraction, transmission electron microscopy and X-ray absorption fine structure. The electrochemical tests of the Pd-Co/C and Pd-Ni/C catalysts were performed by cyclic voltammetry and rotating disk electrode in 0.1 M HClO4. Nearly linear relationship between the lattice constant and nanoparticle size was observed with the Pd-Co and Pd-Ni nanoparticles. The nanoparticle sizes and lattice constants of the Pd-Co/C and Pd-Ni/C electrocatalysts, which influence the Pd d-band center, showed positive and inverse relations with the ORR specific activities, respectively. The mass activities of the Pd-Co/C and Pd-Ni/C electrocatalysts showed an increasing trend with the lattice expansion.
    研究論文(学術雑誌), 英語
  • MEA Pt/C Cathode Catalyst Degradation during Repeated Anode Gas Exchange Cycles: In-Situ XAFS, STEM-EDS and Electrochemical Analysis
    G. Samjeske; K. Higashi; S. Takao; S. Nagamatsu; K. Nagasawa; O. Sekizawa; T. Kaneko; T. Uruga; Y. Iwasawa
    責任著者, ECS Transactions, ELECTROCHEMICAL SOC INC, 64巻, 3号, 掲載ページ 113-119, 出版日 2014年, 査読付, The effects of repeated start-up/shut-down cycles on degradation of Pt/C cathode catalysts in polymer electrolyte fuel cells (PEFC) were investigated by repeated anode gas exchange (AGEX) cycles. The degradation of MEA Pt/C catalysts during the AGEX cycles was examined at three different areas of the MEAs by in-situ XAFS and STEM-EDS. The steady decreases of the electrochemical surface area and ORR performance by the AGEX processes were observed. In contrast to the aspects averaged over the whole MEA areas, in-situ XAFS can provide the position-dependent structural and electronic information on Pt nanoparticles at different positions in the MEA during the AGEX cycles. The white line peak intensity in in-situ XANES spectra at Pt L-III-edge decreased in the order for the MEA regions, top > bottom >= middle. STEM images showed that Pt particles dropped off from the carbon supporting particles in the cathode catalyst layer and large cracks and voids formed in the top area of the MEA. These aspects of the in-situ XANES spectra and STEM images are correlated with each other and the MEA degradation.
    研究論文(国際会議プロシーディングス), 英語
  • In Situ Back-side Illumination Fluorescence XAFS(BI-FXAFS)Studies on Platinum Nanoparticles deposited on a HOPG Surface as a Model Fuel Cell: A New Approach to the Pt-HOPG Electrode/Electrolyte Interface
    H. Uehara; Y. Uemura; T. Ogawa; K. Kono; R. Ueno; Y. Niwa; H. Nitani; H. Abe; S. Takakusagi; M. Nomura; Y. Iwasawa; K. Asakura
    Phys. Chem. Chem. Phys., RSC, 16巻, 27号, 掲載ページ 13748-13754, 出版日 2014年, 査読付, We measured the in situ polarization-dependent X-ray absorption fine structure of platinum nanoparticles (PtNPs) deposited on a flat highly oriented pyrolytic graphite (HOPG) substrate under electrochemical conditions using a back-side illumination method. In this method, the thin HOPG substrate with PtNPs deposited on one side was used as a window for incident and fluorescent X-rays, as well as an electrode. A bent crystal Laue analyzer (BCLA) was applied to the extraction of the Pt L-alpha fluorescent X-ray signals from strong scattered X-rays. Pt L-3 edge XAFS spectra were observed for various electrode potentials and polarization directions.
    研究論文(学術雑誌), 英語
  • In situ Investigation of an Oxidation Reaction on a Pt/C Electrode Using Ambient Pressure Hard X-ray Photoelectron Spectroscopy
    Y. Takagi; H. Wang; Y. Uemura; E. Ikenaga; O. Sekizawa; T. Uruga; H. Ohashi; Y. Senba; H. Yumoto; H. Yamazaki; S. Goto; M. Tada; Y. Iwasawa; T. Yokoyama
    Appl. Phys. Lett, 105巻, 13号, 掲載ページ 131602-131602-5, 出版日 2014年, 査読付, © 2014 AIP Publishing LLC. We have constructed an ambient pressure X-ray photoelectron spectroscopy instrument that uses hard X-ray radiation at the high-performance undulator beamline BL36XU of SPring-8. The dependence of the Au 4f peak intensity from Au foil on the ambient N2 pressure was measured. At a photon energy of 7.94 keV, the Au 4f peak intensity maintained 40% at 3000 Pa compared with that at high vacuum. We designed a polymer electrolyte fuel cell that allows us to perform X-ray photoelectron spectroscopy measurements of an electrode under working conditions. The oxidized Pt peaks were observed in the Pt 3d5/2 level of Pt nanoparticles in the cathode, and the peaks clearly depended on the applied voltage between the anode and cathode. Our apparatus can be applied as a valuable in situ tool for the investigation of the electronic states and adsorbed species of polymer electrolyte fuel cell electrode catalysts under the reaction conditions.
    研究論文(学術雑誌), 英語
  • Performance and Durability of Pt/C Cathode Catalysts with Different Kinds of Carbons for Polymer Electrolyte Fuel Cells Characterized by Electrochemical and In-situ XAFS Techniques
    Kensaku Nagasawa; Shinobu Takao; Kotaro Higashi; Shin-ichi Nagamatsu; Gabor Samjesk?; Yoshiaki Imaizumi; Oki Sekizawa; Takashi Yamamoto; Tomoya Uruga; Yasuhiro Iwasawa
    責任著者, Physical Chemistry Chemical Physics, ROYAL SOC CHEMISTRY, 16巻, 21号, 掲載ページ 10075-10087, 出版日 2014年, 査読付, The electrochemical activity and durability of Pt nanoparticles on different kinds of carbon supports in oxygen reduction reactions (ORR) were investigated using rotating disc electrodes (RDE) and the membrane electrode assemblies (MEA) of polymer electrolyte fuel cells (PEFC). The mass activity of Pt/C catalysts (ORR activity per 1 mg of Pt) at the RDE decreased, according to the type of carbon support, in the following order; Ketjenblack (KB) > acetylene black (AB) > graphene > multiwall carbon nanotube (MW-CNT) > carbon black (CB), whereas the average size of the Pt nanoparticles and the surface specific activity (ORR activity per electrochemical surface area) did not vary significantly between these carbon supports. These results indicate that the different mass activities of the Pt/C catalysts may originate from the differences in the fraction of Pt on the carbon supports which is available for utilization. The durability of the MEAs of the top two active catalysts Pt/KB and Pt/AB among the five catalysts was examined based on ORR performance, TEM and in situ XAFS. It was found that the performance of the Pt/KB cathode catalyst in PEFC MEA decreased significantly over 500 accelerated durability test (ADT) cycles, whereas the performance of the Pt/AB cathode catalyst in PEFC MEA did not decrease significantly during 500 ADT cycles, it was also found that the Pt/AB possesses 8 times higher durability compared with the Pt/KB. In situ Pt LIII-edge XAFS data in the ADT cycles and stepwise potential operations revealed the different oxidation-reduction behaviors of the Pt nanoparticles on the KB and AB supports. The Pt/KB was oxidized to form surface PtO layers more easily than the Pt/AB in the increasing potential operation from 0.4 VRHE to 1.4 VRHE, and the surface PtO layers of the Pt/AB were reduced to the metallic Pt state more readily than those of the Pt/KB in the decreasing potential operation from 1.4 VRHE to 0.4 VRHE. The XAFS analysis for the Pt valences and the coordination numbers of Pt-O and Pt-Pt demonstrated that the Pt/AB catalyst is more durable than the Pt/KB catalyst in PEFC MEAs.
    研究論文(学術雑誌), 英語
  • Polarization-Dependent Total-Reflection Fluorescence X-ray Absorption Fine Structure for 3D Structural Determination and Surface Fine Tuning
    Satoru Takakusagi; Wang-Jae Chun; Hiromitsu Uehara; Kiyotaka Asakura; Yasuhiro Iwasawa
    TOPICS IN CATALYSIS, SPRINGER/PLENUM PUBLISHERS, 56巻, 15-17号, 掲載ページ 1477-1487, 出版日 2013年11月, 査読付, This short review reports the three dimensional structure analysis of oxide-supported metal species and the origin of the metal-support interaction, using single crystal oxide surfaces and polarization-dependent total-reflection X-ray absorption fine structure (PTRF-XAFS) method. The PTRF-XAFS revealed that metal species interact strongly with oxygen anions of oxide surfaces and that surface pre-modification is a promising way to stabilize the surface monoatomic species of easily-aggregating Cu and Au and to prepare finely-tuned surface metal-organic species with regulated molecular structures and orientations.
    研究論文(学術雑誌), 英語
  • Performance and Characterization of a Pt–Sn(oxidized)/C Cathode Catalyst with a SnO2-decorated Pt3Sn Nanostructure for Oxygen Reduction Reaction in a Polymer Electrolyte Fuel Cell
    G. Samjeske; S. Nagamatsu; S. Takao; K. Nagasawa; Y. Imaizumi; O. Sekizawa; T. Yamamoto; Y. Uemura; T. Uruga; Y. Iwasawa
    責任著者, Phys. Chem. Chem. Phys., 15巻, 40号, 掲載ページ 17208-17218, 出版日 2013年10月28日, 査読付, We have prepared and characterized a SnO2-decorated Pt-Sn(oxidized)/C cathode catalyst in a polymer electrolyte fuel cell (PEFC). Oxygen reduction reaction (ORR) performance of Pt/C (TEC10E50E) remained almost unchanged or even tended to reduce in repeated I-V load cycles, whereas the I-V load performance of the Pt-Sn(oxidized)/C prepared by controlled oxidation of a Pt-Sn alloy/C sample with the Pt3Sn phase revealed a significant increase with increasing I-V load cycles. The unique increase in the ORR performance of the Pt-Sn(oxidized)/C catalyst was ascribed to a promoting effect of SnO2 nano-islands formed on the surface of Pt3Sn core nanoparticles. Also in a rotating disk electrode (RDE) setup, the mass activity of an oxidized Pt3Sn/C catalyst was initially much lower than that of a Pt/C catalyst, but it increased remarkably after 5000 rectangular durability cycles and became higher than that of the fresh Pt/C. The maximum power density per electrochemical surface area for the Pt-Sn(oxidized)/C catalyst in a PEFC was about 5 times higher than that for the Pt/C catalyst at 0.1-0.8 A cm -2 of the current density. In situ X-ray absorption near-edge structure (XANES) analysis at the Pt LIII-edge in increasing/decreasing potential operations and at the Sn K-edge in the I-V load cycles revealed a remarkable suppression of Pt oxidation compared with the Pt/C catalyst at higher potentials and no change in the Sn oxidation state, respectively, resulting in higher performance and stability of the Pt-Sn(oxidized)/C catalyst due to the SnO2 nano-islands under the PEFC operation conditions. The SnO2 nano-island decorated Pt-Sn(oxidized)/C catalyst with a Pt3Sn alloy nanostructure is regarded as a promising candidate for a PEFC cathode catalyst. © 2013 the Owner Societies.
    研究論文(学術雑誌), 英語
  • Direct Synthesis of Phenol from Benzene and O2, Regulated by NH3 on Pt/ and Pt-Re/ZSM-5 Catalysts
    L. Wang; S. Yamamoto; S. Malwadkar; S. Nagamatsu; T. Sasaki; K. Hayashizaki; M. Tada; Y. Iwasawa
    責任著者, ChemCatChem, 5巻, 8号, 掲載ページ 2203-2206, 出版日 2013年08月, 査読付
    研究論文(学術雑誌), 英語
  • Potential-Dependent Restructuring and Hysteresis in the Structural and Electronic Transformations of Pt/C, Au(Core)-Pt(Shell)/C, and Pd(Core)-Pt(Shell)/C Cathode Catalysts in Polymer Electrolyte Fuel Cells Characterized by in Situ X-ray Absorption Fine Structure
    Shin-ichi Nagamatsu; Takashi Arai; Masakuni Yamamoto; Takuya Ohkura; Hiroyuki Oyanagi; Takayuld Ishizaka; Hajime Kawanami; Tomoya Uruga; Mizuki Tada; Yasuhiro Lwasawa
    責任著者, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 117巻, 25号, 掲載ページ 13094-13107, 出版日 2013年06月, 査読付, Potential-dependent transformations of surface structures, Pt oxidation states, and Pt-O bondings in Pt/C, Au(core)-Pt(shell)/C (denoted as Au@Pt/C), and Pd(core)-Pt(shell)/C (denoted as Pd@Pt/C) cathode catalysts in polymer electrolyte fuel cells (PEFCs) during the voltage-stepping processes were characterized by in situ (operando) X-ray absorption fine structure (XAFS). The active surface phase of the Au@Pt/C for oxygen reduction reaction (ORR) was suggested to be the Pt3Au alloy layer on Au core nanoparticles, while that of the Pd@Pt/C was the Pt atomic layer on Pd core nanoparticles. The surfaces of the Pt, Au@Pt and Pd@Pt nanoparticles were restructured and disordered at high potentials, which were induced by strong Pt-O bonds, resulting in hysteresis in the structural and electronic transformations in increasing and decreasing voltage operations. The potential-dependent restructuring, disordering, and hysteresis may be relevant to hindered Pt performance, Pt dissolution to the electrolyte, and degradation of the ORR activity.
    研究論文(学術雑誌), 英語
  • Anisotropic growth of a nickel trimer formed on a highly-stepped TiO2(110) surface
    Hiromitsu Uehara; Muhammad Haneef Bin Hanaffi; Yuichiro Koike; Keisuke Fujikawa; Shushi Suzuki; Hiroko Ariga; Satoru Takakusagi; Wang-Jae Chun; Yasuhiro Iwasawa; Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 570巻, 掲載ページ 64-69, 出版日 2013年05月, 査読付, The structures of Ni clusters formed on a highly-stepped TiO2(110) surface were studied by polarization-dependent total reflection fluorescence X-ray absorption fine structure analysis. When 0.8 monolayers of Ni were deposited, three-dimensional Ni clusters with 1-2 nm diameters and heights less than 1 nm were formed. Conversely, when 0.07 monolayers of Ni were deposited, an anisotropic Ni trimer with a Ni-Ni distance of 0.260 nm was created at the [001] step. We revealed that the surface modification to enhance the metal-anion interaction can control the deposited metal structure. (C) 2013 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Selective catalysis and active structures for direct phenol synthesis and CH4 reforming
    Mizuki Tada; Linsheng Wang; Shin-ichi Nagamatsu; Shenghong Zhang; Nozomu Ishiguro; Sadaaki Yamamoto; Yasuhiro Iwasawa
    責任著者, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 245巻, 出版日 2013年04月, 査読付
    英語
  • Fine tuning and orientation control of surface Cu complexes on TiO2(110) premodified with mercapto compounds: the effect of different mercapto group positions
    Satoru Takakusagi; Hirotaka Nojima; Hiroko Ariga; Hiromitsu Uehara; Kotaro Miyazaki; Wang-Jae Chun; Yasuhiro Iwasawa; Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 15巻, 33号, 掲載ページ 14080-14088, 出版日 2013年, 査読付, Three-dimensional structures of vacuum-deposited Cu species formed on TiO2(110) surfaces premodified with three mercaptobenzoic acid (MBA) isomers were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). We explored the possibility of fine tuning and orientation control of the surface Cu structures, including their coordination and configuration against the surface, according to the different mercapto group positions of the three MBA isomers (o(-), m(-), and p-MBA). Almost linear S-Cu-O (lattice O of TiO2) surface compounds were formed on the three MBA-modified TiO2(110) surfaces; however, the orientation of the Cu species on the o- and m-MBA-modified TiO2(110) surfaces (40-45 degrees inclined from the surface normal) was different from that on the p-MBA-modified TiO2(110) surface (60 degrees from the surface normal). This work suggests that the selection of a different MBA isomer for premodification of a single crystal TiO2(110) surface enables fine tuning and orientation control of surface Cu complexes.
    研究論文(学術雑誌), 英語
  • Au Clusters on TiO2(110) (1 × 1) and (1 × 2) Surfaces Examined by Polarization-Dependent Total Reflection Fluorescence XAFS
    W.-J. Chun; K. Miyazaki; N. Watanabe; Y. Koike; S. Takakusagi; K. Fujikawa; M. Nomura; Y. Iwasawa; K. Asakura
    J. Phys. Chem. C, AMER CHEMICAL SOC, 117巻, 1号, 掲載ページ 252-257, 出版日 2013年01月, 査読付, The structure of Au clusters on the TiO2(110) surface and the cluster-substrate interaction were investigated by polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). The TiO2(110) (1 X 1) and (1 X 2) surfaces were compared in terms of substrate structural effects on Au cluster structure. We could not find evidence for the direct Au-substrate bonding and observed that the substrate morphology did not significantly affect the size and structure of Au clusters. Finally, we precisely determined that the Au clusters favored a geometry with icosahedral Au-55 symmetry. We discuss the possible interaction mechanism between Au and TiO2(110) that leads to these results.
    研究論文(学術雑誌), 英語
  • Preparation and structure of a single Au atom on the TiO2(110) surface: control of the Au-metal oxide surface interaction
    Kiyotaka Asakura; Satoru Takakusagi; Hiroko Ariga; Wang-Jae Chun; Shushi Suzuki; Yuichiro Koike; Hiromitsu Uehara; Kotaro Miyazaki; Yasuhiro Iwasawa
    FARADAY DISCUSSIONS, ROYAL SOC CHEMISTRY, 162巻, 掲載ページ 165-177, 出版日 2013年, 査読付, Three-dimensional Au structures on bare and organic-compound-modified TiO2(110) surfaces were interrogated by Au L-3-edge polarization dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) spectroscopy. On the bare TiO2(110) surface, icosahedral Au-55 nanoclusters were the main product found. When the surfaces were modified with ortho or meso mercaptobenzoic acid (o-MBA or m-MBA), Au was atomically dispersed. Sulfur atoms in the o- and m-MBA formed strong covalent bonds with Au to produce stable Au-MBA (o-and m-forms) surface complexes. On the other hand, only oxygen atoms on the surface did not make a strong enough interaction to stabilize the Au species. We discuss how the Au species formed on the modified TiO2(110) surface and the possibility to control the Au structure by the surface modification method.
    研究論文(学術雑誌), 英語
  • New XAFS beamline for structural and electronic dynamics of nanoparticle catalysts in fuel cells under operating conditions
    O. Sekizawa; T. Uruga; M. Tada; K. Nitta; K. Kato; H. Tanida; K. Takeshita; S. Takahashi; M. Sano; H. Aoyagi; A. Watanabe; N. Nariyama; H. Ohashi; H. Yumoto; T. Koyama; Y. Senba; T. Takeuchi; Y. Furukawa; T. Ohata; T. Matsushita; Y. Ishizawa; T. Kudo; H. Kimura; H. Yamazaki; T. Tanaka; T. Bizen; T. Seike; S. Goto; H. Ohno; M. Takata; H. Kitamura; T. Ishikawa; T. Yokoyama; Y. Iwasawa
    責任著者, Journal of Physics: Conference Series, Institute of Physics Publishing, 430巻, 1号, 掲載ページ 012020-1-012020-4, 出版日 2013年, 査読付, We are currently constructing a new X-ray absorption fine structure (XAFS) beamline BL36XU at SPring-8 dedicated for the structural and electronic analysis of the dynamic events on polymer electrolyte fuel cell (PEFC) cathode catalysts for the development of next-generation PEFCs. To investigate the cathode catalyst nanoparticles in PEFCs under the operating conditions, the beamline is designed to provide time- and spatially resolved XAFS techniques having a time resolution of 100 μs, spatial resolution of 200 nm, and depth resolution of 1 μm. We report the outline and design of the new beamline.
    研究論文(国際会議プロシーディングス), 英語
  • Enhanced Oxygen Reduction Reaction Activity and Characterization of Pt−Pd/C Bimetallic Fuel Cell Catalysts with Pt-Enriched Surfaces in Acid Media
    L. Liu; G. Samjeske; S. Nagamatsu; O. Sekizawa; K. Nagasawa; S. Takao; Y. Imaizumi; T. Yamamoto; T. Uruga; Y. Iwasawa
    責任著者, J. Phys. Chem. C, AMER CHEMICAL SOC, 116巻, 44号, 掲載ページ 23453-23464, 出版日 2012年11月, 査読付, Three types of bimetallic Pt-Pd nanoparticles with different core shell structures besides Pt and Pd nanoparticles were synthesized by coreduction and sequential reduction methods in ethylene glycol. The synthesized nanoparticles were supported on carbon to prepare five different electrocatalysts Pt/C, Pd/C, PdPt alloy/C, Pd(core)-Pt(shell)/C, and Pt(core)-Pd(shell)/C for oxygen reduction reaction (ORR) in fuel cells. The minoparticles and supported catalysts were characterized by means of transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and cyclic voltammetry (CV). It was proposed by these characterizations that the PdPt alloy/C, Pd(core)-Pt(shell)/C, and Pt(core)-Pd(shell)/C catalysts constituted Pd4Pt1(core)- Pt(two-layers shell), Pd (core)-Pd2Pt1(three-layers)-Pt(three-layers shell), and Pt(core)-Pt2Pd1(two-layers)-Pd (microcrystal shell), respectively. The Pt surface-enriched catalysts were more stable than the Pd surface-enriched catalysts in long-term CV scanning in acid electrolyte. The Pt/C, PdPt alloy/C, and Pd(core)-Pt(shell)/C catalysts with Pt-enriched surfaces showed much higher ORR specific activity than the Pd/C and Pt(core) Pd(shell)/C catalysts with Pd-enriched surfaces. The Pt surface-enriched bimetal catalysts with core-shell structures showed the higher Pt-based mass activity than the Pt monometal catalyst. The PdPt catalysts with Pd/Pt = 2 ind 4 in an atomic ratio were also prepared by the coreduction method. The Pt-enriched surfaces formed also with these samples, but the ORR specific activity and (Pd + Pt)-based mass activity decreased with increasing Pd/Pt ratios (1, 2, and 4). The present study provided core shell catalysts with better ORR activity, which may be useful for understanding key issues to develop next-generation fuel-cell cathode catalysts.
    研究論文(学術雑誌), 英語
  • Operando Time-Resolved X-ray Absorption Fine Structure Study for Surface Events on a Pt3Co/C Cathode Catalyst in a Polymer Electrolyte Fuel Cell during Voltage-Operating Processes
    Nozomu Ishiguro; Takahiro Saida; Tomoya Uruga; Shin-ichi Nagamatsu; Oki Sekizawa; Kiyofumi Nitta; Takashi Yamamoto; Shin-ichi Ohkoshi; Yasuhiro Iwasawa; Toshihiko Yokoyama; Mizuki Tada
    ACS Catalysis, Vol.2巻, 掲載ページ 1319-1330, 出版日 2012年, 査読付
    研究論文(学術雑誌), 英語
  • Formation and oxidation mechanisms of Pd-Zn nanoparticles on a ZnO supported Pd catalyst studied by in situ time-resolved QXAFS and DXAFS
    Yohei Uemura; Yasuhiro Inada; Yasuhiro Niwa; Masao Kimura; Kyoko K. Bando; Akira Yagishita; Yasuhiro Iwasawa; Masaharu Nomura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 14巻, 7号, 掲載ページ 2152-2158, 出版日 2012年, 査読付, Formation and oxidation processes of PdZn nanoparticles on ZnO were successfully observed by means of in situ time-resolved X-ray absorption fine structure spectroscopy (XAFS), and the analysis of data on near-edge (XANES) and extended (EXAFS) structures revealed detailed changes in Pd during both processes. PdZn nanoparticles were formed on ZnO through a two-step scheme under a hydrogen atmosphere. The first process was the formation of metallic Pd nanoparticles, which was quickly finished within 1 s. The second process was the formation of PdZn nanoparticles, which took several tens of minutes. Oxidation of the PdZn nanoparticles also consisted of two processes. Zn atoms were oxidized prior to Pd atoms and the metallic Pd nanoparticles surrounded by ZnO were formed afterwards. Oxidation of the metallic Pd nanoparticles was scarce and very slow. According to the results of kinetic analyses, the metallic Pd surrounded by ZnO was a stable species under the oxidative atmosphere.
    研究論文(学術雑誌), 英語
  • Pt-Sn(oxidized shell)/C and Pt-Sn(reduced)/C as cathode catalysts for the oxygen reduction reaction in polymer electrolyte fuel cells: Catalyst performances and characterization
    G. Samjeské; S. Nagamatsu; K. Nagasawa; Y. Imaizumi; S. Takao; O. Sekizawa; T. Yamamoto; T. Uruga; Y. Iwasawa
    責任著者, ECS Transactions, 50巻, 2号, 掲載ページ 1651-1657, 出版日 2012年, 査読付, To address the problems (high price, insufficient total activity and deactivation) related to usage of pure Pt as cathode catalysts for oxygen reduction reactions (ORR) in polymer electrolyte fuel cells (PEFC), carbon-supported Pt-Sn(oxidized shell)/C and Pt-Sn(reduced)/C were used as membrane electrode assembly (MEA) cathode catalysts in PEFC. I-V-load curves in the initial load-cycles showed an increase of the performance for Pt-Sn(oxidized shell)/C, but no increase in the performance was observed with Pt-Sn(reduced)/C and standard Pt/C catalysts. The observed increase in the performance for the Pt-Sn(oxidized shell)/C catalyst may be due to an synergy effect of Pt-nanoparticle core and SnOx-cluster shell formed on the Pt nanoparticle surface. In-situ XAFS at Pt LIII-edge and Sn K-edge under the PEFC operating conditions showed the absence of electron transfer from Sn to Pt and also no changes in the Sn state, indicating its stability. The in situ XAFS for the Pt-Sn(oxidized shell)/C also revealed that Pt nanoparticles made Pt-O bondings at higher voltages than 1.0 V vs. RHE, but the coordination number of Pt-O bonds was much smaller than that for Pt/C. Thus, the Pt-Sn(oxidized shell)/C is a promising candidate as a MEA cathode catalyst in a PEFC system. © The Electrochemical Society.
    研究論文(国際会議プロシーディングス), 英語
  • Operando Time-resolved XAFS Study for Surface Events on a Pt3Co/C Cathode Catalyst in a PEFC during Voltage-Operating Processes
    N. Ishiguro; T. Saida; T. Uruga; S. Nagamatsu; O. Sekizawa; K. Nitta; T. Yamamoto; S. Ohkoshi; Y. Iwasawa; T. Yokoyama; M. Tada
    ACS Catal., 2巻, 掲載ページ 1319−1330, 出版日 2012年, 査読付
    研究論文(学術雑誌), 英語
  • The Active Phase of Nickel/Ordered Ce2Zr2Ox Catalysts with a Discontinuity (x=7–8) in Methane Steam Reforming
    M. Tada; S. Zhang; S. Malwadkar; N. Ishiguro; J. Soga; Y. Nagai; K. Tezuka; H. Imoto, S; Otsuka-Yao-Matsuo; S. Ohkoshi; Y. Iwasawa
    責任著者, Angew. Chem. Int. Ed., WILEY-V C H VERLAG GMBH, 51巻, 37号, 掲載ページ 9361-9365, 出版日 2012年, 査読付
    研究論文(学術雑誌), 英語
  • Core-Shell Phase Separation and Structural Transformation of Pt3Sn Alloy Nanoparticles Supported on γ-Al2O3 in the Reduction and Oxidation Processes Characterized by In Situ Time-Resolved XAFS
    Y. Uemura; Y. Inada; K. K. Bando; T. Sasaki; N. Kamiuchi; K. Eguchi; A. Yagishita; M. Nomura; M. Tada; Y. Iwasawa
    責任著者, J. Phys. Chem. C, AMER CHEMICAL SOC, 115巻, 13号, 掲載ページ 5823-5833, 出版日 2011年04月, 査読付, Unique catalytic capabilities of supported bimetallic nanoparticles with synergistic functions mark them as a significant advancement in catalytic technologies. The dynamic behavior and kinetics of structural change of catalysts in the reduction and oxidation processes are fundamental issues to understand their catalytic properties and performances as well as to regulate the structure and composition in alloy nanoparticles. The core-shell phase separation and structural transformation of Pt3Sn alloy nanoparticles on gamma-Al2O3 during the reduction and oxidation processes were characterized by in situ time-resolved energy-dispersive XAFS (DXAFS) and quick XAFS (QXAFS) techniques. The time-resolved XAFS techniques provided the kinetics of the change in structures and oxidation states of the bimetallic nanoparticle catalyst. The oxidation of Pt3Sn nanoparticles on gamma-Al2O3 with O-2 at 673 K proceeded by three successive steps via two intermediates to form NO core nanoparticles with SnO2 shells, whereas the reduction of the oxidized nanoparticles with H-2 at 673 K proceeded as a single process with similar rate constants at Pt and Sit sites. The kinetic parameters and mechanisms for the reduction and oxidation of the Pt3Sn/gamma-Al2O3 catalyst were determined by the time-resolved XAFS techniques.
    研究論文(学術雑誌), 英語
  • In situ time-resolved XAFS study on the structural transformation and phase separation of Pt3Sn and PtSn alloy nanoparticles on carbon in the oxidation process
    Y. Uemura; Y. Inada; K. K. Bando; T. Sasaki; N. Kamiuchi; K. Eguchi; A. Yagishita; M. Nomura; M. Tada; Y. Iwasawa
    責任著者, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 13巻, 35号, 掲載ページ 15833-15844, 出版日 2011年, 査読付, The dynamic behavior and kinetics of the structural transformation of supported bimetallic nanoparticle catalysts with synergistic functions in the oxidation process are fundamental issues to understand their unique catalytic properties as well as to regulate the catalytic capability of alloy nanoparticles. The phase separation and structural transformation of Pt3Sn/C and PtSn/C catalysts during the oxidation process were characterized by in situ time-resolved energy-dispersive XAFS (DXAFS) and quick XAFS (QXAFS) techniques, which are element-selective spectroscopies, at the Pt L-III-edge and the Sn K-edge. The time-resolved XAFS techniques provided the kinetics of the change in structures and oxidation states of the bimetallic nanoparticles on carbon surfaces. The kinetic parameters and mechanisms for the oxidation of the Pt3Sn/C and PtSn/C catalysts were determined by time-resolved XAFS techniques. The oxidation of Pt to PtO in Pt3Sn/C proceeded via two successive processes, while the oxidation of Sn to SnO2 in Pt3Sn/C proceeded as a one step process. The rate constant for the fast Pt oxidation, which was completed in 3 s at 573 K, was the same as that for the Sn oxidation, and the following slow Pt oxidation rate was one fifth of that for the first Pt oxidation process. The rate constant and activation energy for the Sn oxidation in PtSn/C were similar to those for the Sn oxidation in Pt3Sn/C. In the PtSn/C, however, it was hard for Pt oxidation to PtO to proceed at 573 K, where Pt oxidation was strongly affected by the quantity of Sn in the alloy nanoparticles due to swift segregation of SnO2 nanoparticles/layers on the Pt nanoparticles. The mechanisms for the phase separation and structure transformation in the Pt3Sn/C and PtSn/C catalysts are also discussed on the basis of the structural kinetics of the catalysts themselves determined by the in situ time-resolved DXAFS and QXAFS.
    研究論文(学術雑誌), 英語
  • μ-XAFS of a single particle of a practical NiOx/Ce2Zr2Oy catalyst
    Mizuki Tada; Nozomu Ishiguro; Tomoya Uruga; Hajime Tanida; Yasuko Terada; Shin-ichi Nagamatsu; Yasuhiro Iwasawa; Shin-ichi Ohkoshi
    責任著者, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 13巻, 33号, 掲載ページ 14910-14913, 出版日 2011年, 査読付, mu-XAFS analysis using an X-ray mu-beam (1000 nm (h) x 800 nm (v)) was successfully carried out on a single particle of a practical catalyst NiOx/Ce2Zr2Oy (0 <= x <= 1, 7 <= y <= 8). The oxidation state and local coordination structure of the NiOx/Ce2Zr2Oy particle were characterized by Ni K-edge mu-XANES and mu-EXAFS, which showed the catalytically active and inactive phases of a single catalyst particle.
    研究論文(学術雑誌), 英語
  • Irreversible Change in the NO Adsorption State on Pt(111) under High Pressure Studied by AP-XPS, NEXAFS, and STM
    Toru Shimada; Bongjin Simon Mun; Ikuyo F. Nakai; Atsushi Banno; Hitoshi Abe; Yasuhiro Iwasawa; Toshiaki Ohta; Hiroshi Kondoh
    JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 114巻, 40号, 掲載ページ 17030-17035, 出版日 2010年10月, 査読付, Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has been applied to the investigation of NO adsorption on Pt(111) under various pressures of NO (up to 1 Torr) at room temperature. Under 10(-7) Torr, molecular NO occupies the most stable fcc-hollow sites and partially occupies the energetically unfavorable atop sites. NO reversibly desorbs from the atop sites after evacuation. At NO pressures higher than 10(-6) Torr. however, irreversible adsorption or atomic oxygen takes place via NO dissociation, leading to the formation of NO+C) domains. This result is consistent with near-edge X-ray absorption fine structure (NIHXAFS) and scanning tunneling microscopy (STM) results.
    研究論文(学術雑誌), 英語
  • A Novel Mechanism for Spectator CO-Mediated Reaction with Unique cis-(NO)2 Dimer on a Co2+-dimer/γ-Al2O3(110) Model Catalyst: Density Functional Theory Calculations
    T. Taniike; M. Tada; R. Coquet; Y. Morikawa; T. Sasaki; Y. Iwasawa
    責任著者, Catal. Today, ELSEVIER SCIENCE BV, 154巻, 1-2号, 掲載ページ 118-126, 出版日 2010年09月, 査読付, Density functional theory calculations for NO adsorption and NO-CO reaction on a Co2+-dimer/gamma-Al2O3(1 1 0) model catalyst were conducted to understand two new aspects of the increases in the amount and reduction rate of adsorbed NO by gas phase CO molecules which are undetectable at the Co2+-ensemble/gamma-Al2O3 catalyst surface. Three kinds of dinitrosyl adsorbates were found and assigned to normal gem-dinitrosyl species (gem-dinitosyl I and II) and an unique cis-(NO)(2) dimeric species. The gem-dinitrosyl II with a reconstructed structure involving CO-O-surf cleavage was considered as stable species experimentally observed, which is responsible for the spectator CO-promoted NO adsorption. We also found that the cis-(NO)(2) dimeric species specific for the Co2+-ensemble structure possesses a much higher reactivity than the gem-dinitrosyl species, enabling the facile reaction with CO that is very weakly trapped at the surface. In the cis-(NO)(2) dimeric species two adsorbed NO molecules on two adjacent Co2+ sites interact with each other due to the opposed orientation of the unoccupied d orbitals of the two Co2+, resulting in easy formation of a N-N bond through the 2 pi*-2 pi* hybridization. The NO adsorbates modify and activate the surface (Co2+ sites) to make pseudo-compounds (intermediates) with CO at the Co2+ sites in such a way that CO is not detected at the surface. The potential energy surface for the NO-CO reaction is presented and the transition states and intermediates are discussed. (C) 2010 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • In-situ time-resolved DXAFS and Raman spectroscopy for selective ethanol oxidation on supported vanadium catalysts
    Mizuki Tada; Nozomu Ishiguro; Daisuke Murakami; Yasuhiro Iwasawa
    責任著者, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 240巻, 出版日 2010年08月, 査読付
    英語
  • In situ time-resolved DXAFS for the determination of kinetics of structural changes of H-ZSM-5-supported active Re-cluster catalyst in the direct phenol synthesis from benzene and O2
    Mizuki Tada; Yohei Uemura; Rajaram Bal; Yasuhiro Inada; Masaharu Nomura; Yasuhiro Iwasawa
    責任著者, Physical Chemistry Chemical Physics, 12巻, 掲載ページ 5701-5706, 出版日 2010年06月07日, 査読付, Dynamic structural changes and their kinetics of a Re10-cluster catalyst in the direct phenol synthesis from benzene and O2 were investigated by in situ time-resolved Re LIII-edge energy-dispersive XAFS (DXAFS). We have successfully monitored the structural transformation of active Re10 clusters to inactive Re monomers in the course of the selective oxidation of benzene with O2 on the catalyst by the DXAFS technique in a real time. The results obtained suggested that the Re10 cluster transformed directly to the Re monomers, which showed first order kinetics with respect to the quantity of Re10 clusters. The absence of undesirable intermediate structures with low phenol selectivity during the structural transformation may be an advantageous issue for the high phenol selectivity of 93.9% at 9.9% conversion in a pulse reaction and 87.7% at 5.8% conversion in a steady-state reaction on the Re10-cluster catalyst. The reactant benzene inhibited the unfavorable structural transformation of the Re10 cluster to the Re monomers during the selective benzene oxidation to phenol. ? the Owner Societies 2010.
  • Amorphous nano-structured silicas for high-performance carbon dioxide confinement
    Shinichiro Ichikawa; Tsunetake Seki; Mizuki Tada; Yasuhiro Iwasawa; Takao Ikariya
    JOURNAL OF MATERIALS CHEMISTRY, ROYAL SOC CHEMISTRY, 20巻, 16号, 掲載ページ 3163-3165, 出版日 2010年, 査読付, The amorphous silica prepared using a precipitation method served as a highly efficient CO(2) adsorbent, combined with the favorable mass-transfer properties of supercritical CO(2). The CO(2)-capture occurred by the unique pore structure of the silica.
    研究論文(学術雑誌), 英語
  • In-situ Time-resolved DXAFS for Structural Kinetics of an Active Re-Cluster Catalyst for Direct Phenol Synthesis from Benzene and O2
    M. Tada; Y. Uemura; R. Bal; Y. Inada; M. Nomura; Y. Iwasawa
    責任著者, Phys. Chem. Chem. Phys., 12巻, 掲載ページ 5701–5706, 出版日 2010年, 査読付
    研究論文(学術雑誌), 英語
  • First Direct Visualization of Spillover Species Emitted from Pt Nanoparticles
    S. Takakusagi; K.-I. Fukui; R. Tero; K. Asakura; Y. Iwasawa
    責任著者, Langmuir, 26巻, 掲載ページ 16392–16396, 出版日 2010年, 査読付
    研究論文(学術雑誌), 英語
  • Alternative Selective Oxidation Pathways for Aldehyde Oxidation and Alkene Epoxidation on a SiO2-Supported Ru-Monomer Complex Catalyst
    Mizuki Tada; Satoshi Muratsugu; Mutsuo Kinoshita; Takehiko Sasaki; Yasuhiro Iwasawa
    責任著者, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 132巻, 2号, 掲載ページ 713-724, 出版日 2010年01月, 査読付, We have prepared a novel Ru-mononer complex supported on a SiO2 surface by using a Ru-monomer complex precursor with a p-cymene ligand, which was found to be highly active for the selective oxidation of aldehydes and the epoxidation of alkenes using O-2. The structure of the supported Ru catalyst was characterized by means of FT-IR, solid-state NMR, Cliff use-reflectance UV/vis, XPS, Ru K-edge EXAFS, and DFT calculations, which demonstrated the formation of isolatedly located, unsaturated Ru centers behind a p-cymene ligand of the Ru-complex precursor. The site-isolated Ru-monomer complex on SiO2 achieved tremendous TONS (turnover numbers) for the selective oxidation of aldehydes and alkenes; e.g. TONS of 38,800,000 for selective isobutyraldehyde (IBA) oxidation and 2,100,000 for trans-stilbene epoxidation at ambient temperature, which are among the highest TONS in metal-complex catalyzes to our knowledge. We also found that the IBA sole oxidation with an activation energy of 48 kJ mol(-1) much more facile than the trans-stilbene epoxidation with an activation energy of 99 kJ mol(-1) was completely suppressed by the coexistence of trans-stilbene. The switchover of the selective oxidation pathways from the IBA oxidation to the trans-stilbene epoxidation was explained in terms of energy profiles for the alternative selective oxidation pathways, resulting in the preferential coordination of trans-stilbene to the Ru-complex at the surface. This aspect gives an insight into the origin of the efficient catalysis for selective epoxidation of alkenes with IBA/O-2,
    研究論文(学術雑誌), 英語
  • The Genesis and Principle of Catalysis at Oxide Surfaces: Surface-Mediated Dynamic Aspects of Catalytic Dehydration and Dehydrogenation on TiO2(110) by STM and DFT
    Yohei Uemura; Toshiaki Taniike; Takehiko Sasaki; Mizuki Tada; Yasuhiro Iwasawa
    責任著者, Molecular Nano Dynamics: Vol. I: Spectroscopic Methods and Nanostructures / Vol. II: Active Surfaces, Single Crystals and Single Biocells, John Wiley and Sons, 2巻, 掲載ページ 315-335, 出版日 2009年11月27日, 査読付
    論文集(書籍)内論文, 英語
  • Organofunctionalized catalyst surfaces highly active and selective for carbon-carbon bond-forming reactions
    Motokura Ken; Tada Mizuki; Iwasawa Yasuhiro
    責任著者, CATALYSIS TODAY, ELSEVIER SCIENCE BV, 147巻, 3-4号, 掲載ページ 203-210, 出版日 2009年10月, 査読付, This article illustrates two types of organofunctionalized heterogeneous catalysts for variety of organic carbon-carbon bond-forming reactions, summarizing our previous reports and also presenting new data. Organic amines with an alkoxysilane moiety were immobilized on inorganic silica-alumina surfaces (SA-NR2) by simple silane-coupling reactions between the silica-alumina surface (SA) and the alkoxysilane. This SA-NR2 acted as acid-base bifunctional heterogeneous catalysts for carbon-carbon bond-forming reactions, such as cyano-ethoxycarbonylation, Michael reaction of nitriles, and nitro-aldol reaction. These reactions did not occur with either SA or homogeneous amine compounds. In addition, the mixture of SA and homogeneous amine showed low catalytic activity due to undesirable acid-base neutralization reaction. Achiral organic silane-coupling reagents with a variety of functional groups were also immobilized on a SiO2 surface that had been immobilized with chiral bis(oxazoline) (BOX), to which Cu ions were coordinated to make chiral Cu-BOX complexes on the SiO2 surface. The SiO2-supported Cu-BOX complex catalyst functionalized with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels-Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The organofunctionalized catalysts showed much better performances for the C-C bond-forming reactions compared to the corresponding homogeneous systems. The heterogeneous catalysts thus obtained were characterized by solid-state C-13 and Si-29 MAS NMR, FT-IR, UV/vis, XAFS, ESR, XRF, and elemental analysis. (C) 2008 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Surface-Mediated Visible-Light Photo-oxidation on Pure TiO2(001)
    Hiroko Ariga; Toshiaki Taniike; Harumo Morikawa; Mizuki Tada; Byoung Koun Min; Kazuya Watanabe; Yoshiyasu Matsumoto; Susumu Ikeda; Koichiro Saiki; Yasuhiro Iwasawa
    責任著者, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 131巻, 41号, 掲載ページ 14670-+, 出版日 2009年10月, 査読付, We used STM to observe visible tight photo-oxidation reactions of formic acid on the ordered lattice-work structure of a TiO2(001) surface for the first time. The nanostructured surface makes the band gap significantly smaller than 3.0 eV only at the surface layer, and the surface state of the crystal enables a visible light response.
    研究論文(学術雑誌), 英語
  • STM Study of Surface Species Formed by Methanol Adsorption on Stoichiometric and Reduced ZnO(10(1)over-bar0) Surfaces
    Xiang Shao; Ken-ichi Fukui; Hiroshi Kondoh; Mitsuhiko Shionoya; Yasuhiro Iwasawa
    責任著者, JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 113巻, 32号, 掲載ページ 14356-14362, 出版日 2009年08月, 査読付, Methanol adsorption on the stoichiometric and slightly reduced ZnO(10 (1) over bar0) surfaces has been studied by scanning tunneling microscopy (STM). On the stoichiometric surface it was found that adsorbed methanol formed two types of ordered structures by dissociative adsorption in different modes, one of which was a dominant two-dimensional island structure residing on surface zinc atom rows, while the other was a linear chain structure residing between two surface zinc rows. In addition, a mobile phase of molecularly adsorbed methanol was deduced occupying the areas aside the ordered domains and keeping in equilibrium with the island structure. In contrast to the stoichiometric surface, on the slightly reduced surface, only the linear chain structure was observed as an ordered phase, accompanied by an unusual type of line defects. The STM observations indicated that the drastic change of surface properties occurred oil the whole surface not at the specific sites such as point vacancies.
    研究論文(学術雑誌), 英語
  • Michael Reactions Catalyzed by Basic Alkylamines and Dialkylaminopyridine Immobilized on Acidic Silica-Alumina Surfaces
    Motokura Ken; Tomita Mitsuru; Tada Mizuki; Iwasawa Yasuhiro
    責任著者, TOPICS IN CATALYSIS, SPRINGER/PLENUM PUBLISHERS, 52巻, 6-7号, 掲載ページ 579-585, 出版日 2009年06月, 査読付, Acid-base bifunctional catalysts were prepared by immobilization of basic amines on acidic silica-alumina (SA) surfaces. Silane-coupling reagents with various amino-functional groups, such as primary, secondary, and tertiary alkylamines, alkyldiamine, and dialkylaminopyridine, were examined as anchoring reagents for the amines in the preparation of catalysts. The obtained immobilized catalysts (SA-NR'R'') were characterized by solid-state C-13 and Si-29 MAS NMR and elemental analysis. The catalytic activity of tertiary alkylamines for Michael reactions increased dramatically by the immobilization on silica-alumina, whereas a homogeneous tertiary amine scarcely promoted the reaction. Regarding the kind of amines, the dialkylaminopyridine immobilized silica-alumina with low Al content (SA(L)) showed the highest catalytic performance among the amine immobilized catalysts. The solid-state C-13 NMR analysis revealed the interaction between the nitrogen atom on pyridine ring and a surface strong acid site of the silica-alumina support.
    研究論文(学術雑誌), 英語
  • Proton transfer in water-hydroxyl mixed overlayers on Pt(111): Combined approach of laser desorption and spatially-resolved X-ray photoelectron spectroscopy
    Masanari Nagasaka; Hiroshi Kondoh; Kenta Amemiya; Toshiaki Ohta; Yasuhiro Iwasawa
    責任著者, SURFACE SCIENCE, ELSEVIER SCIENCE BV, 603巻, 10-12号, 掲載ページ 1690-1695, 出版日 2009年06月, 査読付, Proton transfer in water-hydroxyl mixed overlayers on a Pt(111) surface was studied by a combination of laser induced thermal desorption (LITD) method and spatially-resolved X-ray photoelectron spectroscopy (micro-XPS). The modulated pattern OH + H2O/H2O/OH + H2O was initially prepared by the LITD method; vacant area with a 400 mu m width was first formed in the mixed OH + H2O overlayer by irradiation of focused laser pulses, and followed by refilling the vacant area with pure H2O. Spatial distribution changes of OH and H2O were measured as a function of time with the micro-XPS technique, which indicated that H2O molecules in the central region flow into the OH + H2O region. From quantitative analyses using a diffusion equation, we found that the proton transfer in the mixed overlayer consists of at least two pathways: direct proton transfer from H2O to OH in the nearest site and the proton transfer to the next-nearest site via H3O+ formation. The time scale of first and second path was estimated to be 5.2 +/- 0.9 ns and 48 +/- 12 ns at 140 K, respectively. In the presence of water capping layer, however, the rate of proton transfer is reduced by an order of magnitude, which would be explained by peripatetic behavior of proton into H2O capping layer. (C) 2009 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Density Functional Theory Study on the Re Cluster/HZSM-5 Catalysis for Direct Phenol Synthesis from Benzene and Molecular Oxygen: Active Re Structure and Reaction Mechanism
    T. Sasaki; M. Tada; Y. Iwasawa
    責任著者, TOPICS IN CATALYSIS, SPRINGER/PLENUM PUBLISHERS, 52巻, 6-7号, 掲載ページ 880-887, 出版日 2009年06月, 査読付, DFT calculations have been achieved to obtain a convincing model for the active structure in a Re cluster/HZSM-5 catalyst active for direct phenol synthesis from benzene and molecular oxygen. Re-10 clusters with interstitial N atoms composed of two Re octahedra edge-shared with each other were concluded as a stable active structure in agreement with the EXAFS analysis. The adsorption and behavior of benzene, oxygen atom and molecule and phenol on the Re cluster were examined to obtain the energy diagram for the phenol synthesis including intermediate and transition states, which explains the reaction steps for the phenol synthesis.
    研究論文(学術雑誌), 英語
  • Layered Materials with Coexisting Acidic and Basic Sites for Catalytic One-Pot Reaction Sequences
    Ken Motokura; Mizuki Tada; Yasuhiro Iwasawa
    責任著者, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 131巻, 23号, 掲載ページ 7944-+, 出版日 2009年06月, 査読付, Acidic montmorillonite-immobilized primary amines (H-mont-NH(2)) were found to be excellent acid-base bifunctional catalysts for one-pot reaction sequences, which are the first materials with coexisting acid. and base sites active for acid-base tamdem reactions.: For example, tandem deacetalization-Knoevenagel condensation proceeded successfully with the H-mont-NH(2), affording the, corresponding condensation product in a. quantitative yield. The acidity of the H-mont-NH(2) was strongly influenced by the preparation solvent, and the base-catalyzed reaction's were enhanced by interlayer acid sites.
    研究論文(学術雑誌), 英語
  • Combined structure analysis of STM and surface XAFS for self-assembly of metal-thiolate complex at equilibrium: Hexanethiolate on Cu(111)
    Mathias Laurin; Xiang Shao; Yuuichi Fujimori; A. Nojima; E. O. Sako; J. Miyawaki; M. Shimojo; Yasuhiro Iwasawa; Toshiaki Ohta; Hiroshi Kondoha
    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, ELSEVIER SCIENCE BV, 172巻, 1-3号, 掲載ページ 88-94, 出版日 2009年05月, 査読付, The structure of 1-hexanethiolate (C(6)H(13)S)self-assembled monolayers adsorbed onto a Cu(1 1 1)surface was studied with a combination of scanning tunneling microscopy (STM), and carbon and sulfur K-edge X-ray absorption fine structure (XAFS) experiments. S K-XAFS confirmed that sulfur adsorbs onto deep three-fold hollow sites. Moreover, these sites appear to shrink with a small anisotropy between adsorption and equilibrium. STM further revealed three different ordered superstructures. Finally,a single long-range ordered phase exhibiting a striped moire pattern is imaged at thermodynamic equilibrium. (C) 2009 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Creation of acid-base bifunctional catalysis for efficient C-C coupling reactions by amines immobilization on SiO2, silica-alumina, and nano-H-ZSM-5
    Ken Motokura; Nagabhatla Viswanadham; Gudimella Murali Dhar; Yasuhiro Iwasawa
    CATALYSIS TODAY, ELSEVIER SCIENCE BV, 141巻, 1-2号, 掲載ページ 19-24, 出版日 2009年03月, 査読付, Silica-supported amines (SiO2-NR2) were found to be excellent heterogeneous catalysts for various organic C-C coupling reactions, namely cyanation, Michael reaction, and nitro-aldol reaction. A wide variety of substrates, such as aromatic, heteroaromatic, aliphatic, and cyclic carbonyl compounds, can be efficiently converted into the corresponding cyano-O-ethoxycarbonylation products. The SiO2-NR2 also promoted Michael reaction of ethyl cyanoacetae with cyclohexen-1-one and nitro-aldol reaction of nitromethane with benzaldehyde. These reactions proceeded on the catalyst surfaces, and the SiO2-NR2 catalysts were able to be reused without any significant loss of catalytic performance. Notably. these reactions were hard to occur either with amines alone or on the SiO2 alone, which indicates a dual activation mechanism of basic amine group and surface silanol. In addition, amines immobilized on more acidic support of silica-alumina showed higher catalytic performances than that of the SiO2-NR2. (C) 2008 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Silica-supported aminopyridinium halides for catalytic transformations of epoxides to cyclic carbonates under atmospheric pressure of carbon dioxide
    Motokura Ken; Itagaki Shintaro; Iwasawa Yasuhiro; Miyaji Akimitsu; Baba Toshihide
    GREEN CHEMISTRY, ROYAL SOC CHEMISTRY, 11巻, 11号, 掲載ページ 1876-1880, 出版日 2009年, 査読付, Silica-supported 4-pyrrolidinopyridinium iodide was prepared by quaternization of 4-pyrrolidinopyridine with silica-supported alkyl iodide. The pyrrolidinopyridinium structure on the silica surface was con. rmed by solid-state (13)C CP MAS NMR. The silica-supported 4-pyrrolidinopyridinium iodide showed excellent catalytic performances for transformations of various epoxides to cyclic carbonates under atmospheric pressure of carbon dioxide (CO(2)). The reactions took place without any solvents or additives other than the catalyst. The catalyst was reusable with retention of activity and selectivity. 1-n-Hexyl-4-pyrrolidinopyridinium as a homogeneous catalyst showed a lower catalytic performance than the supported catalyst. Bifunctional catalysis involving acidic surface silanol and the basic 4-pyrrolidinopyridinium iodide was proposed.
    研究論文(学術雑誌), 英語
  • Bifunctional Heterogeneous Catalysis of Silica-Alumina-Supported Tertiary Amines with Controlled Acid-Base Interactions for Efficient 1,4-Addition Reactions
    Ken Motokura; Satoka Tanaka; Mizuki Tada; Yasuhiro Iwasawa
    CHEMISTRY-A EUROPEAN JOURNAL, WILEY-V C H VERLAG GMBH, 15巻, 41号, 掲載ページ 10871-10879, 出版日 2009年, 査読付, We report the first tunable bifunctional surface of silica-alumina-supported tertiary amines (SA-NEt(2)) active for catalytic 1,4-addition reactions of nitroalkanes and thiols to electron-deficient alkenes. The 1,4-addition reaction of nitroalkanes to electron-deficient alkenes is one of the most useful carbon-carbon bond-forming reactions and applicable toward a wide range of organic syntheses. The reaction between nitroethane and methyl vinyl ketone scarcely proceeded with either SA or homogeneous amines, and a mixture of SA and amines showed very low catalytic activity. In addition, undesirable side reactions occurred in the case of a strong base like sodium ethoxide employed as a catalytic reagent. Only the present SA-supported amine (SA-NEt(2)) catalyst enabled selective formation of a double-alkylated product without promotions of side reactions such as an intramolecular cyclization reaction. The heterogeneous SA-NEt(2) catalyst was easily recovered from the reaction mixture by simple filtration and reusable with retention of its catalytic activity and selectivity. Furthermore, the SA-NEt(2) catalyst system was applicable to the addition reaction of other nitroalkanes and thiols to various electron-deficient alkenes. The solid-state magic-angle spinning (MAS) NMR spectroscopic analyses, including variable-contact-time (13)C cross-polarization (CP)/MAS NMR spectroscopy, revealed that acid-base interactions between surface acid sites and immobilized amines can be controlled by pretreatment of SA at different temperatures. The catalytic activities for these addition reactions were strongly affected by the surface acid-base interactions.
    研究論文(学術雑誌), 英語
  • Conceptual integration of homogeneous and heterogeneous catalyses
    Tada Mizuki; Motokura Ken; Iwasawa Yasuhiro
    TOPICS IN CATALYSIS, SPRINGER/PLENUM PUBLISHERS, 48巻, 1-4号, 掲載ページ 32-40, 出版日 2008年05月, 査読付, This article illustrates how bifunctional catalyst surfaces are created by modifying oxide surfaces with organic functional groups and/or with metal complexes, summarizing our previous reports and also presenting new data. which provide a new class of catalytic materials with a high complexity for selective catalysis including C-C coupling, hydroformylation, and asymmetric reactions. The catalyst surfaces are characterized by in situ physical analysis techniques such as time-resolved XAFS, FT-IR, solid-state MAS NMR and so on.
    研究論文(学術雑誌), 英語
  • Origin of self-regulated cluster growth on the TiO2(110) surface studied using polarization-dependent total reflection fluorescence XAFS
    Yuichiro Koike; Keisuke Fujikawa; Shushi Suzuki; Wang-Jae Chun; Kaoru Ijima; Masaharu Nomura; Yasuhiro Iwasawa; Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 112巻, 12号, 掲載ページ 4667-4675, 出版日 2008年03月, 査読付, Three-dimensional structures of Ni clusters deposited on a TiO2(110) surface were studied using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) analysis. Three-dimensional Ni clusters were formed with a slightly anisotropic structure at 1 x 10(14) atoms/cm(2). The PTRF-XAFS results for a 1 x 10(14) atoms/cm(2) sample revealed the formation of one- atomic -layer Ni clusters with a distorted (110)(fcc) plane structure. We found a Ni-Ni distance of 0.240 nm with Ni-O interaction at 0.23 nm. The structure was stabilized by interaction of surface oxygen atoms. The origin of cluster size self-regulation was the strong Ni-O interaction and matching of the crystal lattice between TiO2(110) and distorted Ni(110) structures.
    研究論文(学術雑誌), 英語
  • Lattice-work structure of a TiO2(001) surface studied by STM, core-level spectroscopies and DFT calculations
    H. Ariga; T. Taniike; H. Morikawa; R. Tero; H. Kondoh; Y. Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 454巻, 4-6号, 掲載ページ 350-354, 出版日 2008年03月, 査読付, The lattice-work structure of a rutile TiO2(001) surface, which is faceted to {114} plane, was studied by combining scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption. ne structure (NEXAFS) and density functional theory (DFT) calculations. Synchrotron XPS and NEXAFS spectra taken for the faceted surface indicated that this surface possesses a stoichiometric composition. We propose a new stoichiometric structure model on the basis of XPS, NEXAFS, and atomically-resolved STM observations. DFT calculations revealed that the present stoichiometric model is energetically more favorable compared to the previously proposed models. (c) 2008 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Proton transfer in a two-dimensional hydrogen-bonding network: Water and hydroxyl on a Pt(111) surface
    M. Nagasaka; H. Kondoh; K. Amemiya; T. Ohta; Y. Iwasawa
    PHYSICAL REVIEW LETTERS, AMER PHYSICAL SOC, 100巻, 10号, 掲載ページ 106101 1-4, 出版日 2008年03月, 査読付, The time scale of proton transfer between H(2)O and OH adsorbed on a Pt(111) surface was determined by a combination of laser-induced thermal desorption (LITD) and microscale x-ray photoelectron spectroscopy (micro-XPS). The patterned distribution OH+H(2)O/H(2)O/OH+H(2)O was initially prepared on the Pt(111) surface by the LITD method and the time evolution of the spatial distribution of H(2)O and OH was observed by the micro-XPS technique. From quantitative analyses based on a diffusion equation, we found two proton-transfer pathways with different time scales of 5.2 +/- 0.9 ns and 48 +/- 12 ns at 140 K, which were attributed to direct proton transfer to the neighbor site and H(3)O(+)-mediated transfer to the next-nearest site, respectively.
    研究論文(学術雑誌), 英語
  • Acid-base bifunctional catalytic surfaces for nucleophilic addition reactions
    Ken Motokura; Mizuki Tada; Yasuhiro Iwasawa
    CHEMISTRY-AN ASIAN JOURNAL, WILEY-V C H VERLAG GMBH, 3巻, 8-9号, 掲載ページ 1230-1236, 出版日 2008年, 査読付, This article illustrates the modification of oxide surfaces with organic amine functional groups to create acid-base bifunctional catalysts, summarizing our previous reports and also presenting new data. Immobilization of organic amines as bases on inorganic solid-acid surfaces afforded highly active acid-base bifunctional catalysts, which enabled various organic transformations including C-C coupling reactions, though these reactions did not proceed with either the homogeneous amine precursors or the acidic supports alone. Spectroscopic characterization, such as by solid-state MAS NMR and FTIR, revealed not only the interactions between acidic and basic sites but also bifunctional catalytic reaction mechanisms.
    研究論文(学術雑誌), 英語
  • Acid-base bifunctional catalysis of silica-alumina-supported organic amines for carbon-carbon bond-forming reactions
    Ken Motokura; Mitsuru Tomita; Mizuki Tada; Yasuhiro Iwasawa
    CHEMISTRY-A EUROPEAN JOURNAL, WILEY-V C H VERLAG GMBH, 14巻, 13号, 掲載ページ 4017-4027, 出版日 2008年, 査読付, Acid-base bifunctional heterogeneous catalysts were prepared by the reaction of an acidic silica-alumina (SA) surface with silane-coupling reagents possessing amino functional groups. The obtained SA-supported amines (SA-NR2) were characterized by solid-state C-13 and Si-29 NMR spectroscopy, FT-IR spectroscopy, and elemental analysis. The solid-state NMR spectra revealed that the amines were immobilized by acid-base interactions at the SA surface. The interactions between the surface acidic sites and the immobilized basic amines were weaker than the interactions between the SA and free amines. The catalytic performances of the SA-NR2 catalysts for various carbon-carbon bond-forming reactions, such as cyano-ethoxycarbonylation, the Michael reaction, and the nitro-aldol reaction, were investigated and compared with those of homogeneous and other heterogeneous catalysts. The SA-NR2 catalysts showed much higher catalytic activities for the carbon-carbon bond-forming reactions than heterogeneous amine catalysts using other supports, such as SiO2 and Al2O3, On the other hand, homogeneous amines hardly promoted these reactions under similar reaction conditions, and the catalytic behavior of SA-NR2 was also different from that of MgO, which was employed as a typical heterogeneous base. An acid-base dual-activation mechanism for the carbon-carbon bond-forming reactions is proposed.
    研究論文(学術雑誌), 英語
  • Immobilized metal ion-containing ionic liquids: Preparation, structure and catalytic performances in Kharasch addition reaction and Suzuki cross-coupling reactions
    Takehiko Sasaki; Mizuki Tada; Chongmin Zhong; Takao Kume; Yasuhiro Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, ELSEVIER SCIENCE BV, 279巻, 2号, 掲載ページ 200-209, 出版日 2008年01月, 査読付, A series of immobilized metal ion-containing ionic liquids on silica surfaces (ImmM_IL) were prepared and characterized by EXAFS, UV-vis, TGA, and elemental analysis. The prepared ImmCu(2+_)IL was found to be more active than unsupported [BMiM](2)CUCl4 ionic liquid and reusable for Kharasch addition reaction between CCl4 and styrene. The prepared IrmmPd(2+_)IL was active and reusable for Suzuki cross-coupling between phenylboronic acid and arylhalide. Throughout this study the present catalyst preparation method was confirmed to give efficient and reusable catalysts. (c) 2007 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Cooperative Catalysis of Primary and Tertiary Amines Immobilized on Oxide Surfaces for One-Pot C-C Bond Forming Reactions
    Ken Motokura; Mizuki Tada; Yasuhiro Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 47巻, 48号, 掲載ページ 9230-9235, 出版日 2008年, 査読付
    研究論文(学術雑誌), 英語
  • Photoinduced Reversible Structural Transformation and Selective Oxidation Catalysis of Unsaturated Ruthenium Complexes Supported on SiO(2)
    Mizuki Tada; Yusaku Akatsuka; Yong Yang; Takehiko Sasaki; Mutsuo Kinoshita; Ken Motokura; Yasuhiro Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 47巻, 48号, 掲載ページ 9252-9255, 出版日 2008年, 査読付
    研究論文(学術雑誌), 英語
  • Advanced design of catalytically active reaction space at surfaces for selective catalysis
    Mizuki Tada; Yasuhiro Iwasawa
    COORDINATION CHEMISTRY REVIEWS, ELSEVIER SCIENCE SA, 251巻, 21-24号, 掲載ページ 2702-2716, 出版日 2007年11月, 査読付, The recent advanced design of surface reaction spaces for heterogeneous selective catalysis in molecular-nano scales is reviewed, focusing on our recent challenges and also presenting new data. Supported metal complexes on oxide surfaces often exhibit tremendous catalytic properties based on their unique coordination structures created at the surfaces. Novel active reaction spaces can be designed by coordination regulation on central metals, chemical interaction at metal-surface interface, and three-dimensional architectures constructed at surfaces. Such molecularly organized surfaces possess advantageous properties of both homogeneous and heterogeneous catalyst systems and provide great opportunities for the tailor-made design of highly selective catalysis for various kinds of catalytic chemical syntheses. (C) 2007 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Switchover of reaction mechanism for the catalytic decomposition of HCOOH on a TiO2(110) surface
    Yohei Uemura; Toshiaki Taniike; Mizuki Tada; Yoshitada Morikawa; Yasuhiro Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 111巻, 44号, 掲載ページ 16379-16386, 出版日 2007年11月, 査読付, Catalytic decomposition of HCOOH on a TiO2(110) surface switches over between unimolecular dehydration (HCOOH -> H2O + CO) and bimolecular dehydrogenation (HCOOH -> H-2 + CO2), depending on the reaction conditions. As the dehydration and dehydrogenation, reactions proceed on acidic and, basic oxide catalyst surfaces, respectively, the aspect observed on the same single crystal surface seems to be not compatible with the conventional acid-base catalysis concept. To clarify the origin of the switchover of the acid-base catalysis, the reaction mechanism of the HCOOH dehydrogenation was studied by density functional theory (DFT) calculations. It was concluded from the DFT calculations together with the rate equation and experimentally determined activation energy that the bimolecular dehydrogenation proceeds between a strongly adsorbed bridging formate anion and a weakly adsorbed HCOOH molecule by cooperative catalysis of three adjacent surface Ti4+ ions as Lewis acidic sites on the surface. This mechanism is entirely different from the previous dehydration mechanism that the dehydration occurs on an oxygen point defect (basic character) formed in situ by H2O desorption from two OH under the catalytic dehydration reaction conditions. Thus, the TiO2(110) surface provides two kinds of active sites for the HCOOH decomposition in a manner different from the traditional acid-base catalysis concept.
    研究論文(学術雑誌), 英語
  • Understanding of novel surface events on a supported Co2+-ensemble catalyst promoted by gas-phase molecules: Increases in the amount and reactivity of adsorbed NO by CO undetectable at the catalyst surface
    Mizuki Tada; Toshiaki Taniike; Yasuhiro Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 111巻, 31号, 掲載ページ 11663-11675, 出版日 2007年08月, 査読付, The paper reports an understanding of the novel surface phenomenon that the amount and reactivity of adsorbed NO on a Co2+-ensemble/gamma-Al2O3 catalyst are increased by gas-phase CO molecules undetectable at the catalyst surface. The nature of adsorbed NO species and the structures of divalent Co species were characterized by FT-IR, DR-UV/vis, XAFS, and DFT calculations. The Co2+-ensemble structure attached on the gamma-Al2O3 surface was crucial for the increase in the NO adsorption equilibrium and the promotion of NO reactivity at the surface by gas-phase CO, while monomeric Co2+ sites did not bring out the promotional effects of CO. DFT calculations and FT-IR study revealed that the coordination structure of Co2+ sites was restructured to form a more stable geminal dinitrosyl species, showing Co-OAl (surface) bond breaking, which is an origin of the increase in NO adsorption. Direct interaction of the adsorbed dinitrosyl with gas-phase CO (Eley-Rideal mechanism) was conceived to be involved in the transition state of the NO reduction to form N2O + CO2. The reactive NO species were assigned to cis-(NO)(2) dimeric species (mononitrosyl pair) with the 2 pi*-2 pi* bonding between the two NO adsorbates on the adjacent two Co2+ sites with unoccupied d orbitals directed to each other. The energy profiles for the NO adsorption and reduction on the Co2+-ensemble catalyst were presented. The present study documents how the ambient gas affects the surface species for adsorption and catalysis, which is regarded to be an essence of catalysis at surfaces.
    研究論文(学術雑誌), 英語
  • Heterogeneous organic base-catalyzed reactions enhanced by acid supports
    Motokura, Ken; Tada, Mizuki; Iwasawa, Yasuhiro
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 129巻, 31号, 掲載ページ 9540-+, 出版日 2007年08月, 査読付, Amorphous silica-alumina-supported amines (SA-NR2) were found to be excellent heterogeneous catalysts for a variety of carbon-carbon bond-forming reactions, such as cyano-O-ethoxycarbonylation, Michael reaction, and nitro-aldol reaction. These reactions were hard to proceed either with amines alone or on the SA alone. Solid-state C-13 MAS NMR analysis revealed the acid-base interaction of the H+ site and amine group on the SA-NR2 surface, which makes an acid-base dual activation mechanism possible for carbon-carbon bond-forming reactions.
    研究論文(学術雑誌), 英語
  • Novel re-cluster/HZSM-5 catalyst for highly selective phenol synthesis from benzene and O-2: Performance and reaction mechanism
    Mizuki Tada; Rajaram Bal; Takehiko Sasaki; Yohei Uemura; Yasuhiro Inada; Satoka Tanaka; Masaharu Nomura; Yasuhiro Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY C, AMER CHEMICAL SOC, 111巻, 27号, 掲載ページ 10095-10104, 出版日 2007年07月, 査読付, This paper reports the catalytically active structure, its structural transformation and dynamics, and the reaction mechanism for direct phenol synthesis from benzene and molecular oxygen on a novel N-interstitial Re-10-cluster/HZSM-5 catalyst, which exhibited remarkable phenol selectivities of 91.6-93.9% at 1.7-9.9% conversions in pulse reactions and 82.4-87.7% at 0.8-5.8% conversions in steady-state reactions. The active N-interstitial Re-10 cluster for the direct phenol synthesis with O-2 as an oxidant was produced by NH3 at 553 K and the phenol synthesis proceeded with the low activation energy of 24 kJ mol(-1). The active Re-10 cluster was converted to inactive Re monomers, while NH3 reproduced the active Re-10 cluster under the reaction conditions. It was found by means of in situ time-resolved XAFS and DFT calculations that the catalytic phenol synthesis proceeded in conjunction with the structural transformation between the Re-10 clusters and the Re monomers. The isosbestic points in energy-dispersive XANES spectra indicated a direct conversion of the Re-10 cluster to the Re monomers without any unfavorable metastable intermediates. The benzene oxidation is proposed to proceed via oxygen addition to a C atom of benzene to form an oxygen-added intermediate with a sp(3) carbon atom in the benzene ring and subsequent insertion of the oxygen to the C-H bond on the Re-10 cluster.
    研究論文(学術雑誌), 英語
  • A New Aspect of Heterogeneous Catalysis: Highly Reactive cis-(NO)2 Dimer and Eley-Rideal Mechanism for NO-CO Reaction on a Co-dimer/γ-Alumina Catalyst
    T. Taniike; M. Tada; R. Coquet; Y. Morikawa; T. Sasaki; Y. Iwasawa
    Chem. Phys. Lett., ELSEVIER SCIENCE BV, 443巻, 1-3号, 掲載ページ 66-70, 出版日 2007年07月, 査読付, A catalytic aspect, 'surface catalytic NO reactions assisted by gas phase CO molecules' on a Co2+ -ensemble/gamma-Al2O3 catalyst, was elucidated by successive density functional theory (DFT) calculations on a Co2+ -dimer/gamma-Al2O3 model surface. Unique cis-(NO)(2) dimeric species formed due to a specific alignment of the unoccupied orbitals on the Co2+ -dimer, whose vibrational frequencies were almost identical to those for conventional gem-dinitrosyl species. The cis-(NO)(2) species showed much higher reactivity with CO than the gem-dinitrosyl species, through the 2 pi*-2 pi* bonding between the two NO adsorbates. Detailed DFT calculations for the reaction pathways indicated an Eley-Rideal mechanism with an unusually large reactive cross-section. (c) 2007 Published by Elsevier B.V.
    研究論文(学術雑誌), 英語
  • TAP study on carbon monoxide oxidation over supported gold catalysts Au/Ti(OH)(4)(*) and Au/Fe(OH)(3)(*): Moisture effect
    Maria Olea; Mizuki Tada; Yasuhiro Iwasawa
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 248巻, 1号, 掲載ページ 60-67, 出版日 2007年05月, 査読付, The effect of moisture on the behavior of the active supported gold catalysts developed by us, Au/Ti(OH)(4)* (1) and Au/Fe(OH)(3)* (II), during CO activation and CO oxidation in the temperature range 298-473 K was investigated by the temporal analysis of products (TAP) technique. The oxidation reaction over the Au/Ti(OH)(4)* catalyst was totally suppressed by the presence of water, independent of the water content of 200 and 1000 ppm, the carbon monoxide-to-oxygen ratio, and the temperature. In contrast, the presence of water vapors showed no effect on CO oxidation over the Au/Fe(OH)* catalyst. For both catalysts, the carbon monoxide adsorption feature was unalterable by the presence of water, namely CO molecules reversibly adsorbed on the catalyst surface, but the amount of CO adsorbed decreased by increasing water content. When a reaction mixture at a 1:1 ratio of CO to O-2 was pulsed on the catalyst in the absence of water, the CO response curve showed two peaks, whereas in the presence of water, the TAP response curve showed only one peak. At a 1:3 CO-to-O-2 ratio, the CO response curve showed only one peak, which shifted to a shorter time and narrowed in the absence of water. The shift was more pronounced on catalyst (II). The TAP experiments provided indirect evidence that CO and water adsorbed together (CO weakly and water strongly) and water blocked [irreversibly for Au/Ti(OH)(4)* and reversibly for Au/Fe(OH)(3)*], the adsorption sites for oxygen. (C) 2007 Elsevier Inc. All rights reserved.
    研究論文(学術雑誌), 英語
  • Strong adhesion of water to CeO2(111)
    S. Gritschneder; Y. Iwasawa; M. Reichling
    NANOTECHNOLOGY, IOP PUBLISHING LTD, 18巻, 4号, 掲載ページ 1-6, 出版日 2007年01月, 査読付, The adsorption of water molecules on a stoichiometric CeO2(111) surface at room temperature is studied with dynamic scanning force microscopy. Atomic resolution imaging reveals spontaneous adsorption as well as deposition of molecules by the tip of the force microscope. Water molecules localize exclusively on one type of site that is associated with the cerium ion sub-lattice and stick to the surface with an estimated surface diffusion barrier of 1 eV. Occasionally adsorbates are moved laterally across the cerium sub-lattice by the action of the scanning tip.
    研究論文(学術雑誌), 英語
  • Energy-gaining formation and catalytic behavior of active structures in a SiO2-supported unsaturated Ru complex catalyst for alkene epoxidation by DFT calculations
    Rudy Coquet; Mizuki Tada; Yasuhiro Iwasawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 9巻, 45号, 掲載ページ 6040-6046, 出版日 2007年, 査読付, The formation and catalytic behavior of active structures in a SiO2-supported unsaturated Ru complex catalyst for alkene epoxidation were studied by means of hybrid density functional theory (DFT) calculations. An energy-gaining route for the catalyst activation was found to allow the formation of active unsaturated Ru complexes and the remarkable alkene epoxidation via an exothermic reaction path between isobutyraldehyde and oxygen. In the proposed Bartlett mechanism, Ru promotes the formation of peracid intermediate and facilitates the intermolecular hydrogen transfer in the peracid intermediate, while alkene molecules do not directly coordinate to the Ru site. It was found that stilbene epoxidation is easier to achieve than ethene epoxidation thanks to the electron donating phenyl groups.
    研究論文(学術雑誌), 英語
  • Low-temperature PROX (preferential oxidation) on novel CeO2-supported Cu-cluster catalysts under fuel-cell operating conditions
    Mizuki Tada; Rajaram Bal; Xindong Mu; Rudy Coquet; Seitaro Namba; Yasuhiro Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 44号, 掲載ページ 4689-4691, 出版日 2007年, 査読付, Cu1+-clusters on a CeO2 support, which were prepared by hydrothermal synthesis using cetyltrimethylammonium bromide (CTAB), were found to be highly active and selective for preferential oxidation (PROX) of CO in excess H-2 with H2O and CO2 under practical fuel-cell operating conditions.
    研究論文(学術雑誌), 英語
  • Enantioselectivity promotion by achiral surface functionalization on SiO2-supported Cu-bis(oxazoline) catalysts for asymmetric Diels-Alder reactions
    Satoka Tanaka; Mizuki Tada; Yasuhiro Iwasawa
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 245巻, 1号, 掲載ページ 173-183, 出版日 2007年01月, 査読付, Novel SiO2-supported chiral Cu-bis(oxazoline) (BOX) complexes for asymmetric Diels-Alder reactions were prepared by combining metalcomplex immobilization with surface functionalization using achiral silane-coupling reagents on SiO2. We found that the surface functionalization of a SiO2-supported Cu-BOX catalyst with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels-Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The Cu-BOX complexes on bare and functionalized SiO2 surfaces were characterized by XAFS, ESR, FT-IR, UV/vis, and Si-29 solid-state MAS NMR. The large increase in enantioselectivity by achiral surface species without chiral center may be due to a glue effect, creating a new chiral ensemble structure at the surface. (c) 2006 Elsevier Inc. All rights reserved.
    研究論文(学術雑誌), 英語
  • Preparation of atomically dispersed Cu species on a TiO2 (110) surface premodified with an organic compound
    Wang-Jae Chun; Yuichiro Koike; Kaoru Ijima; Keisuke Fujikawa; Hidenori Ashima; Masaharu Nomura; Yasuhiro Iwasawa; Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 433巻, 4-6号, 掲載ページ 345-349, 出版日 2007年01月, 査読付, Highly dispersed monoatomic Cu species on a TiO2 (110) surface were successfully prepared by a new method in which the TiO2 (110) surface was premodified with a 3-thiophenecarboxylic layer. Polarization-dependent total reflection fluorescence-X-ray absorption fine structure (PTRF-XAFS) showed the three dimensional structure of the monoatomic Cu species which were stabilized on the surface through the formation of Cu-S (adsorbate) and Cu-O (bridging oxygen) bonds. (c) 2006 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Origin and dynamics of oxygen storage/release in a Pt/ordered CeO2-ZrO2 catalyst studied by time-resolved XAFS analysis
    Takashi Yamamoto; Akane Suzuki; Yasutaka Nagai; Toshitaka Tanabe; Fei Dong; Yasuhiro Inada; Masaharu Nomura; Mizuki Tada; Yasuhiro Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 46巻, 48号, 掲載ページ 9253-9256, 出版日 2007年, 査読付
    研究論文(学術雑誌), 英語
  • Selective formation of a coordinatively unsaturated metal complex at a surface: A SiO2-immobilized, three-coordinate ruthenium catalyst for alkene epoxidation
    Mizuki Tada; Rudy Coquet; Jun Yoshida; Mutsuo Kinoshita; Yasuhiro Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 46巻, 38号, 掲載ページ 7220-7223, 出版日 2007年, 査読付
    研究論文(学術雑誌), 英語
  • In situ time-resolved dynamic surface events on the Pt/C cathode in a fuel cell under operando conditions
    Mizuki Tada; Shigeaki Murata; Takahiko Asakoka; Kazutaka Hiroshima; Kazu Okumura; Hajime Tanida; Tomoya Uruga; Haruyuki Nakanishi; Shin-ichi Matsumoto; Yasuhiro Inada; Masaharu Nomura; Yasuhiro Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 46巻, 23号, 掲載ページ 4310-4315, 出版日 2007年, 査読付
    研究論文(学術雑誌), 英語
  • Ni ion-containing ionic liquid salt and Ni ion-containing immobilized ionic liquid on silica: Application to Suzuki cross-coupling reactions between chloroarenes and arylboronic acids
    Chongmin Zhong; Takehiko Sasaki; Mizuki Tada; Yasuhiro Iwasawa
    Journal of Catalysis, 242巻, 2号, 掲載ページ 357-364, 出版日 2006年09月10日, 査読付, Bis(1-n-butyl-3-methyl-imidazolium)tetrachloronickelate ([Bmim]2[NiCl4]), which is a nickel ion-containing ionic liquid, and immobilized nickel ion-containing ionic liquid (ImmNi2+_IL) on silica surface were prepared and applied as new catalysts for Suzuki cross-coupling reactions between aryl chlorides and arylboronic acids. It was found that pretreatment of the catalysts and the addition of triphenylphosphine to the reaction system greatly promoted the reactions. Before the addition of substrates, [Bmim]2[NiCl4] should be treated with K3PO4 in dioxane at a refluxing temperature for 1 h, and ImmNi2+_IL should be treated with NaOtBu in dioxane at room temperature for 30 min. An active precursor for the catalytic reactions was found to be a Ni carbene species formed by pretreatment with the bases as characterized by NMR and EXAFS. Reusability was confirmed for ImmNi2+_IL. © 2006 Elsevier Inc. All rights reserved.
    研究論文(学術雑誌), 英語
  • Retention of the octahedral metal framework of Nb and Mo halide clusters in catalytic decomposition of phenyl acetate to phenol and ketene
    Satoshi Kamiguchi; Takashi Mori; Masaki Watanabe; Akane Suzuki; Mitsuo Kodomari; Masaharu Nomura; Yasuhiro Iwasawa; Teiji Chihara
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, ELSEVIER SCIENCE BV, 253巻, 1-2号, 掲載ページ 176-186, 出版日 2006年07月, 査読付, When molecular chloride clusters of Nb, Mo, Ta, and W ([ (M6Cl12)Cl-2(H2O)].4H(2)O (M = Nb, Ta) and (H3O)(2)[ (M6Cl8)Cl-6](.)6H(2)O (M = Mo, W)) possessing an octahedral metal framework were treated in a helium stream above 200 degrees C, catalytic activity for the selective decomposition of phenyl acetate to phenol and ketene arose. The Fries rearrangement did not occur. The activity was ascribed to the Bronsted acidity of the hydroxo ligand that was formed by elimination of hydrogen chloride from the chloro and aqua ligands, and the selectivity was attributable to the large counter cluster anion that did not stabilize the intermediate protonated phenyl acetate and acetyl cations. The maximum activities of the Nb and Mo clusters appeared by activation at 250 degrees C and 400 degrees C, respectively, at which temperatures the retention of the octahedral cluster framework was ascertained by XDR analyses, Raman spectrometry, EXAFS spectrometry, and elemental analyses. (c) 2006 Elsevier B.V All rights reserved.
    研究論文(学術雑誌), 英語
  • Surfactant-promoted novel synthesis of supported metallic Cu nanoparticles active for selective dehydrogenation of methanol
    M Tada; R Bal; S Namba; Y Iwasawa
    APPLIED CATALYSIS A-GENERAL, ELSEVIER SCIENCE BV, 307巻, 1号, 掲載ページ 78-84, 出版日 2006年06月, 査読付, We have found that a surfactant cetyltrimethylammonium bromide promoted the formation of metallic Cu nanoparticles on several metal oxides under hydrothermal synthesis conditions without any additive reductants. The Cu nanoclusters and oxide supports were characterized by means of XRD, XRF, XPS, XAFS, BET, SEM, and TEM. We have also found that the supported metallic Cu nanoparticles were active for the selective dehydrogenation of methanol to produce formaldehyde and hydrogen with 100% H-2 selectivity. (c) 2006 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry
    Yasuhito Sekine; Seiji Sugita; Takafumi Shido; Takashi Yamamoto; Yasuhiro Iwasawa; Toshihiko Kadono; Takafumi Matsui
    METEORITICS & PLANETARY SCIENCE, WILEY, 41巻, 5号, 掲載ページ 715-729, 出版日 2006年05月, Fischer-Tropsch catalysis, by which CO and H-2 are converted to CH4 on the surface of transition metals, has been considered to be one of the most important chemical reactions in many planetary processes, such as the fort-nation of the solar and circumplanetary nebulae, the expansion of vapor clouds induced by cometary impacts, and the atmospheric re-entry of vapor condensate due to asteroidal impacts. However, few quantitative experimental studies have been conducted for the catalytic reaction under conditions relevant to these planetary processes. In this study, we conduct Fischer-Tropsch catalytic experiments at low pressures (1.3 x 10(-4) bar <= P <= 5.3 x 10(-1) bar) over a wide range of H-2/CO ratios (0.25-1000) using pure iron, pure nickel, and iron-nickel alloys. We analyze what gas species are produced and measure the CH4 formation rate. Our results indicate that the CH4 formation rate for iron catalysts strongly depends on both pressure and the H-2/CO ratio, and that nickel is a more efficient catalyst at lower pressures and lower H-2/CO ratios. This difference in catalytic properties between iron and nickel may come from the reaction steps concerning disproportionation of CO, hydrogenation of surface carbon, and the poisoning of the catalyst. These results suggest that nickel is important in the atmospheric re-entry of impact condensate, while iron is efficient in circumplanetary subnebulae. Our results also indicate that previous numerical models of iron catalysis based on experimental data at 1 bar considerably overestimate CH4 formation efficiency at lower pressures, such as the solar nebula and the atmospheric re-entry of impact condensate.
    研究論文(学術雑誌), 英語
  • Density functional theoretical calculations for a Co-2/gamma-Al2O3 model catalyst: Structures of the gamma-Al2O3 bulk and surface and attachment sites for Co2+ ions
    T Taniike; M Tada; Y Morikawa; T Sasaki; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 110巻, 10号, 掲載ページ 4929-4936, 出版日 2006年03月, 査読付, First-principle density functional theory (DFT) calculations on the electronic state and structure of a [CO2+](2)/gamma-Al2O3 model catalyst have been performed in relation to catalysis for unique NO-CO reactions on a Coll ensemble/gamma-Al2O3 catalyst. The DFT calculations reveal that a bulk structure of gamma-Al2O3 is energetically most favorable when aluminum vacancies are evenly dispersed at octahedral sites, and that the (110) plane is exposed as a topmost layer by its neutrality. Two Co2+ ions on the (110) surface are supported adjacently to each other in a tetrahedral symmetry. The calculations also demonstrate that the vacant d orbitals of the two Coll ions are directed toward each other, which brings about an adsorbate-adsorbate interaction between two molecules which adsorb on each of the Coll ions. This may be an origin of the unique aspect of Co2+ ensemble/gamma-Al2O3 catalysis.
    研究論文(学術雑誌), 英語
  • Advanced chemical design with supported metal complexes for selective catalysis
    Mizuki Tada; Yasuhiro Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 27号, 掲載ページ 2833-2844, 出版日 2006年, 査読付, This review covers several recent topics of novel catalyst design with supported metal complexes on oxide surfaces for selective catalysis such as chiral self-dimerization to create asymmetric oxidative coupling catalysis, surface functionalization with achiral reagents to promote asymmetric catalysis, and molecular imprinting to design shape-selective catalysis. The new concepts and designs find wide applications to a variety of selective catalysts.
    研究論文(学術雑誌), 英語
  • Direct phenol synthesis by selective oxidation of benzene with molecular oxygen on an interstitial-N/Re cluster/zeolite catalyst
    R Bal; M Tada; T Sasaki; Y Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-BLACKWELL, 45巻, 3号, 掲載ページ 448-452, 出版日 2006年, 査読付
    研究論文(学術雑誌), 英語
  • The role of Fischer-Tropsch catalysis in the origin of methane-rich Titan
    Y Sekine; S Sugita; T Shido; T Yamamoto; Y Iwasawa; T Kadono; T Matsui
    ICARUS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 178巻, 1号, 掲載ページ 154-164, 出版日 2005年11月, 査読付, Fischer-Tropsch catalysis, which converts CO and H-2 into CH4 on the surface of iron catalyst, has been proposed to produce the CH4 on Titan during its formation process in a circum-planetary subnebula. However, Fischer-Tropsch reaction rate under the conditions of subnebula have not been measured quantitatively yet. In this Study, we conduct laboratory experiments to determine CH4 formation rate and also conduct theoretical calculation of clathrate formation to clarify the significance of Fischer-Tropsch catalysis in a subnebula. Our experimental result indicates that the range of conditions where Fischer-Tropsch catalysis proceeds efficiently is narrow (T similar to 500-600 K) in a subnebula because the catalysts are poisoned at temperatures above 600 K under the condition of subnebula (i.e., H-2/CO = 1000). This suggests that an entire subnebula may not become rich in CH4 but rather that only limited region of a subnebula may enriched in CH4 (i.e., CH4-rich band formation). Our experimental result also suggests that both CO and CO2 are converted into CH4 within time significantly shorter than the lifetime of the solar nebula at the optimal temperatures around 550 K. The calculation result of clathration shows that CO2-rich satellitesimals are formed in the catalytically inactive Outer region Of Subnebula. In the catalytically active inner region, CH4 rich satellitesimals Lire formed. The resulting CH4-rich satellitesimals formed in this region play an important role in the origin of CH4 on Titan. When our experimental data Lire applied to a high-pressure model for subnebula evolution, it Would predict that there should be CO2 underneath the lapetus Subsurface and no thick CO2 ice layer on Titan's icy crust. Such surface and subsurface composition, which may be observed by Cassini-Huygens mission, would provide crucial information on the origin of icy satellites. (c) 2005 Elsevier Inc. All rights reserved.
    研究論文(学術雑誌), 英語
  • X-ray Absorption Fine Structure Combined with X-ray Fluorescence Spectrometry. Part 15. Monitoring of Vanadium Site Transformations on Titania and in Mesoporous Titania by Selective Detection of the Vanadium Kα1 Fluorescence
    Yasuo Izumi; Fumitaka Kiyotaki; Nobuhiro Yagi; Aurel Mihai Vlaicu; Atsushi Nisawa; Sei Fukushima; Hideaki Yoshitake; Yasuhiro Iwasawa
    Journal of Physical Chemistry B, AMER CHEMICAL SOC, 109巻, 31号, 掲載ページ 14884-14891, 出版日 2005年08月, 査読付, X-ray absorption fine structure combined with X-ray fluorescence spectrometry was applied to various V+TiO2 hybrid samples. Emitted V Kα1f luorescence from the sample was selectively counted by using a high-energy-resolution (0.4 eV) spectrometer equipped with a Ge(331) crystal. Two advantages of this method, extremely high signal/background ratio and the compatibility of measurements in the atmosphere of reaction gas (in situ study in relation to heterogeneous catalysis), were effective at the V K-edge. Structure transformation of the V sites was spectroscopically followed for the V/TiO2 catalyst. The monooxo tetrahedral vanadate site was demonstrated to exist at 473 K. It transformed into dispersed species of 5-fold coordination in ambient air and further into polymeric VOx species in 0.85 kPa of water at 290 K. In the presence of 3.2 kPa of 2-propanol, dissociative adsorption of 2-propanol on the dispersed V species was strongly suggested at 290-473 K. In situ structure changes of V sites on TiO2 were reported by means of XAFS for the first time. The V(V) sites for the V/TiO2 catalysts were essentially identical with those for V supported on mesoporous (high-surface-area) TiO2 and V-TiO2 sample prepared by the sol-gel method. However, predominant V(IV) sites were found for mesoporous V-TiO2. The V(IV) sites substituted on the Ti sites of TiO2. When the molar ratio of V/Ti increased from 1/100 to 1/5.0, major octahedral V sites in the TiO2 matrix looked to transform into tetrahedral ones.
    英語
  • Chiral self-dimerization of vanadium complexes on a SiO2 surface for asymmetric catalytic coupling of 2-naphthol: Structure, performance, and mechanism
    M Tada; N Kojima; Y Izumi; T Taniike; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 109巻, 20号, 掲載ページ 9905-9916, 出版日 2005年05月, 査読付, Vanadium monomers with chiral tridentate Schiff-base ligands were supported on SiO2 through a chemical reaction with surface silanols, where we found a new chirality creation by the self-dimerization of the vanadyl complexes on the surface. The chiral self-dimerization and the role of surface silanols in the self-assembly were investigated by means of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), diffuse-reflectance ultraviolet/visible (DR-UV/VIS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), electron spin resonance (ESR), and density functional theory (DFT) calculations. The surface vanadyl complexes had a distorted square-pyramidal conformation with a V=O bond. FT-IR spectra revealed that the Ph-O moiety of Schiff-base ligands was converted to Ph-OH by a surface-concerted reaction between the vanadium precursors and surface SiOH groups. The Ph-OH in an attached vanadyl complex interacted with a COO moiety of another vanadyl complex by hydrogen bonding to form a self-dimerized structure at the surface. The interatomic distance of V-V in the surface self-assembly was evaluated to be 0.40 +/- 0.05 nm by ESR after O-2 adsorption. The self-dimerized V structure on SiO2 was modeled by DFT calculations, which demonstrated that two vanadium monomers with Ph-OH linked together by two hydrogen bonds and their V=O groups were directed opposite to each other. The surface self-dimerization of the vanadium precursors fixes the direction of the V=O bond and the plane of the Schiff-base ligand. Thus, a new chiral reaction field was created by two types of chirality: the chiral Schiff-base ligand and the chiral V center. We have also found that the chiral self-dimerized vanadyl complexes exhibit remarkable catalytic performance for the asymmetric oxidative coupling of 2-naphthol: 96% conversion, 100% selectivity to 1;1 '-binaphthol (BINOL), and 90% enantiomeric excess (ee). Increasing the vanadium loading on SiO2 caused a dramatic swell of enantioselectivity, and the maximum 90% ee was observed on the supported catalyst with the full coverage of the vanadyl complex (3.4 wt % vanadium). This value is equivalent to the maximum ee reported in homogeneous catalysis for the coupling reaction. Furthermore, the supported vanadium dimers were reusable without loss of the catalytic performance. To our knowledge, this is the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol.
    研究論文(学術雑誌), 英語
  • Bound site of mo atoms and its local structure in a Mo/HY catalyst characterized by extended x-ray absorption fine structure and density functional calculation
    T Sasaki; F Nakagawa; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 109巻, 6号, 掲載ページ 2128-2138, 出版日 2005年02月, 査読付, The bound site of Mo atoms and its local structure in a Mo/HY catalyst have been determined by detailed analysis of extended X-ray absorption fine structure (EXAFS). Molybdenum was introduced in the supercage of HY zeolite by cycles of saturated adsorption Of MO(CO)6 at room temperature and subsequent thermal decomposition at 573 K. Two Mo atoms per supercage were immobilized in each CVD-thermal treatment cycle. The Mo loading increased linearly with the cycles up to three cycles at saturation, where six Mo atoms were supported. Temperature-programmed decomposition of the adsorbed MO(CO)(6) was also characterized by GC, QMS, and FT-IR, respectively. The EXAFS analysis including multiple scattering based on theoretical calculations revealed that Mo bound with two oxygen atoms connects to A1, where one of the two oxygen atoms had been associated with a proton. The bound site is called the S-III' site. The zeolite framework was significantly distorted by the introduction of low-valent Mo, resulting in isolation of the [MoO2Al] unit from the surrounding zeolite framework due to a quasi-disruption of Si-O bonds adjacent to the unit. In the mild oxidation of the low-valent Mo/HY sample two Mo=O bonds were newly formed and the position of Mo was displaced by 0.06 nm so that the distortion of zeolite framework around the A1 atom was relieved. The structures were also supported by DFT calculations. This study is the first example that the position of metal cation in zeolite was determined unambiguously by the EXAFS analysis.
    研究論文(学術雑誌), 英語
  • XAFS study on the local structure of zirconium containing mesoporous silicas, Zr-MCM-41 and their catalytic properties
    A. Yamaguchi; M. Yokoyama; A. Suzuki; Y. Iwasawa; H. Sakai; M. Yuasa; M. Abe
    PHYSICA SCRIPTA, IOP PUBLISHING LTD, T115巻, 掲載ページ 834-836, 出版日 2005年, 査読付, Zirconium-containing mesoporous silicas Zr-MCM-41 were prepared by two different methods and characterized by XRD, TEM, nitrogen adsorption and EXAFS. In one method, tetraethoxysilane (TEOS) and zirconium tetra-n-propoxide (ZTNP) were mixed and TEOS and ZTNP were hydrolyzed and condensed in aqueous cetyltrimetylammonium bromide solution. EXAFS analysis revealed that zirconium species in Zr-MCM-41 prepared by this method aggregated each other and formed the bonds of Zr-O-Zr. This catalyst had a low catalytic activity for the peroxidative bromination of phenol red. In the other method, ZrCl4 and pure silica MCM-41 were used for impregnation. Zirconium species in this Zr-MCM-41 were highly dispersed as shown in the result of EXAFS analysis. This catalyst exhibited a high catalytic activity for the peroxidative bromination of phenol red. Zirconium species aggregated each other by calcination at 573 K, which caused reduction of catalytic activity.
    研究論文(学術雑誌), 英語
  • Time-resolved energy-dispersive XAFS for in-situ characterization of nano-structures and catalysts
    Yasuhiro Iwasawa; Akane Suzuki; Masaharu Nomura
    PHYSICA SCRIPTA, IOP PUBLISHING LTD, T115巻, 掲載ページ 59-65, 出版日 2005年, 査読付, This paper reviews our recent study on the improvement of time-resolved energy-dispersive X-ray absorption. ne structure (DXAFS) and its application to in situ dynamic characterization for structural changes in nano-structures and catalysts, also presenting new data. The issue addressed in this paper is relevant to deeper understanding of catalytic intermediate structures, elementary steps, and reaction mechanisms.
    研究論文(学術雑誌), 英語
  • Chemical design and in situ characterization of active surfaces for selective catalysis
    M Tada; Y Iwasawa
    ANNUAL REVIEW OF MATERIALS RESEARCH, ANNUAL REVIEWS, 35巻, 掲載ページ 397-426, 出版日 2005年, 査読付, This review illustrates how catalytically active molecular structures are created on oxide surfaces by attachment of metal complexes with subsequent structural transformation and molecular imprinting on the surfaces. Also discussed is how the designed surfaces are characterized in situ by physical techniques including conventional and time-resolved X-ray absorption fine structure. The structural transformation and molecular imprinting for attached metal complexes can provide a new class of catalytic materials with a high complexity for selective catalysis including shape-selective and asymmetric catalysis.
    論文集(書籍)内論文, 英語
  • Surfactant-promoted novel reductive synthesis of supported metallic Cu nanoclusters and their catalytic performances for selective dehydrogenation of methanol
    R Bal; M Tada; Y Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 27号, 掲載ページ 3433-3435, 出版日 2005年, 査読付, We have found a surfactant-promoted novel reductive synthesis of metallic Cu nanoclusters on metal oxides under hydrothermal synthesis conditions, which are active for the selective dehydrogenation of methanol.
    研究論文(学術雑誌), 英語
  • Immobilized metal ion-containing ionic liquids: preparation, structure and catalytic performance in Kharasch addition reaction
    T Sasaki; CM Zhong; M Tada; Y Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 19号, 掲載ページ 2506-2508, 出版日 2005年, 査読付, Immobilized metal ion-containing ionic liquid catalysts were prepared by the reaction between silyl-functionalized imidazolium ionic molecules and surface silanol groups of silica, followed by addition of MnCl2, FeCl2, CoCl2, NiCl2, CuCl2, or PdCl2; only the immobilized copper catalyst, which has a sandwiched CuCl42- moiety, was very active for the Kharasch reaction between styrene and CCl4.
    研究論文(学術雑誌), 英語
  • Observation of element-specific energy-filtered X-ray photoemission electron microscopy images of Au on Ta using a Wien filter type energy analyzer
    H Yasufuku; Y Ohminami; T Tsutsumi; H Niimi; N Matsudaira; K Asakura; M Kato; Y Sakai; Y Kitajima; Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, INST PURE APPLIED PHYSICS, 43巻, 11A号, 掲載ページ 7682-7688, 出版日 2004年11月, 査読付, We have shown the possibility of a Wien filter as an energy analyzer for the energy-filtered X-ray photoemission electron microscopy (EXPEEM) by obtaining images of An islands on a Ta substrate using an inner shell photoelectron excited by an X-ray with a photon energy of 2300 eV. When the photoelectron with kinetic energy of nearly 0 eV was selected, brighter An islands were observed. When the kinetic energies of photoelectrons passing the Wien filter are set at those of Au 3d(5/2) and Ta 3p(3/2) photoelectrons, the An and Ta regions appeared brighter, respectively, indicating that the chemical imaging was successful using a high energy X-ray and a Wien filter energy analyzer.
    研究論文(学術雑誌), 英語
  • Recent progress in energy-filtered high energy X-ray photoemission electron microscopy using a Wien filter type energy analyzer
    H Niimi; T Tsutsumi; H Matsudaira; T Kawasaki; S Suzuki; WJ Chun; M Kato; Y Kitajima; Y Iwasawa; K Asakura
    APPLIED SURFACE SCIENCE, ELSEVIER SCIENCE BV, 237巻, 1-4号, 掲載ページ 641-644, 出版日 2004年10月, 査読付, Energy-filtered X-ray photoemission electron microscopy (EXPEEM) is a microscopy technique which has the potential to provide surface chemical mapping during surface chemical processes on the nanometer scale. We studied the possibilities of EXPEEM using a Wien filter type energy analyzer in the high energy X-ray region above 1000 eV. We have successfully observed the EXPEEM images of Au islands on a Ta sheet using An 3d(5/2) and Ta 3d(5/2) photoelectron peaks which were excited by 2380 eV X-rays emitted from an undulator (BL2A) at Photon Factory. Our recent efforts to improve the sensitivity of the Wien filter energy analyzer will also be discussed. (C) 2004 Elsevier B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Photo-oxidation of methanol and formic acid on rutile TiO2(001) studied by STM
    H. Ariga; R. Tero; Y. Namai; Y. Iwasawa
    Microscopy and Microanalysis, 10巻, S02号, 掲載ページ 482-483, 出版日 2004年09月, 査読付
    研究論文(学術雑誌), 英語
  • Time-scale and sequence of dynamic structural changes in a MgO-attached ruthenium cluster catalyst observed by in situ time-resolved DXAFS
    A Suzuki; A Yamaguchi; T Chihara; Y Inada; M Yuasa; M Abe; M Nomura; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 108巻, 18号, 掲載ページ 5609-5616, 出版日 2004年05月, The structural transformations of a MgO-attached [Ru6C] cluster catalyst during carbonylation under CO/H-2 and decarbonylation under vacuum were studied by energy-dispersive X-ray absorption fine structure (DXAFS). The DXAFS study revealed that the carbonylation of [Ru6C]/MgO to [Ru6C(CO)(11)]/MgO proceeded via two intermediates with the same composition [Ru6C(CO)(6)] with different Ru-Ru bond distances (0.265 and 0.269 nm). First, six CO molecules coordinate to a [Ru6C] framework, and second, the Ru-Ru length expands from 0.265 to 0.269 nm. Finally, five CO molecules coordinate to the [Ru6C(CO)(6)] cluster to produce [Ru6C(CO)(11)] species, where the Ru-Ru distance is further elongated to 0.271 nm. In the decarbonylation process, the [Ru6C(CO)(6)]/MgO is partially decarbonylated to form [Ru6C(CO)(11)]/MgO accompanied with a decrease of Ru-Ru length from 0.271 to 0.269 nm. Then the complete decarbonylation occurs to form [Ru6C] species, keeping the Ru-Ru distance at 0.269 nm. Finally, the cluster framework shrinks to recover the original [Ru6C]/MgO with the Ru-Ru distance of 0.265 nm. There were definite time lags between the first carbonylation and the cluster framework expansion (2-4 s, depending on the temperature) and between the last decarbonylation and the cluster framework shrinkage (3-5 min, depending on the temperature). The activation energies for the structural changes in the Ru cluster framework in every transformation step under CO/H-2 (423-523 K) and vacuum (573-623 K) were estimated by the time-resolved DXAFS analysis. This sort of study is the first to provide structural kinetics of catalytically active metal sites at oxide surfaces.
    研究論文(学術雑誌), 英語
  • Selective oxidation of benzene to phenol with molecular oxygen on rhenium/zeolite catalysts
    T Kusakari; T Sasaki; Y Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 8号, 掲載ページ 992-993, 出版日 2004年04月, 査読付, Zeolite-supported rhenium catalysts are active for selective oxidation of benzene with molecular oxygen, where coexisting ammonia is prerequisite to the direct phenol synthesis.
    研究論文(学術雑誌), 英語
  • Design of a novel molecular-imprinted Rh-amine complex on SiO2 and its shape-selective catalysis for alpha-methylstyrene hydrogenation
    M Tada; T Sasaki; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 108巻, 9号, 掲載ページ 2918-2930, 出版日 2004年03月, 査読付, A new molecular-imprinted Rh-amine complex with a template-shaped cavity acting as a shape-selective reaction space was prepared by metal-complex attaching and molecular imprinting techniques on a SiO2 surface. Rh(eta(3)-C3H5)(3) reacted with SiO2, and the precursor was attached on the surface to form a bidentate structure Rh(C3H5)(OSi)(2). alpha-Methylbenzylamine with a shape similar to that of a half-hydrogenated alkyl intermediate of alpha-methyl styrene coordinated to the attached Rh as a template ligand. Then SiO2-matrix overlayers were stacked on the surface by the hydrolysis-polymerization of Si(OCH3)(4) surrounding the attached Rh complexes with the amine template. Final evacuation at 373 K promoted the removal of the template ligand from the Rh complex embedded in the surface pore of the SiO2-matrix overlayers. All the structures of the attached Rh complexes were characterized by the means of ICP, XPS, ESR, FT-IR, solid-state MAS NMR, EXAFS, DFT, GC, and H-2 adsorption. The imprinted Rh complex has an unsaturated structure Rh-(amine)(OSi)(HOSi) and exhibits high catalytic activity for alpha-methylstyrene hydrogenation. On the contrary, the other supported Rh complexes before imprinting are inactive for the hydrogenation. Furthermore, the active Rh complex is durable under the reaction condition despite the unsaturated conformation which usually tends to gather each other. The imprinted cavity locating on the active Rh center acts as a shape-selective reaction space for alpha-methylstyrene. The inhibition of the hydrogenation by the use of seven amines with different shapes demonstrates the shape-selective behavior of the imprinted Rh complex discriminating one methyl group and the position of the phenyl ring.
    研究論文(学術雑誌), 英語
  • STM study on photoreactions of adsorbed methanol and formic acid on a rutile TiO2(001) surface.
    H Ariga; R Tero; Y Namai; Y Iwasawa
    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 227巻, 掲載ページ U1456-U1456, 出版日 2004年03月, 査読付
    英語
  • The dynamic behaviour of CH3OH and NO2 adsorbed on CeO2(111) studied by noncontact atomic force microscopy
    Y Namai; K Fukui; Y Iwasawa
    NANOTECHNOLOGY, IOP PUBLISHING LTD, 15巻, 2号, 掲載ページ S49-S54, 出版日 2004年02月, 査読付, The adsorption and reaction of methanol (CH3OH) and nitrogen dioxide (NO2) on CeO2 (111) surfaces in different oxidation states were studied by noncontact atomic force microscopy (NC-AFM). After CH3OH exposure, surface oxygen defects without reconstruction of the surrounding oxygen atoms were healed by methoxy species (CH3O). Under a CH3OH atmosphere, a heterogeneous feature in the reactivity of surface oxygen atoms to CH3OH was observed by successive NC-AFM observation: new line defects of oxygen were produced as a result of a chemical event. Successive NC-AFM measurements also revealed that oxygen vacancies on a slightly reduced CeO2 (111) surface were healed by exposure to NO2. The contrast of healed oxygen defects in NC-AFM images was similar to that of other surface oxygen atoms. This indicates that dissociative adsorption of NO2 occurred at the defects. Nitrogen trioxide (NO3) was also observed on a slightly reduced CeO2 (111) surface after NO2 exposure. On a CeO2 (111) surface without surface oxygen defects, neither adsorption of NO2 nor formation of NO3 was observed. The reaction mechanisms for the formation of line defects and NO3 are discussed briefly.
    研究論文(学術雑誌), 英語
  • In-situ STM observation and DFT calculation of the decomposition process of formic acid on TiO2(110)
    M. Aizawa; Y. Morikawa; I. Takahashi; Y. Namai; T. Sasaki; Y. Iwasawa
    Microscopy and Microanalysis, 10巻, 2号, 掲載ページ 480-481, 出版日 2004年, 査読付
    研究論文(国際会議プロシーディングス), 英語
  • Oxide surface-promoted Pd-complex catalysis for intramolecular O-activated alkene hydroamination: catalyst preparation, characterization, and performance
    M Tada; M Shimamoto; T Sasaki; Y Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 22号, 掲載ページ 2562-2563, 出版日 2004年, 査読付, Supported Pd - P and Pd - N complexes prepared by a selective reaction of Pd-monomer precursors with SiO2, Al2O3 and TiO2 surfaces and characterized by EXAFS, XPS, XRF and gas analysis exhibited oxide surface-promoted catalysis for the catalytic intrahydroamination of 3-amino propanol vinyl ether to produce a cyclic amine.
    研究論文(学術雑誌), 英語
  • Chiral self-dimerization of vanadium complexes on a SiO2 surface: the first heterogeneous catalyst for asymmetric 2-naphthol coupling
    M Tada; T Taniike; LM Kantam; Y Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 22号, 掲載ページ 2542-2543, 出版日 2004年, 査読付, The self-dimerized chiral assembly of vanadium - Schiff-base complexes was found to occur on a SiO2 surface and to be the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol with 100% selectivity and 90% enantioselectivity.
    研究論文(学術雑誌), 英語
  • A local structure of low coverage Ni species on the alpha-Al2O3 (0001) surface - a polarization dependent EXAFS study
    K. Ijima; Y. Koike; W. Chun; Y. Saito; Y. Tanizawa; T. Shido; Y. Iwasawa; M. Nomura; K. Asakura
    Chemical Physics Letters, 384巻, 1/3号, 掲載ページ 134-138, 出版日 2004年, 査読付
    英語
  • Dynamic aspects and associated structures of TiO2(110) and CeO2(111) surfaces relevant to oxide catalyses
    K Fukui; S Takakusagi; R Tero; M Aizawa; Y Namai; Y Iwasawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 5巻, 24号, 掲載ページ 5349-5359, 出版日 2003年12月, 査読付, This article gives a topical review of the dynamic behavior of surface species on two representative metal oxide surfaces of TiO2 (110) and CeO2(111) investigated by scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM). In addition, two new aspects, the self-limiting growth of Pt nanoparticles from MeCPPtMe3 on TiO2(110) regulated by a competitive reaction with TiOs suboxides and the inhomogeneous reactivity of surface oxygen atoms on CeO2(111) against methanol, are also imaged by STM and NC-AFM, which are relevant to key issues to understand the surface chemical reactivity and catalysis.
    研究論文(学術雑誌), 英語
  • Atom-resolved noncontact atomic force microscopic and scanning tunneling microscopic observations of the structure and dynamic behavior of CeO2(111) surfaces
    Y Namai; KI Fukui; Y Iwasawa
    CATALYSIS TODAY, ELSEVIER SCIENCE BV, 85巻, 2-4号, 掲載ページ 79-91, 出版日 2003年10月, 査読付, Atomic-scale structures and dynamic behaviors of CeO2 (1 1 1) surfaces were imaged by noncontact atomic force microscopy (NC-AFM) and scanning tunneling microscopy (STM). Hexagonally arranged oxygen atoms, oxygen point vacancies, multiple oxygen vacancies, and hydrogen adatoms at the surfaces were visualized by atom-resolved NC-AFM observations. Multiple defects were stabilized by displacement of the surrounding oxygen atoms around the multiple defects, which gave enhanced brightness in the NC-AFM image due to a geometric reason. Multiple defects without reconstruction of the surrounding oxygen atoms were reactive and were healed by exposure to O2 gas and methanol at RT. Successive NC-AFM and STM measurements of slightly reduced CeO2(1 1 1) surfaces revealed that hopping of surface oxygen atoms faced to the metastable multiple defects was thermally activated even at room temperature (RT) and more promoted at higher temperatures. Heterogeneous feature of the reactivity of surface oxygen atoms with methanol was imaged by successive NC-AFM observations. These observations gave a new insight for understanding the surface structures and behavior of CeO2-x with the facile oxygen reservoir and oxidation-reduction properties related to the unique catalysis. (C) 2003 Elsevier B.X. All rights reserved.
    研究論文(学術雑誌), 英語
  • Atom-resolved noncontact atomic force microscopic observations of CeO2(111) surfaces with different oxidation states: Surface structure and behavior of surface oxygen atoms
    Y Namai; K Fukui; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 107巻, 42号, 掲載ページ 11666-11673, 出版日 2003年10月, 査読付, Hexagonally arranged surface oxygen atoms, oxygen point defects, and multiple oxygen defects at oxygen-terminated CeO2(111) surfaces in different oxidation states were visualized by noncontact atomic force microscopy (NC-AFM). The multiple defects such as line defects and triangular defects were stabilized by a local reconstruction, where edge oxygen atoms surrounding the multiple defects were displaced and gave enhanced brightness due to a geometric reason. Successive NC-AFM measurements of the same area of a slightly reduced CeO2(111) surface revealed that hopping of surface oxygen atoms faced to metastable multiple defects was thermally activated even at room temperature. In contrast, no hopping was observed either at a point oxygen vacancy or a line defect that is stabilized by local reconstruction. It was also confirmed from atom-resolved NC-AFM observations that the surface oxygen defects were easily healed by exposure to O-2 gas at room temperature.
    研究論文(学術雑誌), 英語
  • Wien Filter型EXPEEMによるAu/Taの光電子エネルギー選別像と分散像の観測
    堤 哲也; 大南 祐介; 朝倉 清高; 安福 秀幸; 嘉藤 誠; 境 悠治; 北島 義典; 岩澤 康裕
    表面科学, 公益社団法人 日本表面科学会, 24巻, 8号, 掲載ページ 509-511, 出版日 2003年08月10日, EXPEEM (energy-selected X-ray photoemission electron microscopy) has a potential to give surface chemical mapping by analyzing the X-ray photoelectron kinetic energies. We have successfully observed EXPEEM images of Au islands deposited on a Ta substrate by using a Wien filter type energy analyzer and an undulator synchrotron radiation with a photon energy as high as 2300 eV. The energy and spatial resolution of the EXPEEM were estimated to be 1 eV and 1.6 μm, respectively.
    日本語
  • Self-Limiting Growth of Pt Nanoparticles from [Formula presented] Adsorbed on [Formula presented] Studied by Scanning Tunneling Microscopy
    Satoru Takakusagi; Ken-ichi Fukui; Ryugo Tero; Fumito Nariyuki; Yasuhiro Iwasawa
    Physical Review Letters, 91巻, 6号, 出版日 2003年08月06日, 査読付, The growth of Pt nanoparticles from the metal-organic precursor [[Formula presented]: (methylcyclopentadienyl) trimethyl platinum] on [Formula presented] was studied by scanning tunneling microscopy. 2D-like Pt particles on the surface were formed in a self-limiting growth mode. The inner structure of the particles was resolved as unique tetramerlike bright spots. A mechanism for the self-limiting growth of Pt particles is proposed. © 2003 The American Physical Society.
    研究論文(学術雑誌), 英語
  • Self-limiting growth of pt nanoparticles from MeCpPtMe3 adsorbed on TiO2(110) studied by scanning tunneling microscopy
    S Takakusagi; K Fukui; R Tero; F Nariyuki; Y Iwasawa
    PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 91巻, 6号, 掲載ページ 6-9, 出版日 2003年08月, 査読付, The growth of Pt nanoparticles from the metal-organic precursor [MeCpPtMe3: (methylcyclopentadienyl) trimethyl platinum] on TiO2(110) was studied by scanning tunneling microscopy. 2D-like Pt particles on the surface were formed in a self-limiting growth mode. The inner structure of the particles was resolved as unique tetramerlike bright spots. A mechanism for the self-limiting growth of Pt particles is proposed.
    研究論文(学術雑誌), 英語
  • Atom-resolved surface structures and molecular adsorption on TiO2(001) investigated by scanning Tunneling microscopy
    R Tero; K Fukui; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 107巻, 14号, 掲載ページ 3207-3214, 出版日 2003年04月, 査読付, Well-ordered surface structure was prepared on a rutile TiO2(001) surface and investigated on the atomic scale by scanning tunneling microscopy (STM). The surface had a latticework-like structure with rows running along the [110] and [110] directions. Each row consisted of narrow terraces separated by single-height steps on their slopes at both sides. An added-row structural model that consists of Ti7O12 suboxide row added on each narrow terrace of a {114}-microfacet structure was proposed on the basis of atom-resolved STM images as well as local coordination considerations. The added row had 4-fold coordinated and 5-fold coordinated Ti atoms, each of which was observed as a bright spot in STM images. Formic acid molecules adsorbed on both Ti sites, while methanol adsorbed preferentially on the 4-fold coordinated Ti atoms, which may support the validity of the structural model. The latticework structure was proved to be stable against thermal reactions of formic acid and methanol.
    研究論文(学術雑誌), 英語
  • Atom-resolved surface structures and molecular adsorption on TiO2(001) investigated by scanning tunneling microscopy
    Ryugo Tero; Ken-ichi Fukui; Yasuhiro Iwasawa
    Journal of Physical Chemistry B, 107巻, 14号, 掲載ページ 3207-3214, 出版日 2003年04月, 査読付, Well-ordered surface structure was prepared on a rutile TiO 2 (001) surface and investigated on the atomic scale by scanning tunneling microscopy (STM). The surface had a latticework-like structure with rows running along the [110] and [11̄0] directions. Each row consisted of narrow terraces separated by single-height steps on their slopes at both sides. An added-row structural model that consists of Ti 7 O 12 suboxide row added on each narrow terrace of a {114}-microfacet structure was proposed on the basis of atom-resolved STM images as well as local coordination considerations. The added row had 4-fold coordinated and 5-fold coordinated Ti atoms, each of which was observed as a bright spot in STM images. Formic acid molecules adsorbed on both Ti sites, while methanol adsorbed preferentially on the 4-fold coordinated Ti atoms, which may support the validity of the structural model. The latticework structure was proved to be stable against thermal reactions of formic acid and methanol.
    研究論文(学術雑誌), 英語
  • Vibrational relaxation of adsorbate and adsorbent in the CO-adsorbed DM-20 zeolite system
    K Onda; Y Iwasawa; A Wada
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 370巻, 3-4号, 掲載ページ 437-442, 出版日 2003年03月, 査読付, We made the first observation of transient vibrational spectra of both adsorbate and adsorbent at molecule-adsorbed surface using a two-color infrared picosecond laser system. The transient measurements were carried out on the CO-adsorbed surface hydroxyl group (OD) of DM-20 zeolite by pumping the CO stretching mode (2175 cm(-1)) or OD stretching mode (2470 cm(-1)) and probing over the CO and OD stretching region (2000-2700 cm(-1)). The T(1) lifetime for OD was 5.8 ps and that for CO was 540 ps. By comparison with other CO-adsorbed systems, vibrational relaxation mechanisms of CO on various surfaces are discussed. We also found evidence of energy flows from the vibrational mode of the adsorbent (OD stretching) to that of the adsorbate (CO stretching) via van der Waals interaction. (C) 2003 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Formation of new Re clusters in HZSM-5 and their catalytic property in propene selective oxidation/ammoxidation reactions
    N Viswanadham; T Shido; T Sasaki; Y Iwasawa
    SCIENCE AND TECHNOLOGY IN CATALYSIS 2002, KODANSHA LTD, 145巻, 掲載ページ 189-192, 出版日 2003年, 査読付, A catalyst prepared by chemical vapor deposition (CVD) of CH3ReO3 (WO) on H-ZSM-5 and subsequent treatment at 673 K was active for selective oxidation/ammoxidation of propene. Presence of ammonia was prerequisite for the catalytic selective oxidation of propene to acrolein. The structural change of the Re species during the pretreatment and catalytic reaction was investigated by SS-NMR, and XAFS. MTO interacted with protons of HZSM-5 at 333 K, and the subsequent treatment at 673 K formed tetrahedral [ReO4] monomer species. Ammonia promoted the formation of a new [Re6O17] cluster at 673 K. A proposed cluster structure constituted an octahedral Re-6 framework with terminal and bridge oxygen atoms, which were relevant to the selective oxidation. The active [Re6O17] Clusters were converted to the inactive [ReO4] monomers in the absence of ammonia.
    研究論文(学術雑誌), 英語
  • Time scale and elementary steps of CO-induced disintegration of surface rhodium clusters
    A Suzuki; Y Inada; A Yamaguchi; T Chihara; M Yuasa; M Nomura; Y Iwasawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 42巻, 39号, 掲載ページ 4795-4799, 出版日 2003年, The disintegration of Rh clusters on an Al2O3 surface induced by CO, the elementary steps, and timescale of the reaction are analyzed for the first time by energy-dispersive X-ray absorption fine structure (DXAFS) at a time resolution of 100 ms (see picture). This study by the improved time-resolved DXAFS technique provides a new research area of structural dynamics of catalytically active materials at surfaces.
    研究論文(学術雑誌), 英語
  • Visualization of the Atomic-scale Structure and Reactivity of Metal Carbide Surfaces Using Scanning Tunneling Microscopy
    Ken-ichi Fukui; Rong-Li Lo; Yasuhiro Iwasawa
    Carbon Alloys: Novel Concepts to Develop Carbon Science and Technology, Elsevier Ltd., 掲載ページ 257-267, 出版日 2003年, 査読付, This chapter reviews the recent scanning tunneling microscopy (STM) studies on Mo2C(0001) with the atomic-scale resolution. Molybdenum carbides are representative of the metal carbides with good catalytic performances. α-Mo2C is a stable crystalline form which has an orthorhombic crystal structure. The structure of an α-Mo2C(0001) surface varies depending on the surface coverage by the carbon atoms-which can be regulated by an annealing temperature and reaction time. By careful control of the preparation procedures, well-ordered C-terminated surfaces with (√3*√3) R30°-honeycomb structure and c(2*4)-zigzag row structure were successfully prepared and imaged by the STM. Each carbon atom inside the structures was visualized as a shallow sombrero protrusion at the low tunneling resistances of less than 1 MW. A novel selective etching reaction of the surface carbon atoms by oxygen gas occurred even at room temperature. On a C-terminated Mo2C(0001) surface with both-the (√3*√3) R30°-honeycomb and the c(2*4)-zigzag row structures, the etching reaction selectively occurred on the c(2*4)-zigzag structure, leading to the exposure of an underlying (1*1) molybdenum layer. © 2003 Elsevier B.V. All rights reserved.
    論文集(書籍)内論文, 英語
  • STM study on structures of two kinds of wide strands formed on TiO2(110)
    S.Takakusagi; K.Fukui; F.Nariyuki; Y.Iwasawa
    Surface Science, 523巻, 1/2号, 掲載ページ L41-L46, 出版日 2003年
  • Three-dimensional structure analyses of Cu species dispersed on TiO2(110) surfaces studied by polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS)
    Y. Tanizawa; T. Shido; W. Chun; K. Asakura; M. Nomura; Y. Iwasawa
    Journal of Physical Chemistry B, 107巻, 47号, 掲載ページ 12917-12929, 出版日 2003年, 査読付
    英語
  • 0.6-3.0 wt% of Vanadium on/in titania monitored by X-ray absorption fine structure combined with fluorescence spectrometry
    Y Izumi; F Kiyotaki; H Yoshitake; K Aika; T Sugihara; T Tatsumi; Y Tanizawa; T Shido; Y Iwasawa
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 31巻, 11号, 掲載ページ 1154-1155, 出版日 2002年11月, 査読付, Selective XAFS measurements of 0.6-3.0wt% V sites on/in TiO2 were enabled utilizing a fluorescence spectrometer. The V sites were V-IV species in the case of high-surface-area V-TiO2 in contrast to V-V species in the case of conventional V/TiO2 catalysts, V supported on HSA-TiO2, and V-TiO2 prepared in the absence of dodecylamine (general sol-gel method).
    英語
  • Performance and kinetic behavior of a new SiO2-attached molecular-imprinting Rh-dimer catalyst in size- and shape-selective hydrogenation of alkenes
    M Tada; T Sasaki; Y Iwasawa
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 211巻, 2号, 掲載ページ 496-510, 出版日 2002年10月, 査読付, A new size- and shape-selective Rh-dimer catalyst was designed by combination of a metal-complex-attaching method and a molecular-imprinting method on an Ox.50 surface. Coordinatively unsaturated, air-stable Rh dimers with a Rh-Rh bond of 0.268 nm were prepared in 0.74-nm micropores of SiO2-matrix overlayers on the Ox.50 silica surface by attaching a Rh2Cl2(CO)(4) precursor on the surface (Rh2Cl2(CO)(4)/SiO2), followed by coordination of template ligands P(OCH3)(3) to the attached Rh species (Rh-sup catalyst), and then by surface imprinting of the template with SiO2-matrix overlayers formed by hydrolysis-polymerization of Si(OCH3)(4) (Rh-imp catalyst). The Rh dimers, micropores, and SiO2-matrix overlayers in the molecular-imprinting Rh-imp catalyst were characterized by EXAFS, BET analysis, and Si-29 solid-state MAS NMR, respectively. It was found that activity of the Rh-sup catalyst for hydrogenation of alkenes was promoted remarkably (35-51 times) after the imprinting. The alkene hydrogenation proceeded on the imprinted Rh dimers with a monohydride without any breaking of the Rh-Rh bond. Size and shape selectivities of the molecular-imprinting Rh-imp catalyst were examined by measuring the hydrogenation rates of eight alkenes of different sizes and shapes. It was also found that the Rh-imp catalyst exhibited not only high activity and stability but also size and shape selectivities for the alkene molecules, probably due to a template-size cavity, created behind the removed template ligand, being used as a reaction site. Activation energies and activation entropies for the hydrogenation of large and branched alkenes were much smaller than those for small alkenes, which implies a shift in the rate-determining step in the reaction sequence for alkene hydrogenation. The performance of the molecular-imprinting Rh-dimer catalyst is discussed from structural and kinetic viewpoints. (C) 2002 Elsevier Science (USA).
    研究論文(学術雑誌), 英語
  • Ammonia-promoted rhenium-cluster formation in CH3WO3-encapsulated H-ZSM-5 relevant to the performance of the catalytically selective oxidation/ammoxidation of propene
    N Viswanadham; T Shido; T Sasaki; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 106巻, 42号, 掲載ページ 10955-10963, 出版日 2002年10月, 査読付, HZcvd catalysts, which were prepared by chemical vapor deposition (CVD) of methyl trioxorhenium CH3ReO3 on H-ZSM-5 (HZ) and subsequent treatment at 673 K, exhibited significant activities in the selective oxidation/ammoxidation of propene. The catalytic selective oxidation of propene to acrolein never proceeded in the absence of ammonia. In the HZcvd catalysts, the hydrophilic nature of HZ increased, and the crystallinity of the HZ framework decreased as indicated by XRD. The detailed characterizations by XRD, Si-29 and Al-27 MAS NMR, XANES, and EXAFS at the sequential stages of the catalyst preparation demonstrated the occurrence of structural changes of Re species during the preparation and under the catalytic reaction conditions. CH3ReO3 interacted with protons of HZ at 333 K, the subsequent treatment at 673 K formed tetrahedral [ReO4] monomer, and ammonia promoted the formation of a new [Re6O17] cluster at 673 K. A proposed cluster structure constituted an octahedral Re-6 framework with an Re-Re bond at 0.276 nm and terminal and bridge oxygen atoms (Re=O at 0.172 nm and Re-O at 0.203 nm, respectively). Thirty-two percent of these oxygen atoms were active for the selective oxidation of propene to acrolein. The active [Re6O17] clusters were converted to the inactive [ReO4] monomers in the absence of ammonia.
    研究論文(学術雑誌), 英語
  • The effect of ppm-level Na impurity on the structure of SiO2-supported Mo catalysts prepared in a clean room
    WJ Chun; K Asakura; H Ishii; T Liu; Y Iwasawa
    TOPICS IN CATALYSIS, KLUWER ACADEMIC/PLENUM PUBL, 20巻, 1-4号, 掲載ページ 89-95, 出版日 2002年07月, 査読付, To investigate the effect of alkali impurity in Mo/SiO2 on the MoOx structure on SiO2 surfaces SiO2-supported Mo oxides were prepared with various amounts of Na ions in a class-1 clean bench with a laminar flow in a class-1000 clean room. The Na concentrations were varied in the range 0-5000 ppm, while the Mo loading on SiO2 was maintained at 0.7 wt%. The Mo-Na/SiO2 samples obtained were characterized by diffuse reflectance UV-visible and Raman spectroscopy. Three types of Mo species were identified: octahedral monooxo Mo monomer species, Na2Mo2O7 and MoO3. At less than 100 ppm Na both octahedral Mo monomers and MoO3 species were formed on SiO2. The MoO3 species was transformed to Na2Mo2O7 at 2000 ppm Na, where the Na ions interact directly with the Mo species on the surface. The octahedral monooxo Mo monomer species seems not to be influenced significantly by Na impurity.
    研究論文(学術雑誌), 英語
  • Oxygen adsorption states on Mo(112) surface studied by HREELS
    T Sasaki; Y Goto; R Tero; K Fukui; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 502巻, 掲載ページ 136-143, 出版日 2002年04月, 査読付, Oxygen adsorption on a Mo(112) has been Studied using HREELS, LEED and TPD. Oxygen molecules dissociatively adsorb to occupy quasi-threefold hollow site. long bridge site and atop site oil a clean Mo(112) at 100 K. After annealing this surface to 300 K a loss peak corresponding to the oxygen atoms at atop sites disappears. changing the adsorption sites into quasi-threefold and long bridge sites. Further annealing to 600 K resulted in the change of the location of oxygen atoms from long bridge site to quasi-threefold hollow site. where the Surface shows p(1 x 2) LEED subspots, indicating that the oxygen atoms in the Mo(112)-p(1 x 2)-O Surface Occupy quasi-threefold hollow sites. Oxygen adsorption on the Mo(112)-p(1 x 2)-O Surface was also investigated and it was found that oxygen molecules associatively adsorb on the Surface to give bridged peroxo species, which dissociates at 200 K to yield oxygen atoms at atop sites. The atop oxygen atoms remain on the Surface after annealing to higher temperatures in contrast to the adsorption on clean Mo(112). Further annealing to 800 K resulted in a disordered Surface associated with a molybdenum oxide (MoxOy) layer. (C) 2002 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • 非接触原子間力顕微鏡によるTiO_2(110)及びCeO_2(111)表面上での原子・分子の動的挙動の観察
    福井 賢一; 岩澤 康裕
    表面科学 : hyomen kagaku = Journal of the Surface Science Society of Japan, The Surface Science Society of Japan, 23巻, 3号, 掲載ページ 141-148, 出版日 2002年03月10日, Our recent studies on metal oxide surfaces by noncontact atomic force microscopy (NC-AFM) are reviewed. We have demonstrated that atom-resolved images of a TiO2(110) surface can be obtained by NC-AFM. We have also revealed that isolated species of formate ions and hydrogen adatoms on TiO2(110) can be imaged by NC-AFM. As an example of observation of dynamic behavior of adsorbed molecules by NC-AFM, images of fluctuating molecules of acetate ions at domain boudaries of (2×1)-acetate overlayer on TiO2(110) are presented. CeO2−x has been believed to play a crucial role in automotive exhaust catalysis with its special oxygen storage capacity. Surface oxygen atoms at an oxygen-terminated CeO2(111) surface, oxygen point vacancies, and multiple oxygen vacancies such as triangular defects and line defects were visualized by NC-AFM. Unexpected high mobility of surface oxygen atoms at room temperature was observed on slightly reduced CeO2(111) with multiple defects. This observation is probably relevant to facile oxidation-reduction cycles of CeO2−x.
    日本語
  • In situ time-resolved energy-dispersive X-ray absorption fine structure study on the decarbonylation processes of Mo(CO)(6) entrapped in NaY and HY zeolites
    A Yamaguchi; A Suzuki; T Shido; Y Inada; K Asakura; M Nomura; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 106巻, 9号, 掲載ページ 2415-2422, 出版日 2002年03月, 査読付, Temperature-programmed decarbonylation processes of Mo(CO)(6) entrapped in NaY and HY zeolites were investigated in situ by the time-resolved energy-dispersive X-ray absorption fine structure (DXAFS) technique. The DXAFS study revealed that the decarbonylation of Mo(CO)(6) in both NaY and HY proceeded through molybdenum subcarbonyl species and that the subsequent formation of decarbonylated species is affected by the stability of the subcarbonyl intermediate species. In the case of Mo(CO)(6)/NaY, stable Mo(CO)(3)(O-L)(3) (O-L, oxygen atoms of the zeolite framework) species were formed at 400-500 K and Mo(II) oxocarbide dimeric species Mo-2(C)O-x were formed above 500 K. In the case of Mo(CO)(6)/HY, on the other hand, unstable MO(CO)(3)(O-L)(x) (x = 1-2) species were formed around 450 K and they reacted easily with protons in zeolite supercages to be converted to Mo(II) monomer species. An unstable intermediate species was observed, and its structure was determined by DXAFS for the first time.
    研究論文(学術雑誌), 英語
  • Imaging of surface oxygen atoms and their defect structures on CeO2(111) by noncontact atomic force microscopy
    K Fukui; Y Namai; Y Iwasawa
    APPLIED SURFACE SCIENCE, ELSEVIER SCIENCE BV, 188巻, 3-4号, 掲載ページ 252-256, 出版日 2002年03月, 査読付, Atomic-scale structures of CeO2(1 1 1) were examined by noncontact atomic force microscopy (NC-AFM). Hexagonally arranged surface oxygen atoms at an ideally oxygen-terminated surface, oxygen point vacancies, and multiple oxygen vacancies such as triangular defects and line defects formed depending on different oxidation states of CeO2-x were visualized by NC-AFM. These observations give a new insight to understand the special oxygen storage capacity with facile oxidation-reduction cycles for CeO2-x relevant to automotive exhaust catalysis. (C) 2002 Elsevier Science B.V All rights reserved.
    研究論文(学術雑誌), 英語
  • Structure of low concentrations of vanadium on TiO2 determined by XANES and ab initio calculations
    Y Izumi; F Kiyotaki; H Yoshitake; K Aika; T Sugihara; T Tatsumi; Y Tanizawa; T Shido; Y Iwasawa
    CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 20巻, 20号, 掲載ページ 2402-2403, 出版日 2002年, 査読付, The major local structure of low concentrations (1-3 wt% V) of vanadium on TiO2 was determined to have two terminal oxo groups and in total five oxygen coordination by means of vanadium K-edge XANES and ab initio calculations of XANES spectra.
    英語
  • Design, characterization and performance of a molecular imprinting Rh-dimer hydrogenation catalyst on a SiO2 surface
    M Tada; T Sasaki; T Shido; Y Iwasawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 4巻, 23号, 掲載ページ 5899-5909, 出版日 2002年, 査読付, A new active SiO2-attached Rh-dimer catalyst for the hydrogenation of alkenes was designed by combining two ways of metal-complex immobilization and molecular imprinting on an oxide surface. The preparation was conducted step-by-step in three steps: (i) the attachment of Rh dimer precursor on an Ox.50 surface; (ii) coordination of the template P(OCH3)(3) to the attached Rh dimer; and (iii) subsequent molecular imprinting by hydrolysis-polymerization of Si(OCH3)(4) to form SiO2-matrix overlayers on the surface. Characterizations at each step were performed by means of elemental analysis, FFIR, XPS, ICP, solid-state MAS NMR, BET, EXAFS, and DFT calculation. The attached Rh dimer was converted to a pair of Rh monomers by coordination of two P(OCH3)(3) on a Rh atom. The surface-imprinting process by Si(OCH3)(4) drove the rebonding of the Rh monomer pair and extraction of half of the template ligands. Removal of the template ligands provided both highly active unsaturated Rh dimer with a Rh-Rh bond distance of 0.268 nm and a space of the size of the template around the dimer inside the SiO2-matrix overlayers on the surface. The template P(OCH3)(3) was regarded as an analogue to a half-hydrogenated species of 3-ethylpent-2-ene. The catalytic activity of the imprinted Rh dimer catalyst for hydrogenation of 3-ethylpent-2-ene was 35 times higher than that of the Rh monomer pair before imprinting. For hydrogenation of 4-methylhex-2-ene which possesses an ethyl group at the 4-carbon position of the pent-2-ene main chain and oct-2-ene with a long alkyl chain, promotion of the catalytic activity by the imprinting was relatively slight, indicating shape discrimination of the alkenes by the surface molecular imprinting.
    研究論文(学術雑誌), 英語
  • Novel SiO2-attached molecular-imprinting Rh-monomer catalysts for shape-selective hydrogenation of alkenes; preparation, characterization and performance
    M Tada; T Sasaki; Y Iwasawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS, ROYAL SOC CHEMISTRY, 4巻, 18号, 掲載ページ 4561-4574, 出版日 2002年, 査読付, A combination of two methods for catalyst design, namely metal-complex attaching and molecular imprinting, at oxide surfaces was employed to prepare new SiO2-attached shape-selective Rh-monomer catalysts for hydrogenation of alkenes. Attachment of Rh monomer on SiO2 surface was performed by reaction of RhCl(P(OCH3)(3))(3) precursor with an Ox.50 surface. The attached Rh monomers were characterized to be coordinated with two P(OCH3)(3) ligands (Rh-P = 0.225 nm) and two surface oxygens (Rh-O = 0.204 nm) by EXAFS, XPS, and FT-IR, independent of Rh loading in the range 0.24-0.60 wt. %. Subsequent molecular imprinting of a P(OCH3)(3) ligand in the attached Rh monomers as template ligand by hydrolysis polymerization of Si(OCH3)(4) depended on the Rh loading; the lower loading Rh-monomers were successfully imprinted in uniform micropores formed in SiO2-matrix overlayers on the Ox. 50 surface. Characterizations of the molecular imprinting catalysts with different heights of the SiO2-matrix overlayers were performed by EXAFS, XPS, Si-29 solid-state MAS NMR, BET analysis, and H-2 adsorption. The hydrolysis polymerization of Si(OCH3)(4) to form the SiO2-matrix overlayers on the surface led to removal of a template ligand P(OCH3)(3), and as the result provided a cavity behind the template. Thus, a coordinatively unsaturated active Rh-monomer structure with a remaining P(OCH3)(3) ligand per Rh and the template cavity as catalytic reaction space was created in the micropores of the SiO2-matrix overlayers. The catalytic properties of the imprinted Rh monomers were examined by measuring the hydrogenation rates of nine simple alkenes (C-5-C-8 alkenes). The catalytic activity of the surface Rh monomers was promoted 2.4-13 times by the imprinting, and shape selectivity for the alkenes also appeared by the effect of template cavity, resulting in a shift of the rate-determining step and a large decrease in the activation energy and the activation entropy for alkenes with the larger shapes.
    研究論文(学術雑誌), 英語
  • In situ time-resolved energy-dispersive X-ray absorption fine structure study on the decarbonylation processes of Mo(CO)(6) entrapped in NaY and HY zeolites
    A. Yamaguchi; A. Suzuki; T. Shido; Y. Inada; K. Asakura; M. Nomura; Y. Iwasawa
    Journal of Physical Chemistry B, 106巻, 9号, 掲載ページ 2415-2422, 出版日 2002年, 査読付
    英語
  • Dispersive XAFS study on Cu and Mo species in zeolites during the catalyst preparation
    T. Shido; A. Yamaguchi; Y. Inada; K. Asakura; M. Nomura; Y. Iwasawa
    Topics in Catalysis, 18巻, 18号, 掲載ページ 53-58, 出版日 2002年, 査読付
    英語
  • Characterization of rhodium oxide nanoparticles in MCM-41 and their catalytic performances for NO-CO reactions in excess O-2
    R. Mulukutla; T. Shido; K. Asakura; T. Kogure; Y. Iwasawa
    Applied Catalysis a-General, 228巻, 1/2号, 掲載ページ 305-314, 出版日 2002年, 査読付
    英語
  • In situ energy-dispersive XAFS study of the reduction process of Cu-ZSM-5 catalysts with 1 s time-resolution
    A. Yamaguchi; Y. Inada; T. Shido; K. Asakura; M. Nomura; Y. Iwasawa
    Studies in Surface Science and Catalysis, 132巻, 掲載ページ 785-788, 出版日 2001年12月01日, The reduction processes of Cu-ZSM-5 were investigated by a time-resolved dispersive XAFS (DXAFS) technique. Two Cu-ZSM-5 samples with different Cu loadings were prepared by an ion-exchange method. In the low loading sample (84 % ion exchanged), Cu2+ cations were highly dispersed in the channel of ZSM-5, while CuO particles were formed in the high loading sample (104 % ion exchanged). The isolated Cu2+ cations were reduced to isolated Cu+ cations at 400-450 K and the Cu+ ions were reduced to Cu0 at 550-650 K. The curve fitting analysis of the DXAFS data revealed that Cu4 clusters were initially formed and then grew up to big particles. On the contrary, the CuO particles were reduced directly to Cu0 big metallic particles around 450 K.
  • Studies of the surface deuterioxyl group and adsorbed D2O on γ-Al2O3 using picosecond infrared pump probe spectroscopy
    Ken Onda; Kinuka Tanabe; Hidenori Noguchi; Akihide Wada; Takafumi Shido; Aritomo Yamaguchi; Yasuhiro Iwasawa
    Journal of Physical Chemistry B, 105巻, 46号, 掲載ページ 11456-11461, 出版日 2001年11月22日, 査読付, Picosecond infrared-infrared pump-probe experiments in the OD stretching region were carried out on dehydrated and multilayer water-adsorbed γ-Al2O3. For the dehydrated γ-Al2O3, transient bands assigned to the bleaching and hot bands of the OD stretching mode of isolated surface hydroxyl groups were observed, and the population lifetime (T1 of the vibrational excited state (v = 1) of the mode was 200 ± 10 ps at 293 K. The characteristic temperature dependence of T1 is indicative of a seven-phonon process. For the water-adsorbed γ-Al2O3, the transient bleaching and transient hot bands with a lifetime of 10-12 ps were observed by excitation of the absorption peak at 2630 cm-1. In addition to these bands, weak transient bands were observed in the low-frequency region. These results are considered evidence of the existence of isolated water molecules on the γ-Al2O3 surface. Pure dephasing is also discussed based on the bandwidth of the observed transient bands.
    研究論文(学術雑誌), 英語
  • Characterization of a highly selective hydrogen permeable silica membrane
    ST Oyama; D Lee; S Sugiyama; K Fukui; Y Iwasawa
    JOURNAL OF MATERIALS SCIENCE, KLUWER ACADEMIC PUBL, 36巻, 21号, 掲載ページ 5213-5217, 出版日 2001年11月, 査読付, The permeability properties of a new type of silica membrane for the small gas molecules CO2, CO, Ne, CH4, He, and H-2 are presented. The new membrane, denoted as Nanosil, has unusually high permeance for H-2, but also allows passage of He and to a smaller extent Ne, while excluding all other molecules. The membrane is formed by the decomposition of a silica precursor (tetraethyl orthosilicate) onto a Vycor glass substrate. Nitrogen physisorption isotherms of the Vycor glass substrate indicate that it is a microporous solid with slit-like pores of 3.6 nm diameter, that remains unchanged after the silica deposition. Atomic force microscopy (AFM) shows that the Vycor substrate is made up of rectangular plate-like elements of size 90 nm x 30 nm. Between the plates are found rectangular features of 4 nm breadth which are likely to be the pore mouths. The deposited silica forms a thin layer on top of these plates so as to erase fine structures and increase the average feature size to 110 nm x 50 nm. (C) 2001 Kluwer Academic Publishers.
    研究論文(学術雑誌), 英語
  • Atomic Force Microscopic Study on Thermal and UV-irradiative Formation and Control of Au Nano-particles on TiO2(110) from Au (PPh3)(NO3)
    FUKUI K; SUGIYAMA S; IWASAWA Y
    Phys. Chem. Chem. Phys., 3巻, 17号, 掲載ページ 3871-3877, 出版日 2001年10月02日, 査読付, Formation of Au nano-particles on TiO2(110) from a gold-phosphine complex Au(PPh3)(NO3) was studied by environment-controlled atomic force microscopy (AFM). The Au complex began to agglomerate as particles larger than 4.2 nm in height on calcination in dry air at a temperature as low as 363 K. The size of the agglomerates reduced to 3.0 nm as a result of decomposition and combustion of the ligands by further calcination at 493 K for 4 h. UV irradiation of the Au-complex-deposited sample or of the TiO2(110) substrate before deposition of the Au complex greatly reduced the size of the Au particles formed by the same calcination process to less than 1 nm, which falls in the range that has been claimed to show high catalytic activities for low-temperature CO oxidation. This may be a new preparation method that regulates the size of Au particles on flat oxide substrates.
  • Atom-Resolved Structures of TiO2(001) Surface by Scanning Tunneling Microscopy
    K. I. Fukui; R. Tero; Y. Iwasawa
    Jpn. J. Appl. Phys., 40巻, 6B号, 掲載ページ 4331-4333, 出版日 2001年06月, 査読付, Surface structures of a TiO2(001) surface are examined in atomic scale by scanning tunneling microscopy (STM). Among two ordered phases which depend on annealing temperature as reported from a low energy electron diffraction (LEED) study, an atomic-scale image of the higher temperature phase, which shows a unique surface reactivity, was successfully visualized. The surface consisted of crossed rows along the [1Ī0] direction and the [Ī10] direction. Each row had a bleacher-like structure which formed stairs at both sides with an average slope identical to the {114} face. An atom-resolved STM image showed that each narrow terrace of the stairs is covered with a unit of three bright spots which are ordered in line perpendicular to the step and arranged with a constant separation of 0.65 nm. It was revealed that the STM image is not consistent with the previously proposed {114}-faceted model.
    研究論文(学術雑誌), 英語
  • Behavior of pyridine on a TiO2(110) surface studied by Density Functional theory
    Takehiko Sasaki; Ken ichi Fukui; Yasuhiro Iwasawa
    Studies in Surface Science and Catalysis, 132巻, 掲載ページ 749-752, 出版日 2001年01月, 査読付, Density Functional calculations were performed to explain the behavior of pyridine adsorbed on a TiO2(110) surface observed by STM and to gain a detailed picture for the interaction between pyridine and the surface. Adsorption energies for various conformations of pyridine interacting with defect-free TiO2(110) surface were calculated. The most stable adsorption state for pyridine is the upright conformation with the 2, 6-hydrogen atoms interacting with bridging oxygen atoms via a hydrogen-bond like interaction. The flat-lying pyridine was found with a low surface diffusion barrier along the [001] direction, that corresponds to a movable species observed by STM. The effect of defect sites were also examined and the 4-fold coordinated Ti atom obtained by the removal of two adjacent bridging oxygen atoms was found to be a stronger Lewis acid site than the 5-fold coordinated Ti atom.
    研究論文(学術雑誌), 英語
  • Atomic force microscope studies on condensation of plasmid DNA with functionalized fullerenes
    H Isobe; S Sugiyama; K Fukui; Y Iwasawa; E Nakamura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, WILEY-V C H VERLAG GMBH, 40巻, 18号, 掲載ページ 3364-+, 出版日 2001年, 査読付
    研究論文(学術雑誌), 英語
  • In situ STM study of surface catalytic reactions on TiO2(110) relevant to catalyst design
    Y Iwasawa; H Onishi; K Fukui
    TOPICS IN CATALYSIS, BALTZER SCI PUBL BV, 14巻, 1-4号, 掲載ページ 163-172, 出版日 2001年, 査読付, This paper briefly summarizes our recent work on the characterization of atom-resolved surface images of TiO2(110) composed of Ti atoms, O atoms, defects and hydroxyls by scanning tunneling microscopy (STM) and non-contact atomic force microscopy (NC-AFM). The paper also presents new kinetic aspects in the catalytic dehydration and dehydrogenation of formic acid on the characterized surface. Switchover of the reaction path from the dehydration to the dehydrogenation occurred by the presence of formic acid undetectable at the surface, where acidic formic acid molecules opened the basic catalysis. In situ STM observation revealed that the dehydrogenation reaction at 400-450 K was strongly suppressed in the vicinity of single-atom height steps. The suppressive effect of step ranged over 2.4 nm into terrace. It is likely that the catalyst with flat surfaces larger than 5 nm is active for the dehydrogenation of formic acid.
    研究論文(学術雑誌), 英語
  • Anisotropic ordering of Mo species deposited on TiO2(110) characterized by polarization-dependent total reflection fluorescence EXAFS (PTRF-EXAFS)
    W. Chun; K. Asakura; Y. Iwasawa
    Catalysis Today, 66巻, 1号, 掲載ページ 97-103, 出版日 2001年, 査読付
    英語
  • Time-resolved energy-dispersive XAFS study on the reduction process of Cu-ZSM-5 catalysts
    A. Yamaguchi; Y. Inada; T. Shido; K. Asakura; M. Nomura; Y. Iwasawa
    Journal of Synchrotron Radiation, 8巻, 8号, 掲載ページ 654-656, 出版日 2001年, 査読付
    英語
  • Three-dimensional analysis of the local structure of Cu on TiO2(110) by in situ polarization-dependent total-reflection fluorescence XAFS
    Y. Tanizawa; W. J. Chun; T. Shido; K. Asakura; Y. Iwasawa
    Journal of Synchrotron Radiation, 8巻, 8号, 掲載ページ 508-510, 出版日 2001年, 査読付
    英語
  • Temporal analysis of products (TAP) study of the adsorption of CO, O-2, and CO2 on a Au/Ti(OH)(4)* catalyst
    M. Olea; M. Kunitake; T. Shido; K. Asakura; Y. Iwasawa
    Bulletin of the Chemical Society of Japan, 74巻, 2号, 掲載ページ 255-265, 出版日 2001年, 査読付
    英語
  • Nanoparticles of RhOx in the MCM-41: A novel catalyst for NO-CO reaction in excess O-2
    R. Mulukutla; T. Shido; K. Asakura; Y. Iwasawa
    Scripta Materialia, 44巻, 8/9号, 掲載ページ 1695-1698, 出版日 2001年, 査読付
    英語
  • In situ time-resolved energy-dispersive XAFS study on the reduction processes of Cu-ZSM-5 catalysts
    A. Yamaguchi; T. Shido; Y. Inada; T. Kogure; K. Asakura; M. Nomura; Y. Iwasawa
    Bulletin of the Chemical Society of Japan, 74巻, 5号, 掲載ページ 801-808, 出版日 2001年, 査読付
    英語
  • Energy-dispersive XAFS study on the decarbonylation process of Mo(CO)(6) in NaY zeolite
    A. Yamaguchi; A. Suzuki; T. Shido; Y. Inada; K. Asakura; M. Nomura; Y. Iwasawa
    Catalysis Letters, 71巻, 3/4号, 掲載ページ 203-208, 出版日 2001年, 査読付
    英語
  • DXAFS study on the decarbonylation process of Mo(CO)(6) in NaY supercages
    T. Shido; A. Yamaguchi; A. Suzuki; Y. Inada; K. Asakura; M. Nomura; Y. Iwasawa
    Journal of Synchrotron Radiation, 8巻, 8号, 掲載ページ 628-630, 出版日 2001年, 査読付
    英語
  • Development of an in situ polarization-dependent total-reflection fluorescence XAFS measurement system
    W. J. Chun; Y. Tanizawa; T. Shido; Y. Iwasawa; M. Nomura; K. Asakura
    Journal of Synchrotron Radiation, 8巻, 8号, 掲載ページ 168-172, 出版日 2001年, 査読付
    英語
  • Development of an X-ray photoemission electron microscopy system with multi-probes, and its application to surface imaging at static and dynamic states
    S Takakusagi; M Kato; Y Sakai; K Fukui; K Asakura; Y Iwasawa
    JOURNAL OF MICROSCOPY-OXFORD, BLACKWELL SCIENCE LTD, 200巻, 3号, 掲載ページ 240-250, 出版日 2000年12月, 査読付, We have developed a new X-ray photoemission electron microscopy system combined with low energy electron microscopy, photoemission electron microscopy, mirror electron microscopy (MEM), secondary electron emission microscopy (SEEM) and Auger electron emission microscopy, which provides multi-angle information on the distribution and change of element, chemical state, structure, etc. at solid surfaces under the working conditions such as high temperature and gas atmosphere. The performance of each microscopical method was examined and typical images are presented. The dynamic behaviour of fabricated surfaces has been imaged in real time by SEEM and MEM.
    研究論文(学術雑誌), 英語
  • Performance and characterization of a new crystalline SbRe2O6 catalyst for selective oxidation of methanol to methylal
    Youzhu Yuan; Haichao Liu; Hideo Imoto; Takafumi Shido; Yasuhiro Iwasawa
    Journal of Catalysis, Academic Press Inc., 195巻, 1号, 掲載ページ 51-61, 出版日 2000年10月01日, SbRe2O6, Sb4Re2O13, and SbOReO4·2H2O, and a number of supported Re catalysts were used as catalysts for the selective oxidation of methanol to methylal (3CH3OH + 1/2O2 → CH2(OCH3)2 + 2H2O). At 573 K, a high selectivity of 92.5% was obtained on the novel crystalline catalyst SbRe2O6. No methylal formation or negligible activity was observed with the other catalysts. No structural change in the bulk and surface of the SbRe2O6 catalysts occurred after methanol oxidation <
    600 K. The reaction rate increased with increases in methanol partial pressure, while the selectivity to methylal was independent of methanol partial pressure, as well as O2 partial pressure (<
    10 mol %). There were two kinds of active lattice oxygen species in TPD experiments on SbRe2O6, which were responsible for the methylal formation. The high performance of SbRe2O6 for the selective synthesis of methylal from methanol was attributed to the Re-oxide species stabilized by the specific connection with Sb oxides at the crystal surface.
    研究論文(学術雑誌), 英語
  • Morphology of crystalline alpha-MoO3 thin films spin-coated on Si (100)
    EM Gaigneaux; K Fukui; Y Iwasawa
    THIN SOLID FILMS, ELSEVIER SCIENCE SA, 374巻, 1号, 掲載ページ 49-58, 出版日 2000年10月, 査読付, Thin films of crystalline alpha -MoO3 with thicknesses between 35 and 150 nm were prepared on Si (100) wafers by spin-coating of peroxo-polymolybdic solutions. Variations of the morphology of the films with spin-coating conditions and thermal treatments applied afterwards were investigated by means of confocal laser Raman spectroscopy, X-ray diffraction and scanning electron microscopy. Thickness and uniformity of the films, and size, anisotropy and orientation of alpha -MoO3 crystals with respect to the Si substrate can be tuned by adequately adjusting the concentration of the precursor solution, the solvent, and the spin-rate during spin-coating. Size, anisotropy and orientation of crystals are nevertheless interconnected and cannot be tuned independently. The three variables are themselves dictated by the thickness of the films. However, the choice of the solvent used for the precursor solution seems to provide some additional flexibility in the tuning of the morphology of alpha -MoO3 crystals, while the minimum thickness required to obtain stable crystalline alpha -MoO3 films under the conditions we used for calcination is estimated to be 35 nm. (C) 2000 Elsevier Science S.A. All rights reserved.
    研究論文(学術雑誌), 英語
  • Characterization and catalytic performance of designed surfaces
    T Kawaguchi; N Ichikuni; A Yamaguchi; T Shido; H Onishi; K Fukui; Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, ELSEVIER SCIENCE BV, 158巻, 1号, 掲載ページ 67-83, 出版日 2000年09月, 査読付, This paper attempts to extend our previous studies on the chemical design and characterization of metal atoms/ensembles attached at oxide surfaces and on the in-situ observation of adsorbed molecules on oxide model surfaces. This paper presents a new aspect of catalysis at designed Co/TiO2, Co/Al2O3, Co/SiO2 surfaces characterized by FT-IR and EXAFS, namely "Surface catalytic reactions assisted by gas phase molecules", in which the amount and reactivity of reaction intermediate can be promoted and the structure of reaction intermediate can also be controlled by gas phase molecules undetectable at the surface. This paper also reports the application of one-atomic-layer TiO2 on SiO2 as a unique support for an Mo dimer complex to prepare a supported Mo-dimer catalyst. Finally, a new aspect of regulation of a catalytic reaction by monoatomic-height steps on TiO2(110) relevant to oxide-layer catalysis characterized by STM is also reported. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Novel selective etching reaction of carbon atoms on molybdenum carbide by oxygen at room temperature visualized by scanning tunneling microscopy
    K Fukui; RL Lo; S Otani; Y Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 325巻, 1-3号, 掲載ページ 275-280, 出版日 2000年07月, 査読付, We have succeeded in imaging each surface carbon atom on Mo2C(0001) by scanning tunneling microscopy operated at low tunneling resistances and found a novel selective etching reaction of the surface carbon atoms by oxygen gas exposed at room temperature. On a carbon terminated Mo2C(0001) surface with both (root 3 x root 3)R30 degrees-honeycomb and c(2 x 4)-zigzag row structures, the etching reaction selectively occurred on the c(2 x 4)-zigzag row structure, leading to exposure of the underlying (1 x 1) Mo layer. Energetically excited oxygen formed on the surface is probably responsible for this new reaction event. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Structure and catalytic performance of Mo dimer oxy-carbide species in NaY supercages
    T Shido; KAB Asakura; Y Noguchi; Y Iwasawa
    APPLIED CATALYSIS A-GENERAL, ELSEVIER SCIENCE BV, 194巻, 掲載ページ 365-374, 出版日 2000年03月, 査読付, Mo dimer oxy-carbide species were synthesized in the supercage of NaY zeolite by adsorption of Mo(CO)(6) vapor at saturation, followed by thermal decomposition in vacuum. TPD, EXAFS,: XPS and XRF data revealed that a Mo dimer was attached in a supercage by a saturation adsorption-thermal decomposition at 573 K and that up to four Mo dimers in a supercage were stepwisely formed without aggregation after four cycles, The Mo dimer oxy-carbide species exhibited a unique methanol decomposition reaction to produce CH4, CO2, and H-2 in an approximate ratio of 1 : 1 : 2. This reaction was characteristic of the Mo dimer oxy-carbide species and was never observed fbr other Mo species such as oxidized and reduced Mo species in NaY supercages. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Hydrogen adatoms on TiO2(110)-(1 x 1) characterized by scanning tunneling microscopy and electron stimulated desorption
    S Suzuki; K Fukui; H Onishi; Y Iwasawa
    PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 84巻, 10号, 掲載ページ 2156-2159, 出版日 2000年03月, 査読付, Hydrogen atoms adsorbed on TiO2(110)-(1 x 1) surfaces have been characterized by scanning tunneling microscopy (STM) combined with electron stimulated desorption (ESD) technique. Certain amounts of H atoms are unexpectedly found on the TiO2 surfaces annealed at 900 K. Two forms of adsorption were discriminated in STM images from the different sensitivity to ESD and tentatively assigned to hydroxyl-type (O-H) and hydride-type (Ti-H) species.
    研究論文(学術雑誌), 英語
  • CO adsorption on c(2 × 2)-Li/Cu(100): interaction between CO and Li on unreconstructed Cu(100) surfaces
    R. Tero; T. Sasaki; Y. Iwasawa
    Surface Science, 448巻, 2-3号, 掲載ページ 250-260, 出版日 2000年03月, 査読付, CO adsorption on the Cu(100)-c(2 × 2)-Li surface was studied using high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD) to examine the interaction between CO and Li and the properties of an Li-CO complex on unreconstructed Cu(100) surfaces. The v(Cu-Li) peak appeared at 310 cm -1 for the c(2 × 2)-Li surface with unreconstructed Cu substrate, in addition to a peak at 710 cm -1 which was not observed on the Cu(100)-(2 × 1)-Li surface with a missing-row structure. C - O stretching modes appeared at 1200, 1860 and 2040 cm -1 when the c(2 × 2)-Li surface of 0.3 ML Li coverage was exposed to CO at 130 K. It is considered that these correspond to the Li-CO complex and CO molecules adsorbed at bridge and atop sites respectively. The 1200 cm -1 peak decreased in intensity when the surface was almost saturated with CO. It was proved from the result of the experiment using 13 C 18 O that the Li-CO complex collapses and changes to the CO adsorbed at atop and bridge sites. The v(C - O) of 1200 cm -1 observed in the present study comes in the category which is the lowest among systems of other alkali metals, whereas the CO desorption temperature rises only by 15 K.
    研究論文(学術雑誌), 英語
  • Low-energy electron diffraction analysis of the buried heteroatom type Pd(100)-p(2 x 2)-p4g-Al surface
    H Onishi; H Sakama; T Aruga; A Kawazu; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 444巻, 1-3号, 掲載ページ 7-17, 出版日 2000年01月, 査読付, The structure of the p(2 x 2)-p4g ordered bimetallic phase formed on aluminum-deposited Pd(100) is determined by dynamical low-energy electron diffraction analysis. The best-fitted structure among 29 different model types examined consists of the Pd top layer clock-reconstructed to the hard sphere limit, and a buckled c(2 x 2)-PdAl second layer. The buried-heteroatom scheme, a new mechanism of in-plane atom movements, is proposed to interpret the yielded structure; Al atoms migrate beneath the topmost Pd layer and replace half of the second-layer Pd atoms to demand optimum coordination. Pd-Al bonding interaction forces top-layer Pd atoms to move systematically towards the buried Al. Half of the fourfold hollows of top layer are opened and the other half are deformed as a result of the movements. The top and second layers of the reconstructed surface can be regarded as a surface-limited compound of Pd3Al composition supported on the Pd(100) substrate, because a reduced d-state overlap between the top two layers and the Pd substrate is expected. (C) 2000 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Time-resolved DXAFS study on the reduction processes of Cu cations in ZSM-5
    A. Yamaguchi; T. Shido; Y. Inada; T. Kogure; K. Asakura; M. Nomura; Y. Iwasawa
    Catalysis Letters, 68巻, 3/4号, 掲載ページ 139-145, 出版日 2000年, 査読付
    英語
  • Surface catalytic reactions assisted by gas phase molecules: activation of reaction intermediates
    T. Shido; A. Yamaguchi; K. Asakura; Y. Iwasawa
    Journal of Molecular Catalysis a-Chemical, 163巻, 1/2号, 掲載ページ 67-77, 出版日 2000年, 査読付
    英語
  • Preparation, characterization, and catalytic performance of bismuth-aluminum binary-oxide layers and clusters on an Al2O3 surface
    T. Shido; G. Okita; K. Asakura; Y. Iwasawa
    Journal of Physical Chemistry B, 104巻, 51号, 掲載ページ 12263-12268, 出版日 2000年, 査読付
    英語
  • Polarization-dependent total-reflection fluorescence EXAFS study about active structures on single crystal oxides as model catalyst surfaces
    K. Asakura; W. Chun; Y. Iwasawa
    Topics in Catalysis, 10巻, 10号, 掲載ページ 209-219, 出版日 2000年, 査読付
    英語
  • Characterization and selective oxidation catalysis of modified Pt particles on SbO(x)
    T. Inoue; S. T. Oyama; H. Imoto; K. Asakura; Y. Iwasawa
    Applied Catalysis a-General, 191巻, 1/2号, 掲載ページ 131-140, 出版日 2000年, 査読付
    英語
  • Characterization and kinetic studies on the highly active ammoxidation catalyst MoVNbTeOx
    K. Asakura; K. Nakatani; T. Kubota; Y. Iwasawa
    Journal of Catalysis, 194巻, 2号, 掲載ページ 309-317, 出版日 2000年, 査読付
    英語
  • Real-time observation of the dehydrogenation processes of methanol on clean Ru(001) and Ru(001)-p(2x2)-O surfaces by a temperature-programmed electron-stimulated desorption ion angular distribution/time-of-flight system
    T Sasaki; Y Itai; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 443巻, 1-2号, 掲載ページ 44-56, 出版日 1999年12月, 査読付, Decomposition processes of methanol on clean and oxygen-precovered Ru(001) surfaces have been visualized in real time with a temperature-programmed (TP) electron-stimulated desorption ion angular distribution (ESDIAD)/time-of-flight (TOF) system. The mass of desorbed ions during temperature-programmed surface processes was identified by TOF measurements. In the case of methanol (CH3OD) adsorption on Ru(001)-p(2 x 2)-O, a halo pattern of H+ from the methyl group of methoxy species was observed at 100-200 K, followed by a broad pattern from the methyl group at 230-250 K and by a near-center pattern from O+ ions originating from adsorbed CO above 300 K. The halo pattern is attributed to a perpendicular conformation of the C-O bond axis of the methoxy species, leading to oh-normal C-H bond scission. On the other hand, methanol adsorbed on clean Ru(001) did not give any halo pattern but a broad pattern was observed along the surface normal, indicating that the conformation of the methoxy species is not ordered on the clean surface. Comparison between the ESDIAD images of the oxygen-precovered surface and the clean surface suggests that the precovered oxygen adatoms induce ordering of the methoxy species. Real-time ESDIAD measurements revealed that the oxygen atoms at the Ru(001)-p(2 x 2)-O surface have a positive effect on selective dehydrogenation of the methoxy species to CO+H-2 and a blocking effect on C-O bond breaking of the methoxy species. (C) 1999 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Observation of a new ridge structure along steps on the MgO(100) surface by non-contact atomic force microscopy
    K Fukui; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 441巻, 2-3号, 掲載ページ 529-541, 出版日 1999年11月, 査読付, The surface topography of an MgO(100) surface after annealing at high temperatures followed by Ar+-ion sputtering was examined by non-contact atomic force microscopy (NC-AFM) and X- ray photoelectron spectroscopy (XPS). The calcium impurity (210 ppm in the bulk) was segregated to the surface by annealing above 1200 K and agglomerated as CaOx particles at monolayer or bilayer steps along the [011] direction after annealing at similar to 1600 Ii for 1 h. The step was always accompanied by a band-like structure with a protrusive line running parallel to the step edge with a separation longer than 5 nm. The structure was stable on the surface after removal of the CaOx particles by Ar+-ion sputtering at similar to 1600 K, but eventually disappeared after repeated Ar+-ion sputtering and annealing cycles. This unusual ridge structure is probably due to long-range reconstruction induced by segregated calcium of less than 3% coverage. The calcium-induced structure on MgO(100) is also discussed in relation to the chemical reactivity for methane activation. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • A new aspect of catalysis at designed surfaces: the role of gas phase molecules in surface catalytic reactions
    A Yamaguchi; K Asakura; Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, ELSEVIER SCIENCE BV, 146巻, 1-2号, 掲載ページ 65-76, 出版日 1999年10月, 査読付, This paper attempts to extend our previous studies on the chemical design and characterization of attached metal atoms at surfaces of a Nb/SiO(2) catalysts prepared by using a suitable metal-complex precursor and the elucidation of catalytic reaction mechanisms in a molecular scale. The paper also reports a new aspect of catalysis on a Co/Al(2)O(3) catalyst which includes surface catalytic reactions assisted by gas phase molecules undetectable at the surface. On the basis of this concept, one may design new catalytic systems where the reaction intermediates, stable and unreactive in vacuum, can be activated or controlled by gas phase molecules in situ under catalytic reaction conditions. (C) 1999 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Structure and dynamic behaviour of atoms and molecules at catalyst model surfaces
    S Suzuki; K Fukui; H Onishi; Y Iwasawa
    SURFACE AND INTERFACE ANALYSIS, JOHN WILEY & SONS LTD, 28巻, 1号, 掲載ページ 135-141, 出版日 1999年08月, 査読付, This paper attempts to review our recent work dealing with TiO2(110)-(1 x 1) single crystals and to present new scanning tunnelling microscopy (STM) images of the adsorbed state and condensation reaction of pyridine at 350 K. Combined efforts of STM and non-contact atomic force microscopy (AFM) provided the detail of atom-resolved pictures of TiO2(110) surfaces. In situ STM observation documented the weak and mobile adsorption and the site-specific adsorption of pyridine, and the unexpected condensation of pyridine physisorbed on the surface in the presence of pyridine ambient at 350 K, Copyright (C) 1999 John Whey & Sons, Ltd.
    研究論文(学術雑誌), 英語
  • C-terminated reconstruction and C-chain structure on Mo2C(0001) surface studied by low energy electron diffraction and scanning tunneling microscopy
    RL Lo; K Fukui; S Otani; ST Oyama; Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 38巻, 6B号, 掲載ページ 3813-3815, 出版日 1999年06月, 査読付, The structure of an alpha-Mo2C(0001) surface varies depending on the annealing temperature. At least three phases are observed by low energy electron diffraction (LEED). A well-ordered (root 3 x root 3)R30 degrees structure was observed on alpha-Mo2C(0001) at annealing temperatures below 960 K, which was imaged as a honeycomb structure by scanning tunneling microscopy (STM). A model was proposed for the C-terminated structure where C atoms are located on the threefold hollow sites of a Mo layer, and each carbon atom is observed as a depression of the honeycomb structure by STM. An increase in carbon coverage on the surface transformed the (root 3 x root 3)R30 degrees structure to a c(2x4) structure where zigzag rows running parallel tb each other were observed by STM.
    研究論文(学術雑誌), 英語
  • Space-correlation analysis of formate ions adsorbed on TiO2(110)
    H Onishi; K Fukui; Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 38巻, 6B号, 掲載ページ 3830-3832, 出版日 1999年06月, 査読付, The ability of the space-correlation analysis of scanning tunneling microscope (STM) image to deduct short-rang order is demonstrated on a dilute formate ion (HCOO-) overlayer prepared on a TiO2(110) surface. A c(4 x 2) local older of formate ions is found at 22% of the saturation coverage, whereas the known (2 x 1) long-range order develops over the surface of the complete saturation coverage. The c(4 x 2) order is interpreted as a structure where electrostatic repulsion between formate ions is minimized. The c(4 x 2) order does not develop on the surface when formate coverage is increased; probably due to the formation of formate-hydroxyl-formate-chains on the surface.
    研究論文(学術雑誌), 英語
  • CO-induced destruction of Cu(100)-(2 × 1)Li studied by HREELS
    T. Sasaki; T. Sasaki; R. Tero; T. Sueyoshi; Y. Iwasawa
    Surface Science, 427-428巻, 1-3号, 掲載ページ 408-413, 出版日 1999年06月, 査読付, CO adsorption on Cu(100)-(2 × 1)Li was studied by means of LEED, TPD and HREELS. The (2 × 1) structure is known as a 'missing-row structure', where one of every two [001] copper atomic rows is replaced by a Li atomic row. From LEED observations, it was found that the (2 × 1) subspots of Cu(100)-(2 × 1)Li were weakened by the post-adsorption of CO at 120 K and disappeared after annealing to 200 K. Without CO, the (2 × 1) structure is stable up to 340 K. Vibrational spectra were obtained for these processes by HREELS. Li/Cu(100) gave a v(Li-Cu) peak at 290 cm -1 corresponding to the (2 × 1) structure. After CO adsorption at 100 K with the coverage of 0.21 ML, a C-O stretching frequency [v(C-O)] appeared at 2045 cm -1 , and v(Cu-CO) appeared at 340 cm -1 . Upon annealing to 200 K, a new peak appeared at 1200 cm -1 in correlation with the disappearance of the (2 × 1) order. In the case of CO adsorption on Cu(100)-c(2 × 2)Li with Li atoms located at fourfold hollow sites and without reconstruction of the Cu substrate, the 1200 cm -1 peak was found at 100 K. These results suggest that the formation of the species with v(C-O) of 1200 cm -1 induces destruction of the (2 × 1) order.
    研究論文(学術雑誌), 英語
  • Surface characterization of alpha-Mo2C (0001)
    TP St Clair; ST Oyama; DF Cox; S Otani; Y Ishizawa; RL Lo; K Fukui; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 426巻, 2号, 掲載ページ 187-198, 出版日 1999年05月, 査読付, The (0001) surface of alpha-Mo2C prepared by Ar ion bombardment and annealing was characterized using X-ray photoelectron spectroscopy and low energy electron diffraction (LEED). An ion-bombarded surface annealed to 1000 K exhibits an Mo/C ratio of 2.2, characteristic of an Mo-terminated surface. The Mo-terminated surface exhibits a complex, but predominantly '(1x1)' hexagonal LEED pattern on a diffuse background. This pattern is composed of at least three periodicities: a (1 x 1) hexagonal periodicity, a faint root 3 x root 3 R30 degrees periodicity, and spots of a third, unidentified periodicity. A bulk-terminated, unrelaxed surface is expected to exhibit a (1x1) orthorhombic (i.e. rectangular) periodicity. The observed hexagonal periodicity is explained by LEED simulations as arising from the extinction of certain orthorhombic spots. An ion-bombarded surface annealed to 1500 K exhibits an Mo/C ratio of 1.8-1.9 and a (4 x 4) hexagonal LEED periodicity. The decrease in Mo/C ratio is consistent with the change from an Mo to a C termination. The (4 x 4) hexagonal periodicity is equivalent to three domains of C termination with (2 x 1) orthorhombic symmetry rotationally misaligned by 120 degrees. The presence of rotationally misaligned domains is confirmed by scanning tunneling microscopy. Whereas changes in both the composition and periodicity are associated with the transformation from an Mo to a C-terminated surface, the details of the associated surface structures are not known. (C) 1999 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • The condensation reaction of pyridine on TiO2(110): STM observation in the presence of the reactant atmosphere
    S Suzuki; H Onishi; K Fukui; Y Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 304巻, 3-4号, 掲載ページ 225-230, 出版日 1999年04月, 査読付, The thermally activated reaction of pyridine was studied by STM on a TiO2(110)-(1 x 1) surface. The unexpected condensation of weakly physisorbed pyridine was found. The formation and growth of the product particles were monitored in-situ on the surface heated at reaction temperatures (300-400 K) in the presence of pyridine atmosphere. A physisorbed pyridine molecule was activated at 350 K to form an intermediate, probably a partially dehydrogenated or chemisorbed state of pyridine, The intermediates aggregated into larger particles of nm size. A gas-phase or physisorbed pyridine molecule is also directly involved in the particle growth reaction. (C) 1999 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Imaging of atomic-scale structure of oxide surfaces and adsorbed molecules by noncontact atomic force microscopy
    Ken-Ichi Fukui; Hiroshi Onishi; Yasuhiro Iwasawa
    Applied Surface Science, Elsevier, 140巻, 3-4号, 掲載ページ 259-264, 出版日 1999年, 査読付, Atom-resolved images of a TiO2(110)-(1×1) surface and individual formate and acetate ions adsorbed on the surface were obtained by noncontact atomic force microscopy (NC-AFM) in ultrahigh vacuum. In contrast to previous scanning tunneling microscopic studies imaging five-fold coordinated Ti atoms, outermost atoms of bridge-bound oxygen ridges of the surface were resolved as protruding rows by NC-AFM. High-resolution image of the surface revealed that the bridging oxygen atoms on terraces ordered in a (1×1) periodicity. Randomly distributed point and multiple defects of oxygen atoms were also imaged as dark spots. The (2×1) overlayer of formate and acetate ions were resolved as ordered bright spots. Dispersed formate ions at a low coverage were also observed as bright spots between the bridging oxygen ridges along the [001] direction.
    研究論文(学術雑誌), 英語
  • Reflection-absorption infrared spectroscopic study on a CuOX/SiO2 model catalyst prepared by spin-coating on a SiO2/W/Si(100) buried metal substrate
    K Fukui; Oshima, I; H Oosterbeek; Y Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 299巻, 2号, 掲載ページ 158-164, 出版日 1999年01月, 査読付, CuOx particles were deposited by spin-coating on a SiO2(50 nm)/W(70 nm)/Si(100) buried metal substrate using 2-propanol solution of a Cu precursor followed by oxidation. The CuOx/SiO2/W/Si model catalyst was used to detect vibrational modes of submonolayer adsorbates by reflection-absorption infrared spectroscopy (RAIRS). During methanol reaction on CuOx/SiO2/W/Si, RAIR spectra showed that methoxy species was formed on CuOx particles and spilt over to the SiO2 substrate, replacing hydroxyl species. (C) 1999 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • The selective adsorption and kinetic behaviour of molecules on TiO2(110) observed by STM and NC-AFM
    Y Iwasawa; H Onishi; K Fukui; S Suzuki; T Sasaki
    FARADAY DISCUSSIONS, ROYAL SOC CHEMISTRY, 114巻, 掲載ページ 259-266, 出版日 1999年, 査読付, In the present paper we report a kinetic aspect of molecules on terraces and steps of a TiO2(110)-(1x1) surface as observed by scanning probe microscopy, which may be relevant to oxide catalysis. When the TiO2 surface, heated at 400-450 K, was exposed to a formic acid ambient of 1-2x10(-6) Pa, small particles were formed on terraces. Post-reaction STM observation revealed that the particle formation was strongly suppressed in the vicinity of single-atom height steps. The suppressive effect of the steps ranged 2.4 nm into the terrace. Formate ions (a possible reaction intermediate) were imaged in-situ during formic acid exposure at the reaction temperature. The local density of the formates and hence the product distribution, which were very low near the steps, were simulated by a model. The particles produced were suggested to be carbonates, CO32- on the bridging oxygen atoms of the TiO2(110) surface.
    研究論文(学術雑誌), 英語
  • Study of gold species in iron-oxide-supported gold catalysts derived from gold-phosphine complex Au(PPh3)(NO3) and As-precipitated wet Fe(OH)(3)
    AP Kozlova; AI Kozlov; S Sugiyama; Y Matsui; K Asakura; Y Iwasawa
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC ELSEVIER SCIENCE, 181巻, 1号, 掲載ページ 37-48, 出版日 1999年01月, 査読付, Iron-oxide-supported gold catalysts were prepared by supporting a Au phosphine complex Au(PPh3)(NO3) on as-precipitated wet iron hydroxide Fe(OH)(3)*, followed by temperature-programmed calcination. The Au/Fe(OH); catalysts calcined at the temperatures 573-773 K showed extremely high catalytic performance for CO oxidation at temperatures as low as 203-253 K. Interaction of the Au(PPh3)(NO3) gold precursor with the Fe(OH)(3)* upon supporting, transformation of the precursor during the heat treatments, and state of the gold in the catalysts were studied by FT-IR, XRD, TEM, XPS, and EXAFS. The gold precursor dissociated on the Fe(OH)(3)* surface to produce [Au(PPh3)](+) species which partially decomposed at 473 K and was transformed to small gold metallic particles with coordination numbers of 7.4-8.0 for Au-Au bond at calcination temperatures greater than or equal to 573 K. In contrast, decomposition of the gold complex over crystalline Fe2O3* resulted in large gold particles. The Au/Fe2O3* sample was inactive at 203-253 K and exhibited very low activity for CO oxidation at room temperature. The efficiency of the as-precipitated wet Fe(OH)(3)* as a support is explained in terms of a higher stability of [Au(PPh3)](+) on the Fe(OH)(3)* as compared to the Fe2O3* due to more effective interaction of the Au species with OH groups and defects of the amorphous Fe(OH)(3)* surface. The results demonstrate the importance of support-metal precursor interactions, both upon supporting and during calcination, in the formation of highly active catalysts with small Au particles for low-temperature CO oxidation. (C) 1999 Academic Press.
    研究論文(学術雑誌), 英語
  • X-ray photoemission electron microscopy (XPEEM) as a new promising tool for the real-time chemical imaging of active surfaces
    Y. Yamaguchi; S. Takakusagi; Y. Sakai; M. Kato; K. Asakura; Y. Iwasawa
    Journal of Molecular Catalysis a-Chemical, 141巻, 1/3号, 掲載ページ 129-137, 出版日 1999年, 査読付
    英語
  • Structure and catalytic combustion activity of atomically dispersed Pt species at MgO surface
    K. Asakura; H. Nagahiro; N. Ichikuni; Y. Iwasawa
    Applied Catalysis a-General, 188巻, 1/2号, 掲載ページ 313-324, 出版日 1999年, 査読付
    英語
  • Active oxygen species and mechanism for low-temperature CO oxidation reaction on a TiO2-supported Au catalyst prepared from Au(PPh3)(NO3) and As-precipitated titanium hydroxide
    H. Liu; A. I. Kozlov; A. P. Kozlova; T. Shido; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 185巻, 2号, 掲載ページ 252-264, 出版日 1999年, 査読付
    英語
  • Zeolite-encapsulated vanadium picolinate peroxo complexes active for catalytic hydrocarbon oxidations
    A. Kozlov; A. Kozlova; K. Asakura; Y. Iwasawa
    Journal of Molecular Catalysis a-Chemical, 137巻, 1/3号, 掲載ページ 223-237, 出版日 1999年, 査読付
    英語
  • XAFS study on the structure of Mo species in NaY zeolite derived from Mo(CO)(6)
    K. Asakura; Y. Noguchi; Y. Iwasawa
    Japanese Journal of Applied Physics Part 1-Regular Papers Short Notes & Review Papers, 38巻, 38号, 掲載ページ 85-86, 出版日 1999年, 査読付
    英語
  • Synthesis and characterization of rhodium oxide nanoparticles in mesoporous MCM-41
    R. S. Mulukutla; K. Asakura; T. Kogure; S. Namba; Y. Iwasawa
    Physical Chemistry Chemical Physics, 1巻, 8号, 掲載ページ 2027-2032, 出版日 1999年, 査読付
    英語
  • Stepwise synthesis and structure analysis of Mo dimers in NaY zeolite
    K. Asakura; Y. Noguchi; Y. Iwasawa
    Journal of Physical Chemistry B, 103巻, 7号, 掲載ページ 1051-1058, 出版日 1999年, 査読付
    英語
  • Pt L-3-edge XANES studies about the hydrogen adsorption on small Pt particles
    K. Asakura; T. Kubota; W. J. Chun; Y. Iwasawa; K. Ohtani; T. Fujikawa
    Journal of Synchrotron Radiation, 6巻, 6号, 掲載ページ 439-441, 出版日 1999年, 査読付
    英語
  • Pd L-3-edge XANES spectra of supported Pd particles induced by the adsorption and the absorption of hydrogen
    T. Kubota; Y. Kitajima; K. Asakura; Y. Iwasawa
    Bulletin of the Chemical Society of Japan, 72巻, 4号, 掲載ページ 673-681, 出版日 1999年, 査読付
    英語
  • Characterization of CO- and H-2-adsorbed Au6Pt-phosphine clusters supported on SiO2 by EXAFS, TPD, and FTIR
    Y. Z. Yuan; K. Asakura; H. L. Wan; K. Tsai; Y. Iwasawa
    Bulletin of the Chemical Society of Japan, 72巻, 12号, 掲載ページ 2643-2653, 出版日 1999年, 査読付
    英語
  • Anisotropic arrangement of Mo species highly dispersed on TiO2(110) surface demonstrated by polarization dependent total reflection fluorescence EXAFS
    K. Asakura; W. J. Chun; Y. Iwasawa
    Japanese Journal of Applied Physics Part 1-Regular Papers Short Notes & Review Papers, 38巻, 38号, 掲載ページ 40-43, 出版日 1999年, 査読付
    英語
  • Development of a temperature-programmed electron-stimulated desorption ion angular distribution time-of-flight system for real-time observation of surface processes and its application to adsorbed layers on Ru(001)
    T Sasaki; Y Iwasawa
    REVIEW OF SCIENTIFIC INSTRUMENTS, AMER INST PHYSICS, 69巻, 10号, 掲載ページ 3666-3673, 出版日 1998年10月, 査読付, A temperature-programed (TP) electron-stimulated desorption ion angular distribution (ESDIAD)/time-of-flight (TOF) system was developed in order to observe surface processes in real time by ESDIAD images and to measure TOF spectra of desorbing ions for identification of the mass and the kinetic-energy distribution of ions. The instrumentation of this system is described. This system was applied to (root 3 X root 3)R30 degrees-CO/Ru(001) (0.33 ML) and CO-saturated Ru(001) surfaces. As for the (root 3 X root 3)R30 degrees-CO/Ru(001), the increase of the half width at half maximum of the ESDIAD images upon annealing was found corresponding to the thermal excitation of the bending mode and/or hindered translation. On the other hand, as for the CO-saturated surface, the static disorder of the molecular axis of CO was larger, and apparent thermal excitation was not observed. After partial desorption of CO from the CO-saturated surface where the surface changes into the root 3 X root 3 structure at 400-430 K, the yield of O+ increased due to the change in the adsorption site of CO. TOF spectra for ammonia adlayers (NH3 and ND3) were also measured by the developed system and the isotopic ratios for ESD yields depending on the adsorption states (chemisorbed first layer and physisorbed second layer) were obtained. (C) 1998 American Institute of Physics. [S0034-6748(98)02610-0].
    研究論文(学術雑誌), 英語
  • Selective Oxidation of Methanol by Extra Oxygen Species on One-dimensional Mo Rows of a Mo(112)-(1×2)-O Surface
    Ken Ichi Fukui; Katsuya Motoda; Yasuhiro Iwasawa
    J. Phys. Chem. B, AMER CHEMICAL SOC, 102巻, 44号, 掲載ページ 8825-8833, 出版日 1998年10月, 査読付, Selective oxidation of methanol on oxygen-modified Mo(112) was investigated by temperature-programmed reaction (TPR) and under the catalytic reaction conditions at constant pressures of CH3OH and O2(10-6-10-5Pa). Low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were also used. A Mo(112)-(1 × 2)-O surface (θo= 1.0) has a characteristic structure with alternating one-dimensional Mo rows of Mo2Cand MoNC. The Mo2Crows are affected by preadsorbed oxygen atoms ((1 × 2)-O), whereas the MoNCrows served as the adsorption and reaction sites. Formaldehyde (H2CO) was a major product with 50% selectivity in TPR of methanol on the Mo(112)-(1 × 2)-O surface, whereas CH4, H2, C(a), and O(a) were the products at lower oxygen coverages than the (1 × 2)-O coverage. Extra oxygen species on the MoNCrow of Mo(112)-(1 × 2)-O increased the selectivity to formaldehyde to 88% and decreased the activation energy for the rate-limiting C-H bond scission of methoxy species. In a constant flow of methanol alone, the reaction proceeded for several cycles, but eventually the surface was deactivated by accumulation of carbon. Selective catalytic oxidation of methanol successfully proceeded on Mo(112)-(1 × 2)-O in a constant flow of O2and CH3OH without deactivation because of the presence of the extra oxygen atoms on the MoNCrows during the reaction.
    研究論文(学術雑誌), 英語
  • Supported gold catalysis derived from the interaction of a Au-phosphine complex with as-precipitated titanium hydroxide and titanium oxide
    YZ Yuan; K Asakura; AP Kozlova; HL Wan; KR Tsai; Y Iwasawa
    CATALYSIS TODAY, ELSEVIER SCIENCE BV, 44巻, 1-4号, 掲載ページ 333-342, 出版日 1998年09月, 査読付, Supported gold catalysts derived from interaction of a Au-phosphine complex Au(PPh3)(NO3) (1) with conventional titanium oxide TiO2 and as-precipitated titanium hydroxide Ti(OH)(4)* (*, as-precipitated) have been characterized by means of XRD, XPS, EXAFS, and P-31 CP/MAS-NMR. The Au complex 1 was supported on TiO2 and Ti(OH)(4)* without loss of Au-P bonding at room temperature. The Au complex 1 on TiO2 was readily and completely decomposed to form metallic gold particles by calcination at 473 K, whereas only a small part of the complex 1 on Ti(OH)(4)(*) was transformed to metallic gold particles. By calcination of 1/Ti(OH)(4)* at 573 K the formation of both metallic gold particles and crystalline titanium oxides became notable as evidenced by XRD, XPS and P-31 CP/MAS-NMR. The mean diameter of Au particles in 1/Ti(OH)(4)* calcined at 673 K was less than 30 Angstrom as estimated from Au(2 0 0) diffraction, which was about one-tenth of that for the corresponding 1/TiO2, Thus the as-precipitated titanium hydroxide Ti(OH)(4)* was able to stabilize the Au complex 1 to lead to the simultaneous decomposition of Au complex and Ti(OH);. The catalyst 1/Ti(OH)(4)* calcined at 673 K afforded remarkably high catalytic activity for low-temperature CO oxidation at 273-373 K as compared to the catalyst 1/TiO2. (C) 1998 Elsevier Science B.V. All rights reserved.
    研究論文(学術雑誌), 英語
  • Multiple scattering approach to Pd L-3-edge X-ray absorption near edge structure spectra for small Pd clusters with hydrogen adsorption and absorption
    K Ohtani; T Fujikawa; T Kubota; K Asakura; Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 37巻, 7号, 掲載ページ 4134-4139, 出版日 1998年07月, 査読付, Recent studies on Pd Lj-edge X-ray absorption near edge structure (XANES) spectra for pure small Pd clusters show that the spectra are strongly influenced by hydrogen adsorption and absorption, in this paper, the full multiple scattering method is applied to study the difference in measured spectra. The calculated XANES spectra are not so sensitive to the detailed positions and the electronic structures of the interacting hydrogen atoms, however they are sensitive to the induced structural and electronic state change in the host small Pd clusters. The size effect on the peak at similar to 7 eV from the edge is well explained by the induced lattice expansion after hydrogen absorption.
    研究論文(学術雑誌), 英語
  • Iron-oxide supported gold catalysts derived from gold-phosphine complex Au(PPh3)(NO3): State and structure of the support
    AP Kozlova; S Sugiyama; AI Kozlov; K Asakura; Y Iwasawa
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC, 176巻, 2号, 掲載ページ 426-438, 出版日 1998年06月, 査読付, Iron oxide supported gold catalysts were prepared by supporting the Au-phosphine complex Au(PPh3)(NO3) onto various iron oxide supports. Among the prepared catalysts only the use of amorphous as-precipitated iron hydroxide Fe(OH)(3)* as a support for Au(PPh3)(NO3) allowed us to obtain the tremendously active catalytic material for low-temperature CO oxidation. The supports and the Au catalysts were characterized by BET, SEM, XRD, FT-IR, XPS, and Raman. Initial structures of the employed supports were found to influence dramatically the gold particle size and the catalytic activity. The most active catalyst consisted of small gold particles and poorly crystallized iron oxide support with a mixture of alpha-Fe2O3 and gamma-Fe2O3. The gamma-Fe2O3 formation occurred by the presence of the PPh3 as a ligand for gold. The presence of gamma-Fe2O3 influenced positively the catalytic activity of the Au-containing samples. (C) 1998 Academic Press.
    研究論文(学術雑誌), 英語
  • Characterization of the structure of RuO2-IrO2/Ti electrodes by EXAFS
    Toshihide Arikawa; Yoshio Takasu; Yasushi Murakami; Kiyotaka Asakura; Yasuhiro Iwasawa
    Journal of Physical Chemistry B, American Chemical Society, 102巻, 19号, 掲載ページ 3736-3741, 出版日 1998年05月07日, The structure of oxide layers of the RuO2-IrO2/Ti electrode system and the thermal decomposition processes of RuCl3 and IrCl3 to form their respective oxides have been mainly analyzed by EXAFS (extended X-ray absorption fine structure) and XRD (X-ray diffraction). Upon heating of the respective chlorides in air, both chlorides convert into their respective oxides. The coordination numbers of the oxide ions around both the ruthenium and iridium ions increased with an increase in the calcination temperature and attained 6, which is the theoretical value of the standard samples of rutile RuO2 and IrO2. The changes in the coordination number with respect to the calcination temperature were accompanied by changes in the lattice constants of these oxides. This suggests that the deviation of these parameters from the standard sample is caused by the lattice defects of the oxide ions. A dependence of the radial distribution functions of EXAFS on the composition of the RuO2-IrO2/Ti electrode system showed that RuO2 forms a solid solution with IrO2 for the binary oxide electrode system.
    研究論文(学術雑誌), 英語
  • Structural properties of [ (AuPH3)(6)Pt(H-2)(PH3)](2+): Theoretical study of dihydrogen activation
    Xu, X; YZ Yuan; K Asakura; Y Iwasawa; HL Wan; KR Tsai
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 286巻, 1-2号, 掲載ページ 163-170, 出版日 1998年04月, 査読付, B3LYP studies have been performed on the phosphine-stabilized gold-platinum clusters by using model clusters such as [ (AuPH3)(6)Pt(PH3)](2+) and [ (AuPH3)(6)Pt(H-2)(PH3)](2+). Two stationary points have been located, one dihydrogen complex and the other dihydrido complex, which are the possible intermediates in the H-2-D-2 equilibration. Pt is characterized as being the active site, but Au atoms also play an important role in the activation of H-2. The electron transfer from the metal core to the sigma* anti-bonding orbital of H-2 not only activates the hydrogen molecule, but also induces large metal core movement which provides open Au sites for bonding of the second H-2 or D-2. (C) 1998 Elsevier Science B.V.
    研究論文(学術雑誌), 英語
  • Real time observation of coadsorption layers of acetylene/CO and acetylene/O on Ru(001) using a temperature-programmed ESDIAD/TOF system
    T Sasaki; Y Itai; Y Iwasawa
    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, ELSEVIER SCIENCE BV, 88巻, 掲載ページ 773-778, 出版日 1998年03月, 査読付, Coadsorption layers of acetylene/CO and acetylene/O on Ru(001) were studied by a temperature-programmed (TP) ESDIAD/TOF system, which was developed by us recently for the purpose of utilizing ESDIAD as a real time probe for surface chemical processes. This system can measure ESDIAD images for temperature-programmed surface processes in real time. TOF measurements were also carried out to identify mass of desorbing ions. This temperature-programmed (TP) ESDIAD/TOF system was used to observe coadsorption layers of acetylene and CO on Ru(001), which were previously studied by our group using LEED, TPD and HREELS. The temperature dependence of ESD intensity of O+ originating from CO in the coadsorption layer of CO and acetylene revealed the site occupation of CO, which was suggested to shift from atop site by LEED kinematical calculation. Intensity change of H+ ions versus temperature as well as ESDIAD features reflected the change in decomposition intermediates of the acetylene/CO layer. The ESDIAD images acquired for temperature-programmed surface chemical processes in real time were found to provide new insight into the dynamic behavior of coadsorption layers. (C) 1998 Elsevier Science B.V.
    研究論文(学術雑誌), 英語
  • Chemical control of noble metal catalysis by main group elements
    K Asakura; K Okumura; T Inoue; T Kubota; WJ Chun; Y Iwasawa
    RECENT ADVANCES IN CATALYTIC MATERIALS, MATERIALS RESEARCH SOC, 497巻, 掲載ページ 99-108, 出版日 1998年, 査読付, The catalytic interaction of noble metal and main group elements in Rh/one-atomic layer GeO2/SiO2 and Pt/SbOx was investigated. The high temperature reduction produced RhGe and PtSb bimetallic particles in which Pt and Rh were electronically modified to retard catalytic activity. However, unique selective catalyses of Ph/one-atomic layer GeO2/SiO2 for CO hydrogenation reaction to oxygenate compounds and for NO+CO reaction to N-2 were found. Under the low temperature reduction of Rh/one-atomic layer GeO2/SiO2 and the high temperature calcination of Pt/SbOx, the oxide phases, GeO2 and SbOx, were stable and the selective reduction of ethylacetate to ethanol and the selective oxidation of iso-C4H10 to methacrolein were observed. The high selectivities were ascribed to synergistic interaction between the noble metals and the main group element oxides through the diffusion of adsorbed species and reaction intermediates. The possibility of chemical control of noble metal-catalyses by main group elements is discussed.
    研究論文(国際会議プロシーディングス), 英語
  • Identification of individual 4-methylpyridine molecules physisorbed and chemisorbed on TiO2(110)-(1x1) surface by STM
    S Suzuki; H Onishi; T Sasaki; K Fukui; Y Iwasawa
    CATALYSIS LETTERS, BALTZER SCI PUBL BV, 54巻, 4号, 掲載ページ 177-180, 出版日 1998年, 査読付, We succeeded in identifying geometries of 4-methylpyridine (4-MP) molecules adsorbed on a TiO2(110)-(1 x 1) surface based on sequential STM imaging. Characteristics in mobility, topographic height, and location allowed us to distinguish three adsorption states at room temperature: a chemisorbed state with the upright geometry (A(1)), a Bat-lying state localized at specific sites (A(2)), and a Bat-lying physisorbed state mobile over the surface (B). The concentration of A(1) and A(2) species was restricted at an order of 0.01 ML. The A(2) state was related to the adsorption at oxygen vacancies resident on the vacuum-annealed surface. The present study demonstrates the promising ability of STM to identify the adsorption geometry of small probe molecules, 4-methylpyridine in the present case, and to provide atom-level information on the origin of acidic property of oxide surfaces.
    研究論文(学術雑誌), 英語
  • Study of pyridine and its derivatives adsorbed on a TiO2(110)-(1x1) surface by means of STM, TDS, XPS and MD calculation in relation to surface acid-base interaction
    S Suzuki; Y Yamaguchi; H Onishi; T Sasaki; K Fukui; Y Iwasawa
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, ROYAL SOC CHEMISTRY, 94巻, 1号, 掲載ページ 161-166, 出版日 1998年01月, 査読付, Pyridine, benzene, 2,6-dimethylpyridine (2,6-DMP), and m-xylene molecules adsorbed on a TiO2(110)-(1 x 1) surface have been characterized by scanning tunneling microscopy, thermal desorption spectroscopy, X-ray photoelectron spectroscopy, and molecular dynamics calculation to explore the structural features of acid-base interaction, which is relevant to acid-base catalysis of metal oxides. Individual pyridine and 2,6-DMP admolecules were successfully visualized by STM at room temperature. Those probe molecules were only weakly adsorbed on the surface and desorbed near room temperature. The absence of chemical bonds between the nitrogen atoms of adsorbed pyridine and 2,6-DMP and the Ti4+ atoms exposed to the surface was suggested, despite the presence of enough space for bonding on the Ti4+ atoms at the surface.
    研究論文(学術雑誌), 英語
  • Water-promoted oxygen isotope exchange on a Pt(4+)/MgO catalyst
    H. C. Liu; T. Hirota; K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Faraday Transactions, 94巻, 17号, 掲載ページ 2639-2646, 出版日 1998年, 査読付
    英語
  • Vanadium(IV) complexes with picolinic acids in NaY zeolite cages - Synthesis, characterization and catalytic behaviour
    A. Kozlov; K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Faraday Transactions, 94巻, 6号, 掲載ページ 809-816, 出版日 1998年, 査読付
    英語
  • The structure analysis of MoOx/TiO2(110) by polarization-dependent total-reflection fluorescence X-ray absorption fine structure
    W. J. Chun; K. Asakura; Y. Iwasawa
    Catalysis Today, 44巻, 1/4号, 掲載ページ 309-314, 出版日 1998年, 査読付
    英語
  • Synthesis and characterization of vanadium (IV) complexes in NaY zeolite supercages
    A. Kozlov; K. Asakura; Y. Iwasawa
    Microporous and Mesoporous Materials, 21巻, 4/6号, 掲載ページ 571-579, 出版日 1998年, 査読付
    英語
  • Reversible structure change of one-atomic layer GeO2 on SiO2 surface under the interaction with Rh particles by in situ XAFS studies
    K. Okumura; K. Asakura; Y. Iwasawa
    Catalysis Today, 39巻, 4号, 掲載ページ 343-350, 出版日 1998年, 査読付
    英語
  • Polarization-dependent total-reflection fluorescence XAFS study of Mo oxides on a rutile TiO2(110) single crystal surface
    W. J. Chun; K. Asakura; Y. Iwasawa
    Journal of Physical Chemistry B, 102巻, 45号, 掲載ページ 9006-9014, 出版日 1998年, 査読付
    英語
  • Nanosized rhodium oxide particles in the MCM-41 mesoporous molecular sieve
    R. S. Mulukutla; K. Asakura; S. Namba; Y. Iwasawa
    Chemical Communications, 14号, 掲載ページ 1425-1426, 出版日 1998年, 査読付
    英語
  • Characterization of GeO2 sub-monolayers on SiO2 prepared by chemical vapor deposition of Ge(OMe)(4) by EXAFS, FT-IR, and XRD
    K. Okumura; K. Asakura; Y. Iwasawa
    Langmuir, 14巻, 13号, 掲載ページ 3607-3613, 出版日 1998年, 査読付
    英語
  • Anisotropic structure analysis for Mo oxides on TiO2(110) single crystal surface by polarization-dependent total-reflection fluorescence EXAFS
    W. J. Chun; K. Asakura; Y. Iwasawa
    Chemical Physics Letters, 288巻, 5/6号, 掲載ページ 868-872, 出版日 1998年, 査読付
    英語
  • The interaction of Pt and SbOx in the selective oxidation of isobutylene to methacrolein
    T Inoue; K Asakura; W Li; ST Oyama; Y Iwasawa
    APPLIED CATALYSIS A-GENERAL, ELSEVIER SCIENCE BV, 165巻, 1-2号, 掲載ページ 183-197, 出版日 1997年12月, 査読付, New Pt/SbOx catalysts active for the selective oxidation of iso-C4H10 and iso-C4H8 to methacrolein were investigated by pulse reactivity measurements, X-ray diffraction (XRD) analysis, and Raman spectroscopy. XRD revealed that the main oxide phase in Pt/SbOx catalysts after calcination or reaction condition was Sb6O13 whereas Raman spectroscopy also showed the presence of Sb2O3 (senarmontite), As a result of the interaction between Pt and SbOx the total oxidation chemistry of Pt was shut down, and instead a selective oxidation behavior appeared. Investigation of iso-C4H8 oxidation by lattice oxygen in Pt/SbOx revealed that Pt was essential for SbOx to undergo redox cycles, and that without Pt, not much SbOx was reoxidized under reaction conditions. The overall results were consistent with small Sb2O3 oxide crystallites forming on or around Pt particles, with small highly dispersed antimony species, possibly O=SbOy decorating the surface. These species were responsible for breaking up large Pt ensembles and suppressing the total oxidation reaction. (C) 1997 Elsevier Science B.V.
    研究論文(学術雑誌), 英語
  • Imaging of individual formate ions adsorbed on TiO2(110) surface by non-contact atomic force microscopy
    K Fukui; H Onishi; Y Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 280巻, 3-4号, 掲載ページ 296-301, 出版日 1997年12月, 査読付, We have succeeded in imaging individual formate ions adsorbed on TiO2(110)-(1 X 1) by non-contact atomic force microscopy. Formic acid is dissociatively adsorbed on TiO2(110)-(1 X 1) surface at room temperature to give formate ions (HCOO-) which order in a (2 X 1) periodicity at the saturation coverage of 0.5 ML. Thr (2 X 1)-formate overlayer was resolved as ordered bright spots with a rectangular unit of 0.65 X 0.59 nm(2). Dispersed formate ions of lower coverages were also observed as bright spots between the bridging oxygen ridges along the [001] direction. (C) 1997 Elsevier Science B.V.
    研究論文(学術雑誌), 英語
  • Structural transformation and low-pressure catalysis for ethyl acetate hydrogenation of Rh/one-atomic-layer GeO2/SiO2
    K Okumura; K Asakura; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 101巻, 48号, 掲載ページ 9984-9990, 出版日 1997年11月, 査読付, We prepared a new Rh/one-atomic-layer GeO2/SiO2 Catalyst by supporting Rh-6(CO)(16) precursor on the one-atomic-layer GeO2/SiO2. The obtained catalyst was active for conversion of ethyl acetate to ethanol by H-2 reduction under mild reaction conditions, Three different structures and chemical states of Rh species on the one-atomic-layer GeO2/SiO2, characterized by EXAFS, TPD, TEM, and FT-IR, were formed depending on the prereduction temperature, Rh carbonyl cluster, Rh metal, and RhGe alloy. The Rh atoms in the metallic stare were most active for the ethanol formation, The one-atomic-layer GeO2 was much more effective as support for the Rh metallic particles than three-dimensional GeO2-particles dispersed on SiO2. Rh/bulk-GeO2 and Rh/SiO2 were inactive for this reaction. Ethyl acetate dissociatively adsorbed on the one-atomic-layer GeO2, while hydrogen adsorbed on the Rh metallic particles. The present study exemplifies the advantageous applications of an inorganic oxide monolayer to preparation of supported metal catalysts.
    研究論文(学術雑誌), 英語
  • Atom-resolved image of the TiO2(110) surface by noncontact atomic force microscopy
    K Fukui; H Onishi; Y Iwasawa
    PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 79巻, 21号, 掲載ページ 4202-4205, 出版日 1997年11月, 査読付, Atom-resolved images of a TiO2(110)-(1 X 1) surface were obtained by noncontact atomic force microscopy (NC-AFM) in ultrahigh vacuum. in contrast to previous scanning tunneling microscopy studies, outermost atoms of bridge-bound oxygen ridges were observed as protruding rows by NC-AFM. A high-resolution image of the surface revealed that the bridging oxygen atoms ordered in (1 X 1) periodicity on terraces. Point defects of oxygen atoms were also imaged as dark spots.
    研究論文(学術雑誌), 英語
  • Multiple scattering approach to Pt L-3-edge X-ray absorption near edge structure spectra of small Pt clusters with hydrogen absorption
    K Ohtani; T Fujikawa; T Kubota; K Asakura; Y Iwasawa
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS, JAPAN SOC APPLIED PHYSICS, 36巻, 10号, 掲載ページ 6504-6510, 出版日 1997年10月, 査読付, Recent experimental studies on the Pt L-edge X-ray absorption near edge structure (XANES) spectra of Pt clusters show that the spectra are greatly influenced by hydrogen adsorption. In this paper the full multiple scattering method, which we developed, is applied to study the difference in measured XANES spectra before and after the hydrogen adsorption. Hydrogen atoms are more plausible on adsorbed sites out of the cluster than on absorbed sites inside the cluster though the calculated spectra are not so sensitive to the adsorption sites. The adsorbed hydrogen atoms have rather negative charge due to the charge transfer from Pt atoms, In the charge transfer process Pt 6s (or 6p) electrons play a more important role than 5d electrons, Furthermore the small difference in the XANES spectra for Pt foil and small cluster is studied, and lye find that it is due to the large fraction of surface Pt atoms in the latter system.
    研究論文(学術雑誌), 英語
  • Highly sensitive detection of adsorbed species on a SiO2 surface by reflection-absorption infrared spectroscopy
    K Fukui; H Miyauchi; Y Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 274巻, 1-3号, 掲載ページ 133-139, 出版日 1997年08月, 査読付, A SiO2(50 nm)/buried W(70 nm)/Si(100) sample was prepared and used to detect vibrational modes of submonolayer adsorbates on a SiO2 surface by reflection-absorption infrared spectroscopy (RAIRS). Enhancement of the RAIRS signal by the W layer was clearly shown by comparing nu(OD) signal of surface deuteroxyl species to that on a SiO2(50 nm)/Si(100) sample. Utilizing the SiO2/W/Si sample, RAIRS was used to follow the reversible reaction of surface hydroxyl species of SiO, with methanol to give surface methoxy species. (C) 1997 Elsevier Science B.V.
    研究論文(学術雑誌), 英語
  • Performance and characterization of a [PtMo6]/MgO catalyst: The catalytic activity for NO-CO reactions and structural analysis by EXAFS
    K Tomishige; Y Nagasawa; U Lee; Y Iwasawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 70巻, 7号, 掲載ページ 1607-1614, 出版日 1997年07月, 査読付, The catalytic property of a [PtMo6]/MgO catalyst prepared by using a [PtMo6O24](8-) precursor for NO-CO reactions and a structural analysis by means of PtL3- and Mo K-edge EXAFS spectroscopy was studied. The catalytic activity of the bimetallic ensemble catalyst appeared due to the incorporation of Pt ions into the MgO surface, where Pt4+ ions substituted Mg2+ ions in the first layer of the MgO surface. It seems that the NO-CO reaction proceeded on the Pt sites embedded in the MgO surface by a redox mechanism, whereas metallic Pt particles on MgO were inactive under the present reaction conditions, characterized by an in-situ EXAFS analysis.
    研究論文(学術雑誌), 英語
  • Oxygen atoms on Cu(100) formed at 100 K, active for CO oxidation and water-hydrogen abstraction, characterized by HREELS and TPD
    T Sueyoshi; T Sasaki; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY B, AMER CHEMICAL SOC, 101巻, 23号, 掲載ページ 4648-4655, 出版日 1997年06月, 査読付, The reactivity of oxygen adatoms formed by dissociative adsorption of O-2 on Cu(100) at 100 K for CO oxidation and hydrogen abstraction from water was investigated by means of HREELS and TPD in comparison with the reactivity of adsorbed oxygen in thermally stable phases. The oxygen adatoms formed on the Cu(100) surface by exposure to O-2 at 100 K, designated as as-exposed oxygen, were found to be reactive with coadsorbed CO to yield a CO2 desorption peak at 125 K in TPD. The as-exposed oxygen atoms are suggested to be more active for CO oxidation than the oxygen atoms prepared above room temperature on Pt and Pd, which are the most active metals for CO oxidation. On annealing the oxygen-as-exposed surfaces to 300 K, a change in the loss feature of nu(Cu-O) was observed, which was indicative of formations of a pseudo c(2 x 2)-O phase with O(a) in 4-fold hollow sites and a (root 2 x 2 root 2)R45 degrees-O phase comprised of -Cu-O- chains grown along the [001] direction. On these two phases, CO2 formation in TPD was suppressed by 1 order of magnitude. Isolated oxygen atoms in the as-exposed surface are responsible for the high reactivity for CO oxidation. Hydrogen abstraction from water was also examined as a probe reaction for oxygen adatoms on different phases. The as-exposed surface and the pseudo c(2 x 2)-O phase were found to be reactive and OH(a) was detected by means of HREELS after subsequent exposure to water at 100 K. In contrast, the (root 2 x 2 root 2)-R45 degrees-O phase in which oxygen atoms were incorporated into -Cu-O- chains was inert.
    研究論文(学術雑誌), 英語
  • Selective reactivity of oxygen adatoms on Mo(112) for methanol oxidation
    K Fukui; K Motoda; Y Iwasawa
    3RD WORLD CONGRESS ON OXIDATION CATALYSIS, ELSEVIER SCIENCE PUBL B V, 110巻, 掲載ページ 227-234, 出版日 1997年, 査読付, The selective oxidation of methanol on a Mo(112) surface was investigated by temperature programmed reaction (TPR) and catalytic reaction in a constant flow condition of CH3OH and O-2 (10(-6)-10(-5) Pa). Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to characterize the surface structure and the amount of elements on the surface. It has been found that formaldehyde (H2CO) was a major product during TPR of methanol on a Mo(112)-p(1x2)-O surface (theta(O)=1.0), while CH4, H-2, C(a), and O(a) were the products at lower coverages of preadsorbed oxygen. Besides, this reaction proceeded without formation of H2O and was considered to be a simple dehydrogenation (CH3O(a)--> H2CO(g)+ 1/2H(2)(g)). Excess oxygen adatoms on Mo(112)-p(1x2)-O, which were not incorporated into the p(1x2)-O structure, enhanced the selectivity to formaldehyde from 50 % to 90 % and lowered the activation energy of the methanol oxidation. Such oxygen adatoms were more reactive than the oxygen atoms of the p(1x2)-O structure and reacted with the methoxy species to form H2O by the oxidative dehydrogenation mechanism (CH3O(a) + 1/20(a)--> H2CO(g) + 1/2 H2O(g)). In a constant now of methanol, the reaction proceeded several cycles but was deactivated by C(a) accumulated on the surface. The selective oxidation of methanol in now conditions of CH3OH and O-2 successfully proceeded on the Mo(112)-p(1x2)-O surface without deactivation.
    研究論文(学術雑誌), 英語
  • Quantitative analysis of hydrogen adsorbed on Pt particles on SiO2 in the presence of coadsorbed CO by means of L-3-edge X-ray absorption near-edge structure spectroscopy
    T Kubota; K Asakura; Y Iwasawa
    CATALYSIS LETTERS, BALTZER SCI PUBL BV, 46巻, 3-4号, 掲載ページ 141-144, 出版日 1997年, 査読付, X-ray absorption near-edge structure (XANES) spectra at the Pt L-3-edge for Pt particles supported on SiO2 under CO adsorption and CO + H-2 coadsorption were recorded to analyze the amount of adsorbed hydrogen in the coadsorbed state on the Pt particles. Adsorbed CO on the Pt particles revealed a new peak at 6 eV above the Pt L-3-edge in the difference spectra before and after CO adsorption in the coverage range 0.10-0.51. Subsequent adsorption of hydrogen at various coverages on the CO-preadsorbed Pt particles broadened and shifted the peak to the higher energy side. The peak was deconvoluted to two components due to adsorbed hydrogen and CO by a linear least-squares fitting technique. It was found that the fitting coefficient with respect to adsorbed hydrogen was proportional to the amount of adsorbed hydrogen. The XANES difference spectra provide a quantitative analysis method for adsorbed hydrogen on supported Pt particles in the presence of coadsorbates like CO.
    研究論文(学術雑誌), 英語
  • Real time observation of decomposition of methanol on Ru(001)-p(2X2)-O by a temperature programmed ESDIAD/TOF system
    T Sasaki; Y Itai; Y Iwasawa
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 11号, 掲載ページ 1125-1126, 出版日 1997年, 査読付, For the purpose of utilizing ESDIAD (Electron Stimulated Desorption Ion Angular Distribution) as a real time probe for surface chemical processes, we have developed a new instrument which can measure ESDIAD images and time of flight (TOF) spectra of desorbed ions in temperature programmed surface processes. TOF measurements are carried out to identify the mass of desorbed ions and to determine their kinetic energy distribution. This temperature-programmed (TP)-ESDIAD/TOF system was used to observe the decomposition processes of methanol on Ru(001)-p(2X2)-O. A halo pattern from the methyl group of methoxy species was observed at 100-200 K by the use of CH3OD, followed by a broad pattern from the methyl group at 230-250 K, and by a near-center pattern from the oxygen atom of CO above 300 K.
    研究論文(学術雑誌), 英語
  • Supported Au catalysts prepared from Au phosphine complexes and As-precipitated metal hydroxides: Characterization and low-temperature CO oxidation
    Y. Z. Yuan; A. P. Kozlova; K. Asakura; H. L. Wan; K. Tsai; Y. Iwasawa
    Journal of Catalysis, 170巻, 1号, 掲載ページ 191-199, 出版日 1997年, 査読付
    英語
  • Three-dimensional structure analysis of Mo oxides on TiO2(110) by polarization-dependent total reflection fluorescence XAFS
    W. J. Chun; K. Asakura; Y. Iwasawa
    Journal De Physique Iv, 7巻, 7号, 掲載ページ 921-922, 出版日 1997年, 査読付
    英語
  • Structural transformation and low-pressure catalysis for ethyl acetate hydrogenation of Rh/one-atomic-layer GeO2/SiO2
    K. Okumura; K. Asakura; Y. Iwasawa
    Journal of Physical Chemistry B, 101巻, 48号, 掲載ページ 9984-9990, 出版日 1997年, 査読付
    英語
  • Rh/one-atomic layer GeO2/SiO2 as a new catalyst for ethyl acetate hydrogenation at a low pressure
    K. Okumura; K. Asakura; Y. Iwasawa
    Chemistry Letters, 10号, 掲載ページ 985-986, 出版日 1997年, 査読付
    英語
  • Reversible structural change of Rh particles supported on GeO2 submonolayers-SiO2 in reduction and oxidation by XAFS, XRD, TEM and FTIR
    K. Okumura; N. Ichikuni; K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Faraday Transactions, 93巻, 17号, 掲載ページ 3217-3227, 出版日 1997年, 査読付
    英語
  • Reversible deformation of SiO2-supported PtAu6 cluster induced by the CO adsorption by in situ EXAFS
    K. Asakura; Y. Yuan; Y. Iwasawa
    Journal De Physique Iv, 7巻, 7号, 掲載ページ 863-865, 出版日 1997年, 査読付
    英語
  • In-situ polarization-dependent total-reflection fluorescence XAFS studies on the structure transformation of Pt clusters on alpha-Al2O3(0001)
    K. Asakura; W. J. Chun; M. Shirai; K. Tomishige; Y. Iwasawa
    Journal of Physical Chemistry B, 101巻, 28号, 掲載ページ 5549-5556, 出版日 1997年, 査読付
    英語
  • Characterization of Pt/SbOx catalysts active for selective oxidation of isobutane by means of XRD, TEM, and XAFS
    T. Inoue; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 171巻, 2号, 掲載ページ 457-466, 出版日 1997年, 査読付
    英語
  • Characterization and catalysis of a SiO2-supported Au6Pt cluster (AuPPh3)(6)Pt(PPh3) (2+)/SiO2
    Y. Z. Yuan; K. Asakura; H. L. Wan; K. R. Tsai; Y. Iwasawa
    Journal of Molecular Catalysis a-Chemical, 122巻, 2/3号, 掲載ページ 147-157, 出版日 1997年, 査読付
    英語
  • Catalytic behavior of Pt/SbOx for selective oxidation of i-C4H1O and i-C4H8 in stationary and nonstationary conditions
    T. Inoue; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 171巻, 1号, 掲載ページ 184-190, 出版日 1997年, 査読付
    英語
  • Bis(2-pyridinecarboxylato)vanadium(IV) in NaY zeolite cages: Synthesis and spectroscopic properties
    A. Kozlov; K. Asakura; Y. Iwasawa
    Chemistry Letters, 4号, 掲載ページ 313-314, 出版日 1997年, 査読付
    英語
  • CO adsorption and oxidation on Pd(110)-c(2x4)-O by reflection-absorption infrared spectroscopy
    K Fukui; H Miyauchi; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 100巻, 48号, 掲載ページ 18795-18801, 出版日 1996年11月, 査読付, Adsorption and oxidation of CO on Pd(110)-c(2 x 4)-O were investigated by reflection-absorption infrared spectroscopy (RAIRS), low-energy electron diffraction (LEED), and temperature-programmed reaction (TPR). High-frequency CO at 2140 cm(-1), which was greatly influenced by adsorbed oxygen atoms, was observed by RAIRS even at low CO coverage when the Pd(110)-c(2 x 4)-O surface was exposed to CO at 100 K. This peak developed along with a broad band around 2000 cm(-1) from low CO coverage to the saturation. The reaction of CO and an oxygen atom to form COP on the c(2 x 4)-O surface was observed in the range 100-450 K. Below 250 K, two desorption peaks of CO2 were observed in TPR spectra and the corresponding RAIR spectra showed that Linear CO species (2140-2070 cm(-1)) disappeared by desorption as CO dr reaction with an oxygen atom to form CO2, while there was little decrease of bridge CO species (2020-1880 cm(-1)), It is likely that Linear CO species mainly reacted to form CO2 on Pd(110)-c(2 x 4)-O below 250 K. We successfully followed the constant-flow reaction of CO and O-2 On the Pd(11O)-c(2 x 4)-O at 220 K; however, the reaction ceased with an increase of bridge CO at 1992 cm(-1). RAIR spectra during the reaction of CO and O above 250 K suggest that CO began to form domains separated from oxygen atoms and the substrate structure of (1 x 2) was gradually converted into (1 x 1) according to the local coverage of CO.
    研究論文(学術雑誌), 英語
  • Molecular and atomic adsorption states of oxygen on Cu(111) at 100-300 K
    T Sueyoshi; T Sasaki; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 365巻, 2号, 掲載ページ 310-318, 出版日 1996年09月, 査読付, Adsorption states of oxygen on Cu(111) at 100-300 K were investigated by means of HREELS. Two molecular species were characterized by different O-O stretching frequencies (v(O-O)) at 610 cm(-1) and 820-870 cm(-1), which are assigned to the peroxolike species (O-2(2-)) adsorbed in a bridged form and the one in a bidentate form bound on an atop site, respectively. The bridged peroxo species is preferred at the low coverage and the atop peroxo species becomes dominant at the higher coverage. In addition to the peaks due to the molecular oxygen, a peak assigned to v(Cu-O) of atomic oxygen was observed at 370 cm(-1) at the high coverage. The frequency of this mode was higher than the frequency reported for Cu(111) exposed to oxygen above 300 K, indicating that the adsorption state of atomic oxygen formed at 100 K is different from that above 300 K. The v(O-O) modes became faint after annealing to 170 K because of O-2 dissociation, The v(Cu-O) mode of the atomic oxygen formed at 100 K remained up to 230 K and disappeared after annealing to 300 K. No desorption of O-2 Ras detected on annealing to 300 K. It was also found that vibrational spectra for adsorbed NH3, are influenced by the adsorption states of atomic oxygen on Cu(111).
    研究論文(学術雑誌), 英語
  • Supported Ir and Pt clusters: Reactivity with oxygen investigated by extended X-ray absorption fine structure spectroscopy
    SE Deutsch; JT Miller; K Tomishige; Y Iwasawa; WA Weber; BC Gates
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 100巻, 32号, 掲載ページ 13408-13415, 出版日 1996年08月, 査読付, Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to investigate the effects of oxidation and reduction on supported noble metal clusters. After long-term exposure to laboratory air at room temperature, platinum clusters with an average diameter of approximately 7 Angstrom inside the pores of BaKLTL zeolite were almost completely fragmented. The EXAFS data indicate small, highly disordered platinum-platinum contributions but no bulk platinum oxides. Treatment in H-2 at 450 degrees C led to the formation of platinum clusters about 10 Angstrom in average diameter, and exposure of these to air at room temperature led to the formation of a disordered platinum-oxide-like phase covering a core of platinum atoms. The reactivity of platinum clusters with oxygen is size-dependent, and platinum cluster growth by oxidation-reduction cycles may be inhibited by the size of the zeolite pores. Similarly, iridium clusters on MgO, approximated as Ir-4, were fragmented by treatment in O-2, but treatment of the oxidized iridium clusters with H-2 at 573 K resulted in the formation of clusters with an Ir-Ir coordination number of 2.7 (and an Ir-Ir distance of 2.68 Angstrom), indicating slightly less than four Ir atoms per cluster. These data are nearly the same as those characterizing the original sample prior to oxidation, suggesting that the clusters had been reformed into almost their original state. This is the first evidence of supported metal clusters being oxidized and then regenerated nearly intact, The near reversibility of the oxidation-reduction process may be unique to iridium, being related to its slight but non-negligible oxophilicity and its resistance to sintering.
    研究論文(学術雑誌), 英語
  • Coadsorption of NO and NH3 on Cu(111): The formation of the stabilized (2x2) coadlayer
    T Sueyoshi; T Sasaki; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 100巻, 32号, 掲載ページ 13646-13654, 出版日 1996年08月, 査読付, The coadsorption of NO and NH3 on Cu(111) was investigated by means of LEED, HREELS, and TPD. A new ordered (2 x 2) structure was found after annealing to 180 K NO-NH3 coadlayers prepared from various relative exposures of NO and NH3 at 100 K. A N2O desorption peak from the coadlayer appeared at 220 K, which was 70 K higher than the desorption peak From a pure NO layer. A new NH3 desorption peak also appeared al 220 K, while there was only a broad peak centered at 150 K for a pure ammonia adlayer. These results suggest that the coadlayer is more stabilized than the pure layers owing to the attractive interaction between NO(a) and NH3(a). While NO in pure NO layers adsorbs on atop, bridge, and 3-fold hollow sites, it was found that NO in the (2 x 2) structure occupied only 3-fold hollow sites in a linear configuration and the frequency of v(N-O) shifted downward from that in pure NO layers. This change in adsorption state of NO correlates with enhanced occupation of the antibonding 2 pi* orbital of NO due to charge transfer from NH3 through the substrate, leading to more attractive interaction. A real space model for the (2 x 2) structure was proposed on the basis of the results of TPD and HREELS.
    研究論文(学術雑誌), 英語
  • A new method for quantitative characterization of adsorbed hydrogen on Pt particles by means of Pt L-edge XANES
    T Kubota; K Asakura; N Ichikuni; Y Iwasawa
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 256巻, 4-5号, 掲載ページ 445-448, 出版日 1996年07月, 査読付, We measured Pt L(2,3)-edge X-ray absorption near edge structure (XANES) spectra for the Pt particles supported on SiO2, Al2O3 and MgO with and without adsorbed hydrogen. The new peaks appeared at 6-8 eV above the Pt L(2,3)-edges in difference spectra between those in vacuum and under hydrogen. The intensity of the new peak was found to be proportional to the amount of adsorbed hydrogen but independent of the kind of the supports, These results suggest that the XANES difference spectra provide a new method for in situ characterization of adsorbed hydrogen on supported Pt particles without interference of the support.
    研究論文(学術雑誌), 英語
  • Application of a CdTe solid-state detector to polarization-dependent total-reflection fluorescence XAFS measurements
    WJ Chun; K Asakura; Y Iwasawa
    JOURNAL OF SYNCHROTRON RADIATION, MUNKSGAARD INT PUBL LTD, 3巻, 4号, 掲載ページ 160-162, 出版日 1996年07月, 査読付, A CdTe solid-state detector was applied to the measurement of polarization-dependent total-reflection fluorescence XAFS spectra. The data revealed that the detector has good sensitivity, and this, together with its compact size, make it appropriate for in-situ measurements and removal of X-ray Bragg diffraction. The detector efficiently recorded the high-energy K-edge XAFS spectra for molybdenum oxides supported on TiO2 (110).
    研究論文(学術雑誌), 英語
  • STM observation of surface reactions on a metal oxide
    H Onishi; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 357巻, 1-3号, 掲載ページ 773-776, 出版日 1996年06月, 査読付, We have succeeded in the observation of dynamic processes on a metal-oxide surface by scanning tunneling microscopy. When a vacuum-annealed TiO2(110)-(1 x 1) surface maintained at 800 K is exposed to 1 x 10(-5) Pa of 0(2), hill-like structures are randomly nucleated over terraces. They are further transformed into added rows comprising Ti2O3 and to new terraces. Low valent Ti-n+ ions (n less than or equal to 3), which have been accumulated at interstitial positions during annealing, are vertically transported and oxidized into the additional structures. On the other hand, time-resolved observation reveals the transport kinetics of individual formate ions diffusing into a void fabricated in a formate monolayer. A row of Ti ions of the substrate presents a one-dimensional channel for formate transport. A significant anisotropy in formate-formate interaction is concluded; the repulsive force between the formates neighboring on a Ti-row drives the ions to migrate, whereas the attraction between the formates on adjacent Ti-rows plays a secondary role in regulating overlayer structure.
    研究論文(学術雑誌), 英語
  • Reactive oxygen species on reconstructed Cu(110); Catalytic CO oxidation by reactive oxygen species at Low temperatures
    T Sueyoshi; T Sasaki; Y Iwasawa
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 357巻, 1-3号, 掲載ページ 764-768, 出版日 1996年06月, 査読付, The catalytic reactivity of oxygen atoms on unreconstructed Cu(110) surface, designated as as-adsorbed oxygen, was investigated by mass spectrometry, AES, LEED and HREELS. It was found that the catalytic CO-O-2 reaction proceeded on unreconstructed Cu(110) by the as-adsorbed oxygen at 200-230 K, while the reaction did not occur above 250 K. The growth of the (2 x 1)-O structure caused the halt of the reaction above 200 K. CO2 and N2O formation in CO-NO reaction on Cu(110) was also observed at 200 K. In contrast, reactivity of oxygen atoms on Cu(111) was much lower than the as-adsorbed oxygen on Cu(110).
    研究論文(学術雑誌), 英語
  • Surface structures and catalytic properties of supported niobium oxides
    Nobuyuki Ichikuni; Masayuki Shirai; Yasuhiro Iwasawa
    Catalysis Today, 28巻, 1-2号, 掲載ページ 49-58, 出版日 1996年04月, Surface structures of SiO2-supported niobium catalysts prepared by use of a Nb-monomer complex, a Nb-dimer complex, Nb pentaethoxides and Nb pentachlorides as precursors have been determined by means of EXAFS and XANES. These different Nb structures on SiO2 have been characterized by ethanol dehydrogenation as a test reaction. In contrast to the case of Mo catalysts, the activity and selectivity of the Nb catalysts dramatically depended on the structure of the reaction sites at an atomic scale. Dynamic structural changes of the Nb sites are presented and local structural changes at the interface between the supported Nb atom and the SiO2 surface are proposed to explain the role of support in catalysis.
    研究論文(学術雑誌)
  • Molecularly resolved observation of anisotropic intermolecular force in a formate-ion monolayer on a TiO2(110) surface by scanning tunneling microscopy
    H Onishi; K Fukui; Y Iwasawa
    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, ELSEVIER SCIENCE BV, 109巻, 掲載ページ 335-343, 出版日 1996年04月, 査読付, The diffusion kinetics of adsorbed formate ions have been observed on a TiO2 (110) surface by scanning tunneling microscopy (STM) operated under ultrahigh vacuum. Formate ions in a desired area are removed without damage to the substrate, by rastering the monolayer with a high-biased STM tip. A patch of uncovered substrate is thus created in a (2 x 1)-formate monolayer. Time-resolved STM observation reveals the transport kinetics of individual formate ions filling the void. The anisotropic rate of migration suggests that a row of Ti ions exposed on the substrate presents a one-dimensional channel for formate transport. A significant anisotropy in formate-formate interaction is further postulated from the kinetics; a repulsive force between formate ions neighboring on a Ti row drives them to migrate, whereas an attractive force between formates on adjacent Ti-rows plays a secondary role in regulating overlayer structure. The present study shows how STM images document the anisotropy in intermolecular force regulating an adsorbate overlayer on a solid surface, by taking advantage of the relaxation of a nanometer-sized structure fabricated in the overlayer.
    研究論文(学術雑誌), 英語
  • Atom-resolved observation of Na ensembles activating CO2 adsorption on a TiO2(110)-(1x1) surface as the genesis of basic sites
    H Onishi; Y Iwasawa
    CATALYSIS LETTERS, BALTZER SCI PUBL BV, 38巻, 1-2号, 掲載ページ 89-94, 出版日 1996年, 査読付, We have succeeded in observing the structure-sensitive reaction of CO2 with TiO2(110)-(1 x 1) surfaces modified with Na adatoms by scanning tunneling microscopy. At low coverages (0.4 atom/nm(2) or less) Na adatoms are ionized and adsorbed on the exposed Ti-rows of the substrate. A p(4 x 2) order locally appears at 0.6 atom/nm(2), and a c(4 x 2) order develops at 0.9 atom/nm(2). Those Na-modified surfaces are exposed to 10(2) L CO2 at room temperature. Post-exposure observation finds chains of bright particles on the c(4 x 2) surface. The asymmetric topography of the individual particles is assigned to the distribution of the LUMO of the adsorbed carbonate. In contrast, dispersed Na adatoms at lower coverages are unable to react with CO2 at all. The genesis of strong basic sites is thus suggested not to be linearly correlated with Na quantity, but to be correlated with the ordered structure of Na adatoms.
    研究論文(学術雑誌), 英語
  • Dynamic visualization of a metal-oxide-surface/gas-phase reaction: Time-resolved observation by scanning tunneling microscopy at 800 K
    H Onishi; Y Iwasawa
    PHYSICAL REVIEW LETTERS, AMERICAN PHYSICAL SOC, 76巻, 5号, 掲載ページ 791-794, 出版日 1996年01月, 査読付, A surface/gas-phase reaction on TiO2(110) was visualized in situ by scanning tunneling microscopy. When a vacuum annealed (1 x 1) surface heated at 800 K was exposed to an O-2 ambient of 1 x 10(-5) Pa, hill-like structures were randomly nucleated over terraces. Then they were transformed into new terraces, with added rows comprising double strands. We proposed a reoxidation scheme to interpret the dynamics; partially reduced Ti-n+ ions (n less than or equal to 3), which had been accumulated at interstitial positions in the vacuum annealed crystal, were oxidized at the surface to form the hills, added rows, and new terraces.
    研究論文(学術雑誌), 英語
  • Catalytic CO oxidation on unreconstructed Cu(110) by reactive As-adsorbed oxygen atoms below 230 K
    T Sueyoshi; T Sasaki; Y Iwasawa
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 100巻, 3号, 掲載ページ 1048-1054, 出版日 1996年01月, 査読付, CO oxidation on unreconstructed Cu(110) at low temperatures was studied by mass spectrometry, AES, LEED, and HREELS. It was found that catalytic CO oxidation took place at 200-230 K, while the reaction never proceeded above 250 K and stopped in a short time below 180 K, The surface at the end of reaction above 200 K was covered with the (2 x 1)-O phase. It was deduced that the reactive species was as-adsorbed oxygen atoms which were not incorporated in Cu-O chains of the (2 x 1)-O phase readily formed above 250 K. The apparent activation energy for the catalytic CO-O-2 reaction was obtained to be a negative value, -15.8 kJ/mol. profiles of CO2 production at 200-230 K were analyzed according to a kinetic model based on the Langmuir-Hinshelwood mechanism and the competitive growth of the (2 x 1)-O phase. Measured kinetic data were reproduced well by the simulation using this model. From the analysis, the activation energy of the reaction between CO(a) and O(a) was found to be 34.8 kJ/mol, and that of the growth of the (2 x 1)-O phase was found to be 16.8 kJ/mol. The activity of the reactive oxygen species on Cu(110) seemed comparable to those of the oxygen atoms on Pt, Pd, and Rh.
    研究論文(学術雑誌), 英語
  • A new characterization method for adsorbed hydrogen on supported Pt particles
    K Asakura; T Kubota; N Ichikuni; Y Iwasawa
    11TH INTERNATIONAL CONGRESS ON CATALYSIS - 40TH ANNIVERSARY, PTS A AND B, ELSEVIER SCIENCE PUBL B V, 101巻, 101号, 掲載ページ 911-919, 出版日 1996年, 査読付, We measured Pt L(3), L(2) and L(1)-edges X-ray absorption near edge structure (XANES) spectra of Pt particles dispersed on metal oxide supports (SiO2, Al2O3 and MgO) with and without hydrogen adsorption. The difference spectra obtained by subtracting the spectra in vacuum from the ones with adsorbed hydrogen were independent of kind of the support and only dependent on the amount of adsorbed hydrogen. It was suggested that the change can not be only explained by the change of density of Pt 5d unoccupied state but by creation of a resonance state associated with the localized Pt-H interaction. We also found a linear relation between the change in the XANES spectra and the amount of adsorbed hydrogen, which provides a new characterization method for adsorbed hydrogen on supported Pt particles.
    研究論文(学術雑誌), 英語
  • Supported gold catalysts derived from gold complexes and as-precipitated metal hydroxides, highly active for low-temperature CO oxidation
    YZ Yuan; K Asakura; HL Wan; KR Tsai; Y Iwasawa
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 9号, 掲載ページ 755-756, 出版日 1996年, 査読付, Supported gold catalysts were prepared by attaching phosphine-stabilized gold complex and cluster on as-precipitated metal hydroxides M(OH)*(x) (M=Mn2+, Co2+, Fe3+, Ni2+, Zn2+, Mg2+,and Cu2+), followed by thermal decomposition and calcination. The obtained catalysts were remarkably active for CO oxidation at low temperatures below 273 K.
    研究論文(学術雑誌), 英語
  • Preparation of supported gold catalysts from gold complexes and their catalytic activities for CO oxidation
    YZ Yuan; K Asakura; HL Wan; K Tsai; Y Iwasawa
    CATALYSIS LETTERS, SPRINGER, 42巻, 1-2号, 掲載ページ 15-20, 出版日 1996年, 査読付, A phosphine-stabilized mononuclear gold complex Au(PPh(3))(NO3) (1) and a phosphine-stabilized gold cluster [An(9)(PPh(3))(8)](NO3)(3) (2) were used as precursors for preparation of supported gold catalysts. Both complexes 1 and 2 supported on inorganic oxides such as alpha-Fe2O3, TiO2, and SiO2 were inactive for CO oxidation, whereas the 1 or 2/oxides treated under air or CO or 5% H-2/Ar atmosphere were found to be active for CO oxidation. The catalytic activity depended on not only the treatment conditions but also the kinds of the precursor and the supports used. The catalysts derived from 1 showed higher activity than those derived from 2. alpha-Fe2O3 and TiO2 were much more efficient supports than SiO2 for the gold particles which were characterized by XRD and EXAFS.
    研究論文(学術雑誌), 英語
  • Surface structures and catalytic hydroformylation activities of Rh dimers attached on various inorganic oxide supports
    K. K. Bando; K. Asakura; H. Arakawa; K. Isobe; Y. Iwasawa
    Journal of Physical Chemistry, 100巻, 32号, 掲載ページ 13636-13645, 出版日 1996年, 査読付
    英語
  • Surface structure analysis of dispersed metal sites on single crystal metal oxides by means of polarization-dependent total-reflection fluorescent EXAFS
    W. J. Chun; K. Asakura; Y. Iwasawa
    Applied Surface Science, 100/101巻, 掲載ページ 143-146, 出版日 1996年, 査読付
    英語
  • Structure and catalysis of a SiO2-supported gold-platinum cluster (PPh(3))Pt(PPh(3)Au)(6) (NO3)(2)
    Y. Z. Yuan; K. Asakura; H. L. Wan; K. Tsai; Y. Iwasawa
    Chemistry Letters, 2号, 掲載ページ 129-130, 出版日 1996年, 査読付
    英語
  • PTRF X-ray absorption fine structure as a new technique for catalyst characterization
    W. J. Chun; M. Shirai; K. Tomishige; K. Asakura; Y. Iwasawa
    Journal of Molecular Catalysis a-Chemical, 107巻, 1/3号, 掲載ページ 55-65, 出版日 1996年, 査読付
    英語
  • REACTIVE OXYGEN-ATOMS ON CU(110) FORMED AT 100 K - VIBRATIONAL-SPECTRA AND CO OXIDATION
    T SUEYOSHI; T SASAKI; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 343巻, 1-2号, 掲載ページ 1-16, 出版日 1995年12月, 査読付, The dissociative adsorption of oxygen on Cu(110) at 100 K and its reactivity for CO oxidation were studied by HREELS, TPD and LEED. Oxygen dissociatively adsorbs on Cu(110) at 100 K. These oxygen adatoms, designated as the as-exposed oxygen, form no ordered structure. Annealing this surface above 200 K causes the appearance of the (2 X 1)-O ordered structure which corresponds to the added row type reconstruction. A characteristic change in the loss feature of nu(Cu-O) was found upon annealing Cu(110) covered with the as-exposed oxygen by HREELS, which corresponded to the change from the as-exposed oxygen to oxygen atoms in the (2 x 1)-O phase. The as-exposed oxygen on Cu(110) at 100 K oxidized CO to form CO,, while oxygen atoms in the (2 X I)-O phase were inactive in TPD conditions. It was found that the reactivity of the as-exposed oxygen was more than 25 times higher than that of oxygen in the (2 X 1)-O phase. Four peaks at 125 K (alpha), 150 K(beta), 180 K (gamma) and 210 K (delta) were found in the CO2 TPD spectra. The features of these peaks were discussed based on TPD spectra with various CO coverages at constant coverages of oxygen. In the coadlayer of CO and oxygen, CO species with a nu(Cu-CO) peak at 285 cm(-1) was observed in addition to the nu(Cu-CO) peak at 340 cm(-1) observed for a pure CO adlayer on Cu(110). Both the as-exposed oxygen and the oxygen in the (2 x 1)-O phase caused this downward shift.
    研究論文(学術雑誌), 英語
  • ADSORPTION AND THERMAL OR PHOTODECOMPOSITION OF TRIETHYLGALLIUM AND TRIMETHYLGALLIUM ON SI(111)-7X7
    K FUKUI; W MIZUTANI; H ONISHI; S ICHIMURA; H SHIMIZU; Y IWASAWA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 34巻, 9A号, 掲載ページ 4910-4916, 出版日 1995年09月, 査読付, Adsorption and thermal or photodecomposition of triethylgallium (TEG) and trimethylgallium (TMG) on Si(lll)-7 x 7 were investigated using a home-built scanning tunneling microscope (STM), Auger electron spectroscopy (AES), and thermal desorption spectroscopy (TDS). Adsorption of TEG and TMG at room temperature gave bright protrusions of Ga(C2H5)(x)(a) and Ga(CH3)(x)(a) (x = 2, 3) on atop sites of Si adatoms with a slight preference for center adatoms over comer ones. The Ga(C2H5)(x)(a) and Ga(CH3)(x)(a) species were decomposed by UV irradiation probably due to absorption of UV photons by these adsorbates. Thermal decomposition of TEG on the 7 x 7 surface led to severe carbon deposition, particularly at low initial coverage of TEG, in contrast to the result reported on Si(100)-2 x 1.
    研究論文(学術雑誌), 英語
  • ATOMIC-SCALE SURFACE-STRUCTURES OF TIO2 (110) DETERMINED BY SCANNING-TUNNELING-MICROSCOPY - A NEW SURFACE-LIMITED PHASE OF TITANIUM-OXIDE
    H ONISHI; K FUKUI; Y IWASAWA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 68巻, 9号, 掲載ページ 2447-2458, 出版日 1995年09月, 査読付, The structure transformation of a TiO2(110) surface was observed at atomic-scale resolution by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Irregular corrugations on an argon-bombarded TiO2(110) surface crystallized to stacked (1x1) terraces by vacuum annealing at 600-800 K. The terraces grew in dimension to be as large as 30x30 nm(2) at 900 K. The unoccupied surface states localized on individual Ti4+ ions were resolved on a (1x1) terrace. The position of the Ti4+ ions was probed by imaging adsorbed formate ions. Annealing at higher temperatures resulted in the formation of a wide row structure comprising double strands. Imaging of individual adsorbed formate ions was used to grade possible structure models by probing Ti ions exposed on the surface; thereby, an added Ti2O3 row model, which is a new surface-limited phase of titanium oxide consisting of Ti3+ ions of the optimum six-fold coordination, was concluded for the double-strand structure. These results demonstrate the ability of probing experiments with an adsorbed molecule to determine the chemical nature of imaged sites on multi-component materials by STM.
    研究論文(学術雑誌), 英語
  • CATALYTIC CO OXIDATION ON UNRECONSTRUCTED CU(110) OBSERVED AT LOW-TEMPERATURES
    T SUEYOSHI; T SASAKI; Y IWASAWA
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 241巻, 3号, 掲載ページ 189-194, 出版日 1995年07月, 査読付, CO oxidation on Cu(110) between 150 and 250 K was studied by a mass spectrometer, AES, LEED and HREELS. It was found that catalytic CO oxidation proceeded on an unreconstructed Cu(110) between 200 and 230 K, while the reaction below 180 K halted in a short time. The (2 x 1)-O phase produced under the reaction conditions above 200 K was not reactive and its growth caused a decrease in the number of clean sites, leading to inhibition of the reaction. From the analysis of the CO2 production profiles the activation energy of the CO-O-2 reaction was found to be 34.8 kJ/mol.
    研究論文(学術雑誌), 英語
  • CATALYTIC DECOMPOSITION REACTION OF FORMIC-ACID ON AN AR+-BOMBARDED TIO2(110) SURFACE - STEADY-STATE KINETICS AND MICROSCOPIC SURFACE-STRUCTURE
    Y YAMAGUCHI; H ONISHI; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, ROYAL SOC CHEMISTRY, 91巻, 11号, 掲載ページ 1663-1668, 出版日 1995年06月, The kinetics of the catalytic decomposition reaction of formic acid (DCOOD) were examined under steady-state conditions on Ar+-bombarded and partially annealed TiO2(110) surfaces characterized by scanning tunnelling microscopy (STM), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS). The bombarded surface was rugged and contained a certain number of reduced Ti3+ cations. The (1 x 1) terraces covered the surface annealed at 900 K, while the reoxidation of the Ti3+ cations occurred on the surface annealed at 500 K and was completed at 700 K. The catalytic dehydration and dehydrogenation reactions of formic acid were observed regardless of the annealing history of the bombarded surface. The catalytic performance of the coordinatively unsaturated Ti3+ sites in the decomposition reaction was compared with that of the well ordered (1 x 1) surface.
    研究論文(学術雑誌), 英語
  • CATALYTIC SYNTHESIS OF UNSATURATED NITRILES FROM NO-ALKANE OR NO-ALKENE ON PT-SN/SIO2
    T INOUE; K TOMISHIGE; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 3号, 掲載ページ 329-330, 出版日 1995年02月, 査読付, The Pt-Sn/SiO2 catalysts prepared by selective bimetallic CVD reaction of SnMe(4) with Pt particles on SiO2, characterized by EXAFS (extended X-ray absorption fine structure), yield acrylonitrile from NO + propene and methacrylonitrile from NO + isobutene and NO + isobutane with good selectivities, typically 70-93%, in contrast to negligible activity and selectivity (about one order of magnitude lower) with the monometallic Pt/SiO2 catalyst.
    研究論文(学術雑誌), 英語
  • RESTRAINT OF NH3 DISSOCIATION ON OXYGEN-MODIFIED MO(112)
    T ARUGA; K TATENO; K FUKUI; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 324巻, 1号, 掲載ページ 17-24, 出版日 1995年02月, 査読付, The adsorption and reaction of ammonia (NH3) on clean and oxygen-precovered Mo(112) surfaces has been studied by temperature-programmed desorption and low-energy electron diffraction. NH3 is dissociatively adsorbed on clean Mo(112) giving rise to the desorption of H-2 at 450 K and N-2 at 1050 K. With increasing oxygen precoverage (theta(0)), the saturation NH3 coverage at 330 K decreases, passes a minimum at theta(0) congruent to 0.8, and increases again at higher theta(0). The increase of the saturation NH3 coverage at high-theta(0) surfaces is due to the stabilization of non-dissociatively adsorbed NH2 (x approximate to 2) species on Mo(112)-(1 X 2)-O phase. The NHx(a) species stabilized on Mo(112)-(1 X 2)-O gives rise to simultaneous desorption of H2O, H-2, and NH3 at 650 K with N(a) remaining on the surface, which is ascribed to the successive surface reactions triggered by the N-H bond scission. The NHx(a) species, which persists on Mo(112)-(1 X 2)-O up to unusually high temperatures as compared to that on other transition metal surfaces, may provide a variety of catalytic reaction pathways with co-adsorbed species.
    研究論文(学術雑誌), 英語
  • A novel [PtMo6]/MgO catalyst for alkane-to-alkene conversion
    DI Kondarides; K Tomishige; Y Nagasawa; Y Iwasawa
    PREPARATION OF CATALYSTS VI, ELSEVIER SCIENCE PUBL B V, 91巻, 掲載ページ 141-150, 出版日 1995年, 査読付, A novel [PtMo6]/MgO ensemble catalyst was prepared using a [PtMo6O24](8-) heteropolyanion precursor and characterized by EXAFS. Analysis of the EXAFS spectra showed that after calcination at temperatures above 673 K platinum and molybdenum atoms interact with the support. Platinum ions (Pt4+) replace surface Mg2+ ions of the MgO carrier, while Mo6+ ions locate on the magnesia surface in a distorted octahedrally coordinated framework. Catalytic tests using i-butane, n-butane and propane dehydrogenation as probe reactions showed that the novel ensemble catalyst exhibits a much better catalytic performance compared to conventionally prepared catalysts.
    研究論文(学術雑誌), 英語
  • Anisotropic structures and oriented bonds of active surface sites by in-situ polarized total-reflection fluorescence X-ray absorption fine structure
    M. Shirai; W. J. Chun; K. Tomishige; K. Asakura; Y. Iwasawa
    Science and Technology in Catalysis 1994, 92巻, 92号, 掲載ページ 263-268, 出版日 1995年, 査読付
    英語
  • SURFACE-STRUCTURE CHANGE OF A PT-4(MU-CH3COO)(8) /SIO2 CATALYST ACTIVE FOR THE DECOMPOSITION OF FORMIC-ACID
    W. J. Chun; K. Tomishige; M. Hamakado; Y. Iwasawa; K. Asakura
    Journal of the Chemical Society-Faraday Transactions, 91巻, 22号, 掲載ページ 4161-4170, 出版日 1995年, 査読付
    英語
  • Observation of molecular reaction intermediate and reaction mechanism for NO dissociation and NO-H-2 reaction on Rh-Sn/SiO2 catalysts
    K. Tomishige; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 157巻, 2号, 掲載ページ 472-481, 出版日 1995年, 査読付
    英語
  • IN-SITU ASYMMETRIC STRUCTURE-ANALYSIS OF PT CLUSTERS ON ALPHA-AL2O3(0001) IN H-2 REDUCTION AND NO ADSORPTION
    K. Asakura; K. Tomishige; M. Shirai; W. J. Chun; T. Yokoyama; Y. Iwasawa
    Physica B, 208/209巻, 掲載ページ 637-640, 出版日 1995年, 査読付
    英語
  • Development of a chamber for in situ polarized total-reflection fluorescence x-ray absorption fine structure spectroscopy
    M. Shirai; M. Nomura; K. Asakura; Y. Iwasawa
    Review of Scientific Instruments, 66巻, 12号, 掲載ページ 5493-5498, 出版日 1995年, 査読付
    英語
  • Observation of the Structural Change in the Nb Sites during Ethanol Dehydration on a SiO2-Attached Nb Dimer Catalyst by EXAFS
    Nobuyuki Ichikuni; Yasuhiro Iwasawa
    The Journal of Physical Chemistry, American Chemical Society (ACS), 98巻, 44号, 掲載ページ 11576-11581, 出版日 1994年11月, 査読付
    研究論文(学術雑誌)
  • A REACTIVE OXYGEN ADLAYER ON CU(110) AT 100-K
    T SASAKI; T SUEYOSHI; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 316巻, 3号, 掲載ページ L1081-L1087, 出版日 1994年09月, 査読付, Oxygen adsorbed on Cu(110) has been investigated by means of HREELS, LEED and TPD. We concentrated on a change from an oxygen-as-exposed surface at 100 K to a Cu(110)-(2 X 1)-O surface. Upon annealing the oxygen-as-exposed surface (2 X 1) LEED subspots appeared between 200-300 K. The process of (2 x 1) reconstruction was accompanied by a change in the upsilon(Cu-O) loss feature of the HREEL spectra. It was found that the oxygen-as-exposed surface at 100 K can oxidize CO to form CO2 desorbing below 200 K and that the oxygen in as-exposed surface at 100 K is more reactive by a factor of 25 than that in the (2 x 1) phase.
    英語
  • REMOVAL OF ADSORBED ORGANIC-MOLECULES WITH SCANNING TUNNELING MICROSCOPE - FORMATE ANIONS ON TIO2(110) SURFACE
    H ONISHI; Y IWASAWA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS, JAPAN SOC APPLIED PHYSICS, 33巻, 9B号, 掲載ページ L1338-L1341, 出版日 1994年09月, 査読付, A scanning tunneling microscope (STM) operated under ultrahigh vacuum enabled us to eliminate individual formate anions (DCOO-) adsorbed on a TiO2(110) surface. When bias voltages of +3.7 V or more were applied on the sample, the formate anions were removed under the STM tip. In contrast, much higher voltages, +5.0 V or more, were required to damage the underlying TiO2 surface. Thus Ne could strip off the formate anions in a desired area without damage to the substrate, to create patchworks of uncovered substrate in the monolayer of adsorbed formate anions. The threshold bias voltage for the elimination showed a small dependence on tunneling current, suggesting that the removal process is through field evaporation rather than direct excitation or thermal activation by tunneling electrons.
    研究論文(学術雑誌), 英語
  • Role of alkali promoters on Mn3O4 in the selective reduction of nitrobenzene
    A. Maltha; H. F. Kist; T. L.F. Favre; H. G. Karge; F. Asmussen; H. Onishi; Y. Iwasawa; V. Ponec
    Applied Catalysis A, General, 115巻, 1号, 掲載ページ 85-101, 出版日 1994年08月04日, 査読付, The influence of Li+, Na+ and K+ ions on the activity and selectivity of Mn3O4 in the selective reduction of nitrobenzene has been studied. The alkali ions show both a promoting (low concentrations) and a blocking (higher concentrations) effect. Reducibility measurements of the various catalysts (thermogravimetry, temperature-programmed reduction), adsorption heat experiments (heat-flow microcalorimetry) and determination of the composition of the surface layers (X-ray photoelectron spectroscopy) exclude an influence of the promoter on the reducibility of the catalyst, on the heat of adsorption of nitrobenzene and on the oxidation state of manganese. It can be seen that most of the alkali ions are present in the surface layers of the catalyst. The most likely mechanism is that by which the promoter influences a certain adsorption mode of nitrobenzene existing at the reaction temperature on the surface of Mn3O4. © 1994.
    研究論文(学術雑誌), 英語
  • STM-IMAGING OF FORMATE INTERMEDIATES ADSORBED ON A TIO2 (110) SURFACE
    H ONISHI; Y IWASAWA
    CHEMICAL PHYSICS LETTERS, ELSEVIER SCIENCE BV, 226巻, 1-2号, 掲載ページ 111-114, 出版日 1994年08月, 査読付, We have succeeded in STM-imaging of formates adsorbed on TiO2(110) With atomic-scale resolution, formates being regarded as intermediates for catalytic decomposition reaction of formic acid on TiO2(110). Dispersive and (2 x 1)-ordered overlayers of formates were resolved with positive sample bias voltages. The formates were adsorbed on the rows of fivefold coordinated Ti4+ cations along the [001] axis. Their individual images were elongated in the [110BAR] direction. The anisotropic feature reflects the distribution of the tunneling orbital, the LUMO, of the formates.
    研究論文(学術雑誌), 英語
  • NA2O OVERLAYERS EPITAXIALLY PREPARED ON PD(100) AND STRUCTURE-SENSITIVE CO2 ADSORPTION
    H ONISHI; T ARUGA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 310巻, 1-3号, 掲載ページ 135-146, 出版日 1994年05月, 査読付, Sodium oxide overlayers prepared on Pd(100) were examined with AES, LEED and XPS. The oxides were grown by cycles of Na deposition followed by oxidation, maintaining the composition of Na2O. The surface structure of the deposited oxide was sensitive to the annealing temperature after oxidation. The Na2O/Pd(100) surfaces gave rise to a (3 x 3) LEED pattern when annealed at 600 K under vacuum. A model based on Na2O(100) was proposed for the (3 x 3) overlayers, where the oxide was epitaxially aligned in a square periodicity on the substrate. Multilayered Na2O was prepared maintaining the (3 x 3) pattern, by repeated cycles of preparation. Annealing at 700 K caused a c(4 x 6) pattern, for which a model based on Na2O(110) was proposed. CO2 was adsorbed on the (3 x 3) oxide of various thickness to form carbonate at 350 K, whereas the c(4 x 6) oxide was inert. The relationship of structure and reactivity is discussed in relation to the microscopic design of metal-oxide surfaces for base-catalysis.
    研究論文(学術雑誌), 英語
  • The active sites of manganese- and cobalt-containing catalysts in the selective gas phase reduction of nitrobenzene
    A. Maltha; H. F. Kist; B. Brunet; J. Ziolkowski; H. Onishi; Y. Iwasawa; V. Ponec
    Journal of Catalysis, 149巻, 2号, 掲載ページ 356-363, 出版日 1994年, 査読付, The active sites of the spinels Mn3O4 and Co3O4 in the selective reduction of nitrobenzene to nitrosobenzene have been investigated, by total and partial substitution of Mnn+ (Con+) ions in tetrahedral position and/or Mnn+ (Con+) ions in octahedral position by redox-inactive ions. Investigation of the catalytic activities of the totally substituted manganese spinel ZnMn2O4 and that of the totally substituted cobalt spinels CoAl2O4 and ZnCo2O4 showed that the manganese and cobalt ions in octahedral position were responsible for the activity of the reaction. MnAl2O4, however, also showed some activity for the selective reduction of nitrobenzene, which should be due to surface enrichment and/or oxidative transfer of manganese from tetrahedral sites to octahedral sites. XRD results of the partially substituted spinels MnxZn1-xAl2O4 showed that there was a linear correlation between the manganese concentration expressed by x and the lattice constant. Moreover, each sample showed segregation of Al2O3: again there was a linear correlation between x in a certain series of MnxZn1-xAl2O4 and the amount of free Al2O3. This points to an oxidative transfer of manganese from tetrahedral sites to octahedral sites. XPS showed that the concentration of manganese in the surface layer corresponded roughly to the value x, but the concentration of zinc in the surface layers was much smaller that expected. The catalytic activities of the MnxZn1-xAl2O4 series of catalysts are larger than would be expected from the results on ZnMn2O4 and ZnCo2O4. © 1994 by Academic Press, Inc.
    研究論文(学術雑誌), 英語
  • Switchover of reaction paths in the catalytic decomposition of formic acid on TiO2(110) surface
    H. Onishi; T. Aruga; Y. Iwasawa
    Journal of Catalysis, 146巻, 2号, 掲載ページ 557-567, 出版日 1994年, 査読付, The decomposition reaction of formic acid (DCOOD) was examined on a rutile TiO2(110) surface in catalytic and noncatalytic conditions. The kinetic behavior of the catalytic reaction was recorded by MS under DCOOD atmosphere of 10-6-10-3 Pa at 500-800 K, whereas TDS, LEED, AES, XPS, and UPS were used to chracterize adsorbed species derived from formic acid and their non-catalytic surface reactions under vacuum. Formic acid was dissociated to form formates and hydroxyl groups on TiO2(110) at 250 K. Bridge formates (0.5 ML) were arranged in a (2 × 1) order below 350 K. Formates (0.1 ML) were desorbed under vacuum at 350 K to relax the (2 × 1) overlayer. The evolution of D2 was observed at 400 K and assigned to recombination of the hydroxyl groups. Residual formates unimolecularly decompose at 570 K with an activation energy of 120 ± 10 kJ/mol and a pre-exponential factor of 2 × 109±1s-1, releasing a mixture of CO, CO2, D2, D2O, and DCOOD in TDS. On the other hand, it was found that TiO2(110) catalyzed two selective reactions: dehydration and dehydrogenation. TiO2(110) shows a preference for the dehydrogenation reaction into D2 + CO2 below 500 K. This is in contrast to the selective activity for the dehydration to D2O + CO reported on TiO2 powder catalysts. The rate of the catalytic dehydration was nearly independent of the pressure of formic acid below 700 K, but increased with surface temperature. An activation energy of 120 ± 10 kJ/mol was again observed in the catalytic dehydration reaction, suggesting that the unimolecular decomposition of formates at the surface is rate controlling. The rate of the catalytic dehydrogenation reaction depended on both the coverage of formate and the pressure of DCOOD, with a small activation energy of 15 ± 10 kJ/mol. The catalytic dehydrogenation reaction is thus suggested to proceed in a bimolecular process of a formate and a DCOOD molecule. A kinetic simulation supports the mechanisms, showing a switchover of the reaction paths by the second reactant molecule. These results are discussed, along with previous works on powder catalysts and single crystals. © 1994 Academic Press, Inc.
    研究論文(学術雑誌), 英語
  • CO-BREATHING STRUCTURE CHANGE AND CATALYSIS FOR OXYGENATE SYNTHESIS FROM CO/H-2 ON SUPPORTED [RU6C] CLUSTERS - STRUCTURAL AND CHEMICAL CONTROLS BY INTERSTITIAL CARBIDO CARBON
    Y IZUMI; T CHIHARA; H YAMAZAKI; Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 98巻, 2号, 掲載ページ 594-602, 出版日 1994年01月, 査読付, Catalysis and structures of supported ruthenium carbido clusters [Ru6C(CO)16/(CH3)]-/oxides were investigated in comparison with those of supported non-carbido clusters prepared from [Ru-6(CO)(18)](2-) and traditional ruthenium catalysts prepared from Ru(NO)(NO3)(3). Oxygenate synthesis (methanol, dimethyl ether, and formaldehyde) in CO/H-2 reaction was observed on the supported carbido clusters in contrast to the preferential formation of methane and hydrocarbons on the conventional Ru catalysts and the supported non-carbido clusters. The active structure for oxygenate synthesis crucially depended on the kind of oxides; on basic oxides (MgO and La2O3) the cluster of framework was incorporated with surface oxygen atoms and expanded or shrunk under CO/H-2 reaction conditions depending on the CO pressure. The reversible expansion-shrinking of the cluster framework was correlated with the activated CO adsorption (CO breathing-induced structural change). On TiO2 the [Ru6C] framework always held a shrunk structure as proved by EXAFS. The expanded clusters showed high selectivities in oxygenate synthesis. The shrunk [Ru6C]/TiO2 also showed much higher activity than the non-carbido cluster or the traditional catalyst. IR,and hydrogen isotope effects suggested the formation of oxygenates through a mu 2-formyl intermediate. The switchover of reaction path from the formation of methane and hydrocarbons to oxygenate synthesis is ascribed to the interstitial carbido carbon which has structural effect like a central spring and electronic effect as a four-electron donor on the behavior of the cluster framework.
    研究論文(学術雑誌), 英語
  • POLARIZED TOTAL-REFLECTION FLUORESCENCE EXAFS STUDY OF ANISOTROPIC STRUCTURE-ANALYSIS FOR CO OXIDES ON ALPHA-AL2O3 (0001) AS MODEL SURFACES FOR ACTIVE OXIDATION CATALYSTS
    M. Shirai; T. Inoue; H. Onishi; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 145巻, 1号, 掲載ページ 159-165, 出版日 1994年, 査読付
    英語
  • DESIGN AND CHARACTERIZATION BY EXAFS, FTIR, AND TEM OF RH-SN/SIO2 CATALYSTS ACTIVE FOR NO-H-2 REACTION
    K. Tomishige; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 149巻, 1号, 掲載ページ 70-80, 出版日 1994年, 査読付
    英語
  • IN-SITU POLARIZED TOTAL-REFLECTION FLUORESCENCE X-RAY-ABSORPTION NEAR-EDGE STRUCTURE SPECTROSCOPY FOR THE ANALYSIS OF ORIENTED STRUCTURE OF VANADIUM-OXIDES ON ZRO2(100)
    M. Shirai; K. Asakura; Y. Iwasawa
    Catalysis Letters, 26巻, 26号, 掲載ページ 229-234, 出版日 1994年, 査読付
    英語
  • IN-SITU EXAFS OBSERVATION OF THE MOLECULAR REACTION INTERMEDIATE FOR NO-H-2 REACTION ON HIGHLY-ACTIVE RH-SN/SIO2 CATALYSTS
    K. Tomishige; K. Asakura; Y. Iwasawa
    Chemistry Letters, 2号, 掲載ページ 235-238, 出版日 1994年, 査読付
    英語
  • SELECTIVE CARBONYL INSERTION AND ETHENE HYDROFORMYLATION ON A [RU6C(CO)16ME]--SIO2 CATALYST
    Y IZUMI; T CHIHARA; H YAMAZAKI; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 24号, 掲載ページ 3667-3673, 出版日 1993年12月, 査読付, Stoichiometric acetaldehyde formation by insertion of CO into the methyl ligand and catalytic ethene hydroformylation on the cluster, [Ru6C(CO)16Me]- supported on silica at 373-473 K have been investigated to understand the effects of the catalysis on the metal cluster framework and also to develop new catalytic systems on a molecular scale. Two elementary steps for stoichiometric acetaldehyde formation, (i) from methyl to acetyl and (ii) from acetyl to acetaldehyde, were observed by Fourier-transform IR spectroscopy. The rate of (i) in CO + H-2 was faster than that in CO, suggesting a hydride-promoted mechanism for carbonyl insertion (acetyl formation). The hydride promotion and hydrogen pressure dependence suggested dissociative adsorption of H-2 so as to bridge a Ru-Ru and the incorporation of the multi-Ru sites in the acetaldehyde formation mechanism. The reductive elimination of hydride and methyl ligands upon methane formation was much slower than the reductive elimination of H and MeO for acetaldehyde formation as well as the insertion of CO (methyl migration) for acetyl formation. In terms of this specific feature the catalytic hydroformylation of ethene was found to proceed on the catalyst with nearly 100% selectivity at 398 K in the case of highly dehydrated SiO2 (823 K). The retention of the cluster framework under the reaction conditions was confirmed by extended X-ray adsorption fine structure curve-fitting analysis. On the contrary, [Ru6C(CO)16Me]- in a homogeneous system did not catalyse this reaction and conventional impregnation Ru-SiO2 catalysts showed only 0-0.09% selectivities. A reaction mechanism is presented.
    研究論文(学術雑誌), 英語
  • Catalytic Reactions on a Metal Oxide Single Crystal: Switchover of the Reaction Paths in Formic Acid Decomposition on TiO2(110)
    Hiroshi Onishi; Tetsuya Aruga; Yasuhiro Iwasawa
    Journal of the American Chemical Society, 115巻, 22号, 掲載ページ 10460-10461, 出版日 1993年11月01日, 査読付
    研究論文(学術雑誌), 英語
  • Novel reaction path induced by selective blocking of surface atoms: methanol dehydrogenation on Mo(112)-(1 × 2)-O
    K.-i. Fukui; T. Aruga; Y. Iwasawa
    Surface Science, 295巻, 1-2号, 掲載ページ 160-168, 出版日 1993年09月20日, 査読付
    英語
  • HREELS study on CO adsorbed on clean, nitrided and oxidized Fe Ru(001) surfaces
    T. Sasaki; T. Aruga; Y. Iwasawa
    Surface Science, 291巻, 3号, 掲載ページ 429-438, 出版日 1993年07月10日, 査読付
    英語
  • CO-BREATHING RUTHENIUM CARBIDO CLUSTERS ON MGO IN CO/H-2 REACTION CONDITIONS
    Y IZUMI; T CHIHARA; H YAMAZAKI; Y IWASAWA
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 115巻, 14号, 掲載ページ 6462-6463, 出版日 1993年07月, 査読付
    英語
  • Structures and catalysis of new Nb dimers on SiO2
    Nobuyuki Ichikuni; Yasuhiro Iwasawa
    Catalysis Today, Elsevier BV, 16巻, 3-4号, 掲載ページ 427-434, 出版日 1993年05月03日, 査読付
    研究論文(学術雑誌)
  • PHOTOCHEMICAL DECOMPOSITION OF TRIETHYLGALLIUM ON SI(111) STUDIED BY MEANS OF STM, LEED, AES AND MASS-SPECTROSCOPY
    J INUKAI; W MIZUTANI; K FUKUI; H SHIMIZU; Y IWASAWA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 32巻, 4号, 掲載ページ 1768-1771, 出版日 1993年04月, 査読付, Adsorption and photochemical decomposition of triethylgallium [Ga(C2H5)3] on Si(111) at room temperature were investigated by means of low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), scanning tunneling microscopy (STM) and mass spectroscopy (MS). Ga(C2H5)3 was adsorbed on Si(111) until its saturation, at which point LEED and STM indicated disordered adsorption of the molecules. Irradiation of ultraviolet light onto the Ga(C2H5)3-saturated surface caused carbon incorporation contrary to the case of pyrolysis. Ethyl species were proposed to result from the photon absorption processes of the molecules.
    研究論文(学術雑誌), 英語
  • An unusual adsorption state of hydrogen on the Pd(100)-p(2 × 2)-p4g-Al bimetallic surface
    Hiroshi Onishi; Tetsuya Aruga; Yasuhiro Iwasawa
    Surface Science, 283巻, 1-3号, 掲載ページ 213-216, 出版日 1993年03月01日, 査読付, A Pd(100) surface modified by aluminum was investigated with AES, LEED and H2-TPD. The Al/Pd(100) surface gives an ordered surface alloy with p(2 × 2)-p4g symmetry upon annealing at 700 K. Molecular hydrogen dissociates spontaneously on the p(2 × 2)-p4g surface alloy, whereas the Al monolayer deposited at 300 K prevents the adsorption of H2. A recombinative desorption (δ-H2) process starts on the alloy at 360 K with first-order kinetics. The activation energy and the pre-exponential factor for the δ desorption state are evaluated to be 144 ± 10 kJ/mol and 4 × 1020±1 s-1, respectively. These unusually ascribed to bimetallic ensembles on the ordered surface alloy. © 1993.
    研究論文(学術雑誌), 英語
  • Chemisorption of CO and H2 on clean and oxygen-modified Mo(112)
    K.-i. Fukui; T. Aruga; Y. Iwasawa
    Surface Science, 281巻, 3号, 掲載ページ 241-252, 出版日 1993年02月01日, 査読付
    英語
  • Reactant-promoted reaction mechanism for water-gas shift reaction on Rh-doped CeO2
    Takafumi Shido; Yasuhiro Iwasawa
    Journal of Catalysis, 141巻, 1号, 掲載ページ 71-81, 出版日 1993年, Reactant-promoted reaction mechanism for catalytic water-gas shift reaction (WGSR) on Rh-doped CeO2, including the activation of intermediate by a reactant, has been investigated by FT-IR. The intermediate of WGSR on Rh/CeO2 is bidentate formate produced from CO and terminal (on-top) surface OH groups on Ce ions: 65% of the surface formates decomposed to -OH + CO (backward decomposition) and only 35% of them decomposed to H2 + CO2 (forward decomposition) in vacuum. In the coexistence of second-adsorbed water molecules, almost 100% of the formate decomposed to H2 + CO2. Besides the direct change of decomposition selectivity, the rate constant of the forward decomposition and the activation energy were surprisingly affected by water coadsorption. The rate constant increased one hundred times and the activation energy decreased from 55.6 to 33.3 kJ mol−1. The rate-determining step for catalytic WGSR on Rh/CeO2 is the decomposition of the bidentate formate to H2 and unidentate carbonate. The desorption of CO2 by the decomposition of unidentate carbonate was also promoted by H2O coexistence. The phenomena observed on Rh/CeO2 are entirely different from those on pure CeO2 and similar to the case of ZnO surface. The reactant-promoted reaction mechanism for WGSR is illustrated. © 1993 Academic Press, Inc.
    研究論文(学術雑誌), 英語
  • In situ d electron density of Pt particles on supports by XANES
    Nobuyuki Ichikuni; Yasuhiro Iwasawa
    Catalysis Letters, Springer Science and Business Media LLC, 20巻, 1-2号, 掲載ページ 87-95, 出版日 1993年, 査読付
    研究論文(学術雑誌)
  • NEW SURFACE NB-DIMERS CHEMICALLY INTERACTED WITH SIO2 - REGULATION OF THE CATALYSIS BY MOLECULAR DESIGN OF REACTION SITES
    N ICHIKUNI; Y IWASAWA; GA SOMORJAJ; JW HIGHTOWER; D WANG; RW JOYNER; H KUNG; K JERABEK; JC VOLTA
    STUDIES IN SURFACE SCIENCE AND CATALYSIS, ELSEVIER SCIENCE BV, 75巻, 掲載ページ 477-487, 出版日 1993年, 査読付, New Nb dimers on a SiO2 surface prepared by using [Nb(eta5-C5H5)H-mu-(eta5, eta1-C5H4)]2 were found to have an oxygen-bridged dimeric structure(Nb-O(surface)=0.193 nm; Nb--Si=0.328 nm; Nb--Nb=0.303 nm) by EXAFS. The attached Nb dimers were active for ethanol dehydration in contrast to the dehydrogenation ability of the Nb monomer catalyst. The regulation of the catalysis from dehydrogenation to dehydration, or equivalently from basic property to acidic property, was achieved by the nucleation of one Nb atom to two Nb atoms in active structures. The inverse isotope effect for ethene formation through the late-transition state of reaction was observed. The rate constant for ethene formation reduced by the second ethanol adsorption on the adjacent Nb site. It was also found that the selectivity of ethanol reaction was affected by the separation of Nb-Nb on SiO2.
    研究論文(学術雑誌), 英語
  • PROMOTING EFFECT AND HYDROGEN SPILLOVER IN SUPPORTED SERH6- CLUSTER CATALYSTS
    Y IZUMI; Y IWASAWA
    STUDIES IN SURFACE SCIENCE AND CATALYSIS, ELSEVIER SCIENCE BV, 77巻, 掲載ページ 241-246, 出版日 1993年, 査読付, The promoting effect of Se additive and the catalysis including hydrogen spillover for ethene hydroformylation on supported Rh6 cluster were investigated. Se enhanced propanal formation by 1.9 times at Se/Rh6 = 0.6 and the selectivity toward propanal formation increased from 17% to 50% at Se/Rh6 = 1.0. The retention of the cluster framework after Se doping and catalytic reactions was proved by EXAFS and FT-IR. The observed non-integer ratio of Se/Rh6 (=0.6) for the maximum activity implies that hydrogen atoms adsorbed on Rh6 clusters without Se spilled over to Rh6 clusters doped with Se on which propanal was selectively formed. In this case the hydrogen supply to Se-doped Rh6 clusters on MgO is rate-datermining. The addition of Pt (0.15 wt%) enhanced the rate of propanal formation on SeRh6/MgO (Se/Rh = 1.0). This observation provides evidence on the important contribution of hydrogen spillover from metallic Pt to Rh6 with Se atom on MgO to ethene hydroformylation catalysis.
    研究論文(学術雑誌), 英語
  • CONTROL OF THE METHANOL REACTION PATHWAY BY OXYGEN ADSORBED ON MO(112)
    T ARUGA; K FUKUI; Y IWASAWA
    CATALYTIC SELECTIVE OXIDATION, AMER CHEMICAL SOC, 523巻, 掲載ページ 110-121, 出版日 1993年, 査読付
    研究論文(国際会議プロシーディングス), 英語
  • PROMOTING EFFECTS OF SN ON NO DISSOCIATION AND NO REDUCTION WITH H-2 ON RH-SN/SIO2 CATALYSTS
    K TOMISHIGE; K ASAKURA; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 2号, 掲載ページ 184-185, 出版日 1993年01月, 査読付, The Rh-Sn/SiO2 catalysts prepared by the selective reaction of Me4Sn with Rh/SiO2 show remarkably high activities for NO dissociation and NO catalytic reduction with H-2 as compared with Rh/SiO2.
    研究論文(学術雑誌), 英語
  • POLARIZED TOTAL-REFLECTION FLUORESCENCE EXAFS STUDIES ON ASYMMETRIC SURFACE-STRUCTURES OF CATALYSTS
    M SHIRAI; K ASAKURA; Y IWASAWA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, JAPAN J APPLIED PHYSICS, 32巻, 32号, 掲載ページ 413-415, 出版日 1993年, 査読付, Asymmetiric structures of active metal oxides (Cu oxide, Co oxide) on single crystal surfaces were determined by polarized total-reflection fluorescence XAFS spectroscopy (PTRF-XAFS). An asymmetric particle structure (or growth mode) of small spinel-like Co3O4 was directly demonstrated by this method.
    研究論文(学術雑誌), 英語
  • REVERSIBLE ACTIVITY ENHANCEMENT OF SIO2-SUPPORTED GROUP-VIII METAL-CATALYSTS BY PRETREATMENT TEMPERATURE
    J. J. Inukai; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 143巻, 1号, 掲載ページ 22-31, 出版日 1993年, 査読付
    英語
  • CHARACTERIZATION OF BIMETALLIC SURFACE-STRUCTURES OF HIGHLY-ACTIVE RH-SN/SIO2 CATALYSTS FOR NO-H2 REACTION BY EXAFS
    K. Tomishige; K. Asakura; Y. Iwasawa
    Catalysis Letters, 20巻, 20号, 掲載ページ 15-22, 出版日 1993年, 査読付
    英語
  • ASYMMETRIC STRUCTURE-ANALYSIS OF ACTIVE SURFACE-SITES BY IN-SITU POLARIZED TOTAL-REFLECTION FLUORESCENCE EXAFS
    K. Asakura; M. Shirai; Y. Iwasawa
    Catalysis Letters, 20巻, 20号, 掲載ページ 117-124, 出版日 1993年, 査読付
    英語
  • SELENIUM-DOPED RH6 CARBONYL CLUSTERS ON MGO - STRUCTURES AND PROMOTING EFFECTS IN ETHENE HYDROFORMYLATION
    Y IZUMI; Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 96巻, 26号, 掲載ページ 10942-10948, 出版日 1992年12月, 査読付, Selenium-modified Rh6(CO)16/MgO catalysts were prepared by the reaction of Rh6(CO)16/MgO with (CH3)2Se in order to examine the promoting effect of an electronegative additive on Rh catalysis for ethene hydroformylation. The deposited Se (Se/Rh6 = 0.6) enhanced the rate of propanal formation 1.9 times as compared with the case of an undeposited catalyst. The selectivity of the hydroformylation was improved from 20 to 50% by the Se addition. To the contrary, the monotonous suppression of ethane formation by increasing the Se amount was observed. Further doping of Se reduced the hydroformylation activity. TPD, IR, and Se K-edge and Rh K-edge EXAFS revealed that (CH3)2Se reacted with the Rh atoms of partially-decarbonylated Rh6 species on the MgO surface, forming Se-Rh bonds at a distance of 0.244 nm. XPS data suggested that the oxidation state of Se in the catalyst is Se-, while Rh is in a nearly metallic state. CO adsorbs on the rhodium atoms bonded to Se, which is contrasted to blocking of the neighboring Rh sites by Se atom observed with usual impregnated Rh catalysts. The structures of the Se-undoped and -doped Rh6 clusters on MgO are presented in relation to the active site of the cluster catalyst. The data indicate an advantage of molecular clusters over impregnated particles in adsorption capability and catalysis.
    英語
  • COADSORPTION OF C2H2 AND CO ON RU(001) - FORMATION OF MIXED ADLAYER AND THE EFFECT OF CO ON ACETYLENE ADSORPTION AND DECOMPOSITION
    T SASAKI; F KAWADA; T ARUGA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 278巻, 3号, 掲載ページ 291-302, 出版日 1992年11月, 査読付, The coadsorption of CO and acetylene (C2H2) on Ru(001) has been investigated by LEED, TPD and HREELS. CO and C2H2 form an ordered mixed adlayer. A structure model for the mixed adlayer of CO and C2H2 is proposed. C2H2 in a pure layer exhibits different features at low and high coverages. C2H2 coadsorbed with CO shows the loss features characteristic of the low-coverage phase in a pure C2H2 layer irrespective of theta(C2H2) and theta(CO). The effect of coadsorbed CO on the dissociation of C2H2 has also been examined. The coadsorbed CO increased the decomposition temperature for ethylidyne derived from C2H2, while it promoted the dissociation of CxH.
    研究論文(学術雑誌), 英語
  • SELECTIVE SYNTHESIS OF OXYGENATES IN THE CO-H2 REACTION ON SUPPORTED RUTHENIUM CARBIDO-CLUSTER CATALYSTS
    Y IZUMI; T CHIHARA; H YAMAZAKI; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 96巻, 19号, 掲載ページ 1395-1396, 出版日 1992年10月, 査読付, Supported ruthenium carbido-cluster catalysts ([Ru6C(CO)16Me]-/oxide) selectively produced methanol, dimethyl ether, and formaldehyde in CO-H-2, in contrast to the preferential formation of methane and hydrocarbons on supported ruthenium cluster catalysts {[Ru6(CO)18]2-/oxide} without the interstitial carbon and conventional metallic Ru catalysts.
    研究論文(学術雑誌), 英語
  • COADSORPTION OF CO AND METHYLAMINE ON RU(001) - REACTION PATHS OF METHYLAMINE INDUCED BY CO IN ORDERED COADSORBED STRUCTURES
    T SASAKI; T ARUGA; H KURODA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 276巻, 1-3号, 掲載ページ 69-85, 出版日 1992年10月, 査読付, The coadsorption of CO and methylamine on Ru(001) has been investigated by LEED, TPD and HREELS to clarify coadsorbate-induced reaction phenomena in ordered coadsorbed layers. CO and methylamine formed mixed adsorption layers accompanied with the change of adsorption site for CO by the interaction with methylamine. The dissociation process of methylamine changed as a function of partial CO coverage. For methylamine alone on Ru(001), the C-H, N-H, and C-N bonds dissociate simultaneously at 280-320 K. In the presence of low-coverage CO molecules (theta almost-equal-to 0.3), NH2 species was formed and persisted on the surface up to 380 K whereas the coadsorbed CO molecules behaved as a spectator for the dissociation of the C-H bonds. In the presence of high-coverage (0.5-0.68) CO, a well ordered (2 x 2) phase was formed and the new partial dehydrogenation of methylamine takes place to produce a species containing a C=N double bond as a stable intermediate, followed by complete dissociation at higher temperatures. The control of reaction path by coadsorbates is discussed.
    研究論文(学術雑誌), 英語
  • REVERSIBLE STRUCTURE TRANSFORMATION OF ZRO2 ON PD BLACK
    K ASAKURA; Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 96巻, 18号, 掲載ページ 7386-7389, 出版日 1992年09月, 査読付, The structure and behavior of ZrO2 on Pd black were studied by means of extended X-ray absorption fine structure (EXAFS). The reversible structure change of ZrO2 with the reduction at 773 K and oxidation at 673 K was observed. The Zr-Zr distances on ZrO2/Pd after oxidation at 673 K were determined to be 0.345 and 0.363 nm (named delta-ZrO2), while ZrO2/Pd after reduction at 773 K showed the tetragonal ZrO2 structure with a Zr-Zr distance at 0.366 nm. The delta-structure is stable against the H-2 reduction at 473 K. The delta-ZrO2 Structure is suggested to be stabilized by the interface Pd oxide.
    研究論文(学術雑誌), 英語
  • Control of reaction path on ordered oxygen/Mo(112)
    Tetsuya Aruga; Ken ichi Fukui; Yasuhiro Iwasawa
    American Chemical Society, Division of Petroleum Chemistry, Preprints, 37巻, 4号, 掲載ページ 1038-1043, 出版日 1992年08月01日, In order to acquire the means to modify the electronic properties and steric confinement of the surface, we have examined the modification of the Mo(112) surface by atomic oxygen. Our aim was as follows: First, the electronic effect of oxygen adatoms on the first-layer of Mo atoms can be probed directly by the adsorption of simple molecules, since oxygen atoms are expected to occupy trough sites and the first-layer atoms are accessible for gas-phase molecules. Second, the selective blocking of the second-layer Mo atoms, with seven nearest neighbors, would alter catalytic reaction paths, since high-coordintation metal sites exhibit high electronic fluctuations and are believed to play a major role in structure-sensitive catalytic reactions. The result of the CO adsorption experiment for oxygen-modified Mo(112) deemonstrrates the possibility of quantitative control of the electronic structure of the Mo atoms. The selective blocking of the second-layer Mo atoms gave rise to a new dehydrogenation path of methanol, unlike the oxidative dehydrogenation usually observed on Mo oxides.
    研究論文(学術雑誌), 英語
  • METHYLRUTHENIUM CARBIDOCARBONYL CLUSTERS SUPPORTED ON INORGANIC OXIDES - CHARACTERIZATION AND SELECTIVE ACETALDEHYDE FORMATION
    Y IZUMI; TH LIU; K ASAKURA; T CHIHARA; H YAMAZAKI; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS, ROYAL SOC CHEMISTRY, 14号, 掲載ページ 2287-2297, 出版日 1992年07月, 査読付, The clusters [Ru6C(CO)16Me]- supported on SiO2, Al2O3 and TiO2 were characterized by means of extended X-ray absorption fine structure (EXAFS), temperature-programmed desorption (TPD) and Fourier-transform IR spectroscopy in relation to developments of new catalytic systems. The EXAFS analysis revealed that the Ru6C cluster framework which has an interstitial carbon atom was stable at 473 (SiO2), 523 (Al2O3) and 473 K (TiO2) under CO or CO + H-2. The supported clusters produced methane upon heating in vacuum by the reaction with surface hydrogen-bonded OH groups, whereas in the presence of CO + H-2 acetaldehyde was preferably produced, unlike [Ru6C(CO)16Me]- in a homogeneous system where only methane was formed. The selectivity to acetaldehyde was larger with SiO2 (77%) than with Al2O3 (15) or TiO2 (10%).
    研究論文(学術雑誌), 英語
  • A NEW STRUCTURE AND HYDROGENATION ACTIVITY OF FE3(CO)12 SUPPORTED ON SIRX(RCH3, C6H5)-MODIFIED SIO2 SURFACES
    K ASAKURA; K OOI; Y IWASAWA
    JOURNAL OF MOLECULAR CATALYSIS, ELSEVIER SCIENCE BV, 74巻, 1-3号, 掲載ページ 345-351, 出版日 1992年07月, 査読付, A new Fe carbonyl cluster [Fe3(CO)6] with a Fe-Fe distance of 0.273 nm, which is longer than that in Fe3(CO)12 (0.262 nm) and in Fe metal (0.248 nm), was prepared by supporting Fe3(CO)12 On SiRx/SiO2(R=CH3, C6H5) followed by treatment at 368 K in vacuum. The Fe clusters on SiMe2/SiO2 showed a higher activity - by a factor of 200 - than the Fe species on SiO2 for propene hydrogenation.
    研究論文(学術雑誌), 英語
  • STRUCTURES AND CATALYTIC ACTIVITY OF PT-MO BIMETALLIC ENSEMBLES DERIVED FROM A NEW PLANAR [PTMO6O24]8- HETEROPOLYANION SUPPORTED ON AL2O3 AND SIO2
    T LIU; K ASAKURA; U LEE; Y MATSUI; Y IWASAWA
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS, 135巻, 2号, 掲載ページ 367-385, 出版日 1992年06月, 査読付
    研究論文(学術雑誌), 英語
  • ASYMMETRIC STRUCTURE DETERMINATION OF COPPER-OXIDE ON ALPHA-QUARTZ(0001) SURFACE BY POLARIZED TOTAL-REFLECTION FLUORESCENCE EXTENDED X-RAY ABSORPTION FINE-STRUCTURE SPECTROSCOPY
    M SHIRAI; K ASAKURA; Y IWASAWA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 6号, 掲載ページ 1037-1040, 出版日 1992年06月, 査読付, Cu oxides were supported on alpha-quartz(0001) by CVD of Cu(DPM)2 (DPM: dipyvaloylmethanate) and the subsequent calcination. The structure of the Cu species in the submonolayer was determined by polarized total-reflection fluorescence extended X-ray absorption fine structure (EXAFS) spectroscopy. Both s- and p-polarized EXAFS data revealed that Cu atoms were dispersed in a monomer form on the three-fold hollow sites of the quartz surface with the Cu-O distance of 0.201 nm.
    研究論文(学術雑誌), 英語
  • Regulation of reaction intermediate by reactant in the water-gas shift reaction on CeO2, in relation to reactant-promoted mechanism
    Takafumi Shido; Yasuhiro Iwasawa
    Journal of Catalysis, 136巻, 2号, 掲載ページ 493-503, 出版日 1992年, Reaction regulation by intermediate-reactant interaction in the water-gas shift reaction (H2O + CO → H2 + CO2
    WGSR) on CeO2 was investigated in relation to the reactant-promoted mechanism on MgO and ZnO by FT-IR. Terminal OH groups on partially reduced CeO2 reacted with CO to produce bridge formates. Bridge formates were converted to bidentate formates above 443 K, and this transformation occurred at room temperature when water coexisted. The decomposition of the surface formates was affected by the water molecule
    70% of the bidentate formates decomposed to OH + CO (backward decomposition) and 30% of them decomposed to H2 + CO2 (forward decompose to H2 and unidentate carbonates. The decomposition of the unidentate carbonates to CO2 was promoted by coadsorbed water. The results are also discussed in comparison with the formates increased from 94 kJ mol-1 without water to 193 kJ mol-1 with water. Isotope effects were observed on the hydrogen atoms of both formate and hydroxyl, giving a proposed transition state in the reaction mechanism. The bidentate formates reacted with the adjacent hollow-site OH to decompose to H2 and unidentate carbonates. The decomposition of the unidentate carbonates to CO2 was promoted by coadsorbed water. The results are also discussed in comparison with the results for WGSR on MgO and ZnO. © 1992.
    研究論文(学術雑誌), 英語
  • Methylruthenium carbidocarbonyl clusters supported on inorganic oxides: Characterization and selective acetaldehyde formation
    Yasuo Izumi; Tai-Hui Liu; Kiyotaka Asakura; Teiji Chihara; Hiroshi Yamazaki; Yasuhiro Iwasawa
    Journal of the Chemical Society, Dalton Transactions, 14号, 掲載ページ 2287-2297, 出版日 1992年, 査読付, The clusters [Ru6C(CO)16Me]- supported on SiO2, Al2O3 and TiO2 were characterized by means of extended X-ray absorption fine structure (EXAFS), temperature-programmed desorption (TPD) and Fourier-transform IR spectroscopy in relation to developments of new catalytic systems. The EXAFS analysis revealed that the Ru6C cluster framework which has an interstitial carbon atom was stable at 473 (SiO2), 523 (Al2O3) and 473 K (TiO2) under CO or CO + H2. The supported clusters produced methane upon heating in vacuum by the reaction with surface hydrogen-bonded OH groups, whereas in the presence of CO + H2 acetaldehyde was preferably produced, unlike [Ru6C(CO)16Me]- in a homogeneous system where only methane was formed. The selectivity to acetaldehyde was larger with SiO2 (77%) than with Al2O3 (15) or TiO2 (10%).
    研究論文(学術雑誌), 英語
  • ZIRCONIUM-OXIDE SUPPORTED ON PD(100) - CHARACTERIZATION BY SCANNING TUNNELING MICROSCOPY AND TUNNELING SPECTROSCOPY
    K ASAKURA; Y IWASAWA; SK PURNELL; BA WATSON; MA BARTEAU; BC GATES
    CATALYSIS LETTERS, BALTZER SCI PUBL BV, 15巻, 4号, 掲載ページ 317-327, 出版日 1992年, 査読付, Scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) were used to characterize the structure of a model metal-supported dispersed metal oxide, ZrO2 on Pd(100). STM images illustrate changes in the surface morphology of the ZrO2 resulting from various chemical treatments. When the sample was treated in O2, the ZrO2 appeared as a smooth, featureless overlayer of varying thickness wetting the Pd. After treatment in H-2, the ZrO2 formed non-wetting particles on the Pd, with a sharp Pd-ZrO2 interface. TS provided a fingerprint that verified the presence of a semiconducting overlayer on a metallic support. These results appear to be consistent with X-ray absorption spectra of ZrO2 supported on Pd black, reported elsewhere.
    研究論文(学術雑誌), 英語
  • ANISOTROPIC STRUCTURE-ANALYSIS FOR COBALT OXIDES ON ALPHA-AL2O3 (0001) BY POLARIZED TOTAL-REFLECTION FLUORESCENCE EXTENDED X-RAY ABSORPTION FINE-STRUCTURE
    M SHIRAI; K ASAKURA; Y IWASAWA
    CATALYSIS LETTERS, BALTZER SCI PUBL BV, 15巻, 3号, 掲載ページ 247-254, 出版日 1992年, 査読付, Anisotropic structure analyses for [CoO(x)]/alpha-Al2O3 (0001) and [Co3O4]n/alpha-Al2O3 (0001) which were derived from Co2(CO)8/alpha-Al2O3 (0001) were performed by a polarized total-reflection fluorescence extended X-ray absorption fine structure (EXAFS) technique. Both s- and p-polarized EXAFS data revealed that the cobalt atoms of [CoO(x)] were located on three-fold hollow sites of alpha-Al2O3 (0001) in a monomer form and that a thin spinel structure [Co3O4] grew with the (001) plane parallel to alpha-Al2O3 (0001).
    研究論文(学術雑誌), 英語
  • STRUCTURE OF ONE-ATOMIC-LAYER TITANIUM-OXIDE ON SILICON-OXIDE AND ITS PALLADIUM-MEDIATED RESTRUCTURING
    K ASAKURA; J INUKAI; Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 96巻, 2号, 掲載ページ 829-834, 出版日 1992年01月, 査読付, The SiO2-attached one-atomic-layer titanium oxides (TiO2) were prepared by using the surface reaction between the OH groups of SiO2 and Ti(i-OC3H4)4 followed by calcination at 773 K. The one atomic layer TiO2 was characterized to have an anatase-like one-atomic-layer structure with (101) orientation by means of extended X-ray absorption fine structure spectra, X-ray diffraction, and X-ray fluorescence. The Pt or Pd supported on the one atomic layer TiO2 was also studied from chemical and structural interests. The amount of H-2 or CO adsorbed on these samples did not decrease with the reduction in H-2 at 773 K unlike the large suppression of the adsorption on Pt/TiO2 or Pd/TiO2 catalysts in the strong metal-support interaction state. The anatase structure of the one atomic layer TiO2 was maintained for the Pt-deposited sample, whereas the anatase structure was transformed to a rutile structure with (110) orientation keeping the one atomic layer structure for the Pd-deposited sample. The transformation from anatase to rutile structure could be mediated by interaction with Pd particles.
    研究論文(学術雑誌), 英語
  • COADSORPTION OF CO AND METHYLAMINE ON RU(001) - EFFECT OF COADSORBED CO ON DISSOCIATION PATHS OF METHYLAMINE
    T SASAKI; T ARUGA; H KURODA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 249巻, 1-3号, 掲載ページ L347-L353, 出版日 1991年06月, 査読付, The effect of coadsorbed CO on dissociation paths of methylamine on Ru(001) has been examined by LEED, TPD and HREELS. It was found that the effect of CO considerably changes as a function of partial CO coverage. For methylamine alone on Ru(001), the C-H and N-H bonds are dissociated simultaneously at 280-320 K. In the presence of low-coverage (approximately 0.3) CO molecules, an NH2 species is formed persisting on the surface up to > 350 K, resulting in a relative enhancement of C-H bond scission. In the presence of high-coverage (0.5-0.68) CO, a well ordered (2 x 2) phase forms and partial dehydrogenation of methylamine takes place forming a species containing a C = N double bond as a stable intermediate, followed by complete dissociation at higher temperatures.
    英語
  • Study on d state of platinum in Pt/SiO2 and Na/Pt/SiO2 catalysts under C=C hydrogenation conditions by X-ray absorption near-edge structure spectroscopy
    Hideaki Yoshitake; Yasuhiro Iwasawa
    Journal of Physical Chemistry, 95巻, 19号, 掲載ページ 7368-7372, 出版日 1991年, The change in the d-electron density of platinum during D2 + CH2=CHX reactions on Pt/SiO2 and Na/Pt/SiO2 catalysts and its influence on the catalysis were studied by X-ray absorption near-edge structure (XANES) spectroscopy, kinetics and FT-IR. It was demonstrated from the change of the white lines in XANES spectra at Pt L2 and L3 edges that CH2=CHX (X = H, CH3, COCH3, CF3, and CN) is adsorbed on the Pt surface and extracts the electrons of the d state. Hence, the deuterogenation rate is reduced as the value of Hammett's σp increases. The linear free energy relationship between the reaction rate and σp was observed for the deuterogenation of CH2=CHX. The rate of ethene deuterogenation was promoted by Na2O addition. The electron density of unoccupied d states of Pt under vacuum decreased by Na2O addition, indicating the electron donation from Na2O to Pt particles. However, most of these additional electrons were observed to move to ethene under reaction conditions. The acceptor of the electrons was suggested to be di-σ-ethene by the shift of ν(C-H). The kinetic parameters are discussed in relation to the change in the d state of Pt as a function of σp and Na quantity. © 1991 American Chemical Society.
    研究論文(学術雑誌), 英語
  • STRUCTURES AND CATALYSIS OF PLANE [PTMO6O24]8- POLYANION SUPPORTED ON AL2O3 AND SIO2
    T LIU; Y MATSUI; U LEE; K ASAKURA; Y IWASAWA
    CATALYTIC SCIENCE AND TECHNOLOGY, VOL 1, KODANSHA LTD, 1巻, 掲載ページ 267-272, 出版日 1991年, 査読付
    研究論文(国際会議プロシーディングス), 英語
  • SELF TERMINATING REACTION OF DIPIVALOYLMETHANATE COMPLEXES WITH HYDROXYL-GROUPS ON OXIDE SURFACE
    R SEKINE; M KAWAI; K ASAKURA; Y IWASAWA
    ATOMIC LAYER GROWTH AND PROCESSING, MATERIALS RESEARCH SOC, 222巻, 掲載ページ 333-338, 出版日 1991年, 査読付
    研究論文(国際会議プロシーディングス), 英語
  • Short- and long-range promotion by sodium additive in D2+CH2=CH2 reaction over silica-supported platinum catalysts
    Yasuhiro Iwasawa
    Journal of Catalysis, 131巻, 掲載ページ 276-284, 出版日 1991年, 査読付
    研究論文(学術雑誌), 英語
  • PROMOTING EFFECTS OF SE ON RH/SIO2 CATALYSIS FOR ETHENE HYDROFORMYLATION
    Y. Izumi; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 132巻, 2号, 掲載ページ 566-570, 出版日 1991年, 査読付
    英語
  • PROMOTING EFFECTS OF SE ON RH/ZRO2 CATALYSIS FOR ETHENE HYDROFORMYLATION
    Y. Izumi; K. Asakura; Y. Iwasawa
    Journal of Catalysis, 127巻, 2号, 掲載ページ 631-644, 出版日 1991年, 査読付
    英語
  • PREPARATION AND CATALYTIC PROPERTIES OF A NEW SIO2-ATTACHED NB-DIMER CATALYST - REGULATION OF ACIDITY BASICITY BY THE NUMBER OF METAL ATOMS IN SURFACE-ACTIVE SITES
    N. Ichikuni; K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Chemical Communications, 2号, 掲載ページ 112-113, 出版日 1991年, 査読付
    英語
  • TEMPERATURE-DEPENDENCE OF EXAFS SPECTRA OF SUPPORTED SMALL METAL PARTICLES
    H. Kuroda; T. Yokoyama; K. Asakura; Y. Iwasawa
    Faraday Discussions, 92巻, 92号, 掲載ページ 189-198, 出版日 1991年, 査読付
    英語
  • SYNTHESIS, CHARACTERIZATION, AND CATALYTIC PROPERTIES OF SIO2-ATTACHED ONE-ATOMIC-LAYER NIOBIUM OXIDE CATALYSTS
    K. Asakura; Y. Iwasawa
    Journal of Physical Chemistry, 95巻, 4号, 掲載ページ 1711-1716, 出版日 1991年, 査読付
    英語
  • STRUCTURE AND ELECTRONIC STATE OF MOLYBDENUM SUBCARBONYL SPECIES ENCAGED IN ZEOLITE
    Y. Okamoto; T. Imanaka; K. Asakura; Y. Iwasawa
    Journal of Physical Chemistry, 95巻, 9号, 掲載ページ 3700-3705, 出版日 1991年, 査読付
    英語
  • MONOLAYER STRUCTURES OF NIOBIC ACIDS SUPPORTED ON SIO2 AND THEIR CATALYTIC ACTIVITIES FOR ESTERIFICATION OF ACETIC-ACID WITH ETHANOL
    M. Shirai; K. Asakura; Y. Iwasawa
    Journal of Physical Chemistry, 95巻, 24号, 掲載ページ 9999-10004, 出版日 1991年, 査読付
    英語
  • METAL-ASSISTED HYDROFORMYLATION ON A SIO2-ATTACHED RH DIMER - INSITU EXAFS AND FT-IR OBSERVATIONS OF THE DYNAMIC BEHAVIORS OF THE DIMER SITE
    K ASAKURA; K KITAMURABANDO; Y IWASAWA; H ARAKAWA; K ISOBE
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 112巻, 25号, 掲載ページ 9096-9104, 出版日 1990年12月, 査読付
    研究論文(学術雑誌), 英語
  • INTERACTION BETWEEN CO AND NH3 COADSORBED ON RU(001) - ITS EFFECTS ON THE ORDERING IN MIXED ADLAYERS AND THE AMMONIA DISSOCIATION
    T SASAKI; T ARUGA; H KURODA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 240巻, 1-3号, 掲載ページ 223-244, 出版日 1990年12月, 査読付, The coadsorption of CO and ammonia on Ru(001) has been investigated by low-energy electron diffraction (LEED), temperature-programmed desorption (TPD) and high-resolution electron energy-loss spectroscopy (HREELS). The main focus has been on the interaction between different admolecules on the surface and its important role in surface reaction. Exposing CO-precovered Ru(001) to ammonia at 100 K leads to the formation of mixed ordered layers with a (2 x 2) periodicity. It was found that two types of (2 x 2) structures are formed depending on the CO precoverage. One of the (2 x 2) structures (alpha-phase) contains one CO and two ammonia molecules per (2 x 2) unit cell and the other (beta-phase) contains two CO and one ammonia. Structure models for the two phases are proposed based on vibrational spectra measured for the coadsorbed phases of CO and ammonia ((NH3)-N-15) or ND3). TPD results suggest that the ammonia dissociation takes place on clean and CO-precovered Ru(001). The amount of dissociated ammonia decreased initially with increasing CO precoverage, passed a minimum at theta-CO = 0.25, increased with a further increase of CO coverage, and eventually reached a saturation value above theta-CO = 0.5. The dissociation of ammonia in the beta-(2 x 2) structure was found to be enhanced by a factor of 4-6 as compared with the dissociation in the alpha-(2 x 2) structure. The HREEL spectra indicated that the C3V molecular axis of ammonia is titled in the coadsorbed layers, the tilting being most pronounced in the beta-(2 x 2) phase with a high CO partial coverage. This observation suggests that the tilting of ammonia due to the interaction with CO facilitates electron donation from Ru4d to LUMO of ammonia, leading to the N-H bond dissociation. The microscopic model for the CO-NH3 interaction on metal surfaces is presented.
    研究論文(学術雑誌), 英語
  • Photoelectron spectroscopic study of clean and CO adsorbed NI/TiO2(110) interfaces
    Hiroshi Onishi; Tetsuya Aruga; Chikashi Egawa; Yasuhiro Iwasawa
    Surface Science, 233巻, 3号, 掲載ページ 261-268, 出版日 1990年07月02日, 査読付, Nickel deposited on a rutile TiO2(110) surface was examined by XPS, AES, UPS and LEED. The nickel deposits formed an atomic layer at 300 K with a density of 8 × 1014 cm-2. A three-dimensional agglomeration was detected above 1 ML, by analyzing the forward scattering of photoelectrons from the Ni 2p core level. The work function deduced from UPS decreased with Ni coverage with a minimum at 0.5 ML. From its initial decrease by 0.7 eV we evaluated the outward dipole to be 0.5 debye per Ni atom. This dipole was attributed to an electron transfer from the Ni deposits into the substrate. The charge transferred was estimated to be not more than 0.1 electron per Ni adatom. As the overlayer grew more dense, the lateral interaction between Ni adatoms predominated and inhibited the electron transfer through the interface. XPS and UPS data revealed that CO was adsorbed molecularly on the Ni/TiO2(110) surfaces at 300 K for all coverages. The uptake of CO increased proportionally to the Ni coverage below 1 ML. © 1990.
    研究論文(学術雑誌), 英語
  • STRUCTURE AND BEHAVIOR OF RU3(CO)12 SUPPORTED ON INORGANIC OXIDE SURFACES, STUDIES BY EXAFS, INFRARED-SPECTROSCOPY AND TEMPERATURE-PROGRAMMED DECOMPOSITION
    K ASAKURA; KK BANDO; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, ROYAL SOC CHEMISTRY, 86巻, 14号, 掲載ページ 2645-2655, 出版日 1990年07月, 査読付
    研究論文(学術雑誌), 英語
  • SURFACE-STRUCTURE AND CATALYSIS FOR CO HYDROGENATION OF THE SUPPORTED RU SPECIES DERIVED FROM THE RU3(CO)12 INORGANIC OXIDES
    K ASAKURA; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, ROYAL SOC CHEMISTRY, 86巻, 14号, 掲載ページ 2657-2662, 出版日 1990年07月, 査読付
    研究論文(学術雑誌), 英語
  • THE POLYMER-PROTECTED PD-PT BIMETALLIC CLUSTERS HAVING CATALYTIC ACTIVITY FOR SELECTIVE HYDROGENATION OF DIENE - PREPARATION AND EXAFS INVESTIGATION ON THE STRUCTURE
    N TOSHIMA; T YONEZAWA; M HARADA; K ASAKURA; Y IWASAWA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 5号, 掲載ページ 815-818, 出版日 1990年05月, 査読付
    研究論文(学術雑誌), 英語
  • METAL-ASSISTED CO INSERTION REACTION ON A NEW SURFACE RHODIUM DIMER CATALYST OBSERVED BY AN INSITU EXTENDED X-RAY ABSORPTION FINE-STRUCTURE TECHNIQUE
    K ASAKURA; K KITAMURABANDO; K ISOBE; H ARAKAWA; Y IWASAWA
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, AMER CHEMICAL SOC, 112巻, 8号, 掲載ページ 3242-3244, 出版日 1990年04月, 査読付
    英語
  • REACTANT-PROMOTED REACTION-MECHANISM FOR CATALYTIC WATER GAS SHIFT REACTION ON MGO
    T SHIDO; K ASAKURA; Y IWASAWA
    JOURNAL OF CATALYSIS, ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS, 122巻, 1号, 掲載ページ 55-67, 出版日 1990年03月, 査読付
    研究論文(学術雑誌), 英語
  • DIRECT OBSERVATION OF UNUSUAL CO INSERTION ON A NEW SIO2-ATTACHED RH DIMER CATALYST BY FTIR
    K KITAMURABANDO; K ASAKURA; H ARAKAWA; Y SUGI; K ISOBE; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 3号, 掲載ページ 253-255, 出版日 1990年02月, 査読付
    研究論文(学術雑誌), 英語
  • Infrared studies of CO adsorbed on supported PtCo catalysts
    M. J. Dees; T. Shido; Y. Iwasawa; V. Ponec
    Journal of Catalysis, 124巻, 2号, 掲載ページ 530-540, 出版日 1990年, The IR spectra of CO adsorbed on aerosil-supported Pt, Co, and several PtCo bimetallics have been investigated. It is observed that the addition of Co to Pt causes a decrease in the IR band wavenumber from 2075 to 2040 cu-1 at a given coverage φ(CO). A decrease in the coverage φ(CO) of the Pt and PtCo bimetallic surfaces also gives rise to a red shift, down to 2040 cm-1. For this reason the effect of Co can be regarded as a geometric effect (dilution of the CO layer). The addition of Co to Pt results in the appearance of a second absorption maximum (above 2000 cm-1. at 2086-2083 cm-1. This maximum disappears relatively quickly following pretreatment in n-hexane. It is ascribed here to the adsorption of CO on smooth surfaces. The monometallic Co system differs considerably from the other systems in that (a) its surface is not blocked easily by n-hexane and (b) passing CO at elevated temperatures results in the formation of CO-carbonyl species. In the bimetallic catalysts no Co with this behavior (unalloyed Co) could be detected. © 1990.
    研究論文(学術雑誌), 英語
  • PREPARATIONS AND CATALYTIC PROPERTIES OF SINGLE, PAIR, AND MONOLAYER NIOBIUM CATALYSTS
    M SHIRAI; N ICHIKUNI; K ASAKURA; Y IWASAWA
    CATALYSIS TODAY, VOL 8, NO 1, ELSEVIER SCIENCE PUBL B V, 掲載ページ 57-66, 出版日 1990年, 査読付
    研究論文(国際会議プロシーディングス), 英語
  • TEMPERATURE-DEPENDENCE OF EXTENDED X-RAY ABSORPTION FINE-STRUCTURE SPECTRA OF RH AND PD CATALYSTS IN THE STRONG METAL SUPPORT INTERACTION STATE
    T YOKOYAMA; K ASAKURA; Y IWASAWA; H KURODA
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 93巻, 26号, 掲載ページ 8323-8327, 出版日 1989年12月, 査読付
    研究論文(学術雑誌), 英語
  • SPECTROSCOPIC EVIDENCE FOR A SURFACE NB CARBENE IN A NEW SIO2-ATTACHED NB CATALYST ACTIVE FOR PROPENE METATHESIS
    K ASAKURA; M NISHIMURA; Y IWASAWA
    JOURNAL OF MOLECULAR CATALYSIS, ELSEVIER SCIENCE BV, 55巻, 1-3号, 掲載ページ 159-169, 出版日 1989年11月, 査読付
    研究論文(学術雑誌), 英語
  • CHEMICAL ENVIRONMENTS AROUND ACTIVE-SITES AND REACTION-MECHANISMS FOR DEUTERIUM ACROLEIN REACTION OVER IR/NB2O5 IN NORMAL AND SMSI STATES
    H YOSHITAKE; K ASAKURA; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I, ROYAL SOC CHEMISTRY, 85巻, 8号, 掲載ページ 2021-2034, 出版日 1989年08月, 査読付
    研究論文(学術雑誌), 英語
  • EXAFS STUDIES ON MOLECULAR PHENOMENA ON SOLID CATALYSTS IN A WORKING STATE
    K ASAKURA; Y IWASAWA
    PHYSICA B, ELSEVIER SCIENCE BV, 158巻, 1-3号, 掲載ページ 142-144, 出版日 1989年06月, 査読付
    研究論文(学術雑誌), 英語
  • EXAFS STUDIES ABOUT THE MECHANISM OF THE CO-OXIDATION REACTION ON THE CO TETRAMER CATALYST
    K ASAKURA; Y IWASAWA
    PHYSICA B, ELSEVIER SCIENCE BV, 158巻, 1-3号, 掲載ページ 152-153, 出版日 1989年06月, 査読付
    研究論文(学術雑誌), 英語
  • EXTENDED X-RAY ABSORPTION FINE-STRUCTURE STUDIES ON THE STRUCTURE CHANGE OF THE AL2O3-ATTACHED [CO-2]4 CATALYST DURING A CO OXIDATION REACTION
    K ASAKURA; Y IWASAWA
    JOURNAL OF PHYSICAL CHEMISTRY, AMER CHEMICAL SOC, 93巻, 10号, 掲載ページ 4213-4218, 出版日 1989年05月, 査読付
    研究論文(学術雑誌), 英語
  • INFLUENCE OF PREDEPOSITED AND POSTDEPOSITED AU ON COADSORBED CO ON RU(001)
    K SAWABE; C EGAWA; T ARUGA; Y IWASAWA
    LANGMUIR, AMER CHEMICAL SOC, 5巻, 2号, 掲載ページ 348-352, 出版日 1989年03月, 査読付
    研究論文(学術雑誌), 英語
  • THE HYDROGEN-EXCHANGE REACTION OF SURFACE DEUTEROXYL GROUPS ON MGO WITH H2
    T SHIDO; K ASAKURA; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I, ROYAL SOC CHEMISTRY, 85巻, 2号, 掲載ページ 441-453, 出版日 1989年02月, 査読付
    研究論文(学術雑誌), 英語
  • Active structures and electronic states for adsorption of CO2 and NO on an Na/TiO2 (110) surface
    Hiroshi Onishi; Tetsuya Aruga; Chikashi Egawa; Yasuhiro Iwasawa
    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 85巻, 8号, 掲載ページ 2597-2604, 出版日 1989年, 査読付, X.p.s. and u.p.s. studies have shown that submonolayer coverages of Na deposited on a rutile TiO2(110) surface remarkably enhance the adsorption of carbon dioxide and nitrogen monoxide forming carbonate and nitride, respectively. The amount of adsorbed CO2 varied with Na coverage showing an S-shaped dependence, where a critical Na coverage of 0.3 monolayer for CO2 adsorption was observed. This threshold coincides with the onset of a c(4 × 2) structure derived from ordered 'Na 2O-dimers', which suggests that the basicity of oxygen atoms on the TiO2(110) surface is markedly enhanced by the 'Na2O-dimer' ensemble of four Na atoms. Single or paired Na atoms play a negligible role in the basic promotion. In contrast, NO decomposes on the Ti3+ cation reduced by Na deposits. The oxidation state of Ti dominates the decomposition of NO.
    研究論文(学術雑誌), 英語
  • Coadsorption of NH3 and CO on Ru(001): The ordering in mixed layers and the effect of intermolecular interactions on NH3 dissociation
    T. Sasaki; T. Aruga; H. Kuroda; Y. Iwasawa
    Surface Science, 224巻, 1-3号, 掲載ページ L969-L978, 出版日 1989年, 査読付
    英語
  • SELECTIVE ISOPENTANE FORMATION FROM CH3OH ON A NEW ONE-ATOMIC LAYER ZrO2/ZSM-5 HYBRID CATALYST
    Kiyotaka Asakura; Mutsuto Aoki; Yasuhiro Iwasawa
    CATALYSIS LETTERS, SPRINGER, 1巻, 11号, 掲載ページ 395-403, 出版日 1988年11月, 査読付, A new-one-atomic layer ZrO2/ZSM-5 hybrid catalyst was prepared by using the repeated reactions between Zr(OC2H5)(4) and of the OH groups of the external surfaces of ZSM-5, followed by calcination. The one-atomic layer ZrO2 attached on the ZSM-5 surface was characterized by means of X-ray diffraction, X-ray fluorescence and EXAFS. The ZrO2 overlayer is suggested to epitaxially grow on the ZSM-5(001) plane in a [111] direction of tetragonal ZrO2. The one-atomic layer ZrO2/ZSM-5 is a unique catalyst which produces selectively isopentane from CH3OH.
    研究論文(学術雑誌), 英語
  • 異種金属接合の表面化学
    有賀哲也; 岩澤康裕
    表面科学, The Surface Science Society of Japan, 9巻, 9号, 掲載ページ 664-669, 出版日 1988年, 査読付, Experimental and theoretical efforts toward the unde standing of the chemical properties of heterometallic junctions are reviewed. The main focus is b ought onto the valence electronic structure of interfaces and its relevance to the adsorption of carbon monoxide. Examples such as Cu/Ru (001), Fe/Ru (001), Pd/Ta (110), Pd/Al (111) and Pd/Au (111) are presented and models describing dominant interaction in these systems are outlined to discuss the nature and origin of unique properties of the heterometallic junction.
    研究論文(学術雑誌), 日本語
  • Adsorption of CH3OH, HCOOH and SO2 on TiO2(110) and stepped TiO2(441) surfaces
    Hiroshi Onishi; Tetsuya Aruga; Chikashi Egawa; Yasuhiro Iwasawa
    Surface Science, 193巻, 1-2号, 掲載ページ 33-46, 出版日 1988年, 査読付, A TiO2(441) surface was prepared whose electronic states and chemisorption properties for CH3OH, HCOOH and SO2 were compared with those of a TiO2(110) surface by means of XPS, UPS and LEED at 298 K. The (441) surface had a regular step structure which is indexed as [3(110) × (111)]. Its work function was smaller by 0.7 eV than that of the (110) surface due to the pinned Fermi level originated from a small amount of Ti3+ species. CH3OH and HCOOH were molecularly adsorbed on both the surfaces, giving a p(2×1) structure for HCOOH adsorbed on (110). It was suggested from the change of the work function that they were absorbed with their dipole axes normal to the local crystal plane on the step sites, thus the adsorbed species at step sites being more inclined as compared with those on the (110) terrace. SO2 was absorbed on (441) forming SO2-3 and also reacted with Ti3+ probably at the step to form S2-, while only SO2-3 was detected on the (110) surface. © 1988.
    研究論文(学術雑誌), 英語
  • Modification of surface electronic structure on TiO2(110) and TiO2(441) by Na deposition
    Hiroshi Onishi; Tetsuya Aruga; Chikashi Egawa; Yasuhiro Iwasawa
    Surface Science, 199巻, 1-2号, 掲載ページ 54-66, 出版日 1988年, 査読付, The geometric and electronic properties of Na overlayers deposited on TiO2 (rutile) (110) and stepped (441) surfaces have been examined by means of XPS, UPS, XAES (X-ray excited Auger electron spectroscopy), EELS and LEED. Na atoms form a smooth atomic layer interacting with surface oxygen atoms on TiO2(110). A surface model consisting of ordered Na2O dimers is proposed for a c(4×2) structure which appears at 0.5 ML Na coverage. At the first monolayer, the Na2O units are considered to complete an array along the [001] direction in (1×1) periodicity. Bonding of Na with oxygen causes charge transfer to the substrate, resulting in a downward band bending toward the surface. With the increase of the band bending, the Fermi level crosses an unfilled surface state localized in five-fold coordinated Ti4+ ions, which leads to the reduction of these Ti4+ to Ti3+. The strong interaction of the TiO2(110) surface toward the Na overlayer is ascribed to surface states just above the valence band maximum localized on protruded ridge oxygen atoms, from comparison with previous results for a flat MgO(100) surface. Almost the same picture is drawn for a stepped TiO2 (441) surface. © 1988.
    研究論文(学術雑誌), 英語
  • PROMOTING EFFECTS OF SE ON THE ACTIVITY AND SELECTIVITY OF RH-ZRO2 CATALYST FOR ETHENE HYDROFORMYLATION
    Y. Izumi; K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Chemical Communications, 19号, 掲載ページ 1327-1328, 出版日 1988年, 査読付
    英語
  • THE STRUCTURES AND SYNERGISTIC CATALYZES OF FERU/AL2O3 CATALYSTS DERIVED FROM FEXRU3-X(CO)12 (X = 0, 1, 2, 3) .1. THE STRUCTURES OF AL2O3-SUPPORTED FEXRU3-X(CO)12 CLUSTERS
    K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Faraday Transactions I, 84巻, 7号, 掲載ページ 2445-2456, 出版日 1988年, 査読付
    英語
  • STRUCTURES AND SYNERGISTIC CATALYZES OF FERU/AL2O3 CATALYSTS DERIVED FROM FEXRU3-X(CO)12 (X = 0, 1, 2, 3) .2. STRUCTURES AND CATALYZES OF FERU CATALYSTS REDUCED WITH H2
    K. Asakura; Y. Iwasawa; M. Yamada
    Journal of the Chemical Society-Faraday Transactions I, 84巻, 7号, 掲載ページ 2457-2464, 出版日 1988年, 査読付
    英語
  • NEW REVERSIBLE ENHANCEMENT DEPRESSION PHENOMENON ON CATALYSIS OF PLATINUM SUPPORTED ON ONE-ATOMIC LAYER NIOBIUM OXIDE FOR ETHENE HYDROGENATION
    K. Asakura; Y. Iwasawa
    Chemistry Letters, 4号, 掲載ページ 633-636, 出版日 1988年, 査読付
    英語
  • LOCAL REACTION ENVIRONMENTS AND THEIR PROPERTIES FOR ETHENE DEUTEROGENATION ON THE SURFACES OF SMSI CATALYSTS
    H. Yoshitake; K. Asakura; Y. Iwasawa
    Journal of the Chemical Society-Faraday Transactions I, 84巻, 12号, 掲載ページ 4337-4346, 出版日 1988年, 査読付
    英語
  • A STRUCTURE MODEL AS THE ORIGIN OF CATALYTIC PROPERTIES OF METAL-DOPED MGO SYSTEMS
    K. Asakura; Y. Iwasawa
    Materials Chemistry and Physics, 18巻, 5/6号, 掲載ページ 499-512, 出版日 1988年, 査読付
    英語
  • A NEW TIO2-ATTACHED RHODIUM METAL CATALYST - CATALYST CHARACTERIZATION AND NON-SMSI BEHAVIOR
    K. Asakura; Y. Iwasawa; H. Kuroda
    Journal of the Chemical Society-Faraday Transactions I, 84巻, 84号, 掲載ページ 1329-&, 出版日 1988年, 査読付
    英語
  • EPITAXIAL-GROWTH OF FE OVERLAYERS ON THE RU(001) SURFACE
    C EGAWA; T ARUGA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 188巻, 3号, 掲載ページ 563-574, 出版日 1987年10月, 査読付
    研究論文(学術雑誌), 英語
  • Epitaxial growth of an Fe overlayer on a Ru(001) surface and adsorption of CO and NH3 on the Fe commensurate overlayer
    Chikashi Egawa; Tetsuya Aruga; Yasuhiro Iwasawa
    Surface Science Letters, 185巻, 1-2号, 掲載ページ L506-L510, 出版日 1987年06月02日, The growth and structure of Fe overlayers on a Ru(001) surface have been studied by means of AES, LEED and TDS. The evaporation of Fe at 520 K caused a layer-by-layer (Van der Merwe) two-dimensional epitaxial growth. The first Fe monolayer was suggested to have an expanded fcc(111) structure commensurate with the structure of the Ru substrate, while the second Fe overlayer thoroughly relaxed to a (110) surface structure of bcc Fe. The binding energy of dissociatively adsorbed CO was most strengthened on the elongated Fe first overlayer among the surfaces with Fe coverages of 0-2.3 ML. The adsorption of NH3 on the Fe overlayers gave a new (√7×√7)R19° ordered structure. © 1987.
    研究論文(学術雑誌), 英語
  • EPITAXIAL-GROWTH OF AN FE OVERLAYER ON A RU(001) SURFACE AND ADSORPTION OF CO AND NH3 ON THE FE COMMENSURATE OVERLAYER
    C EGAWA; T ARUGA; Y IWASAWA
    SURFACE SCIENCE, ELSEVIER SCIENCE BV, 185巻, 1-2号, 掲載ページ L506-L510, 出版日 1987年06月, 査読付
    英語
  • Adsorption of Na atoms and oxygen-containing molecules on MgO(100) and (111) surfaces
    Hiroshi Onishi; Chikashi Egawa; Tetsuya Aruga; Yasuhiro Iwasawa
    Surface Science, 191巻, 3号, 掲載ページ 479-491, 出版日 1987年, 査読付, The adsorption of Na atoms and oxygen-containing molecules such as H2O, CH3OH, CO2, HCOOH and HCOOCH3 has been studied on the annealed MgO(100) and (111) surfaces by means of XPS, UPS and LEED. Annealing a (111) surface at 1000 K yielded microfacets ~ 20 Å across. This faceted (111) surface showed a high adsorption activity compared with the flat (100) surface. Hence it is suggested that the coordinatively unsaturated edge-sites or the multicentered valley-sites on the microfaceted surface play important roles in the chemisorption. © 1987, All rights reserved.
    研究論文(学術雑誌), 英語
  • CARBON-MONOXIDE HYDROGENATION ON SIO2-ATTACHED, AL2O3-ATTACHED, OR TIO2-ATTACHED NB-MONOMER CATALYSTS
    M NISHIMURA; K ASAKURA; Y IWASAWA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 4号, 掲載ページ 573-576, 出版日 1987年, 査読付
    研究論文(学術雑誌), 英語
  • EXAFS AND XANES STUDIES ON THE LOCAL STRUCTURES OF METAL-IONS IN METAL DOPED MGO SYSTEMS
    K ASAKURA; Y IWASAWA; H KURODA
    JOURNAL DE PHYSIQUE, EDP SCIENCES S A, 47巻, C-8号, 掲載ページ 317-320, 出版日 1986年12月, 査読付
    研究論文(学術雑誌), 英語
  • TEMPERATURE-DEPENDENCE OF THE PT L3-EDGE EXAFS OF PLATINUM CLUSTERS SUPPORTED ON NAY-ZEOLITE
    T YOKOYAMA; N KOSUGI; K ASAKURA; Y IWASAWA; H KURODA
    JOURNAL DE PHYSIQUE, EDP SCIENCES S A, 47巻, C-8号, 掲載ページ 273-276, 出版日 1986年12月, 査読付
    研究論文(学術雑誌), 英語
  • NEW SIO2-SUPPORTED NIOBIUM MONOMER CATALYSTS FOR DEHYDROGENATION OF ETHANOL
    M NISHIMURA; K ASAKURA; Y IWASAWA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 22号, 掲載ページ 1660-1661, 出版日 1986年11月, 査読付
    研究論文(学術雑誌), 英語
  • THE STRUCTURE DETERMINATION OF RU3(CO)12 CATALYSTS SUPPORTED ON INORGANIC OXIDES BY MEANS OF EXAFS
    K ASAKURA; Y IWASAWA; H KURODA
    NIPPON KAGAKU KAISHI, CHEMICAL SOC JAPAN, 11号, 掲載ページ 1539-1546, 出版日 1986年11月, 査読付
    研究論文(学術雑誌), 日本語
  • NEW INORGANIC OXIDE-ATTACHED NB CATALYSTS ACTIVE FOR PROPENE METATHESIS
    M NISHIMURA; K ASAKURA; Y IWASAWA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 9号, 掲載ページ 1457-1460, 出版日 1986年09月, 査読付
    研究論文(学術雑誌), 英語
  • NEW PD ULTRA-THIN AMORPHOUS-OXIDE LAYER ZSM-5 CATALYSTS FOR SELECTIVE FORMATION OF PROPANE FROM CO/H2
    A KASE; K ASAKURA; C EGAWA; Y IWASAWA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 6号, 掲載ページ 855-858, 出版日 1986年06月, 査読付
    研究論文(学術雑誌), 英語
  • THE SURFACE-STRUCTURE AND CATALYTIC PROPERTIES OF ONE-ATOMIC LAYER AMORPHOUS NIOBIUM-OXIDE ATTACHED ON SIO2
    K ASAKURA; Y IWASAWA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 6号, 掲載ページ 859-862, 出版日 1986年06月, 査読付
    研究論文(学術雑誌), 英語
  • EXAFS STUDIES OF THE BEHAVIOR OF RH6(CO)16 SUPPORTED ON GAMMA-AL2O3 SURFACE
    K ASAKURA; Y IWASAWA; H KURODA
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, CHEMICAL SOC JAPAN, 59巻, 2号, 掲載ページ 647-648, 出版日 1986年02月, 査読付
    研究論文(学術雑誌), 英語
  • NEW SIO2-BOUND MO DIMERS - ACTIVE CATALYSTS FOR SELECTIVE OXIDATION OF PROPENE TO ACRYLALDEHYDE
    Y IWASAWA; N ITO; H ISHII; H KURODA
    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS, ROYAL SOC CHEMISTRY, 12号, 掲載ページ 827-828, 出版日 1985年, 査読付
    研究論文(学術雑誌), 英語
  • ACTIVITY SEQUENCE OF MO(II) STRUCTURES CHEMICALLY ATTACHED ON SIO2 IN THE CATALYTIC-HYDROGENATION OF ETHENE AND 1,3-BUTADIENE
    Y IWASAWA; N ITO; T CHIBA; H ISHII; H KURODA
    CHEMISTRY LETTERS, CHEMICAL SOC JAPAN, 8号, 掲載ページ 1141-1144, 出版日 1985年, 査読付
    研究論文(学術雑誌), 英語
  • DYNAMIC BEHAVIOR OF ACTIVE-SITES OF A SIO2-ATTACHED MO(VI)-DIMER CATALYST DURING ETHANOL OXIDATION OBSERVED BY MEANS OF EXAFS
    Y. Iwasawa; K. Asakura; H. Ishii; H. Kuroda
    Zeitschrift Fur Physikalische Chemie Neue Folge, 144巻, 144号, 掲載ページ 105-115, 出版日 1985年, 査読付
    英語
  • SPECTROSCOPIC STUDIES ON THE SURFACE-STRUCTURES OF RUTHENIUM CATALYSTS DERIVED FROM RU3 (CO)12/GAMMA-AL2O3 OR SIO2
    K. Asakura; M. Yamada; Y. Iwasawa; H. Kuroda
    Chemistry Letters, 4号, 掲載ページ 511-514, 出版日 1985年, 査読付
    英語

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    朝倉清高; HU Bing; 轟直人; 和田山智正; 東晃太朗; 宇留賀朋哉; 宇留賀朋哉; 岩澤康裕; 三輪(有賀)寛子; 高草木達
    出版日 2022年, 触媒討論会講演予稿集(CD-ROM), 129th巻, 2187-5928, 202202288976608672
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    宇留賀朋哉; 宇留賀朋哉; 三輪寛子; 吉田健文; 金子拓真; 佐々木岳彦; 東晃太朗; 坂田智裕; 関澤央輝; 関澤央輝; 松井公佑; 朝倉清高; 唯美津木; 岩澤康裕
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    鷹尾忍; 関澤央輝; 金子拓真; 東晃太朗; 坂田智裕; 山本孝; 宇留賀朋哉; 宇留賀朋哉; 岩澤康裕
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    金子拓真; 坂田智裕; 東晃太朗; 関澤央輝; 鷹尾忍; 吉田祐介; 山本孝; 宇留賀朋哉; 宇留賀朋哉; 岩澤康裕
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    坂田智裕; 東晃太朗; 金子拓真; 関澤央輝; 関澤央輝; 田口宗孝; 朝倉清高; 宇留賀朋哉; 宇留賀朋哉; 岩澤康裕
    出版日 2019年, 日本放射光学会年会・放射光科学合同シンポジウム(Web), 32nd巻, 202002225112744014
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    長尾哲郎; 高橋俊太郎; FEITEN Felix; 脇坂祐輝; 轟直人; 妙智力也; 関澤央輝; 坂田智裕; 東晃太朗; 宇留賀朋哉; 岩澤康裕; 朝倉清高; 和田山智正
    出版日 2018年, 電気化学会大会講演要旨集(CD-ROM), 85th巻, 201802287844622771
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    坂田智裕; 宇留賀朋哉; 宇留賀朋哉; 関澤央輝; 関澤央輝; 東晃太朗; 金子拓真; 朝倉清高; 岩澤康裕
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    出版日 2013年, 燃料電池シンポジウム講演予稿集, 20th巻, 201302276362209994
  • 雰囲気制御型硬X線光電子分光装置によるAu箔のin-situ測定
    高木康多; 高木康多; WANG H.; 池永英司; 関澤央輝; 宇留賀朋哉; 宇留賀朋哉; 湯本博勝; 仙波泰徳; 大橋治彦; 山崎裕史; 後藤俊治; 唯美津木; 唯美津木; 岩澤康裕; 横山利彦; 横山利彦
    出版日 2013年, 日本物理学会講演概要集, 68巻, 2号, 1342-8349, 201302266654877836
  • 固体高分子形燃料電池Pt/C触媒の酸素還元反応活性と電位サイクル耐久性に及ぼす炭素担体効果
    長澤兼作; 永松伸一; 鷹尾忍; SAMJESKE Gabor; 今泉吉明; 関澤央輝; 山本孝; 宇留賀朋哉; 岩澤康裕
    出版日 2013年, 日本化学会講演予稿集, 93rd巻, 2号, 0285-7626, 201302237717169616
  • 耐久試験後の燃料電池膜/電極接合体中における白金化学種の空間分布に関する研究
    鷹尾忍; 関澤央輝; 金子拓真; 永松伸一; 今泉吉明; 東晃太朗; GABOR Samjeske; 長澤兼作; 三浦芳樹; 山本孝; 宇留賀朋哉; 宇留賀朋哉; 岩澤康裕
    出版日 2013年, 触媒討論会討論会A予稿集, 112th巻, 1343-9936, 201302211708964684
  • Pdコア・Ptシェル型の固体高分子形燃料電池カソード触媒の電位制御反応過程におけるin-situ時間分解XAFS解析
    永松伸一; 鷹尾忍; 今泉吉明; 山本孝; SAMJESKE Gabor; 関澤央輝; 長澤兼作; LIU Licheng; 宇留賀朋哉; 岩澤康裕
    出版日 2013年, 日本化学会講演予稿集, 93rd巻, 2号, 0285-7626, 201302240061623839
  • 新規Ptコア-SnO2シェル燃料電池触媒の活性構造に関する研究
    鷹尾忍; 長澤兼作; 鷹尾康一朗; 塚原剛彦; 永松伸一; SAMJESKE Gabor; 今泉吉明; 山本孝; 関澤央輝; 宇留賀朋哉; 岩澤康裕
    出版日 2013年, 日本化学会講演予稿集, 93rd巻, 2号, 0285-7626, 201302293781449735
  • New XAFS beamline BL36XU for Catalytic Reaction Dynamics for Fuel Cells
    T. Uruga; M. Tada; Y. Iwasawa
    出版日 2013年, SPring-8 Research Frontiers 2012, 掲載ページ 139-140, 英語, 記事・総説・解説・論説等(その他)
  • 先端触媒構造反応リアルタイム計測ビームライン BL36XUの稼働状況
    宇留賀朋哉; 関澤央輝; 唯 美津木; 横山利彦; 岩澤康裕
    出版日 2013年, SPring-8利用者情報誌, 2月号, 掲載ページ 14-17, 日本語, 記事・総説・解説・論説等(その他)
  • In-situ時間分解XAFS法によるPt-Co/C燃料電池カソード触媒の触媒構造速度論解析
    石黒志; 石黒志; 才田隆広; 永松伸一; 関澤央輝; 宇留賀朋哉; 宇留賀朋哉; 新田清文; 山本孝; 大越慎一; 岩澤康裕; 横山利彦; 唯美津木
    出版日 2012年, 日本放射光学会年会・放射光科学合同シンポジウム予稿集, 25th巻, 201202290932145710
  • 我が国の科学・技術を真に強くする方策と展望―パネルディスカッション―
    岩澤康裕; 永宮正治
    出版日 2012年, 学術の動向, 1月号, 掲載ページ 40-41, 日本語, 記事・総説・解説・論説等(その他)
  • 化学の挑戦、30年後の夢ロードマップ
    岩澤康裕
    化学工業日報社, 出版日 2012年, 化学経済, 59巻, 5月号, 掲載ページ 10-17, 日本語, 記事・総説・解説・論説等(その他), 0453-0683, 40019314733, AN00037008
  • 先端触媒構造反応リアルタイム計測ビームラインBL36XUの計画概要
    宇留賀朋哉; 唯 美津木; 岩澤康裕
    出版日 2012年, SPring-8利用者情報誌, 16号, 掲載ページ 81-84, 日本語, 査読付, 記事・総説・解説・論説等(その他)
  • 次世代燃料電池開発のためのin situ XAFS法による燃料電池触媒の解析評価
    サミエスケ・ガボー; 永松伸一; 岩澤康裕
    広信社, 出版日 2011年, 表面, 49巻, 7号, 掲載ページ 223-236, 日本語, 査読付, 記事・総説・解説・論説等(その他), 0367-648X, 40019148923, AN00211091
  • 国立大学法人電気通信大学「燃料電池イノベーション研究センター」紹介
    岩澤康裕
    燃料電池開発情報センター, 出版日 2011年, 燃料電池, 10巻, 3号, 掲載ページ 92-95, 日本語, 記事・総説・解説・論説等(その他), 1346-6623, 40018710479
  • 2011世界化学年 -全世界が化学一色になる年-
    岩澤康裕
    東京化学同人, 出版日 2011年, 現代化学, 1月号, 掲載ページ 25-27, 日本語, 記事・総説・解説・論説等(その他), 0386-961X, 40017400296, AN00078479
  • 科学・技術による力強い日本の構築-我が国の科学・技術の進むべき方向と必要な政策-
    岩澤康裕
    日本生物工学会, 出版日 2010年, 生物工学会誌, 88巻, 11号, 掲載ページ 571-575, 日本語, 記事・総説・解説・論説等(その他), 0919-3758, 110007989524, AN10401118
  • 原子分子レベルの触媒表面科学
    岩澤康裕
    出版日 2010年, 表面科学, 31巻, 掲載ページ 73-80, 日本語, 記事・総説・解説・論説等(その他)
  • フェノール直接合成触媒の開発 CO2排出量削減に取り組む化学関連製品・技術
    唯 美津木; 岩澤康裕
    化学工業日報社, 出版日 2010年, 化学経済, 57巻, 1月号, 掲載ページ 85-89, 日本語, 記事・総説・解説・論説等(その他), 0453-0683, 40016951361, AN00037008
  • 異分野の学会が連携する時代
    岩澤康裕; 石原宏; 北 潔; 松木則夫
    東京化学同人, 出版日 2010年, 現代化学, 5月号, 掲載ページ 20-26, 日本語, 記事・総説・解説・論説等(その他), 0386-961X, 40017061858, AN00078479
  • Atomically Dispersed Cu Species on a TiO2(110) Surface Precovered with Acetic Anhydride
    W.-J. Chun; Y. Koike; H. Ashima; K. Kinoshita; K. Ijima; K. Fujikawa; S. Suzuki; M. Nomura; Y. Iwasawa; K. Asakura
    出版日 2009年, Chem. Phys. Lett., 470巻, 掲載ページ 99-102, 英語, 査読付, 速報,短報,研究ノート等(学術雑誌)
  • プロトン交換モンモリロナイト層間での酸塩基両機能創出と連続触媒反応への応用
    本倉 健; 岩澤康裕
    Acidic montmorillonite(H-mont)-immobilized primary amines (H-mont-NH_2) were prepared and characterized by XRD, solid-state NMR, and elemental analysis. This H-mont-NH_2 was found to be excellent acid-base bifunctional catalysts for one-pot acid-base reaction sequences. For example, tandem deacetalization-Knoevenagel condensation proceeded successfully with the H-mont-NH_2, affording the corresponding condensation product in a quantitative yield. The acidity of the H-mont-NH_2 was strongly influenced by preparation solvent. In addition, the base-catalyzed reactions were enhanced by interlayer acid sites., 一般社団法人 日本粘土学会, 出版日 2009年, 粘土科学, 48巻, 2号, 掲載ページ 58-63, 日本語, 査読付, 記事・総説・解説・論説等(その他), 0470-6455, 110007340455, AN00199972
  • 無機酸化物表面の有機官能基化による高効率有機合成触媒の創出
    本倉健; 岩澤康裕
    広信社, 出版日 2008年, 表面, 46巻, 10号, 掲載ページ 1-29, 日本語, 査読付, 記事・総説・解説・論説等(その他), 0367-648X, 40016329730, AN00211091
  • 固定化金属錯体のモレキュラーインプリンティング―人工酵素型触媒設計に向けて
    唯美津木; 岩澤康裕
    触媒学会, 出版日 2008年, 触媒, 50巻, 4号, 掲載ページ 319-325, 日本語, 査読付, 記事・総説・解説・論説等(その他), 0559-8958, 10021070271, AN00117719
  • 金属媒体を用いた表面上の3次元活性構造の構築と触媒作用
    唯美津木; 岩澤康裕
    出版日 2008年, 表面, 46巻, 掲載ページ 33-49, 日本語, 査読付, 記事・総説・解説・論説等(その他)
  • Syntheses, structures, and properties of a series of metal ion-containing dialkylimidazolium ionic liquids
    Chongmin Zhong; Takehiko Sasaki; Akiko Jimbo-Kobayashi; Emiko Fujiwara; Akiko Kobayashi; Mizuki Tada; Yasuhiro Iwasawa
    A series of metal ion-containing ionic liquids [Bmim](2)[MCl4] (M=Sn, Cu, Ni, Mn, Fe, Co, Zn, and Pt; [Bmim]=1-butyl-3-methylimidazolium) and [Bmim](2)[ZrCl6] were synthesized and their single-crystal structures were determined by X-ray crystallographic analysis. The crystal structures showed the existence of an interaction between chlorometalate anions and imidazolium cations via C - H center dot center dot center dot Cl hydrogen bonding as well as an interaction between the cations through C - H center dot center dot center dot pi hydrogen bonding and/or pi center dot center dot center dot pi stack interaction. The melting points of the metal salts were found to correlate with the number of halide ions coordinated to each metal ion and the overall symmetry of the chlorometalate anions. Ionic conductivity measured in super-cooled states of the synthesized salts unambiguously confirmed that these salts behaved as ionic liquids. The synthesized salts have a high thermal stability as evaluated by TGA and negligible vapor pressure before decomposition., CHEMICAL SOC JAPAN, 出版日 2007年12月, BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 80巻, 12号, 掲載ページ 2365-2374, 英語, 0009-2673, 1348-0634, 10020275688, WOS:000252141000013
  • ゼオライト担持窒素内包型Reクラスター触媒によるベンゼンと酸素からのフェノール直接合成反応の機構解明
    唯 美津木; 上村 洋平; 佐々木 岳彦; BAL Rajaram; 稲田 康宏; 野村 昌治; 岩澤 康裕
    触媒学会, 出版日 2007年09月, 触媒, 49巻, 6号, 掲載ページ 406-408, 日本語, 0559-8958, 10019844419
  • In-situ 時間分解XAFS法によるPt/C燃料電池触媒の起電過程の解明
    唯 美津木; 村田 成亮; 朝岡 賢彦; 廣嶋 一崇; 奥村 和; 谷田 肇; 宇留賀 朋哉; 稲田 康宏; 野村 昌治; 中西 治通; 松本 信一; 岩澤 康裕
    触媒学会, 出版日 2007年03月10日, 触媒 = Catalysts & Catalysis, 49巻, 2号, 掲載ページ 93-95, 日本語, 0559-8958, 10018571185, AN00117719
  • 走査トンネル顕微鏡とX線光電子回折によるMo(112)-p(2x1)-P構造とチオフェン分子の吸着及び分解挙動の解明
    幸田 竜; 近藤 寛; 有賀 寛子; 谷池 俊明; 佐々木 岳彦; Laurin Mathias; 島田 透; 岩澤 康裕
    P修飾Mo(112)-p(2x1)がチオフェンの脱硫反応に高い活性をもつことを見出した。この表面構造においてはDFT計算によっていくつかのモデルが提案されているが未だ表面構造は不明である。特にチオフェン分解活性と表面構造との対応は触媒原理を明らかにする上で重要である。本研究では、走査トンネル顕微鏡とX線光電子回折を用いて構造を決定することに成功した。また、走査トンネル顕微鏡を用いてチオフェンの分解過程を観察した。, The Surface Science Society of Japan, 出版日 2007年, 表面科学講演大会講演要旨集, 27巻, 0号, 掲載ページ 90-90, 日本語, 130004673877
  • 2007年ノーベル化学賞:固体表面の化学反応機構 触媒反応のブラックボックス解明をして
    岩澤康裕
    東京化学同人, 出版日 2007年, 現代化学, 12月号巻, 441号, 掲載ページ 32-35, 日本語, 記事・総説・解説・論説等(その他), 0386-961X, 40015708175, AN00078479
  • ノーベル化学賞:受賞者の素顔と研究業績
    岩澤康裕
    丸善, 出版日 2007年, パリティ, 22巻, 12号, 掲載ページ 32-34, 日本語, 記事・総説・解説・論説等(その他), 0911-4815, 40015701897, AN10017131
  • 表面モレキュラーインプリンティング固定化金属錯体触媒
    唯美津木; 岩澤康裕
    シーエムシー出版, 出版日 2007年, ファインケミカル「有機金属錯体触媒の最前線」, 36巻, 6号, 掲載ページ 33-41, 日本語, 査読付, 記事・総説・解説・論説等(その他), 0913-6150, 40015356223, AN00015672
  • 世界一のフェノール合成Re触媒の発見とその触媒活性構造の解明
    唯美津木; 岩澤康裕
    出版日 2007年, 放射光, 20巻, 掲載ページ 99-105, 日本語, 査読付, 記事・総説・解説・論説等(その他)
  • 二酸化チタン表面上での可視光誘起光反応とその反応機構
    有賀寛子; 谷池俊明; 唯美津木; 渡邊一也; 松本吉泰; 池田進; 斉木幸一朗; 岩澤康裕
    出版日 2006年11月21日, 固体・表面光化学討論会講演要旨集, 25th巻, 掲載ページ 50-51, 日本語, 200902213101542551
  • TiO2(001)表面階段状格子構造上で発現する可視光応答反応とその反応機構の解明
    有賀寛子; 谷池俊明; 守川春雲; MIN Byoung Koun; 唯美津木; 渡邊一也; 松本吉泰; 池田進; 斉木幸一朗; 岩澤康裕
    出版日 2006年09月26日, 触媒討論会討論会A予稿集, 98th巻, 掲載ページ 258, 日本語, 1343-9936, 200902264620442126
  • シリカ固定化Ru錯体を用いたアルケンエポキシ化反応とその活性構造の検討
    唯美 津木; 吉田 淳; Coquet Rudy; 谷池 俊明; 岩澤 康裕
    触媒学会, 出版日 2006年09月10日, 触媒 = Catalysts & Catalysis, 48巻, 6号, 掲載ページ 421-423, 日本語, 0559-8958, 10018063757, AN00117719
  • INOR 872-Novel N-interstitial re-cluster catalysts supported on HZSM-5 for direct phenol synthesis from benzene and molecular oxygen
    Mizuki Tada; Rajaram Bal; Takehiko Sasaki; Yohei Uemura; Yasuhiro Iwasawa
    AMER CHEMICAL SOC, 出版日 2006年09月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 232巻, 英語, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:000207781606723
  • COLL 616-In situ time-resolved study on the reaction mechanism of a Pt/C fuel cell by time-gating Quick XAFS
    Mizuki Tada; Yasuhiro Iwasawa; N. Murata; H. Nakanishi; S. Matsumoto; T. Asaoka; K. Hiroshima; K. Okumura; H. Tanida; T. Uruga
    AMER CHEMICAL SOC, 出版日 2006年09月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 232巻, 英語, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:000207781603653
  • 偏光全反射蛍光EXAFSによる金属単原子の三次元吸着構造解析
    小池 祐一郎; 居島 薫; 芦間 英典; 藤川 敬介; 鈴木 秀士; 野村 昌治; 岩澤 康裕; 田 旺帝; 朝倉 清高
    We developed a UHV-Polarization dependent Total-Reflection Fluorescence Extended X-ray Absorption Fine Structure System (UHV-PTRF-EXAFS System), which enables us to prepare a clean and well-defined oxide single crystal surface. We have determined the adsorption sites and structures of highly dispersed Ni atoms on α-Al2O3(0001) and TiO2(110) using the system. In both cases, Ni atoms adsorbed at imaginary cation sites, where metal cations in next layer should be located. These results have indicated that Ni atoms selectively interact with oxygen dangling bonds., 日本表面科学会, 出版日 2006年07月10日, 表面科学 = Journal of The Surface Science Society of Japan, 27巻, 7号, 掲載ページ 414-419, 日本語, 0388-5321, 10017617506, AN00334149
  • Synthesis of nanocrystalline zeolite beta in supercritical fluids, characterization and catalytic activity
    ML Kantam; BPC Rao; BM Choudary; KK Rao; B Sreedhar; Y Iwasawa; T Sasaki
    Nanocrystalline zeolite beta with Si/Al ratios 12.5-50 has been synthesized by applying a two-stage varying temperature synthesis and supercritical fluid aided crystallization. Low temperature nucleation of clear aluminosilicate gel and SCF aided crystallization gave quantitative yields of nanocrystalline zeolite beta in shorter crystallization time without the use of alkali cations and seeded gel. The obtained nanocrystalline zeolite beta catalysts are thoroughly characterized by X-ray diffraction, N-2 adsorption, Si-29 and Al-27 MAS NMR, IR spectroscopy and Al incorporation in framework was studied by XPS. These nanocrystalline zeolite beta catalysts displayed good activity and high selectivity towards 4-nitro-o-xylene in the nitration of o-xylene when compared to microcrystalline zeolite beta. (c) 2006 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2006年06月, JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 252巻, 1-2号, 掲載ページ 76-84, 英語, 1381-1169, 80019140810, WOS:000237695400012
  • TiO2(001)表面階段状格子構造上での可視光応答光触媒反応
    有賀寛子; 谷池俊明; 守川春雲; MIN Byoung Koun; 唯美津木; 池田進; 斉木幸一朗; 岩澤康裕
    出版日 2006年03月13日, 日本化学会講演予稿集, 86th巻, 1号, 掲載ページ 306, 日本語, 0285-7626, 200902210240565192
  • TiO2(001)表面上における可視光応答反応とその機構解明
    有賀 寛子; 谷池 俊明; 唯 美津木; 渡辺 一也; 松本 吉泰; 池田 進; 斉木 幸一朗; 岩澤 康裕
    TiO<SUB>2</SUB>(001)単結晶表面上で酸素共存下、可視光照射によりギ酸が光分解することを見いだした。EELS、UPS、2PPES測定及びDFT計算から、この可視光応答性が発現したのは、この表面特有の階段状格子構造から由来する表面準位がbulkのband gap(3.0 eV)内に形成されたためであること、また、生成した正孔・電子の酸化還元反応の機構を明らかにした。, The Surface Science Society of Japan, 出版日 2006年, 表面科学講演大会講演要旨集, 26巻, 0号, 掲載ページ 190-190, 130004673449
  • 偏光全反射蛍光EXAFSによる金属単原子の三次元吸着構造解析
    小池祐一郎; 居島薫; 芦間英典; 藤川敬介; 鈴木秀士; 野村昌治; 岩澤康裕; 田旺帝; 朝倉清高
    出版日 2006年, 表面科学, 27巻, 掲載ページ 414-419, 英語, 査読付, 速報,短報,研究ノート等(学術雑誌)
  • Structure of low coverage Ni atoms on the TiO2(110) surface - Polarization dependent Total-Reflection Fluorescence EXAFS study ?
    Y. Koike; K. Ijima; W.-J. Chun; H. Ashima; T. Yamamoto; K. Fujikawa; S. Suzuki; Y. Iwasawa; M. Nomura; K. Asakura
    出版日 2006年, Chem. Phys. Lett., 421巻, 掲載ページ 27-30, 英語, 査読付, 速報,短報,研究ノート等(学術雑誌)
  • Oxygen vacancy promoting catalytic dehydration of formic acid on TiO2(110) by in situ scanning tunneling microscopic observation
    M Aizawa; Y Morikawa; Y Namai; H Morikawa; Y Iwasawa
    The catalytic dehydration reaction processes of formic acid on a TiO2(110) surface at 350 K have been studied to visualize reaction intermediates and their dynamic behaviors by scanning tunneling microscopy. Three types of configurations of adsorbed formates on the surface were identified by their shapes and positions in STM images. Successive STM observations revealed transformations among the three configurations, i.e., bridge formate on a 5-fold coordinated Ti4+ row, bridge formate on an oxygen vacancy site with an oxygen atom of formate and on a 5-fold coordinated Ti4+ ion and with the other formate oxygen atom, and a monodentate formate on an oxygen vacancy site with an oxygen atom of formate. The decomposition of the monodentate formate to carbon monoxide and hydroxyl was also imaged, which is a rate-determining step in the catalytic dehydration of formic acid. Combined with first-principle DFT calculations, the overall reaction processes of the catalytic dehydration of formic acid on the surface have been elucidated. Oxygen vacancies on the surface that can be produced by dehydration of two hydroxyls in situ under the catalytic reaction conditions are essential for the reaction., AMER CHEMICAL SOC, 出版日 2005年10月, JOURNAL OF PHYSICAL CHEMISTRY B, 109巻, 40号, 掲載ページ 18831-18838, 英語, 1520-6106, WOS:000232482100017
  • XAFS characterization of Pt-Fe/zeolite catalysts for preferential oxidation of CO in hydrogen fuel gases
    M Kotobuki; T Shido; M Tada; H Uchida; H Yamashita; Y Iwasawa; M Watanabe
    We have developed a new Pt-Fe/mordenite (Pt-Fe/M) catalyst which shows remarkably high activity and selectivity for the oxidation of CO in H-2-rich gas compared with Pt/M. In the present work, to understand the role and structure of Pt and Fe in the Pt-Fe/M catalyst, the states of metallic components in ion-exchanged, H-2 pre-treated and post-PROX (preferential oxidation of CO) samples have been studied by means of XAFS. It was confirmed that Pt forms the metallic clusters after H-2 pretreatment or the PROX experiment, whereas a large part of Fe exists as oxides even after the H-2 treatment. At post-analysis of the catalysts used for the PROX experiment, an increase in coordination number of Fe-O was observed. Pt clusters in the Pt-Fe(2:1 weight ratio)/M catalyst, which showed the highest PROX performance, were found to have a different electronic structure from the other catalysts. Additionally, preferential CO adsorption onto Pt sites at Pt-Fe/M was clearly demonstrated by infrared spectroscopy analysis in a stream of 1% CO containing H-2. Based on these results, the superior PROX mechanism was discussed., SPRINGER, 出版日 2005年10月, CATALYSIS LETTERS, 103巻, 3-4号, 掲載ページ 263-269, 英語, 1011-372X, WOS:000232030200015
  • STMによるTiO2(001)表面上でのギ酸の可視光分解反応に関する研究
    有賀寛子; 谷池俊明; 守川春雲; MIN Byoung Koun; 唯美津木; 岩沢康裕
    出版日 2005年09月20日, 触媒討論会討論会A予稿集, 96th巻, 掲載ページ 108, 日本語, 1343-9936, 200902296084197333
  • 単結晶二酸化チタンを用いた可視光応答光触媒反応
    有賀寛子; 谷池俊明; 守川春雲; MIN Byoung Koun; 唯美津木; 岩沢康裕
    出版日 2005年09月07日, 応用物理学会学術講演会講演予稿集, 66th巻, 2号, 掲載ページ 515, 日本語, 200902264901377919
  • Direct Phenol Synthesis from Benzene with Molecular Oxygen on Rhenium/Zeolite Catalysts (第95回触媒討論会B講演予稿 テーマ「ナノ構造の触媒化学--制御・解析・機能」)
    Bal Rajaram; Tada Mizuki; Kusakari Toshiaki; IWASAWA Yasuhiro
    触媒学会, 出版日 2005年03月01日, 触媒 = Catalysts & Catalysis, 47巻, 2号, 掲載ページ 72-74, 英語, 0559-8958, 10015432764, AN00117719
  • Controlled Surface structure of Cu species by modified TiO2(110) surface with chemisorbed acetic acid
    W.J. Chun; Y. Koike; K. Ijima; H. Ashima; K. Fujikawa; K. Asakura; Y. Iwasawa
    出版日 2005年, PF activity Report, 22号, 掲載ページ 51
  • A Development of a New EXPEEM System (3) - Chemical Mapping of TaOx
    T. Tsutsumi; T. Kawasaki; T. Miyamoto; H. Niimi; S. Suzuki; W.-J. Chun; K. Asakura; Y. Iwasawa
    出版日 2005年, Photon Factory Activity Report 2004, 22B巻, 掲載ページ 53, 英語, 速報,短報,研究ノート等(大学,研究機関紀要)
  • The Role of Carbon Dioxide in Chemoselective Hydrogenation of Halonitroaromatics over Supported Noble Metal Catalysts in Supercritical Carbon Dioxide
    S. Ichikawa; M. Tada; Y. Iwasawa; T. Ikariya
    出版日 2005年, Chem. Commun., 掲載ページ 924-926
  • First-principles theoretical study and scanning tunneling microscopic observation of dehydration process of formic acid on a TiO2(110) surface
    Y Morikawa; Takahashi, I; M Aizawa; Y Namai; T Sasaki; Y Iwasawa
    We have studied the dehydration process of formic acid on a TiO2(110) surface by using first-principles theoretical calculations. Formic acid dissociatively adsorbs to form formate and hydroxyl. It turns out that simple decomposition processes of the formate on the stoichiometric surface are energetically unfavorable. The formation of H2O and O vacancies from two neighboring bridging hydroxyls is relatively easy and the activation barrier is calculated to be 114 kJ/mol. On the TiO2(110) surface with oxygen defect sites, formate adsorbs with one O at a defect site and with the other O on a five-fold Ti, forming a bridging configuration. Further decomposition of the formate occurs through a monodentate configuration with an activation barrier of 129 kJ/mol. We have also performed STM observation corresponding to the theoretical results. It was imaged that some formates were located along the oxygen row and at an intermediate position between the oxygen row and the Ti row at elevated temperatures at which reaction takes place, indicative of the interaction between oxygen vacancy and formate. The catalytic dehydration cycle is discussed based on these results., AMER CHEMICAL SOC, 出版日 2004年09月, JOURNAL OF PHYSICAL CHEMISTRY B, 108巻, 38号, 掲載ページ 14446-14451, 英語, 1520-6106, WOS:000223922500032
  • In-situ DXAFS法による時間分解触媒活性種の解析
    鈴木 あかね; 岩澤 康裕; 野村 昌治
    広信社, 出版日 2004年09月, 表面, 42巻, 9号, 掲載ページ 255-265, 日本語, 0367-648X, 40006701167, AN00211091
  • TiO2(001)表面上のメタノールとギ酸の光酸化過程のSTM観察
    有賀寛子; 手老龍吾; 生井勝康; 岩沢康裕
    出版日 2004年03月11日, 日本化学会講演予稿集, 84th巻, 1号, 掲載ページ 123, 日本語, 0285-7626, 200902230633484667
  • An experimental study on Fischer-Tropsch catalysis: Implications for planetary science
    Y Sekine; T Shido; S Sugita; T Matsui; T Yamamoto; Y Iwasawa
    PERGAMON-ELSEVIER SCIENCE LTD, 出版日 2003年09月, GEOCHIMICA ET COSMOCHIMICA ACTA, 67巻, 18号, 掲載ページ A422-A422, 英語, 研究発表ペーパー・要旨(国際会議), 0016-7037, WOS:000185517600831
  • Structure and reactivity of metal clusters at oxide surfaces characterized by time-resolved DXAFS and STM.
    Y Iwasawa; K Fukui; S Takakusagi; A Suzuki; M Nomura
    AMER CHEMICAL SOC, 出版日 2003年09月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 226巻, 掲載ページ U281-U281, 英語, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:000187062501360
  • Approaches to design of active structures by attaching and molecular imprinting of metal complexes on oxide surfaces
    M Tada; Y Iwasawa
    This paper attempts to review recent examples of chemical design of catalytically active metal-complexes on oxide surfaces by means of attaching and molecular imprinting techniques. Metal complexes formed on oxide surfaces have generally different structures from their homogeneous analogues and often exhibit remarkable reactivities and catalyses based on the unique structures. Recently, functionalized catalytic sites have been combined to attached metal complexes for design of molecular shape selective space regulating catalyses. Here, we pick up several recent interesting supported metal-complex catalysts with different metal units. We also introduce new design of catalytic sites achieved by combining two methods of metal-complex attaching and molecular imprinting on oxide surfaces. (C) 2003 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2003年09月, JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 204巻, 掲載ページ 27-53, 英語, 書評論文,書評,文献紹介等, 1381-1169, WOS:000185387900002
  • Molecular-imprinted metal complexes for design of catalytic structures.
    M Tada; T Sasaki; Y Iwasawa
    AMER CHEMICAL SOC, 出版日 2003年09月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 226巻, 掲載ページ U742-U742, 英語, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:000187062403555
  • Design of molecular-imprinting metal-complex catalysts
    M Tada; Y Iwasawa
    This article attempted to review novel metal-complex catalysts prepared by molecular-imprinting methods, presenting our work on recent catalyst design at surfaces. Molecular imprinting is a way to produce cavity with a particular molecule (template) by polymerization of organic and inorganic materials and removal of the template. The cavity with memory of the template provides shape-selective reaction space for the molecule which has similar shape to the template: Recently, the application to metal-complex catalysts has been achieved to exploit unique property different from homogeneous and simple supported metal-complex catalysts. Imprinting metal-complex catalysts prepared by using reaction intermediate or transition state analogues as templates for asymmetric hydride transfer reduction of ketones, aldol condensation, and shape-selective hydrogenation of simple alkenes without any functional groups are focused in the viewpoint of new approaches in design of shape-selective metal-complex catalysts. (C) 2003 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2003年05月, JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 199巻, 1-2号, 掲載ページ 115-137, 英語, 書評論文,書評,文献紹介等, 1381-1169, WOS:000183057900014
  • Electronic structure of alkali halide-metal interface: LiCl(001)/Cu(001)
    M Kiguchi; H Inoue; K Saiki; T Sasaki; Y Iwasawa; A Koma
    Electronic structure of the heteroepitaxial LiCl thin film grown on Cu(001) was studied using electron energy loss spectroscopy (EELS) and ultraviolet photoelectron spectroscopy (UPS), as a model system of the insulator/metal interface. The EELS results did not show any change in the band gap of the LiCl film, though the Anderson's prediction indicated that the band gap of an insulator decreased at the insulator/metal interface. The change in the band gap of the LiCl film is discussed by considering Madelung potential and many body effects. The UPS results, on the other hand, showed an upward shift of the Cl 3p with an increasing film thickness. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2003年01月, SURFACE SCIENCE, 522巻, 1-3号, 掲載ページ 84-89, 英語, 0039-6028, WOS:000180103700015
  • Yasufuku, H., Y. Ohminami, T. Tsutsumi, K. Asakura, M. Kato, Y. Sakai, Y. Kitajima and Y. Iwasawa:"Observation of Energy Filtered Image for X-ray Photoemission Electron Microscopy(XPEEM) Using a Retarding Wien Filter Energy Analyzer",Chem.Lett.:842-843・・・
    H Yasufuku; Y Ohminami; T Tsutsumi; K Asakura; M Kato; Y Sakai; Y Kitajima; Y Iwasawa
    Yasufuku, H., Y. Ohminami, T. Tsutsumi, K. Asakura, M. Kato, Y. Sakai, Y. Kitajima and Y. Iwasawa:"Observation of Energy Filtered Image for X-ray Photoemission Electron Microscopy(XPEEM) Using a Retarding Wien Filter Energy Analyzer",Chem.Lett.:842-843(2002).*, CHEMICAL SOC JAPAN, 出版日 2002年08月, CHEMISTRY LETTERS, 8号, 掲載ページ 842-843, 英語, 0366-7022, 1348-0715, WOS:000177576100037
  • 時間分解XAFSを用いた触媒調製過程の研究
    紫藤 貴文; 山口 有朋; 鈴木 あかね; 稲田 康宏; 朝倉 清高; 野村 昌治; 岩澤 康裕
    日本表面科学会, 出版日 2002年06月10日, 表面科学, 23巻, 6号, 掲載ページ 339-344, 日本語, 0388-5321, 10008563736
  • 偏光全反射蛍光XAFSを用いた金属 : 酸化物基板界面構造の研究
    朝倉 清高; 岩澤 康裕
    日本表面科学会, 出版日 2002年06月10日, 表面科学, 23巻, 6号, 掲載ページ 332-338, 日本語, 0388-5321, 10008563694
  • Atomic and electronic structures of MgO/Ag(001) heterointerface
    M Kiguchi; T Goto; K Saiki; T Sasaki; Y Iwasawa; A Koma
    Thin film growth of MgO on Ag(0 0 1) was studied using reflection high-energy electron diffraction, Auger electron spectroscopy, electron energy loss spectroscopy (EELS), and ultraviolet photoemission spectroscopy (UPS), as a model system of the oxide/metal interface. At a substrate temperature of 450 K, a single-domain MgO film ([10 0](film)// [10 0]s(ubstrate)) grew heteroepitaxially on Ag(0 0 1). The in-plane lattice constant of the film changed continuously from the value of the substrate to that of the film, as is the case with the heteroepitaxial growth of alkali halides. The density functional calculations were performed for model clusters in order to investigate the initial adsorption structure. MgO adsorbed preferentially with the 0 atom above the Ag atom, and the Mg atom on the hollow site. EELS results showed that the band gap energy did not change for MgO thickness from I to 20 ML, indicating that the band gap energy of a I ML thick MgO film adjacent to a metal substrate was same as that of MgO surface. The UPS results, on the other hand, showed an upward shift of the valence band with decreasing film thickness. These UPS results could be explained by the image charge screening of a hole created by photoionization in the near presence of a metal. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2002年06月, SURFACE SCIENCE, 512巻, 1-2号, 掲載ページ 97-106, 英語, 0039-6028, 1879-2758, WOS:000176646200018
  • Design of catalytic sites at oxide surfaces by metal-complex attaching and molecular imprinting techniques
    A Suzuki; M Tada; T Sasaki; T Shido; Y Iwasawa
    This paper attempts to summarize our recent studies on the chemical design and characterization of catalytic sites at oxide surfaces such as Nb monomer, dimer and monolayer on SiO2, Rh dimers on SiO2, TiO2, Al2O3, and MgO, and An nanoparticles on TiO2 (110), prepared by using suitable metal-complex precursors in a molecular scale. The paper also reports performances of new molecular imprinting catalysts, SiO2 overlayers/(alpha-Al2O3 and Rh-SiO2 overlayers/SiO2, designed by surface molecular imprinting techniques. (C) 2002 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2002年05月, JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 182巻, 1号, 掲載ページ 125-136, 英語, 1381-1169, WOS:000176269200013
  • Multiple scattering approach to the Pt L-2-edge XANES of CO adsorption on small Pt particles
    Y Notoya; K Hayakawa; T Fujikawa; T Kubota; T Shido; K Asakura; Y Iwasawa
    A recent experimental result shows that Pt L-edge XANES spectra for Pt small cluster with similar to20 Pt atoms are sensitive to CO adsorption. In the present study we try to extract useful information about geometric and electronic structures of these cluster by applying a full multiple-scattering approach for the XANES analyses. Although IR analyses show that [CO](top)/[CO](bridge) is nearly constant for wide range of [Co](ad), it is difficult to estimate the ratio because of the large difference of the IR transition intensity for different adsorbed CO molecules. The present XANES analyses provide us useful new information [CO](top)/[CO](bridge) = 1-2. (C) 2002 Published by Elsevier Science B.V., ELSEVIER SCIENCE BV, 出版日 2002年05月, CHEMICAL PHYSICS LETTERS, 357巻, 5-6号, 掲載ページ 365-370, 英語, 0009-2614, WOS:000175958900007
  • Structural characterization of tungsten phosphide (WP) hydrotreating catalysts by X-ray absorption spectroscopy and nuclear magnetic resonance spectroscopy
    S. T. Oyama; P. Clark; X. Wang; T. Shido; Y. Iwasawa; S. Hayashi; J. M. Ramallo-López; F. G. Requejo
    This paper presents a detailed discussion of the structure of tungsten phosphide and its relationship to simpler crystalline forms. The structure (space group Pbnm) is based on distorted hexagonal prisms with the phosphorus atoms forming P-P chains. Measurements by 31P magic angle spinning nuclear magnetic resonance show that there is only one type of phosphorus with a Knight shift of 255 ppm from 85% H3PO4, which is located in a highly anisotropic environment. Numerical simulations of extended X-ray absorption fine structure data at the W L3-edge give good agreement with crystallographic data. The W-P distance in WP was found to be 0.246 nm compared to the value of 0.247 nm obtained by X-ray diffraction. The catalytic activity of tungsten phosphide in the hydrotreating of a simulated petroleum feed is reported and compared to those of other tungsten compounds on an areal basis. Bulk (WP) and supported tungsten phosphide (WP/SiO2) are found to be more active in HDS and HDN than tungsten carbide (WC), tungsten nitride (W2N), tungsten sulfide (WS2), and more active in HDN than a commercial Ni-Mo-S/Al2O3 catalyst. The enhanced activity may be related to a considerably reduced white line area in the X-ray absorption edge of WP and WP/SiO2 compared to W metal, which makes their electronic structure resemble those of the highly active elements, Os and Ir, to the right in the periodic table., 出版日 2002年02月28日, Journal of Physical Chemistry B, 106巻, 8号, 掲載ページ 1913-1920, 英語, 1089-5647, 80015125310, 0037187107
  • 多重散乱理論によるCO/PtクラスターのPt L-edge XANES解析
    能登屋 康晴; 早川 久仁子; 藤川 高志; 久保田 岳志; 紫藤 貴文; 朝倉 清高; 岩澤 康裕
    日本表面科学会, 出版日 2001年08月10日, 表面科学, 22巻, 8号, 掲載ページ 517-521, 日本語, 0388-5321, 10007560583
  • Heteroepitaxial growth of LiCl on Cu(001)
    M Kiguchi; K Saiki; T Sasaki; Y Iwasawa; A Koma
    Thin film growth of LiCl on a Cu(001) substrate is studied using reflection high-energy electron diffraction and Auger electron spectroscopy. A LiCl film was found to grow heteroepitaxially on a Cu(001) substrate. At a substrate temperature of 300 K, a single-domain LiCl film ([100](film)//[110](film)//[110](substrate)) grows in a layer-by-layer fashion, while a double-domain LiCl film ([100](film)//[100](substrate) and [100](film)//[110](substrate)) grows at substrate temperatures higher than 470 K. The density-functional calculations are performed for model clusters in order to investigate the initial adsorption structure. It is found in the calculation that the LiCl island is adsorbed more stably on the fourfold hollow site of the first Cu layer than on the atop site. The effective charge of Li and Cl of the LiCl molecule decreases with adsorption on Cu(001), due to the shielding by Cu 4s and 4p free electrons., AMER PHYSICAL SOC, 出版日 2001年05月, PHYSICAL REVIEW B, 63巻, 20号, 英語, 1098-0121, 1550-235X, WOS:000168937200092
  • Molecular design and characterization of active surfaces for molecular-level understanding and development of catalysis.
    Y Iwasawa; T Shido; K Fukui
    AMER CHEMICAL SOC, 出版日 2001年04月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 221巻, 掲載ページ U310-U310, 英語, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:000168824702268
  • Observation of the surface chemical process on micro-structured surface by emission electron microscopy and related techniques
    K. Asakura; Y. Ohminami; K. Ijima; S. Suzuki; Y. Yamaguchi; S. Takakusagi; Y. Iwasawa; M. Kato; Y. Sasaki
    出版日 2001年, Proceedings of 6th International Symposium on Advanced Physical Fields, Growth of well-defined Nanostructures 2001, 掲載ページ 60, 英語, 速報,短報,研究ノート等(学術雑誌)
  • "Observation of individual adsorbed pyridine, ammonia, and water on TiO2(110) by means of scanning tunneling microscopy"
    S. Suzuki; H. Onishi; K. Fukui; T. Sasaki; Y. Iwasawa
    出版日 2001年, Stud. in Surf. Sci. and Catal., 132巻, 掲載ページ 753-756, 英語, 査読付, 速報,短報,研究ノート等(学術雑誌)
  • Supported Gold Catalysts Prepared from a Gold Phosphine Precursor and as-Precipitated Metal Hydroxide Precursors: Effect of Preparation Conditions on the Catalytic Performance Kozlov, A. I., Kozlova, A. P., Asakura, K., Matsui, Y., Kogure, T., Shido, ・・・
    AI Kozlov; AP Kozlova; K Asakura; Y Matsui; T Kogure; T Shido; Y Iwasawa
    Supported Gold Catalysts Prepared from a Gold Phosphine Precursor and as-Precipitated Metal Hydroxide Precursors: Effect of Preparation Conditions on the Catalytic Performance

    Kozlov, A. I., Kozlova, A. P., Asakura, K., Matsui, Y., Kogure, T., Shido, T. and Iwasawa, Y., J. Catal., 196, 56-65 (2000)*, ACADEMIC PRESS INC, 出版日 2000年11月, JOURNAL OF CATALYSIS, 196巻, 1号, 掲載ページ 56-65, 英語, 0021-9517, WOS:000165598200006
  • Fluctuation of acetate ions in the (2 x 1)-acetate overlayer on TiO2(110)-(1 x 1) observed by noncontact atomic force microscopy
    K Fukui; Y Iwasawa
    Fluctuating molecules of acetate ions in the (2 x 1)-acetate overlayer on TiO2(110)-(1 x 1) were observed by noncontact atomic force microscopy. Each acetate ion adsorbed on its stable site was observed as bright round protrusion ordered in a (2 x 1) periodicity. On the other hand, acetate ions at a boundary between domains with different phases along the [001] direction moved along the [001] direction during scanning and gave fragmentary images. As a result, unstable regions for acetate ions were formed at domain boundaries. This phenomenon was explained in terms of repulsive and attractive interactions worked between acetate ions and hydroxyl hydrogen atoms, which are formed by dissociative adsorption of acetic acid. (C) 2000 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 2000年10月, SURFACE SCIENCE, 464巻, 2-3号, 掲載ページ L719-L726, 英語, 速報,短報,研究ノート等(学術雑誌), 0039-6028, WOS:000090098000001
  • 24pZN-3 非接触原子間力顕微鏡の触媒科学への応用
    福井 賢一; 岩澤 康裕
    一般社団法人日本物理学会, 出版日 2000年03月10日, 日本物理学会講演概要集, 55巻, 1号, 掲載ページ 799-799, 日本語, 1342-8349, 110001916933, AA11439205
  • Kinetic aspect of surface catalytic reactions on TIO2(110) characterized by in situ STM, relevant to oxide-catalyst design.
    Y Iwasawa; H Onishi; K Fukui; S Suzuki
    AMER CHEMICAL SOC, 出版日 2000年03月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 219巻, 掲載ページ U517-U517, 英語, 査読付, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:000087246102796
  • High resolution images of Mo2C(0001)-(root 3 x root 3)R30 degrees structure by scanning tunneling microscopy
    RL Lo; K Fukui; S Otani; Y Iwasawa
    A (root 3x root 3)R30 degrees C-terminated structure on Mo2C(0001) was observed by scanning tunneling microscopy. The structure was observed as a honeycomb structure with dark depressions corresponding to C atoms which make up the (root 3 x root 3)R30 degrees lattice. High resolution imaging was possible at low tunneling resistance less than 1 M Ohm. Each C atom appears as a shallow sombrero protrusion predicted by theoretical calculations of C atoms on a metal substrates. It is concluded that the C atoms occupied threefold hollow sites of the (1 x 1) Mo layer of the substrate and a model for the (root 3 x root 3)R30 degrees structure is proposed. (C) 1999 Elsevier Science B.V. All rights reserved., ELSEVIER SCIENCE BV, 出版日 1999年10月, SURFACE SCIENCE, 440巻, 3号, 掲載ページ L857-L862, 英語, 速報,短報,研究ノート等(学術雑誌), 0039-6028, WOS:000083245800003
  • NaY細孔内に合成されたMoダイマーオキシカーバイド種の構造とメタノール分解反応
    朝倉 清高; 紫藤 貴文; 野口 義明; 岩澤 康裕
    触媒学会, 出版日 1999年03月10日, 触媒, 41巻, 2号, 掲載ページ 116-118, 日本語, 0559-8958, 10001991105
  • 偏光全反射蛍光X線吸収微細構造分光法によるTiO_2(110)表面上のMo種の配向
    朝倉 清高; 田 旺帝; 岩澤 康裕
    出版日 1999年03月, 真空, 42巻, 3号, 日本語, 0559-8516, 10002476805
  • Temperature-programmed ESDIAD/TOF system as a new technique for characterization of adsorbed molecules and reaction intermediates
    T Sasaki; Y Itai; Y Iwasawa
    A temperature-programmed (TP-) electron stimulated desorption ion angular distribution (ESDIAD) / time-of-flight (TOF) system was developed to monitor changes in adsorbed layers in real time. This system can measure ESDIAD images and TOF spectra of desorbing ions stimulated by pulsed electron beam in temperature programmed surface processes. The coadsorption layers of CO and ammonia, the coadsorption layers of CO and methylamine, and the coadsorption layer of CO and acetylene on Ru(001), which were previously studied by our group using LEED, TPD and HREELS, have been observed by this system. The change in configuration of admolecules, the change in site occupation and the thermal evolution of adspecies can be monitored., VSP BV, 出版日 1999年, RESEARCH ON CHEMICAL INTERMEDIATES, 25巻, 2号, 掲載ページ 157-175, 英語, 書評論文,書評,文献紹介等, 0922-6168, WOS:000079162300002
  • XANES分光法によるPd微粒子吸蔵,吸着,サブサーフェス水素のキャラクタリゼーション
    久保田 岳志; 朝倉 清高; 北島 義典; 岩澤 康裕
    触媒学会, 出版日 1998年09月10日, 触媒, 40巻, 6号, 掲載ページ 380-383, 日本語, 0559-8958, 10001989822, AN00117719
  • LEEM, PEEM, SEEM, AEEMおよびXPEEM複合顕微鏡の開発
    山口 良隆; 高草木 達; 嘉藤 誠; 境 悠治; 朝倉 清高; 岩沢 康裕
    日本表面科学会, 出版日 1998年08月10日, 表面科学, 19巻, 8号, 掲載ページ 498-502, 日本語, 0388-5321, 10009863067, AN00334149
  • 水素-パラジウム相互作用のXANESスペクトルによる研究
    大谷 国広; 藤川 高志; 久保田 岳志; 朝倉 清高; 岩沢 康裕
    日本表面科学会, 出版日 1998年08月10日, 表面科学, 19巻, 8号, 掲載ページ 486-490, 日本語, 0388-5321, 10009863032, AN00334149
  • Structures and dynamic behavior of catalyst model surfaces characterized by modern physical techniques
    Y. Yamaguchi; W.-J. Chun; S. Suzuki; H. Onishi; K. Asakura; Y. Iwasawa
    出版日 1998年, Res. Chem. Intermed., 24巻, 掲載ページ 151-168, 英語, 査読付, 速報,短報,研究ノート等(学術雑誌)
  • STM visualization of site-specific adsorption of pyridine on TiO2(110)
    S. Suzuki; Y. Yamaguchi; H. Onishi; K. Fukui; T. Sasaki; Y. Iwasawa
    出版日 1998年, Catal. Lett., 50巻, 掲載ページ 117-123, 英語, 査読付, 速報,短報,研究ノート等(学術雑誌)
  • Low-energy electron diffraction analysis of the Pd(100)-p(2x2)-p4g-Al surface: a buried-heteroatom structure
    H Onishi; H Sakama; T Aruga; A Kawazu; Y Iwasawa
    Dynamical low-energy electron diffraction analysis reveals that the p(2 x 2)-p4g ordered bimetallic phase formed on aluminum-deposited Pd(100) consists of a clock-reconstructed Pd top layer and a strongly buckled c(2 x 2)-PdAl second layer. A buried-heteroatom model is proposed to interpret the obtained structure. The Pd-Al heteroatomic bonding interaction forces the top-layer Pd atoms to move systematically to make Pd-Al-Pd units. The four-fold hollows of the top layer open up only as a result of the systematic unit formation, in contrast to the squeezed-adatom type p(2 x 2)-p4g C/Ni(100) surface. (C) 1997 Elsevier Science B.V., ELSEVIER SCIENCE BV, 出版日 1997年12月, SURFACE SCIENCE, 392巻, 1-3号, 掲載ページ L51-L55, 英語, 速報,短報,研究ノート等(学術雑誌), 0039-6028, WOS:A1997YL16200010
  • Real-time observation of coadsorption layers on Ru(001) using a temperature-programmed ESDIAD/TOF system
    T Sasaki; Y Itai; Y Iwasawa
    For the purpose of utilizing ESDIAD as a real-time probe for surface processes, we have developed an instrument which can measure ESDIAD images and time of flight (TOF) spectra of desorbing ions in temperature-programmed surface processes. TOF measurements are carried out to identify the mass and to determine the kinetic energy distribution of the desorbed ions. This temperature-programmed (TP-) ESDIAD/TOF system was used to observe coadsorption layers of methylamine and CO on Ru(001) which have been previously studied by our group using LEED, TPD and HREELS, also drawing upon a comparison of findings with the coadsorption system of CO and ammonia. ESDIAD images acquired for temperature-programmed surface processes in real time were found to provide new insight into the dynamic behaviour of the coadsorption layers. As to the pure adsorption of ammonia and methylamine, the second and the first (chemisorbed) layers can be easily discriminated in their different ESD detection efficiency due to the difference in neutralization rate. The intensity change of H+ ions with temperature shows the process of the decomposition of methylamine to be dependent on CO coverage. The intensity of O+ originating from CO changes due to the change of CO adsorption site in the reaction process. The angular distribution of H+ ions which correspond to CH2=NH ... Ru species appears at 250-300 K in the presence of high CO pre-coverage. (C) 1997 Elsevier Science B.V., ELSEVIER SCIENCE BV, 出版日 1997年11月, SURFACE SCIENCE, 390巻, 1-3号, 掲載ページ 17-22, 英語, 0039-6028, 80010011190, WOS:A1997YK13500004
  • Reactive phase of oxygen on Cu(100) at 100 K studied by HREELS and TPD
    T Sueyoshi; T Sasaki; Y Iwasawa
    The reactivity of oxygen adatoms formed by dissociative adsorption of oxygen at 100 K on Cu(100) for CO oxidation was investigated by means of HREELS and TPD in comparison with the reactivity of adsorbed oxygen in thermally stable phases. On Cu(100) covered with oxygen adatoms formed at 100 K, designated as oxygen-as-exposed surface, post-dosed CO was oxidized at 125 K in TPD. On annealing the as-exposed surface to 300 K, a change in the loss feature of nu(Cu-O) was observed, indicating the formation of mixed phases comprised of pseudo c(2 x 2)-O with O(a) in fourfold hollow sites and (root 2 x 2 root 2)R45 degrees-O with -Cu-O-chains along the [001] direction. On these two phases, CO2 formation in TPD was reduced to one-ninth as compared to that on the as-exposed surface. These results may provide a new insight into the adsorbed phase of surface oxygen active for oxidation reaction and a way to develop a promising catalytic material with Cu metal. (C) 1997 Elsevier Science B.V., ELSEVIER SCIENCE BV, 出版日 1997年11月, APPLIED SURFACE SCIENCE, 121巻, 掲載ページ 562-566, 英語, 0169-4332, 80010024278, WOS:A1997YG44800114
  • TiO_2(110)表面上のMoダイマー生成と偏光全反射蛍光EXAFS法による非対称・異方性表面構造解析
    田 旺帝; 朝倉 清高; 岩澤 康裕
    触媒学会, 出版日 1997年09月10日, 触媒, 39巻, 6号, 掲載ページ 510-513, 日本語, 0559-8958, 10001987886
  • Coadsorption of CO and ammonia on Ru(001) studied by a temperature-programmed ESDIAD/TOF system
    T Sasaki; Y Iwasawa
    A temperature-programmed ESDIAD/TOF system was developed in order to monitor temperature-programmed surface reactions. This system was used to observe coadsorption layers of CO and ammonia oil Ru(001). The tilt of the molecular axis of ammonia due to coadsorption with CO, which was suggested by HREELS measurements, was confirmed by observed ESDIAD images. The configuration of the second layer of ammonia depends on CO coverage. The ESD cross section of H+ from ammonia was enhanced by coadsorption with CO, while those of O+ and CO+ from CO were suppressed compared to pure CO adsorption. Temperature-programmed ESDIAD measurements were found to be effective to observe chemical change in adsorption layers during annealing processes. (C) 1997 Elsevier Science B.V., ELSEVIER SCIENCE BV, 出版日 1997年07月, SURFACE SCIENCE, 384巻, 1-3号, 掲載ページ L798-L804, 英語, 速報,短報,研究ノート等(学術雑誌), 0039-6028, WOS:A1997XZ01500003
  • 31a-A-10 水素吸着した白金のPt-L_<2, 3>-edge XANESスペクトルの理論解析
    大谷 国広; 藤川 高志; 久保田 岳志; 朝倉 清高; 岩沢 康裕
    社団法人日本物理学会, 出版日 1997年03月17日, 日本物理学会講演概要集, 52巻, 1号, 日本語, 1342-8349, 110002237816
  • Oxygen atoms on Cu(100)formed at 100K, active for CO oxidation and water-hydrogen abstraction, characterized by HREELS and TPD
    SUEYOSHI T; SASAKI T; IWASAWA Y
    出版日 1997年, Journal of Physical Chemistry B, 101巻, 23号, 掲載ページ 4648-4655, 1089-5647, 80009726170
  • Pt/SbOx触媒のキャラクタリゼーションとアルカンの選択酸化触媒作用
    井上 朋也; 朝倉 清高; 岩澤 康裕
    触媒学会, 出版日 1996年09月10日, 触媒, 38巻, 6号, 掲載ページ 502-505, 日本語, 0559-8958, 10001861971, AN00117719
  • Temperature-jump STM observation of reaction intermediate on metal-oxide surfaces
    H Onishi; Y Yamaguchi; K Fukui; Y Iwasawa
    We have succeeded in monitoring the reaction of an acetate-covered TiO2(110) surface by scanning tunneling microscopy (STM) operated in a temperature-jump mode. Acetate ions were individually resolved at high temperatures, where they started decomposing, due to restricted mobility on the metal-oxide surface. The microscopic kinetics of the decomposition reaction determined by molecular counting in sequential STM images agreed with the macroscopic rate law deduced from a thermal desorption study. The present study demonstrated the ability of STM for monitoring reaction of ionic intermediates liberated on metal-oxide surfaces., AMER CHEMICAL SOC, 出版日 1996年06月, JOURNAL OF PHYSICAL CHEMISTRY, 100巻, 23号, 掲載ページ 9582-9584, 英語, 速報,短報,研究ノート等(学術雑誌), 0022-3654, WOS:A1996UP70600004
  • 呼吸する金属クラスター触媒
    泉 康雄; 岩澤康裕
    出版日 1995年, 現代化学, 295巻, 10号, 掲載ページ 16-23, 日本語, 招待, 記事・総説・解説・論説等(学術雑誌)
  • OBSERVATION OF ANISOTROPIC MIGRATION OF ADSORBED ORGANIC-SPECIES USING NANOSCALE PATCHWORKS FABRICATED WITH A SCANNING TUNNELING MICROSCOPE
    H ONISHI; Y IWASAWA
    A scanning tunneling microscope (STM) operated under ultrahigh vacuum enabled us to observe the migration of the individual formate ion (DCOO-) adsorbed on a TiO2(110) surface. We could remove off the formate ions in a desired area without damage to the substrate, by rastering the STM tip biased at an appropriate voltage. The patchwork of uncovered substrate was then created in the saturated (2 x 1) monolayer of the formate ions. The residual ions outside diffused into the patches driven by the mutual repulsion in the monolayer. Serial STM images revealed the microkinetics of the migration; the transport of the formate anion along the one-dimensional row of Ti cations was an order of magnitude faster than that across the Ti row. These results demonstrate the potential for application of the scanning tunneling microscopy in tailoring nanometer-sized structures in a distribution far from equilibrium and taking advantage of the reconstruction on the surface in kinetic measurements., AMER CHEMICAL SOC, 出版日 1994年12月, LANGMUIR, 10巻, 12号, 掲載ページ 4414-4416, 英語, 速報,短報,研究ノート等(学術雑誌), 0743-7463, WOS:A1994PY60400004
  • CO-BREATHING RUTHENIUM AND RHODIUM CLUSTERS
    Y IZUMI; Y IWASAWA
    AMER CHEMICAL SOC, 出版日 1994年07月, CHEMTECH, 24巻, 7号, 掲載ページ 20-27, 英語, 査読付, 0009-2703, 20440018, 0028463081, WOS:A1994NX03600007
  • RECONSTRUCTION OF TIO2(110) SURFACE - STM STUDY WITH ATOMIC-SCALE RESOLUTION
    H ONISHI; Y IWASAWA
    We succeeded in STM imaging of TiO2(110) with atomic-scale resolution. Sputtering and subsequent annealing under UHV at 600-900 K resulted in the (110)-(1 x 1) terraces bounded by steps parallel to the [111BAR] or [001] direction. Five-fold coordinated Ti4+ cations ordered in (1 x 1) periodicity were resolved on the terraces. Further annealing at 900-1100 K formed strings composed of double ridges along the [001] direction on the (110)-(1 x 1) terraces. The strings covered the surface to give a (1 x 2) superstructure when annealed at 1150 K. LEED patterns consistent with the transformations were observed., ELSEVIER SCIENCE BV, 出版日 1994年06月, SURFACE SCIENCE, 313巻, 1-2号, 掲載ページ L783-L789, 英語, 速報,短報,研究ノート等(学術雑誌), 0039-6028, WOS:A1994NT05300002
  • Rh-Sn/SiO2上のNO-H2反応におけるSnの添加効果と反応中間体の構造 (〔触媒学会〕第72回触媒討論会講演予稿)
    富重 圭一; 朝倉 清高; 岩沢 康裕
    触媒学会, 出版日 1993年09月, 触媒, 35巻, 6号, 掲載ページ p398-401, 日本語, 0559-8958, 40001842433, AN00117719
  • CO-BREATHING SUPPORTED-[RU6C] CLUSTERS AND THEIR CATALYSIS FOR SELECTIVE OXYGENATE SYNTHESIS FROM CO/H2
    Y IZUMI; Y IWASAWA
    AMER CHEMICAL SOC, 出版日 1993年03月, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 205巻, 掲載ページ 31-PETR, 英語, 研究発表ペーパー・要旨(国際会議), 0065-7727, WOS:A1993KQ98300531
  • CONTROL OF THE METHANOL REACTION PATHWAY BY OXYGEN ADSORBED ON MO(112)
    T ARUGA; K FUKUI; Y IWASAWA
    The effect of oxygen adatoms on the reaction path of methanol on the Mo(112) surface has been examined in relation to the genesis of solid catalysis as well as the creation of new active surfaces. It has been found that the formation of a p(1 x 2)-O layer results in a new methanol dehydrogenation path, which differs from the oxidative dehydrogenation usually observed on molybdenum oxides. The CO adsorption experiment indicated that half the first-layer Mo atoms on the Mo(112)-p(1 x 2) surface are completely blocked while the rest are almost free from the electronic effect of oxygen modifiers, suggesting that the new dehydrogenation path is due to the selective blocking of the second-layer Mo atoms, leaving one-dimensional rows of bare Mo atoms., AMER CHEMICAL SOC, 出版日 1993年, ACS SYMPOSIUM SERIES, 523巻, 掲載ページ 110-121, 英語, 書評論文,書評,文献紹介等, 0097-6156, WOS:A1993KZ55600009
  • ORDERED OXYGEN ON MO(112) - MODIFICATION OF SURFACE ELECTRONIC-STRUCTURE AND CONTROL OF REACTION-PATH
    T ARUGA; K FUKUI; Y IWASAWA
    AMER CHEMICAL SOC, 出版日 1992年06月, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 114巻, 12号, 掲載ページ 4911-4912, 英語, 記事・総説・解説・論説等(学術雑誌), 0002-7863, WOS:A1992HX81500071
  • 吸着分子の高分解能電子エネルギー損失分光
    佐々木 岳彦; 岩澤 康裕
    固体表面上の吸着分子を検出し,吸着種の振動スペクトルを測定する手段として高分解能電子エネルギー損失分光法(HREELS)は重要であり,広く用いられている分光法である。本稿では原理,特徴を述べた後に,金属,半導体,酸化物,有機物層表面での測定,ならびに時間分解測定について解説する。, The Surface Science Society of Japan, 出版日 1992年, 表面科学, 13巻, 2号, 掲載ページ 71-78, 日本語, 0388-5321, 80006343102
  • SiO2固定化TiO2超薄膜担持金属触媒の構造と物性 (〔第65回〕触媒討論会特集号(予稿))
    朝倉 清高; 岩沢 康裕
    触媒学会, 出版日 1990年03月, 触媒, 32巻, 2号, 掲載ページ p55-58, 日本語, 0559-8958, 40001842031, AN00117719
  • EXTENDED X-RAY ABSORPTION FINE-STRUCTURE AND XE-129 NUCLEAR-MAGNETIC-RESONANCE EVIDENCE FOR HIGHLY DISPERSED MOLYBDENUM CLUSTERS IN ZEOLITE-Y
    JM CODDINGTON; RF HOWE; YS YONG; K ASAKURA; Y IWASAWA
    ROYAL SOC CHEMISTRY, 出版日 1990年03月, JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 86巻, 6号, 掲載ページ 1015-1016, 英語, 記事・総説・解説・論説等(学術雑誌), 0956-5000, WOS:A1990CW17400021
  • 水性ガスシフト反応における反応中間体の挙動と触媒反応機構 (第64回触媒討論会特集号(予稿))
    紫藤 貴文; 朝倉 清高; 岩沢 康裕
    触媒学会, 出版日 1989年09月, 触媒, 31巻, 6号, 掲載ページ p449-452, 日本語, 0559-8958, 40001841882, AN00117719
  • EXAFS Studies on the Se-Nb Catalyst Obtained by Use of the Two-step Fixation Reaction
    Kiyotaka Asakura; Yasuo Izumi; Rika Kuwabara; Hideaki Yoshitake; Junji Inukai; Yasuhiro Iwasawa; Haruo Kuroda
    出版日 1989年, Photon Factory Activity Report 1987, 5巻, 掲載ページ 182-182, 英語, 速報,短報,研究ノート等(大学,研究機関紀要)
  • 化学設計した単結晶表面の触媒機能 (固体表面の化学設計と機能<特集>)
    岩沢 康裕
    触媒学会, 出版日 1988年10月, 触媒, 30巻, 7号, 掲載ページ p546-554, 日本語, 0559-8958, 40001841786, AN00117719
  • SMSI効果に誘起される反応場と水素化反応機構 (第62回触媒討論会特集号(予稿))
    吉武 英昭; 朝倉 清高; 岩沢 康裕
    触媒学会, 出版日 1988年09月, 触媒, 30巻, 6号, 掲載ページ p380-383, 日本語, 0559-8958, 40001841733, AN00117719
  • 固定化コバルト酸化物クラスタ-触媒上におけるCO酸化反応のEXAFSによる研究 (〔第59回〕触媒討論会特集号--表面の新しい機能を探る触媒討論会(予稿)) -- (「新しい機能を持った触媒」セッション)
    朝倉 清高; 紫藤 貴文; 岩沢 康裕
    触媒学会, 出版日 1987年03月, 触媒, 29巻, 2号, 掲載ページ p166-169, 日本語, 0559-8958, 40001841576, AN00117719
  • 酸化マグネシウム(MgO)に添加した金属イオンの周辺構造とMgOの触媒物性に与える影響に関する研究 (〔第57回〕触媒討論会特集号(予稿))
    朝倉 清高; 岩沢 康裕; 黒田 晴雄
    触媒学会, 出版日 1986年03月, 触媒, 28巻, 2号, 掲載ページ p120-122, 日本語, 0559-8958, 40001841422, AN00117719
  • シリカ固定化超薄膜アモルファス酸化ニオブ触媒の調製とその触媒特性に関する研究 (第56回触媒討論会特集号(予稿)) -- (合金触媒など)
    朝倉 清高; 岩沢 康裕; 黒田 晴雄
    触媒学会, 出版日 1985年09月, 触媒, 27巻, 6号, 掲載ページ p371-373, 日本語, 0559-8958, 40001841346, AN00117719
  • Surface Structure of SMSI Catalyst I. Rh/TiO2 Catalyst
    H. Kuroda; N. Kosugi; K. Asakura; H. Ishii; T. Yokoyama; Y. Iwasawa
    出版日 1983年, Photon Factory Activity Report 1982/83, VI-59, National Laboratory for High Energy Physics, KEK, 英語, 速報,短報,研究ノート等(大学,研究機関紀要)

書籍等出版物

  • ベーシック表面化学 (11刷)
    岩澤康裕、中村潤児、福井賢一、吉信淳
    化学同人, 出版日 2023年10月
  • 膜電極接合体(MEA)の先端評価解析; in: モビリティ用電池の化学
    岩澤康裕, 鷹尾忍
    分担執筆, 第18章, 化学同人, 出版日 2022年03月
  • Recent Progress in Advanced SR Characterization of Fuel Cells at SPring-8
    Y. Iwasawa
    単著, SPring-8/SACLA Research Frontiers 2020, 出版日 2021年08月
  • Advanced Characterization of Nanostructured Materials, Chapter 8 "X-ray Absorption Fine Structure Techniques for Nano-Catalytic Materials"
    N. Ichikuni; K. Okumura; Y. Iwasawa
    学術書, 英語, 共著, Chapter 8 "X-ray Absorption Fine Structure Techniques for Nano-Catalytic Materials", World Scientific, Singapore, 出版日 2021年03月
  • in situ XAFS測定による活性構造と劣化挙動の観察・評価
    岩澤康裕
    分担執筆, 第4章第2節, 技術情報協会, 出版日 2020年11月
  • 触媒化学
    岩澤康裕; 小林修; 冨重圭一; 関根泰; 上野雅晴; 唯美津木
    教科書・概説・概論, 日本語, 共著, 裳華房, 出版日 2019年05月
  • 燃料電池開発への応用
    岩澤康裕
    分担執筆, 21章5節5項, 加速器ハンドブック(日本加速器学会編), 丸善, 出版日 2018年04月
  • 基本物理化学
    岩澤康裕; 北川禎三
    教科書・概説・概論, 日本語, 共訳, 東京化学同人, 出版日 2018年04月
  • 次世代燃料電池触媒の開発設計因子:世界オンリーワンSPring-8 BL36XUビームライン計測システムからのフィードバック
    岩澤康裕
    分担執筆, 車載テクノロジー, 技術情報協会, 出版日 2017年
  • XAFS Techniques for Catalysts, Nanomaterials, and Surfaces
    Y. Iwasawa; K. Asakura; M. Tada
    学術書, 英語, 共編者(共編著者), 第1章 著者、第25章 共著者、全編の編集, Springer, 出版日 2016年11月
  • 触媒の設計・反応制御 事例集
    岩澤康裕
    日本語, 単著, 第13章第7節 触媒作用の動的挙動測定, 技術情報協会, 出版日 2013年05月
  • 現代表面科学シリーズ1 表面科学こと始め
    中村潤児; 岩澤康裕
    日本語, 共著, 第13章 触媒反応の機構解明と固体表面のリアルタイム観察, 共立出版社, 出版日 2012年03月
  • 現代表面科学シリーズ1 終章
    岩澤康裕
    日本語, 単著, 終章, 共立出版社, 出版日 2012年03月
  • ニュートン別冊
    岩澤康裕; 桜井弘
    日本語, 監修, 化学の“カラクリ”がよくわかる イオンと元素 ( 増補改訂版), ニュートンプレス, 出版日 2011年
  • ベーシック表面化学
    岩澤康裕; 中村潤児; 福井賢一; 吉信淳
    日本語, 共著, 化学同人, 出版日 2010年04月
  • 触媒便覧
    小野喜夫; 御園生誠; 岩澤康裕
    事典・辞書, 日本語, 講談社, 出版日 2008年
  • Handbook of Heterogeneous Catalysis-Second,Compeletely Revised and Enlarged Edition
    M. Tada; Y. Iwasawa
    英語, 共著, Supported Catalysts from Chemical Vapor Deposition and Related Techniques, Wiley-VCH, 出版日 2008年
  • 5分で理科が好きになる本(小学3年、4年)
    岩澤康裕
    日本語, 編者(編著者), 全章, 講談社, 出版日 2007年
  • 固定化媒体のルネッサンス
    唯美津木; 岩澤康裕
    日本語, 共著, 固体表面を媒体とした触媒反応, シーエムシー出版, 出版日 2007年
  • 表面物性工学ハンドブック第2版
    唯美津木; 岩澤康裕
    日本語, 共著, 設計表面の触媒反応, 丸善, 出版日 2007年
  • Newton
    岩澤康裕; 桜井弘
    日本語, 監修, 「イオン」のすべて 身近な化学変化の“カラクリ”がわかる, ニュートン, 出版日 2007年
  • 生命科学系のための物理化学
    岩澤康裕; 北川禎三; 浜口宏夫
    英語, 共訳, MacMillan Publishing Compnay, New York, 出版日 2005年
  • 化学便覧基礎編
    岩澤康裕
    事典・辞書, 日本語, 丸善, 出版日 2004年
  • 化学と生命科学のための物理化学
    岩澤康裕; 北川禎三; 浜口宏夫
    日本語, 共訳, 全章, 東京化学同人, 出版日 2003年
  • 界面ハンドブック
    岩澤康裕; 梅澤喜夫; 澤田嗣郎; 辻薫
    日本語, 監修, 全章, ㈱エヌティエス, 出版日 2001年
  • X-ray Absorption Fine Structure for Catalysts and Surfaces
    岩澤康裕
    英語, 編者(編著者), World Scientific, Singapore, 出版日 1996年
  • 基礎物理化学
    渡辺啓; 岩澤康裕
    日本語, 共著, 裳華房, 出版日 1995年
  • 表面の化学
    岩澤康裕; 小間篤
    日本語, 共著, 丸善, 出版日 1994年
  • 大学院物理化学
    妹尾学; 廣田穣; 田隅三生; 岩澤康裕
    日本語, 共著, 講談社サイエンティフィック, 出版日 1992年
  • Tailored Metal Catalysts
    岩澤康裕
    英語, 編者(編著者), Reidel Publishing Company, Holland, 出版日 1986年

講演・口頭発表等

  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2020年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(基調), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2020年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2019年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2019年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2018年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2018年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2017年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(基調), 英語, 岩澤研HP参照, 招待, 岩澤研HP参照, 岩澤研HP参照, http://www.iwasawalab.pc.uec.ac.jp/, 岩澤研HP参照, 国際会議
    発表日 2017年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2016年
  • http://www.iwasawalab.pc.uec.ac.jp/
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, http://www.iwasawalab.pc.uec.ac.jp/, 招待, 国際会議
    発表日 2016年
  • 岩澤研HP参照
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, 岩澤研HP参照, 招待, 岩澤研HP参照, 岩澤研HP参照, 岩澤研HP参照, 国際会議
    発表日 2015年
  • 岩澤研HP参照
    Yasuhiro Iwasawa
    口頭発表(招待・特別), 英語, 岩澤研HP参照, 招待, 岩澤研HP参照, 岩澤研HP参照, http://www.iwasawalab.pc.uec.ac.jp/, 岩澤研HP参照, 国際会議
    発表日 2015年

担当経験のある科目_授業

  • 今年度から講義・単位授与を受け持っておりません
    The University of Electro-Communications
  • 電子物性工学
    The University of Electro-Communications
  • 電子物性工学
    電気通信大学
  • 現代化学
    The University of Electro-Communications
  • 現代化学
    電気通信大学
  • 化学反応論
    千葉大学
  • 化学反応論
    千葉大学
  • 化学特別講義
    慶応大学
  • 化学特別講義
    慶応大学
  • Modern Chemistry
    The University of Electro-Communications
  • 現代化学
    電気通信大学
  • 科学史
    東京大学大学院理学系研究科
  • 科学史
    東京大学大学院理学系研究科
  • Chemical Reactions
    Chiba University
  • 化学反応論
    千葉大学
  • Reaction Kinetics
    The University of Tokyo
  • 化学反応学
    東京大学

所属学協会

  • 2007年04月 - 2023年09月
    日本学術会議(元第3部長)
  • インドマテリアル科学会(名誉会員)
  • 中国化学会(名誉会員)
  • 日本表面科学会(元会長)
  • 触媒学会(元会長)
  • 英国王立化学会 (Fellow)
  • アメリカ化学会
  • 日本化学会(元会長)
  • 日本化学連合 (現会長)

共同研究・競争的資金等の研究課題

  • 共通課題解決型基盤技術開発/プラットフォーム材料の解析及び解析技術の高度化の技術開発
    岩澤康裕
    NEDO, 燃料電池等利用の飛躍的拡大に向けた共通課題解決型産学官連携研究開発事業, 研究代表者
    研究期間 2020年07月 - 2025年03月
  • 時間空間分解XAFS等計測技術を用いた燃料電池触媒構造反応解析
    岩澤康裕
    NEDO, 固体高分子形燃料電池利用高度化技術開発/普及拡大化基盤技術開発, 研究代表者
    研究期間 2015年05月 - 2020年02月
  • C-H結合の低温選択的活性化のための新規細孔内シングルサイト触媒の設計
    岩澤 康裕; GHOSH SHILPI
    日本学術振興会, 科学研究費助成事業, 電気通信大学, 特別研究員奨励費, 研究者らはこれまでにアルカリ金属及びアルカリ土類金属のなかでも大きいイオン半径を有するRbとCsをβゼオライトにイオン交換法で担持したRb/βおよびCs/β触媒が、触媒反応の中でも困難な反応とされるベンゼンのフェノールへの直接酸化反応を、N2Oを酸化剤として用いることで高選択的に高い転化率をもって進行させることを見出してきた。 前年度までで反応条件の最適化やXAFS, XPS, XRD, DFT計算によるRb/βおよびCs/β触媒の構造解析および反応機構解析を行ってきた。当該年度では、論文化を進めるうえで不足していたβゼオライトに担持するアルカリ金属及びアルカリ土類金属のイオン半径と触媒活性及び選択性の相関の解析およびTPDによる触媒活性点となる酸点の分析を行った。 イオン半径と反応活性及び選択性の相関を調べるためにMg, Ca, K, Rb, Csをβゼオライトに担持したものを調製し、ベンゼンの直接酸化反応に用いた。選択性はどの触媒でも高く>99%のフェノール選択性を示した。対して転化率はイオン半径の増加に伴い増加する傾向が確認され、イオン半径と活性の相関が明らかとなった。 また、CO2-TPD及びCH3CN-TPDによりCs/βおよびRb/β触媒の酸点と塩基点の分析を行ったところ、CO2-TPDの結果からは塩基点の存在が確認されず、CH3CN-TPDからは弱い酸点が確認された。このことからゼオライト細孔中のRbイオンおよびCsイオンが弱いルイス酸として働くことが分かった。 以上の成果をまとめて、ACS Catalysisに投稿した。, 16F16383
    研究期間 2016年11月07日 - 2019年03月31日
  • 前例のないナノ塩基性金属酸化物/ゼオライト触媒による新規高選択的フェノール合成
    岩澤 康裕; ACHARYYA SHANKHA
    日本学術振興会, 科学研究費助成事業, 電気通信大学, 特別研究員奨励費, これまでにアルカリ金属/ゼオライト及びアルカリ土類金属/ゼオライト触媒のなかでもCs/β触媒が、触媒反応の中でも困難な反応とされるベンゼンのフェノールへの直接酸化反応をアンモニア共存下で高選択的に高い転化率をもって進行させることを見出してきた。 当該年度では、酸塩基触媒であるCs/βにより酸化反応が進行するという特異な反応機構の解析を主目的として、X線分光測定や理論計算により反応機構の解析を行った。 各アルカリ金属(Na, K, Rb, Cs)及びアルカリ土類金属(Mg, Ca, Sr, Ba)をβゼオライトにイオン交換で担持させた触媒に関して、各金属イオンのイオン半径とベンゼン転化率及びフェノール選択率の相関を調べると、イオン半径の増加に伴い転化率と選択率が増加する傾向があり、特にイオン半径が150 pmを超えるRbとCsで高い転化率がみられた。 XPS, XAFSによりCs/β触媒のCsの構造を調べるとCsはCs+のシングルサイトとして存在していることが分かった。そこでβ細孔中に固定されたCsイオンを活性構造と仮定して、DFT計算から反応機構解析を行った結果、ベンゼンと酸素、アンモニアがCsイオン上に共吸着し、アンモニアによる酸素分子の解離とベンゼンへの酸素の結合が協奏的に起こるという反応機構が推定された。 以上から、Csのように大きいイオン半径を有する金属イオンを反応場として用いることで、通常の酸化反応のような金属種の酸化過程を経ずに、金属シングルサイト上で協奏的に各反応物が活性化し、反応が進行するような反応場を提供するといった前例のない新しい触媒作用の開発に成功した。, 16F16078
    研究期間 2016年04月22日 - 2018年03月31日
  • 時空間分解X線吸収微細構造(XAFS)計測技術の開発と燃料電池触媒構造反応解析
    岩澤康裕
    NEDO, 研究助成, 研究代表者
    研究期間 2010年04月 - 2015年02月
  • 高効率選択酸化及び燃料電池酸化触媒の開発とリアルタイム構造情報に関する研究
    岩澤康裕
    研究代表者
    研究期間 2007年04月 - 2011年03月
  • 時間分解XAFSを用いたダイナミック燃料電池触媒の構造と電子状態解析およびXAFS解析技術評価
    岩澤康裕
    NEDO, 委託, 研究代表者
    研究期間 2008年 - 2009年
  • 新規高効率触媒作用創出のための完全反応制御と反応原理解明に関する分子理論的研究
    岩澤康裕
    研究代表者
    研究期間 2008年 - 2009年
  • 燃料電池のin-situ時間分解XAFS計測評価
    岩澤康裕、唯美津木
    トヨタ自動車, トヨタ自動車, 共同研究
    研究期間 2004年04月 - 2007年03月
  • サブナノ秒時間分解XAFS実験法の開発
    野村 昌治; 岩澤 康裕; 朝倉 清高; 稲田 康宏; 唯 美津木; 丹羽 尉博; 佐々木 岳彦; 鈴木 あかね
    日本学術振興会, 科学研究費助成事業, 大学共同利用機関法人高エネルギー加速器研究機構, 基盤研究(A), 構造や電子状態が不明な溶液中および固体表面での短寿命金属化学種を対象とし、サブナノ秒までの時間分解能でその場構造解析およびその場電子状態解析を行なうための時間分解XAFS実験法の開発を目的とした。平成16年度にはNW2Aビームラインでの放射光X線パルスとPF-ARリングのRFマスタークロック信号とのジッターを評価し、サブナノ秒での時間分解に十分な13.3psであることを確認した。平成17〜18年度には、XAFSスペクトルとして必要なX線エネルギー領域全体を一度に測定するための分散型XAFS装置に適用する一次元検出器として、通常は二次元検出器として用いられるCCD素子を1行の一次元検出部+残り行の電荷メモリ部として使用することにより、CCD素子上の電荷の行転送を用いて時間分解記録を行うための高速一次元X線検出システムの開発を行った。X線のパルス間隔(1.26μs)以内に行転送が可能な素子としてATMEL社製のTH7888Aを採用し、約800nsでの行転送をRFマスタークロック信号で駆動するための回路およびメモリ部に展開した電荷データをユニポーラ16ビットのADCで読み出す回路の設計と開発を行った。また、短寿命な光励起状態を生み出すための高出力パルスNd : YAGレーザー(POWERLITE 8000)を平成18年度に導入し、平成19年度にかけてナノ秒パルスレーザーと放射光X線パルスとの同期によるポンプープローブ測定システムを確定した。入射X線はCCD素子に光学カップリングして取り付けたP46蛍光体付きテーパー型ファイバープレートで可視光へ変換して検出した。また、CCD素子上の検出行以外のエリアへ光が入射するのを防ぐためのスリットシステムを開発した。この高速CCD検出システムをキネティックスモードで動作した時のスペクトル測定の結果、1パルスのX線での吸収端近傍構造の検出にも成功し、1.26μsで繰り返されるX線パルスをそのままの時間スケールで約1000本まで測定することが可能な世界最速の一次元検出システムの開発に成功した。, 16205005
    研究期間 2004年 - 2007年
  • 分子系の極微構造反応の計測とダイナミクス
    増原 宏; 福村 裕史; 岩澤 康裕; 入江 正浩; 魚崎 浩平; 朝日 剛
    日本学術振興会, 科学研究費助成事業, 特定領域研究, 本特定領域研究は平成16-18年度の領域研究として採択され,3年間にわたり86研究課題が連携して研究を展開し基盤研究を展開してきた。その結果,各研究課題の研究のみならず,多くの班内・班間の領域内共同研究を生み出すことができた。 平成19年度はこの3年間の領域研究で生まれた成果のとりまとめ作業を行った。 具体的には,研究成果報告書として下記の3冊の発行を行い,領域研究者や外国人を含む領域アドバイザーに配布した。 1.成果報告書(その1研究課題別成果報告書):339ページ 計画研究課題は3年間,公募研究課題は2年間の各研究課題の研究成果をA4サイズ2ページの文章(和英)とA4サイズ2ページ図表(英文)によりまとめた。 2.成果報告書(その2共同研究成果報告書):130ぺージ 領域内の共同研究65件の研究成果を共同研究成果報告書としてまとめた。 3.成果報告書(その3成果発表リスト):247ページ 各研究課題の代表者および分担者による本領域研究に関する論文全1235報・総説解説220報・著書183件・国際会議発表1192件・特許41件の全リストを成果発表リストとしてまとめた。 加えて,本領域研究の若手研究者により「極微構造若手の会」が組織され研究会を行ったが,その内容をレポートにまとめ,「極微構造若手の会」発行の冊子体として出版した。(成果報告書その2付録)また,別途この成果を世界に向けて発信するための英文書を出版するための準備を行った。, 16072101
    研究期間 2004年 - 2007年
  • 時空間における分子振動計測の極限化:分子から細胞まで物質組織化機構の解明に向けて
    濱口 宏夫; 岩澤 康裕; 岩田 耕一; 高塚 和夫; 加納 英明; 田原 太平; 佐藤 伸
    日本学術振興会, 科学研究費助成事業, 東京大学, 学術創成研究費, 平成19年度の研究の過程で、β-カロテンなど対称心を持つ共役色素の電子遷移が、近接する溶媒分子のハイパーラマン散乱強度を顕著に増大させるという新しい現象(分子近接場効果)を発見した。分子近接場効果を用いると、プローブ分子の近傍のみを選択的に計測する新しいナノメートル局所振動分光法が誕生する可能性がある。この可能性をさらに探求するために、研究計画を当初計画(平成19年度終了)より1年間(平成20年度まで)延長することを申請し、承認された。延長後の1年間に、ハイパーラマン散乱測定装置の高速化および励起波長の可変化に取り組み、β-カロテンの共鳴ハイパーラマン散乱の励起プロファイルを観測して、先に提出していた分子近接場効果の理論を裏付ける結果を得た。また、分子近接場効果を示す溶媒のスペクトルが、バルクのものと顕著に異なることを見出した。さらに、より簡単な色素であるヨウ素も分子近接場効果を示すことを見出し、この効果が一般性を持つことを確かめた。このように、1年間の研究期間延長により、分子近接場効果の機構に対する理解が深まり、ナノメートル、フェムト秒の時空間分解振動分光の実現に向けて一歩前進することができた。平成19および20年度を通じて、ピコ秒時間分解ラマン分光による光励起されたtrans-スチルベン分子の振動冷却過程の研究をさらに進展させた。6種のイオン液体中での冷却曲線を得て、これを熱拡散方程式により解析し、イオン液体中の局所構造のサイズに関する情報を得た。顕微CARS分光システムの開発をさらに推進し、近赤外のサブピコ秒レーザーを用いた装置を新たに開発し、従来測定が困難であった生細胞の指紋領域での分光イメージングを可能にした。近赤外共焦点顕微ラマン分光装置を製作し、植物細胞など蛍光の妨害により顕微ラマン分光測定が不可能な生体試料の振動スペクトル測定を可能にした。, 15GS0204
    研究期間 2003年 - 2007年
  • 触媒表面構造ダイナミクス
    岩澤康裕
    研究代表者
    研究期間 2004年 - 2006年
  • 21世紀COEプログラム「動的分子論に立脚したフロンティア基礎化学」
    岩澤康裕
    研究代表者
    研究期間 2002年 - 2006年
  • 表面を媒体とするモレキュラーインプリンティング不斉金属錯体触媒の創成と制御
    岩澤 康裕; 佐々木 岳彦
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定領域研究, 不斉シッフ塩基を配位したバナジウム単核錯体をシリカ表面のシラノール基と選択的に反応させて固定化し、シリカ表面で2つのシッフ塩基バナジウム錯体が自発的に会合する不斉自己組織化現象を初めて見出した。ダィマーの会合体内部に不斉バナジウム中心とカップリング反応に有利な不斉反応空間が形成され、この構造をDFT計算によって明らかにした。2-ナフトールの不斉カップリング反応において、この固定化ダイマーは高い活性と選択性を示し、シリカ表面上のバナジウム錯体の被覆率が最大のとき最高不斉選択性90%eeを示した。 不斉ビスオキサゾリン(BOX)配位子をシリカ表面に固定化し、その表面の空間をメタクリル基やオクタデシル基などの有機官能基を有する複数のシランカップリング剤で修飾し、表面修飾Cu-BOX錯体触媒を調製した。Diels-Alder反応の触媒反応活性を検討したところ、均一系のCu-BOX錯体では触媒活性が非常に低かったのに対し、シリカ固定化触媒は高い触媒活性を示すことを見出した。更に、表面の有機官能基修飾により、不斉選択性が飛躍的に増加することを見出した。表面の不斉選択性は、表面修飾シランカップリング剤に大きく依存し、メタクリル基を有したシランカップリング剤が最も高い不斉選択性の増大効果を示すことを見出した。表面修飾メタクリル基と表面のBOX配位子の間に水素結合が働き、、固定化したBOX配位子の周辺に表面修飾基が集まり、かさ高い不斉構造が形成されたことで、高い不斉選択性の増幅効果が得られたものと考えられる。, 16033217
    研究期間 2004年 - 2005年
  • 学術研究システムの改革のための資源配分および研究人材養成に関する調査研究
    山本 眞一; 岩澤 康裕; 鈴木 久敏; 大野 弘幸; 小田切 宏之; 加藤 毅; 小林 信一
    日本学術振興会, 科学研究費助成事業, 筑波大学, 特別研究促進費, われわれの研究グループでは、これまで平成10年度、平成14年度の二時点にわたり大学における学術研究環境の現状や新しい動向などについて定量的な調査を実施してきた。第三回目にあたる今次の調査研究では、時系列の変化を踏まえた上で、重点化あるいは競争化などの学術研究資源の配分方式の変化が現場に及ぼしている影響を明らかにすること、および「フローの増加によるストックの侵食を通じた衰退の危機」という問題状況を定量的に明らかにすることなどを目的として、調査設計を行った。主要な分析結果の概要は、以下の通りである。 1.大規模な研究体制は、ほとんどの場合、高額の政府競争資金や科研費によって財政的に支えられている。矩期間のうちに評価にさらされる不安定な研究体制が多くを占めるなかで、少数ながら、所属機関からの経常費に支えられた安定性の高い大規模研究が、大学共同利用機関法人を中心として実施されている。 2.学術研究活動のボーダレス化という傾向は、さらに強まっていることが明らかになった。唯一の例外はポスドクの進路であり、依然として研究者養成過程として位置づけられている。 3.研究時間の不足という問題は、さらに深刻化していることが明らかになった。特に理工系では、その他の職務に費やされる時間が長くなっている。 4.プロジェクト研究費を受け入れるための研究基盤が整備されているものは、全体の1/4に満たない少数派となっている。ただし、現在恵まれた研究体制のもとで高い生産性を上げているグループに限定した場合、およそ半数は研究基盤が整備されていると回答している。, 15800001
    研究期間 2003年 - 2005年
  • モレキュラーインプリンティング不斉触媒の開発と分子認識機能の創出に関する研究
    岩澤康裕
    研究代表者
    研究期間 2003年 - 2005年
  • 革新的表面ナノバイオトロニクスに関する調査研究-次世代ポストゲノム医理工連携研究の促進を目指して-
    庭野 道夫; 宇理須 恒雄; 岩澤 康裕; 岩崎 裕; 吉信 達夫; 荻野 俊郎
    日本学術振興会, 科学研究費助成事業, 東北大学, 基盤研究(C), DNAの塩基配列の解読により、生命現象を解析するプロテオミクスや、SNP(単一塩基多型)解析に基づいたオーダーメイド医療の実現など、21世紀のバイオテクノロジーを牽引する研究が活発になりつつある。これらの研究を進展させるためには、生体関連物質の高感度分析・解析技術の開発が必要不可欠であり、その技術開発には,20世紀に成熟した半導体エレクトロニクス技術、特に表面ナノスケール制御・解析技術と,バイオテクノロジーとのインテリジェントな融合が有効である.この融合をわれわれは「表面ナノバイオトロニクス」と名づける。この「表面ナノバイオトロニクス」の目標は,表面という2次元空間を作業空間として、生体情報を物理信号(エレクトロン(電子)やフォトン(光子)など)に高効率に変換し,また,その逆に物理信号を生体系にフィードバックするような、高度なバイオ・インタフェイスシステムを構築することである。国内外を見るに、現在,この種の研究は緒についたばかりである。そこで本研究は、半導体工学や表面科学の研究者と、生命科学、バイオテクノロジー分野の研究者が、有機的な医理工連携を図ることにより、「表面ナノバイオトロニクス」技術の戦略目標を討論することを目的とした。 平成16年(2004年)には、応用物理学会秋季大会シンポジウム「ナノバイオテクノロジーにおける表面・界面の課題」を開催し、本研究のメンバーを中心に講演・討論を行った。さらに、平成16年10月に内外の著名な研究者を招待して国際研究集会「International Workshop on Surface-Biotronics」(東京)を開催し、表面バイオトロニクスに関する研究調査を行い、関連情報の収集に努めた。 以上の調査研究に基づいて、平成17年度発足の特定領域研究「生体階層構造に適合した表面バイオトロニクスの創成」(代表:岩崎裕)を申請した。, 16631010
    研究期間 2004年 - 2004年
  • 分子認識人工酵素機能を付加した界面での光触媒設計と構造-機能相関の研究
    岩澤 康裕; 佐々木 岳彦
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定領域研究, TiO_2は機能性材料として広範に利用されている。当研究室ではこれまで、ルチルTiO_2(001)表面の特殊な構造な上でメタノールやギ酸の光分解反応が可視光によって進行することを見いだした。本年度は実験、理論の両側面から反応の詳細を調べた。まず、詳細な走査トンネル顕微鏡観察から、この表面の構造を決定し、この表面は高活性な4配位Tiが露出したものであることがわかった。また、反応の照射光エネルギー依存性から、この表面ではバンドギャップがバルクの値3.0eVから2.1eV程度に狭まっていることがわかった。このバンドギャップの狭まりは第一原理計算によっても確認され、表面に露出した4配位Tiに起因することがわかった。すなわち、見いだされた可視光反応性はこの表面に露出した4配位Ti由来の表面状態によるものである可能性が高い。 人工酵素型の高い立体形状選択性、分子認識能を有した新規触媒表面の構築のために、酸化物表面上に固定化した新規金属錯体触媒およびその表面におけるモレキュラーインプリンティングを組み合わせた表面インプリンティング触媒の新規設計を行った。Rh-アミン錯体を配位させた新規シリカ固定化Rh単核錯体を調製し、表面モレキュラーインプリンティングを行い、表面マトリックスを作成した後、テンプレートとしたアミンを脱離させることにより、配位不飽和な活性Rh種とその近傍のテンプレート形状の反応空間キャビティーを設計した。実際、表面インプリント触媒のみが高い活性と高い選択性を示した。形状の異なるアミン配位子を反応阻害剤として導入したところ、表面の反応サイトの阻害効果に顕著な差が見られ、アミン配位子の立体形状に応じた高い立体選択能を有していることが明らかになった。 Mn4核クラスター触媒の酸化物表面固定化及びそのインプリンティング触媒の調製も行い、光酸化反応の選択制御も検討している。, 15033218
    研究期間 2003年 - 2004年
  • 表面を媒体とするモレキュラーインプリンティング不斉金属錯体触媒の創成と制御
    岩澤 康裕; 佐々木 岳彦
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定領域研究, 本研究は、表面を媒体としてMolecular Imprinting(分子刷り込み)不斉触媒を開発し高次不斉触媒機能の創出を図ることを目的とする。 本研究において新規不斉バナジウム固定化錯体触媒の設計と2-ナフトールの酸化的カップリング反応に成功した。2,2'-Dihydroxy-1,1'-binaphthyl (BINOL)は、 binaphthyl基を骨格とする様々な不斉配位子の直接原料であり、需要の高い重要な物質である。安価な2-ナフトールの酸化的カップリング反応によって合成されるが、その用途から触媒的に不斉合成できることが強く望まれている。しかしながら、その不斉触媒反応はCu, Ru, Vの不斉錯体を用いた均一系反応の数例が報告されているのみで、工業的にも有利な不均一系での不斉カップリング反応は現在までに全く報告されていない。また、一般に均一系不斉錯体を単に担持したものでは、触媒性能は大きく減少するのみであり、不均一系触媒の設計には表面を利用した独自の戦略が必要となる。本研究では、アミノ酸骨格の不斉3座配位子を有する不斉バナジウム単核錯体をSiO_2表面に固定化し、その配位子の表面上における反応を選択的に制御することにより、2-ナフトール不斉カップリング反応に最高90%の高い不斉収率を示す新規高活性表面Vダイマー構造の創出に成功した。, 15036218
    研究期間 2003年 - 2003年
  • 分子認識人工酵素機能を付加した界面での光触媒設計と構造・機能相関の研究
    岩澤 康裕; 紫藤 貴文
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定領域研究, 界面におけるナノ組織構造体では、原子・分子あるいは固体などでは見いだすことのできない、また従来にはない構造や物性そして触媒機能を創出することができる。本研究では、生体酵素システムを越える光触媒反応系の実現のために、界面を媒体とする無限の展開が可能な人工酵素型の分子認識能を持つMolecular Imprinting触媒を構築し、新光触媒機能の創出を図った。さらに時間分解エネルギー分散型X線吸収微細構造(DXAFS)法及び光電子放出顕微鏡(PEEM)を用いて表面構造及び電子状態ダイナミクスを追跡した。 その結果、界面を利用したMolecular Imprinting触媒の設計に成功した。新規触媒では、反応分子のメチル基、エチル基を識別することが可能であり、さらに通常のRh錯体の触媒に比べて約50倍も活性が高いことを見いだした。一方、Ag-Ni/Si(100)上のUV照射PEEM像の新規現象を発見した。30・m幅のAg-Ni格子パターンをSi(100)上に形成させUV光を照射すると、放出電子収量が時間と共に変化し、それまで明るく観察されていたAg領域が次第に暗くなり、相対的に暗く観察されていたNi領域が明るくなり、光照射後約14分で輝度が逆転する表面ナノ構造の関与する光誘起現象と思われる。さらに、時間分解DXAFSにより、表面上のRuクラスターの構造ダイナミクスを追跡することに成功し、従来法では得られないクラスター骨格変化の時間スケール、結合の形成/切断の順序、及びそれらのアレニウスパラメーターが明らかにされた。, 14050030
    研究期間 2002年 - 2002年
  • 研究資源の供給と研究成果との関係についての調査研究
    山本 眞一; 小林 信一; 大野 弘幸; 岩澤 康裕; 加藤 毅; 鈴木 久敏; 小田切 宏之
    日本学術振興会, 科学研究費助成事業, 筑波大学, 特別研究促進費, 本研究は,限られた研究資源(いわゆるヒト・モノ・カネ)の中で,優れた研究成果を数多く算出するためにはこの資源をどのように投入すればよいかについて調査研究を行い,今後の学術研究施策に資することを目的とするものである。 初年度には,既存調査の分析,大規模研究グループへの聞き取り調査,海外における研究資金配分の実態調査を行い,研究全体の枠組を検討した。2年度には,前年度からの議論を踏まえて,大規模なアンケート調査「学術研究活動のボーダレス化と資金供給システムに関する実態調査」を全国国公私立大学の研究者に対して実施し,2,513名から回答を得た。調査結果の分析の仕組みについて検討し,3年度にはアンケート調査結果のデータ解析・分析を行った。 アンケート調査にあたっては,研究資源配分の際に有効な意思決定に使えるよう,研究成果の判断の材料となる情報を調査・分析を通じてよりよい研究資源配分システムの構築を目指すこと,またその際は研究資金とともに研究資金以外の研究資源(ヒト・モノ・施設など)の配分システムの改善にも資することを目的とした。 その結果,例えば,研究費の多寡に関わらず,すべての研究者はマクロで見た場合,過去3年間にほぼ3割研究費が増加していること,ただし研究費に加えて必要とする研究資源は,人文社会科学分野では研究時間や図書,旅費など,自然科学分野では研究補助者や研究スペースなどを挙げる者が多いこと,また研究活動に関する諸規制の緩和などを要望する者は人文社会科学分野より自然科学分野が多いことなど,現状における学術研究環境や問題点,ニーズ等は研究分野によってそれぞれ異なっているという実態について定量的に明らかにした。また,研究分野別の差異,研究資源の多寡あるいは国立と私立などの設置者別の状況等も明らかにした。, 12800006
    研究期間 2000年 - 2002年
  • 原子分子のナノ力学-フォースプローブ法による原子分子の力学的分光と制御-
    森田 精三; 山田 啓文; 猪飼 篤; 塚田 捷; 岩澤 康裕; 吉森 昭夫
    日本学術振興会, 科学研究費助成事業, 大阪大学, 特定領域研究, 研究目標は、中間ヒアリング時に追加した極低温や磁性材料の原子間力分光と制御など多くの新テーマも含めて、ほぼ完全に達成した。本特定研究の実施により、「原子分子のナノカ学」と言う新しい学問・研究・技術分野が創設された。さらに、発足時には予定していなかった数多くの研究成果が得られた。理論班と実験班の協力が理想的な共同研究に発展して、多くの成果が得られた。 日本学術振興会ナノプローブテクノロジー第167委員会が行った原子間力顕微鏡(AFM)に関する未来予測で予測された「元素の力学的非破壊同定」や「原子の力学的操作」の達成時期が、本特定研究の実施により、それぞれ、1〜6年と5〜11年早く実現した。 学会誌などに合計303件発表した。また、Physical ReviewやPhysical Review Letterなどのランクの高い雑誌に数多く採択された。国際会議や国内会議での数多くの招待講演を含め合計512件の口頭発表を行った。合計43件の出版に寄与した。特筆すべきなのは、『世界最初の本分野の英語専門書』である"Noncontact Atomic Force Microscopy"を、領域代表者の森田清三が筆頭エディターとなって、世界の主要グループを取りまとめる形でSpringer杜から出版した事である。また、『世界最初の本分野の教科書』「原子・分子のナノ力学」を丸善から出版した。合計16件のプレス発表、合計7件の受賞、合計12件の特許申請を達成した。 2001年に第4回非接触原子間力顕微鏡法国際会議を京都で開催した。この会議は、日本が提唱して1998年に第1回会議を大阪で開催した。その後、スイス、ドイツ、日本、カナダと毎年開催されているが、海外開催も含めて日本の発表件数が世界第1位を保持している。これも、本特定研究実施の成果の一つである。, 11226101
    研究期間 1999年 - 2002年
  • 遷移金属炭化物表面の原子配列及び電子状態制御による高機能表面の創出
    岩澤 康裕; 福井 賢一
    日本学術振興会, 科学研究費助成事業, 東京大学, 基盤研究(B), 本研究の目的は、セラミックス的な性質と金属的な性質を併せ持つ物性的に興味ある物質系である遷移金属炭化物のうち、白金系貴金属に匹敵するような優秀な触媒活性・選択性を示すモリブデン炭化物(Mo_2C)の単結晶(0001)表面の原子配列及び電子状態を精密にコントロールすることにより高機能表面を創出することである。主に走査トンネル顕微鏡(STM)を用いて研究を展開し、さらに精密な表面電子状態測定のための走査トンネル分光(STS)を整備した。 1.構造選択的新規エッチング反応の発見 (√<3x>√<3>)R30°-honeycomb構造、c(2x4)-ジグザク列構造、炭素クラスター構造など複数種の表面炭素組織構造で覆われたMo_2C(0001)表面を酸素ガスに露出すると、表面に強く結合しているはずの表面炭素原子が室温という低い温度でもエッチングを受けること、そのエッチングのされ方に構造選択性があることをSTM観察により見いだした。ジグザグ列をなしている表面炭素原子が選択的に酸素と反応して一酸化炭素として離脱し、下地の(1x1)-Mo層の領域が現れてくる様子が高分解能STM観察により明らかになった。モリブデンカーバイド上の炭素組織構造の特異な反応性を反映した結果と考えられる。 2.COプローブ吸着分子の表面ダイナミック挙動の直接観察 COは(ν3xν3)R30°-honeycomb構造やc(2x4)-ジグザク列構造への吸着確立が低く、(1x1)-Mo層が露出した領域に優先的に吸着し、その領域からhoneycomb構造やジグザグ列構造へ吸着COがhoppingして行くというダイナミック挙動を高分解能STM観察により直接画像化することに成功した。, 12450019
    研究期間 2000年 - 2001年
  • 走査プローブ顕微鏡によるモリブデンカーバイド単結晶表面の新規反応性に関する研究
    岩澤 康裕; 福井 賢一
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定領域研究(A), 本研究の目的は、金属ともセラミックスとも異なる物性と高い表面反応性を有するモリブデンカーバイド表面の構造、電子状態を解析した上で、新しい物性と反応性を創出するための機構を明らかにすることである。走査トンネル顕微鏡(STM)、非接触原子間力顕微鏡(NC-AFM)などの走査プローブ顕微鏡(SPM)を用いて研究を展開し、モリブデンカーバイド(Mo_2C)単結晶(0001)表面上の個々のモリブデンおよび炭素原子の原子配列、局所的な電子状態を観測するとともに、SPMその場観察技術を応用し、吸着させたプローブ分子のダイナミック挙動を動画像解析する。 1.高分解能STM解析による表面電子状態の検討 Mo_2C(0001)試料表面温度の精緻な制御を可能にすることで、(【square root】3x【square root】3)R30°-honeycomb構造、c(2x4)-ジグザグ列構造、炭素クラスター構造などの表面炭素組織構造を再現性よく作製することに成功し、その原子分解能STM観察にも成功した。高分解能STM観察により表面炭素近傍にはMo原子との配位環境に依存して特異な電子状態が形成されていることが示唆された。 2.COプローブ吸着分子の表面ダイナミック挙動の直接観察 COは炭素終端Mo_2C(0001)表面構造である(【square root】3x【square root】3)R30°-honeycomb構造やc(2x4)-ジグザグ列構造への吸着確率が低く、(1x1)-Mo層が露出した領域に優先的に吸着し、その領域からhoneycomb構造やジグザグ列構造へ吸着COがhoppingして行くというダイナミック挙動を高分解能STM観察により直接画像化することに成功した。, 12042224
    研究期間 2000年 - 2001年
  • 時分割XAFSによる反応中間体構造の動的研究法の開発
    野村 昌治; 岩澤 康裕; 朝倉 清高; 松下 正; 稲田 康宏; 舟橋 重信
    日本学術振興会, 科学研究費助成事業, 高エネルギー加速器研究機構, 基盤研究(B), エネルギー分散型XAFS実験装置に設置できるように小型の弯曲機構を備えたミラーベント機構およびミラーを開発し、鉛直方向のビームの集光および高次光の抑制に効果的であることを確認した。フォトダイオードアレーを検出器として用いて光学系および検出系の評価実験を行った。本XAFS実験光学系では試料をビームの集光点付近に設置するが、従来行われていた二等辺三角形の分光結晶の底辺を保持しながら頂点を押す方式では十分に小さい集光を得られない。このため試料の厚さむらがスペクトルに反映してしまう問題があった。この問題点を解決するために長方形の分光結晶を円形に弯曲させる結晶ベント機構およびこのベント機構を分光器に取り付けるためのベント機構取付台を製作し、集光の評価を行った。また、フォトダイオードアレーの場合は読み出し速度に限界があり、将来の高速時分割実験の律速となるため、CCDをキネティックスモードで使用することとし、このためのキネティックス用光学システムを製作した。 in situ触媒反応について、銅を担持したCu-ZSM-5触媒はNOの分解に対して高い活性を示し、この活性が銅のredox反応と関係していることが知られている。今回はこの触媒の40Torrの水素中における昇温還元反応を時間分解能1秒の時分割XAFS法で追跡し、反応開始時に二価であった銅が400〜450K付近で一価に還元され、更に550〜650Kで0価に還元されていることが分かった。XAFSの解析より、550K付近では平均としてCu_3構造をとっていたものが昇温とともにクラスターがZSM-5のケージから外に移動して成長し、670KではCu_<7.8>となっていると解釈できる。 ストップトフロー反応装置を用いた溶液反応については予備的な実験を行い、本研究で用いた光学系、検出系を用いて解析に耐えるスペクトルを得られることを確認した。, 11440180
    研究期間 1999年 - 2000年
  • 層状金属カーボンアロイ表面上の炭素組織構造の物性と反応性に関する研究
    岩澤 康裕; 福井 賢一
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定領域研究(A), 本研究の目的は、金属ともセラミックスとも異なる物性と優れた触媒反応特性を示す層状金属カーボンアロイの一つであるモリブデン炭化物(Mo_2C)単結晶(0001)表面上で、表面炭素量とアニーリング温度を制御することにより新規炭素組織構造を生成させる条件を明らかにし、その生成過程と微細構造を超高真空走査トンネル顕微鏡(UHV-STM)を主に用いて決定することである。STMによる組織構造の電子状態の測定および吸着種の反応過程のその場観察技術を用いて、新しい物性と反応性の発現を念頭に置いた研究を展開してきた。 1.新規炭素組織構造の生成過程と微細構造の検討 Mo_2C(0001)表面のUHV-STM観察により、表面近傍の炭素量に依存してMo上の孤立炭素原子からなる(√<3>×√<3>)R30° -honeycomb構造、一次元的zigzag chainからなるc(2×4)構造、炭素含有クラスターなどの組織化された炭素表面構造が生成することを明らかにし、非常に特殊なトンネル条件を用いることで、これらの構造中の炭素原子一つ一つを浮き出させて高分解能観察することに初めて成功した。 2.組織構造に選択的な新規エッチング反応の発見 ごく最近、炭素組織構造で覆われたMo_2C(0001)表面を酸素ガスに露出すると、表面に強く結合している表面炭素原子が室温でもetchingされること、そのetchingのされ方に構造選択性があることを見いだした。表面炭素原子が酸素と反応して脱離し、高分解能STM観察することで下地の(1×1)Mo層の領域が観察された。しかもこの新規エッチング反応はzigzag chain構造で選択的に起こり、honeycomb構造は元のまま保たれることが明らかになった。これらの成果は層状金属カーボンアロイ表面上にできる炭素組織構造の特異な物性と反応性の理解に大きく寄与するものと考えられる。, 11124210
    研究期間 1999年 - 1999年
  • 学術研究に対する資金供給システムに関する基礎的調査研究
    山本 眞一; 鈴木 久敏; 小林 信一; 岩澤 康裕; 加藤 毅; 矢野 眞和; 柿沼 澄男
    日本学術振興会, 科学研究費助成事業, 筑波大学, 基盤研究(B), 3年間の最終年度にあたる本年は、主として、昨年度に実施した「学術研究に対する資金供給システムに関する実態調査」の分析作業を行った。1.回答者の基本的属性、2.グループ研究のタイプや研究のスタイル、3.現在の学術研究環境(実態及び希望)、4.計画している研究プロジェクトの規模やスタイル、5.研究費と研究成果との関連、6.研究成果の評価、7.自由記述、という7節からなる調査を分析した結果、以下のような知見を得た。 1)平成9年度の年間研究費総額は、平成7年度及び8年度の研究費総額との相関が高く(いずれも0.1%有意)、同時に、専有している実験計測機器の金額や使用している研究スペース(平成9年度)との相関も高くなっていた(工学分野の研究スペース以外はいずれも0.1%有意)。この結果は、研究資源が重点的に投入されていることを示している。さらに因子分析を行ったところ、過去3年間の年間研究費と専有している実験計測機器の金額がある一つの潜在因子によって規定されているという結果を得た。 2)研究費と研究成果との関係についてみると、「研究費が一定の水準に達しなければ優れた研究成果を得ることはできない」「研究費にほぼ比例して研究成果も増加する」「研究費が一定の水準を越えるとそれ以上研究成果は増加しない」という意見が多くなっている。また、理工系で高額の年間研究費を得ているケースでは「研究費がどれだけ多くなっても研究成果は増加しつづける」という意見がやや多くみられる。 3)研究資源と研究成果との関連をみたところ、研究資源の投入量が多いほど多くの研究成果が多く、同時に、研究成果が多くなっているほど研究資源の投入量も大きい、という一般的な傾向が観察された。, 09400006
    研究期間 1997年 - 1999年
  • 単一金属系新反応
    村井 真二; 真島 和志; 直田 健; 澤村 正也; 溝部 裕司; 水野 一彦; 光藤 武明; 村上 正浩; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 大阪大学, 特定領域研究(A), 当初から述べているように、本研究では単一金属系新反応の分野における新概念の開拓と蓄積をはかり、合成化学的応用に結びつけることを目的としている。これらの単一金属としては遷移金属元素や前周期遷移金属元素を主にとりあげ、典型金属元素もとりあげている。 本年度も引き続き、炭素共有結合形成のための新手法の開発を行った。そのため、遷移金属元素を中心として、これらと種々の型式の有機化合物ないし、有機化合物中の官能基との相互作用を極めて広範囲に調査し、これらを通じて得られる異常現象、非古典的現象の芽を蓄積し、専門の異なる研究者がチームをつくりつつ、これらの新現象の普遍化への方策を開拓した。 研究成果の一例として、前年度に導入した高性能な核磁気共鳴吸収装置は、引き続き順調に稼働しており、C-H/オレフィンカップリング反応機構をさらに深く追及していくことができた(村井)。14族有機金属化合物の光誘起電子移動反応の新たな解明にむけての成果が得られた(水野)。また、炭素間単結合間に分子内のオレフィンが挿入するという新触媒反応を見い出した(村上)。 さらに、本年度導入した反応解析モニタリングシステム(React IR 1000)は順調に稼働しており、反応の機構や経路についての重要なデータを鋭意蓄積しつつある(澤村)。 全体として、本年度は計画通り順調に研究が進展したといえる。, 09238103
    研究期間 1997年 - 1999年
  • 新しい表面リアルタイムイメージング法による精密反応プロセスの解析に関する研究
    岩澤 康裕; 佐々木 岳彦; 大西 洋; 朝倉 清高
    日本学術振興会, 科学研究費助成事業, 東京大学, 基盤研究(B), 次世代化合物半導体デバイスや100%の選択性を有する高効率完全触媒の開発には、表面の反応を利用し、原子・分子レベルで精密に制御された表面を作る技術の確立が必要であるが、これを達成するためには、原子・分子レベルでの表面化学現象を追跡し、化学反応素過程を解明する必要があるだけでなく、それらが集合して形成する原子集団やその表面における化学反応プロセス全体の挙動を明らかにする必要がある。特に、このサブミクロン〜ミクロン領域における表面化学反応の結果、脱離してくる反応生成物の種類やその脱離方向の角度分布をリアルタイムで調べることにより、表面反応プロセスを総合的に理解することができる。そこで本研究では、新しいリアルタイム表面イメージングシステムであるin-situ複合表面イメージングシステムを開発し、STM(走査トンネル顕微鏡)とESDIAD(電子刺激脱離イオン角度分布)を組み合わせて、表面の化学状態や原子の動きと反応脱離生成物の同定および脱離角度分布をリアルタイムで観察し、反応素過程の原子・分子レベルでの解明を行うことを目的とした。その結果、半導体や酸化物半導体上における金属の空間的な動きを直接PEEMやMEM法などの表面イメージング法でリアルタイムに観察することに成功するとともに、吸着種1個1個を分離して、STM観測することに成功した。さらに、メタノールの分解反応過程を直接追跡し、分解反応に必要な表面との相互作用を明らかにした。, 09440195
    研究期間 1997年 - 1998年
  • 特殊反応場の触媒活性点の分子・原子レベルデザイン
    御園生 誠; 瀬川 幸一; 岩澤 康裕; 泉 有亮; 吉田 郷弘; 上野 晃史
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 本研究は、特殊反応場で高機能を発揮する触媒活性点を原子あるいは分子レベルデザインする事を目的とした。明示的に活性点を原子レベルで記述または設計すること、環境触媒などを実用条件に十分配慮することを必要条件とし以下の3分野に関して重要な知見を得た。(1)ヘテロポリ酸触媒-分子設計と応用への展開(2)表面化学と理論化学-触媒設計の重要なツール(3)モデル反応-新特殊反応場の提案と実証。 例えば、泉はヘテロポリ酸をポーラスなシリカマトリックス中に固定化した独自の環境調和型固体酸触媒について、高いイオン交換能を確認するとともに、固定化法に工夫を加え実用、汎用化に道をつけた。御園生には、特殊反応場である凝液相を生かしたメチルタ-シャリ-ブチルエーテルの低温高速合成、混合配位ポリアニオンを触媒とするベンゼン、アルカンの過酸化水素による高選択的酸化反応を実現している。 岩澤は、触媒設計の基盤となる金属及び金属表面の原子レベルの構造および吸着ピリジン構造を新しい測定手法で明らかにした。川合は、ニッケル金属表面におけるCO分子の吸着、反応の素過程、エネルギープロフィールを詳細な測定と解析により解明した。内島は、メタノール合成反応の素過程、活性点についてリアリスティックな原子レベルの描像を画いた。田中は、Pt-Rhバイメタル表面に生成するCO-NO反応に活性で反応中に形成される新構造を明らかにした。渡辺は、アドアトム法により制御した二元金属の概念を展開し燃料電池に必須の高純度水素合成用の高選択的Pt-Ru/ゼオライト触媒を実現している。 吉田は、アモルファス合金の構造を解析した後、NO還元反応に適応し活性点について貴重な知見を得た。瀬川は超臨界流体という特殊反応場を生かしブテンによるイソブタンのアルキル化反応中の活性劣化制御を試み効果を上げた。, 07242103
    研究期間 1995年 - 1997年
  • 分子クラスターの反応動力学
    三上 直彦; 岩澤 康裕; 山下 晃一; 本間 健二; 土屋 荘次; 遠藤 泰樹; 吉良 満夫
    日本学術振興会, 科学研究費助成事業, 東北大学, 重点領域研究, これまでに開発した分光法や新しい装置を用いて、クラスター構造解析、反応ダイナミクス解析を更に展開した。 三上は、サイズ選別したクラスター構造解析のための振動分光法を確立し、赤外・紫外2重共鳴分光法のみならず誘導ラマン・紫外2重共鳴分光法を駆使して、ベンゾニトリル溶媒和クラスターのOH伸縮振動およびCN伸縮振動領域の振動スペクトル観測を行い、量子化学的計算解析を併用して分子間水素結合構造を研究した。また、クラスターアニオンの分光計測を目標としたレーザー誘起光電子付着法の開発改良を行い、(CS_2)_nクラスターアニオンの近赤外〜可視領域の吸収スペクトルを測定し、光誘起による電子脱離や反応過程を解析し、(CS_2)_nクラスターでは2量体アニオン(CS_2)_2がコアであること、およびC_2S_2が生成する新奇な反応経路を見いだして、それらの競合過程を量子化学計算に基づいて検討した。 鈴木信三は、金属の配位した炭素クラスターの生成過程を光電子スペクトルの観点から考察し、生成過程によって異なる異性体が生成している証拠を見いだした。 山下は、ヘリウムクラスターの量子液体性に注目し、量子クラスターのシミュレーションに必要なモンテカルロ経路積分法を新たに開発し、モデル実験解析に適用した。 吉良は、フェニルジシランのシアノ置換体の分子内電荷移動過程がジェット冷却気体の孤立分子でも起きることを見いだし、クラスター形成による電荷移動励起状態生成の促進効果を調べた。, 07240101
    研究期間 1995年 - 1997年
  • 新しいX線光電子顕微鏡を用いた表面反応プロセスのリアルタイム解析に関する研究
    岩澤 康裕; 福井 賢一; 大西 洋; 朝倉 清高
    日本学術振興会, 科学研究費助成事業, 東京大学, 基盤研究(B), 固体表面の化学反応は、基礎的・応用的な観点から今日もっとも注目されている化学現象の一つである。本研究の目的は、新しい原理に基づくX線光電子顕微鏡(XPEEM)を開発して反応中の表面をその場観察し、表面上の化学種の動きをリアルタイムに追跡することである。 そのための手段として、既存の低速電子顕微鏡(LEEM)を基本にして、新しいXPEEM装置を設計・製作した。LEEM装置の顕微鏡部に電子エネルギー弁別器(ウィーンフィルター)を付加することによって、X線励起による光電子をエネルギー弁別したうえで空間分析を高分解能で測定し、固体表面の元素別、あるいは化学状態別の分布図をリアルタイムに記録できるように設計した。これまでに、エネルギー弁別器の取付とたち上げが完了し、現在、XPEEMシステムとしての最適化を行っている。その過程で、シリコン表面のX線励起による全光電子像(位置分解能〜1μm)と、金4f光電子のエネルギースペクトルの測定に成功している。 XPEEM装置の製作と平行して、二酸化チタン単結晶表面上に蒸着した金属原子・吸着分子の加熱・気相分子共存下における反応過程を走査トンネル顕微鏡(STM)を用いてリアルタイム観察した。また、タングステン層を埋め込んだシリコンウェファー上にSiO_2薄膜を作成し、さらに銅超微粒子をスピンコートすることによって担持金属触媒のモデル表面を作成した。埋め込まれたタングステン層によって吸着分子の赤外吸収が増強され、通常不可能な反射吸収測定によって吸着分子の振動状態を解析できることを実証した。これらの手法にXPEEMを組み合わせ相補的に用いることによって、これら表面の元素分布あるいは化学状態分布の動きを、反応中に可視化することをめざす。, 08454176
    研究期間 1996年 - 1996年
  • 水素媒介新物質の物理と化学
    尾浦 憲治郎; 安田 幸夫; 岩澤 康裕; 上田 一之; 塚田 捷; 河津 璋
    日本学術振興会, 科学研究費助成事業, 大阪大学, 基盤研究(B), 水素は地球上に無尽蔵に存在する元素であり、最も単純で小さな反応性元素である。最近、水素が様々な材料作製プロセスや表面プロセスに大きな影響を及ぼして、物性や構造、あるいは反応性を支配することがわかってきた。それらは、Siやダイヤモンドなどの半導体、アモルファス金属、あるいは酸化物表面に担持された金属超微粒子であり、いずれも高度情報、エネルギー、資源などの当面する緊急の課題に密接な物質群である。これら諸問題に対処し解決するためには、水素の役割を理解し、水素に関連した物質科学を発展させ、水素を媒介とする新物質創製・制御プロセスを構築することが必要である。本研究では、水素を媒介として新物質・新構造を創製するための科学技術を確立するために、これを重点領域研究分野として申請・創設するための調査・企画・立案を行なうことを目的とした。研究連絡会議や研究成果報告講演会の開催をとおして、各研究者が連絡を密にとりながら、(1)水素変性表面の物理、(2)水素のその場解析と化学反応プロセスの制御、(3)水素による高精度シリコンデバイスプロセスの研究開発、(4)水素媒介による新物質創製の各分担課題について調査を行ない、問題点の整理、重点課題、具体的な研究手法、研究推進のための組織などについて検討を行なった。, 08355002
    研究期間 1996年 - 1996年
  • 走査トンネル顕微鏡によるTiO_2(110)表面上の光反応微視過程のその場観察
    岩澤 康裕; 佐々木 岳彦; 大西 洋
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 固体表面の光化学反応は、基礎的・応用的な観点から今日もっとも注目されている化学現象の一つである。本研究では、走査トンネル顕微鏡で熱反応過程を動的観察するとともに、光反応中の表面をその場観察することによって、これまで間接的にしか得られなかった金属酸化物表面の反応過程を原子レベルでとらえることを目標とした。 まず、ルチル型二酸化チタン(TiO_2)の(110)表面を清浄化し、(1×1)清浄表面の原子像をはじめて観察した。得られた原子像がチタンあるいは酸素いづれに対応するものであるかを、ギ酸イオンの吸着を利用して判別した。次いで、顕微鏡ステージに紫外・可視励起光を入射して光照射下の表面反応をその場観察できる光学系を整備し、われわれは昨年度、顕微鏡ステージに励起光を入射して光照射下の表面反応をその場観察できる光学系を整備した。本年度さらに光照射下の表面温度上昇を抑制するために100Kまで試料を冷却できるよう試料ホルダーを改造して実験をすすめたところ、100W超高圧水銀灯による200時間連続照射によっても、TiO_2(110)表面に吸着したギ酸イオンを反応させることはできなかった。おそらく、光励起によって生成したキャリア(この場合は正孔)が、固体内部のバンド歪曲によってギ酸イオン吸着種へ到達できないのであろう。そこで、10^<-3>Pa程度の酸素、水、水素ガスを顕微鏡チャンバー内に導入して光照射をおこない、ガス雰囲気によって表面ポテンシャルを制御して有効な電荷分離を促進することを現在こころみている。 また、光励起反応と相補的な情報を得るために、電子刺激脱離を利用した反応中間体検出法を開発し、固体表面の環境場が吸着分子の光反応におよぼす影響を検討している。, 08218214
    研究期間 1996年 - 1996年
  • 天然ガスの科学的転換利用技術
    藤元 薫; YAN Youn Bin; 岩澤 康裕; 諸岡 良彦; フィリモノフ I.; ロゾフスキー A.Y.; サディユフ V.A.; ヤン Y.B.; クリロフ O.V.; シーロフ A.V.; 山田 宗慶; 八嶋 建明; 水野 光一; 菊地 英一; 乾 智行; 市川 勝
    日本学術振興会, 科学研究費助成事業, 東京大学, 国際学術研究, 平成7年9月19日から9月29日まで、日本側から大学教授ら7人はロシアのモスクワとノボシビルスクを訪問し、ロシア科学アカデミー化学物理研究所、石油化学研究所、触媒研究所、有機化学研究所;全ロシア石油精製技術研究所、Kapotnya石油精製工場、モスクワ製油所などを見学し、交流を行った。訪問した研究所などでは若手研究者が極度に減少しており、大学院学生を含め研究に従事している活動状況は困難を極めている状況である。研究に必要な分析解析装置は老朽化しており日本の大学、研究機関での15-20年前の状況である。また、研究機器の維持管理、補修などは全くなされていない。中心的研究指導者である教授や研究員の大半は海外への共同研究などで不在であり、研究内容の質的評価は極めて危機的状況にあるといえる。学術的基礎研究へのサポートが少なく、企業研究の受託による実用化のための応用改良研究といった短期間プロジェクトが大半の研究内容であるため、総合的インセンティブな本質的創造的研究成果が少なく、将来展望の上で多くの問題を抱えている。ガス関係の工場では設備は古く、メンテナンスも貧弱である。 平成8年1月5日から12日まで日本側一人はモスクワのロシア科学アカデミー石油化学研究所、有機化学研究所;全ロシア石油精製技術研究所、モスクワ製油所を訪問しました。やはりロシアの財政難による研究の遂行は困難である。 平成8年2月4日から3月31日までロシア側一人(東京大学に2年間留学したことがある。現在石油ガス工業省の研究部門に勤務している)は日本に滞在した。東京大学と京都大学で天然ガス関係の触媒開発を行った。 平成8年6月23日から7月3日まで若手中心であるロシア側の天然ガス研究者および研究管理者5人を招聘し、東京大学、東京工業大学、筑波の資源環境技術総合研究所、京都大学、大阪大学を見学させた。日本の天然ガスに関する研究および技術開発の現状を紹介した。ロシア、特にロシア極東地域天然ガスの利用についても討論した。天然ガスはよくLNG(液化天然ガス)にして輸送されているが、日本の新技術を応用して、現地で炭酸ガスと反応させてジメチルエーテル化されてから輸送されると、コスト削減と環境保全により適当であると認識した。 9月13日から9月23日まで、日本側から藤元ら二人とロシア側一人はシベリア地区にあるロシア最大の天然ガス産地であるヤク-ツクと、同地区のイルク-ツク、ハバロフスクへ行って、ロシアの天然ガス産業現状を調査した。同国の経済事情によって、各天然ガス会社も厳しい市場経済の中で競争しないといけない。大部分の会社では生産装置の老朽化は著しく、生産効率は低下している。酷寒の環境にも関わらず、中には従業員の給料支払いは数ヶ月も遅れた会社も有った。自活するため、カナダなどの海外パートナーと提携して、現地の金、白金、ダイヤなどを採掘している会社もあった。 10月15日から10月25日まで日本側諸岡ら3人はロシアのモスクワとノボンビルスクへ行って、ロシアにおける天然ガスの利用に関する研究調査をした。モスクワではロシアアカデミー化学物理研究所と石油化学研究所、モスクワ大学、人民友好大学、ロシアアカデミー本部を訪問して講演を行った。ノボシビルスクではロシアアカデミー触媒研究所を見学して交流会も開催した。研究経費の不足によって、ロシアの天然ガス関係の研究は世界のトップレベルと比較すると、まだ距離があると感じた。しかし、ロシア側は外国と連携して豊富な天然ガス資源の開発と利用にかなり期待している。, 07044126
    研究期間 1995年 - 1996年
  • 原子レベルのトンネル物性
    河津 璋; 長谷川 哲也; 富取 正彦; 重川 秀実; 小川 恵一; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 本研究班の主な目的は、STM/STSにより、固体表面の性質あるいは原子分子過程を原子的スケールでしらべることにあり、以下の成果が得られた。 Si(001)表面上のGa,Ag原子の吸着2次元相における個々の原子の電子状態、構造、形成過程等に関する詳細な知見を得た。また、高指数ではあるが安定な表面であるSi(113)上のIII族原子の吸着2次元相についても同様の研究を行ない、種々の重要な知見を得た(河津 璋)。 二酸化チタンの(110)清浄表面、及び、この表面上の蒸着金属原子、吸着有機分子の高分解能観察からイオン性物質表面でのトンネル機構を考察し、さらに、吸着分子の表面拡散過程、吸着分子の熱分解反応等の表面反応過程のその場観察に成功した(岩澤康裕)。 Si(111)-7×7及びMoS_2へき開面のArイオン照射効果、Si(111)-7×7ドメインの核形成・成長過程、および、Bi系高温超伝導体のCuO_2面について、STM/STS観察を行い、原子、電子レベルの種々の重要な知見を得た(小川恵一)。 Si(100)表面超構造の揺らぎとダイナミックスについてしらべ、タイマー列の位相のずれを引き起こす位相欠陥の存在と、6K辺りの極低温において、同欠陥のダイナミックスにより、C(4×2)とp(2×2)の間の揺らぎが発現することを見出した(重川秀実)。 超高真空中で[111]方位のW単結晶針を高電圧を印加したまま加熱して先鋭化させたbuild-up探針を用いることにより、Si(111)7×7構造表面について、信頼性の高いSTM/STS測定を行うことができた(富取正彦)。 室温から極低温までの広い温度範囲及び強磁場下でも安定に動作する超高真空STM/STS装置の開発を行ない、高温超伝導体や遷移金属カルコゲナイドなどの層状物質の局所状態密度の空間変化を原子レベルで詳細にしらべた(長谷川哲也)。, 05245101
    研究期間 1993年 - 1996年
  • 飛行時間型電子刺激脱離共鳴多光子イオン化法によるエピタキシ-素過程の研究
    岩澤 康裕; 佐々木 岳彦; 大西 洋; 朝倉 清高
    日本学術振興会, 科学研究費助成事業, 東京大学, 一般研究(B), 本研究の目的は、電子線励起により固体表面から脱離する中性化学種を共鳴多光子イオン化法で選択的にイオン化し、飛行時間および脱離方位を独立に決定することによって、脱離種の角度分布と並進エネルギー分布を測定し、表面吸着種の配向状態・量子状態・分子間相互作用などを決定することによって、光励起選択エピタキシ-反応過程を原子・分子レベルで解明することにある。本年度われわれは脱離イオン種の角度分布と飛行時間を同時に測定できるESDIAD/TOF装置を開発した。 本ESDIAD/TOF装置は半球型の4枚グリッドとマイクロチャネルプレートからなる検出系と偏向によるチョッピングでパルス化が可能な電子銃からなる。連続電子ビームによるESDIAD観察モードの他にパルス電子を用いたESDIAD観察と脱離イオンのTOF測定が行える。パルス電子(パルス幅100ns以上で可変)によるESDIAD観察は、脱離イオンの飛行に影響を与えないようパルスに同期した断続的通電加熱によって、試料表面で起きる反応を20msの時間分解能で観察できる。これにより、反応中の吸着分子の配向変化、反応中間体を検出できる。TOF測定は100nsの幅のパルス電子を入射し10msの時間分解能で脱離イオンをパルスカウンティングする。1KH_2〜10KH_2でパルス電子を入射して、積算することにより0.1〜1s単位の変化を追跡することができる。TOF測定により、脱離種の同定と並進エネルギー分布の測定が可能となる。 装置製作と並行して、Cu(110)表面上の吸着酸素をHREELS、TPDを用いて調べ、再構成していない銅表面に吸着した酸素原子が酸化反応に活性であることを明らかにした。反応活性が高い吸着直後の酸素原子と、再構成した表面にとりこまれた不活性な酸素原子をESDIAD/TOFで比較して、酸素の結合状態の反応性の相関を明らかにする予定である。, 07454146
    研究期間 1995年 - 1995年
  • 固体表面による金属クラスターの活性化と触媒反応制御
    岩澤 康裕; 大西 洋; 朝倉 清高
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 我々はこれまで、金属の有機錯体やカルボニル化合物をSiO_2などの無機酸化物担体上に担持分散した固定化触媒を調製し、その表面構造をEXAFSなどの分光法を用いて明かにしてきた。明確な構造と組成を持つ前駆体を用いことによって、表面構造を精緻に設計し、触媒作用を支配する基本的因子を原子・分子レベルで調べることが可能となる。さらに、表面での構造変換により、全く新しい触媒機能を生み出すことも期待できるからである。 金は化学的に安定で触媒的には不活性な元素に分類されてきた。しかし、Pt(111)表面にAuを添加して表面合金を形成させるとシクロヘキセンの脱水素反応に高活性を示す。また、TiO_2、Fe_2O_3などに強固に担持されたAuの微粒子はCOなどの低温酸化反応に極めて高い活性を示す。これら顕著な例にもかかわらず、クラスター微粒子に取り込まれたAuの触媒作用は明らかでない。 本研究ではこれらの観点から、アルカリ金属的電子状態のAuクラスター骨格に1個のPt原子を埋め込んだ[PtAu_6]クラスターをSiO_2表面に固定化した新しい金バイメタル触媒を調製し、その触媒特性を検討した。通常複数個のPt原子の存在により初めて活性化される水素の解離、エチレンの水素化反応、COの酸化反応を選び、Auクラスター骨格に埋め込まれたPt原子の反応性を調べた。これらの触媒反応、特にH_2-D_2交換反応においては、本新規触媒がかなり高い触媒活性を示すことを見いだした。反応中、バイメタルクラスター骨格が保たれているかどうかを、PtおよびAuのEXAFSスペクトルから解析したところ、447Kまでは完全にクラスター骨格が保たれていることが分かった。これらの結果は、Pt-Au結合のアシストによってPt原子1個が触媒作用を発揮しうることを示しており、不均一系金属触媒作用を考えるうえで重要な示唆を与える。, 07240208
    研究期間 1995年 - 1995年
  • 小分子活性化を目的とする固体表面の構造制御
    岩澤 康裕; 吉田 郷弘; 藤嶋 昭; 中戸 義禮; 市川 勝; 板谷 謹悟
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, N2、CH_4、およびCO_2のような不活性小分子を活性化するための固体表面構造の設計と開発に関する研究を6名が分担して行った。 分子の活性化を詳細に調べ、効率的な活性化プロセスを開発するためには、固体表面の構造解析を行う必要がある。3方向で構造を解析することが可能な偏光全反射蛍光 EXAFS装置を開発して、それを用いてAl_2O_3単結晶上に分散したPt微粒子の雰囲気構造変化を追跡することに成功した。また、高感度反射吸収IR分光法の開発も併せて行った。 CO_2の活性化機構を調べる目的で、Pt単結晶の種々の構造面を用いて、CO_2の脱離のダイナミックスを調べ、結晶面の異方性を反映した脱離分布を見いだした。CO_2をH_2により還元してメタノールに転換する新規Pt触媒の開発に成功した。Pt触媒はCO_2還元によるメタノール合成に不活性てあるが、PtとWおよびCrを含むバイメタル錯体を用いると選択的にメタノールが生成することを見いだした。一方、SiO_2上にTiO_2やV_2O_5を高分散させ、さらにPtあるいはCuを添加した触媒が、CO_2の光還元に有効であることを見いだした。Cuの微粒子で表面修飾したp型Si半導体電極を用いて、太陽光によるCO_2の光電気化学的還元を行い、Cu電極に比べて遙に効率的にエチレンなどの生成物を得た。 ゼオライト細孔内Ru触媒がメタンを活性化してC_2-C_4の炭化水素化合物を得るのに有効な触媒となりうることを観察した。, 04241103
    研究期間 1994年 - 1994年
  • 新しい複合型表面化学プロセス解析装置の開発と光励起選択エピタキシ-の機構解明
    岩澤 康裕; 佐々木 岳彦; 大西 洋; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 試験研究(B), 本申請者らは飛行時間フーリエ変換型イオン分光器という超高効率検出器を開発し、新しい表面吸着種解析法である角度分解刺激脱離イオン分光法(AR-SDIS)を開拓した。本研究は、このAR-SDISを、表面吸着種の振動スペクトルを超高感度・高分解能に測定しうる反射型赤外吸収分光法(RAIRS)と複合化することにより、表面吸着種の配向、エネルギー状態・吸着サイト・吸着構造などにかんする包括的な情報をうるための測定手法を開発することを目的とした。 市販のフーリエ変換赤外分光器を改造して反射型赤外吸収分光器を製作し、超高真空から常圧までの広い圧力範囲にわたって反応ガスを取り扱うことができる反応セルを反射型赤外吸収分光器に接続した。これにより、実際の工業プロセスに近い条件で光励起選択エピタキシ-を進行させ、光化学反応中の表面状態をin-situの条件で観察できる環境を実現した。 連続電子ビームによる角度分解観察モードの他にパルス電子を用いた観察と脱離イオンの飛行時間測定が可能な飛行時間フーリエ変換型イオン分光器を製作した。励起電子線をパルス化することにより、試料を高温に保ちつつ試料表面で起きる化学反応を20msの時間分解能で観察することができる。これにより、従来困難であった化学反応が進行する際の吸着分子の配向変化、反応中間体の検出などが可能になると期待できる。 さらに、光励起選択エピタキシ-に関する基礎研究として、Si(111)-(7×7)表面に吸着したトリメチルガリウム(TMG)・トリエチルガリウム(TEG)分子の光分解過程を、超高真空走査トンネル顕微鏡(UHV-STM)をもちいて観察した。熱あるいは紫外光の照射によりTMG・TEG分子が分解していく過程を分子レベルの分解能で初めてとらえることができた。また、STMによる吸着有機分子のナノ加工にも成功した。, 05554019
    研究期間 1993年 - 1994年
  • 不活性小分子の活性化
    干鯛 眞信; 岩澤 康裕; 齊藤 太郎; 藤元 薫; 村井 真二; 吉田 善一; 長倉 三郎
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 本研究の目標は、地球上に豊富に存在する小分子、窒素分子(N_2)とメタン(CH_4)、および化石燃料の利用から派生し地球規模での環境問題となりつつある二酸化炭素(CO_2)を化学原料として用いて、有機化合物の重要な構成元素である炭素および窒素を効率よく供給する物質変換法を確立することである。すなわち、二酸化炭素およびメタンを最小単位の炭素資源として、また窒素分子を最小単位の窒素資源として利用することにより、究極の化学プロセスの確立を目指した基礎研究である。 ここで取り扱う小分子は化学的に最も不活性な化合物の代表例であり、その効率的な活性化と化学的利用は化学における最も挑戦的な課題の一つである。以下に主な研究成果を述べる。 (1)モリブデンあるいはタングステンに配位結合した窒素分子が温和な条件下に有機化合物と反応し、ピロール、アミノピロールなどの複素環化合物に変換される反応が開発された。チタン系でもインドール誘導体などが合成された。これらは窒素分子から温和な条件下に様々な含窒素有機化合物を合成する新しい化学の幕開けとなろう。 (2)二酸化炭素を銅電極を用いて電解還元するとメタン、エチレン、エタノールなどが生成することが明らかとなり、これらの反応が一酸化炭素を中間体として進行することが判明した。 (3)酸化還元酵素の機能を電気化学的還元に利用することにより、世界にさきがけ、二酸化炭素を高選択的にメタノールに還元することに成功した。 (4)p型シリコン表面上に銅の超微粒子を付着させて二酸化炭素の光電解還元を行い、銅電極より正の電位でメタンとエチレンを生成させることに成功した。 (5)銅系の触媒を用いてメタンと一酸化炭素から酢酸が生成する新規な反応が開発された。これらは温和な条件下でのメタンのC-C結合形成反応の最初の例と言える。, 04241104
    研究期間 1992年 - 1994年
  • 高感度反射赤外分光と電子刺激脱離による準安定表面反応中間体の構造と反応過程の研究
    岩澤 康裕; 大西 洋; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 一般研究(B), 次世代機能素子や高度表面機能材料の作製には、分子線エピタキシー(MBE)、X線・荷電粒子線リソグラフィ等の極先端技術の確立が重要となっている。そのためには、これらの表面プロセスを支配する化学現象、特に化学反応素過程を理解しなくてはならない。しかし、従来の表面研究手法の多くは、単に組成分析のためだけのものであったり、平衡状態にある安定な表面のみを対象としたものであるため、時々刻々進行する表面反応の素過程を分子レベルで明らかにしうるものではない。本研究では、固体表面上で進行する化学反応の準安定反応中間体を捉えうる新しい表面分光法の開拓をめざし、高感度反射赤外分光法と電子刺激脱離イオン分光法を組合せた手法の開発を行ない、表面反応の基礎過程の解明を目指した。本研究者らが新たに開発した飛行時間フーリェ変換型イオン分光器を完成させた後、やはり新たに製作した超高真空対応2軸回転機構に搭載して、超高真空槽内に設置した。飛行時間フーリェ変換型イオン分光器は静電型分析器の低エネルギーにおける分解能の悪さ、通常の飛行時間型の検出効率の低さを同時に克服するものであり、本研究者らの独自の考案によるものである。また、フーリェ変換型赤外分光光度計を利用して、高感度反射赤外分光装置を設計製作した。この超高真空槽には、ほかに表面構造解析のための低速電子回折装置、昇温脱離測定のための四重極質量分析計、直視型電子刺激脱離装置などが設置されている。予備実験として、Ru(001)上に吸着した一酸化炭素の電子刺激脱離の測定を行った。また、Ru(001)表面上における一酸化炭素とメチルアミン、アセチレンなどとの共吸着過程、Mo(112)表面の酸素による化学修飾に関する研究を進めた。, 04453005
    研究期間 1992年 - 1992年
  • 角度分解電子刺激脱離分光装置とそれを用いた表面励起吸着種検出法の開発
    岩澤 康裕; 大西 洋; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 試験研究(B), 価電子系の励起により固体表面から脱離するイオンや中性化学種は、親吸着種の基底及び励起電子状態のポテンシャル曲面に関する豊富な情報を担っている.これを利用すれば、反応中間体を含む表面吸着種の吸着結合状態を探るうえできわめて有力な実験手法が実現されるので、多くの関心を集めいている.しかし、従来の分析器は検出効率が低く、解析上重要な角度分布・並進エネルギー分布・内部状態分布の同時測定は不可能であった.本研究では、表面反応ダイナミックスの解明に決定的に重要な短寿命励起種の検出とキャラクタリゼーションの実験的方法論の確立をめざして、新しい角度分解電子刺激脱離分光装置の開発をおこなった.昨年度は、本研究者らが新たに開発した飛行時間フーリエ変換型イオン分光器を完成させた後、やはり新たに製作した超高真空対応2軸転機構に塔載して、超高真空槽内に設置した.飛行時間フーリエ変換型イオン分光器は静電型分析器の低エネルギーにおける分解能の悪さ、通常の飛行時間型の検出効率の低さを同時に克服するものであり、本研究者らの独自の考案によるものである.この超高真空槽には、ほかに表面構造解析のための低速電子回折装置、昇温脱離測定のための四重極質量分析計、直視型電子刺激脱離装置などが設置されている.今年度は、Ru(001)上に吸着した一酸化炭素の電子刺激脱離の測定を行なった.酸素イオンと一酸化炭素イオンの脱離を検出し、その飛行時間スペクトルを得ることができた.また、装置上の問題点を明らかにし、改良をおこなった.さらに、表面化学反応の素過程の解明を目指して、Ru(001)表面上における一酸化炭素とメチルアミン、アセチレンなどとの共吸着過程、Mo(112)表面の酸素による化学修飾に関する研究を進めた., 03554015
    研究期間 1991年 - 1992年
  • 典型元素および遷移金属化合物の接点
    中村 晃; 鳥居 滋; 高谷 秀正; 村橋 俊一; 杉森 彰; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 大阪大学, 重点領域研究, 典型元素は一般に原子価が決って居り,その族に応じて一定の値をとるものと思われて来たが,近年の研究の発展によって,異常な原子価を持つ化合物が見出され,その方面の基礎研究が盛んとなって来ている。一方遷移金属は,原子価が変り易く,場合によって極めて複雑な状況を生んで来た。本研究では,典型元素の異常原子価状態と遷移金属化合物での原子価状態との「つながり」を深く立入って研究し,この両方の分野に共通のものを見出し,化学での異常原子価という概念に新たな展開をはかり,新しい応用へつなげようとするものである。 具体的な研究としては,諸態は高度な分子軌道法計算による異常原子価状態の理論解析,特に中心元素と配位子間の結合の強さと配位子間の結合角について定量的に評価する研究方法を確立し,多くの実例についてこの方法の優れた点を明らかにした。奥田は,典型的な超原子価化合物である[C_6H_5NH_3]SbCl_6などについてNQRによる研究を行い,Sbの持つ6ケのSbー ^3Cl結合の内1ケは異常に長く,[SbCl_5]^<2ー>状態に近い事,更に同型の[SbBr_6]^<3ー>イオンでは無限鎖状の[SbBr_5]^<2ー>が存在している事を明らかにしている。中村は5族のニオグ,タンタルが典型元素の硫黄,セレンと結合した際に見られる異常な配位状態を調べ,ニオグと硫黄との間のπ結合生成による新しい効果や,タンタルの硫黄クラスタ-生成による新型鋸体の合成とその構造解析,次いで反応の解析を行っている。低原子価ニチニウム錯体によるニトリルのαーCH結合の特異的活性化や新しいラクタム合成反応(村橋),ベ-タ・ラクタム類の特異的官能基変換でのビスマス/亜鉛系試剤の利用(鳥居),新型イリジウム・ホスフィン錯体の不斉還元触媒作用によるカルボニル基の水添(高谷)など反応面での特異性も見出されている。コバルト,ロジウムを含むメタラカルゲゲノレン錯体での特徴的な新反応も発見されている(杉森), 03233102
    研究期間 1991年 - 1992年
  • 典型元素および遷移金属化合物の接点
    中村 晃; 鳥居 滋; 高谷 秀正; 村橋 俊一; 杉森 彰; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 大阪大学, 重点領域研究, 前年度にひきつづき、各種の金属化合物の特異的な結合、構造、反応性を明らかにするため協力して研究を進めた。特に典型元素と遷移金属の両方が組合はさった有機金属錯体について研究を集中的に実施した。セレンとロジウムが結合したSeRhbやS_2Rhbという新型クラスターを、MgO上に担持した触媒によるエチレンのヒドロホルミル化(岩沢)、ルテニウムにリン化合物を結合させた触媒によるラクタム合成(村橋)、硫黄やセレンガキレート状にコバルトやロジウムに結合したメタラジカルコゲエド錯体の芳香後性の発見と触媒作用(杉森)、有機スズ化合物に銅やパラジウムを組合せた新しい複合素反応剤によるβ-ラクタムの合成(鳥居)などの研究が行われた。 また結合状態が異常と見られる化合物としては、ゲルマニウム錯体、RGeX_3についてNQRなどの物理化学測定による3中心4電子結合の特徴となる物性の確定(奥田)、タンタル(III)の新型アルル錯体の合成と異常な16電子構造が反応性に与える効果の基礎的研究(中村)、典型元素の超原子価状態について、高いレベルの分子軌道計算を行い特に5配位状態でのケイ素化合物の示す異常な反応性が解明された(渚熊)。 特殊な構造のキレート状のリン配位子を持つルテニウム化合物を触媒として用いる反応を研究し、新しいクラスター状ルテニウムの構造の発見及びこれを用いた有用な高分子原料モノマーの合成、さらにイリジウムに上氾リン配位子を結合させた新しく触媒によるシクロアルカノンの不斉水素化に高い選択性を持つ反応の開発(高谷)。など夛くのすぐれた研究が行われた。, 04217103
    研究期間 1990年 - 1992年
  • 典型元素および遷移金属化合物の接点
    中村 晃; 鳥居 滋; 高谷 秀正; 村橋 俊一; 杉森 彰; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 大阪大学, 重点領域研究, 典型元素と遷移金属の間に接点となる種々の化合物の新合成にはじまり、結合状態、反応性の特徴など、従来見られなかった特性を見出すため、分子軌道計算、触媒反応、分子構造決定など班員各自が得意とする分野に於て研究を実施した。具体的には、ケイ素の5配位状態での電子状態を詳しく調べるため、SiーH結合とカルボニル基の相互作用を非経験的分子軌道計算を行い、SiーHよりまずHがカルボニル炭素に移動し、次いで、SiーO結合が生ずる機構が妥当である事がわかり、RuーH結合とC=O結合の反応にも適用した。コバルタジカルコゲノレン錯体とジアゾカルカンの附加反応はカルコゲン部分が、セレンの場合,超原子価状態を経る反応段階が著しく加速され、カルベン附加体が容易に生ずる新反応が見出された(杉森)。 新型ビス(トリアリ-ル)ホスヒンを各種光学純度高く合成し、ルテニウム錯体としたあとβケト酸の不斉水添を行い、モノヒドリド錯体を中間体として進行する新しいメカニズムを確定した(高谷)。SbCl_5^<2ー>とSbCl_6^<3ー>でのSbーCl結合状態の「配位数によるちがい」を基礎的にNQRにて調べた(奥田)。ロジウムの表面でのRhーSe結合の特徴をEXAFSと触媒活性の両方によってしらべSeの独得のeffectを確定した(岩沢)。2核型Rh錯体をSiO_2に固定して、Hydroformyl他での活性を見出した(岩沢)。ニオブ(V)に配位したチオラト配位子が容易に分子内転位して、スルフィド配位子を生成する反応の検討中、7ヶの硫黄配位子を持つ新型の7配位錯体を合成し、その結合状態を明らかにした(中村)。などの研究が行われ、各方面で基礎的に重要な成果を収めた。, 02247102
    研究期間 1990年 - 1992年
  • 不活性小分子の活性化に関する研究計画立案
    干鯛 眞信; 岩澤 康裕; 斉藤 太郎; 生越 久靖; 伊藤 要
    日本学術振興会, 科学研究費助成事業, 東京大学, 総合研究(B), 平成4年度科学研究費補助金「重点領域研究」の候補研究領域として選定された「不活性小分子の活性化」に関する研究計画立案および準備を行なった。物質のうちで、特に有機化合物はその数と機能の多様性において圧倒的である。この有機化合物は炭素,水素,窒素および酸素などの元素からなる。本領域研究の目的は,この有機化合物の重要な構成元素である炭素および窒素を、地球上に豊富に存在する,あるには化石燃料の利用から派生する単純な小分子,窒素分子,二酸化炭素およびメタンから効率よく供給する物質変換法を確立することである。本領域では、不活性分子の種類により、「窒素分子の活性化と化学的利用」、「二酸化炭素の活性化と化学的固定・変換」および「メタンの活性化とそれを用いた有機合成反応」の3つの研究項目を取り上げ,さらにこれら小分子の活性化手法の開発を無機合成化学および固体表面化学の立場から強力に支援する目的で、「小分子活性化を目的とする金属クラスタ-錯体の合成」および「小分子活性化を目的とする固体表面の構造制御」の2つの研究項目を設けた。各研究項目について研究計画の具体的案を作成するとともに,全体としての研究計画打ち合せを行い,本研究領域の目標が達成できる機能的な研究組織を作り上げた。ここで取り上げる不活性小分子の効率的活性化の手法は多岐にわたるが,幅広い共通の基盤の上に立脚するものであり,有機金属化学,錯体化学,有機合成化学,触媒化学,電気化学,光化学などの研究者からなる強力な共同研究体制を確立した。, 03353013
    研究期間 1991年 - 1991年
  • 表面反応の研究
    村田 好正; 岩澤 康裕; 吉野 淳二; 堀池 靖浩; 川崎 三津夫; 正畠 宏祐
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, エキシマ-レ-ザ-励起による表面反応では、熱の影響、気相分子の励起が無い条件で、すなわち、価電子励起に伴う表面反応をPt(001)ーNOについては共鳴多光子イオン化法による状態弁別した脱離NO分子の検出を、Si(111)ーClについて光照射前後での走査トンネル顕微鏡の変化を測定し、高い反応選択性に起因する顕著な現象を見いだした。その原因を探るため、低速電子回折、角度分解紫外光電子分光の測定、反射吸収赤外分光法の開発を行った。さらに前者では、励起光の波長依存性、入射角依存性の測定から、NO分子の脱離のメカニズムを調べ、第一段階は基盤が励起され、1光子過程によるNO^ー生成であることを明らかにした。一方後者では、光励起に特徴的な縞状パタ-ンを観測したが、これはSiCl_2,SiCl_3の選択的は脱離に起因することを明らかにした。 反応性イオンエッチングでのエキシマ-レ-ザ-照射により、SiーF系では、エッチング速度が1.5倍の正の効果が、SiーCl系では低下する負の効果が測定され、これらの反応選択性のメカニズムを反応生成物の飛行時間測定から考察し、次の発展へのモデルを提出した。 SOR励起エッチングでは、SiO_2,βーSiCのSF_6雰囲気下での反応の波長依存性、濃度依存性の測定から、波長域によって基盤の励起が起こる厚さが1〜3原子層の範囲で異なってくるモデルを提唱した。SiH_4の光分解で生成するSiH_3ラジカルによる膜成長表面反応を線光分光法により追跡し、その基本的特徴を明らかにした。 新しい表面反応の測定法として、脱離イオンの並進エネルギ-分布が効率よく測定できる飛行時間フ-リエ変換型イオン分光器を開発し、Ru(001)表面上のCOから生じる酸素イオンについて予備的実験をし、所期の性能が得られることを確認した。, 03239102
    研究期間 1991年 - 1991年
  • 振動分光法と偏光鈑射蛍光EXAFS法によるレ-ザ-・デポジション素過程の解明
    岩澤 康裕; 朝倉 清高; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, レ-ザ-・デポジション法は、半導体基板上に直接サブミクロン・オ-ダ-の回路パタ-ンを作製しうる次世代極微細デバイス作製技術として多くの注目を集めている.その実現のためにはキ-プロセスである表面反応素過程を解明する必要がある.本研究では、界面構造を基板表面にたいして平行方向と垂直方向に独立に決定しうる新しい表面構造解析手法である偏光全反射蛍光EXAFSと、表面での化学反応過程の解明にきわめて有効な高感度振動分光法である高分解能電子エネルギ-損失分光法を用いて、表面での化学反応により超薄膜形成過程の追跡を試みてきた.今年度は、主としてα‐アルミナ表面上にジコバルトオクタカルボニル(dicobaltoctacarbonyl)のCVDにより成長させた酸化コバルト超薄層に関して、偏光全反射蛍光EXAFSにより検討した.実験は、高エネルギ-物理学研究所放射光実験施設のビ-ムラインBLー7CおよびBLー14Aにおいて行なった.s偏光、p偏光のいずれの場合にも、高いS/B比のEXAFSスペクトルが得られた.これのフ-リエ変換により得られた動径分布関数のピ-ク位置は、スピネル構造を有するバルクCo_3O_4と一致した.しかし、各ピ-クの強度比はs偏光とp偏光とで著しく異なった.このことから、α‐アルミナ(0001)表面上にCo_3O_4の超薄層が特定の方位に成長していることがわかった.さらに、モデルを用いたシミュレ-ションにより、Co_3O_4とα‐アルミナとのエピタキシャル関係を明らかにした., 03216207
    研究期間 1991年 - 1991年
  • 複合系の反応制御
    伊藤 嘉彦; 村橋 俊一; 金岡 祐一; 岩澤 康裕; 内本 喜一朗
    日本学術振興会, 科学研究費助成事業, 京都大学, 重点領域研究, 1.光学活性ホスフィンを配位子とするキラルなメチルパラジウム(II)錯体を触媒として3,6ージーpートリルー1,2ージイソシアノベンゼンのオリゴメリゼ-ションを行い、5量体のペンタ(2,3ーキノキサリン)パラジウム(II)ホスフィンを単離し、これをHPLCによって2つの右巻き、左巻きディアステレオマ-に分離することに成功した。2.ノプロパノイルー1,3ーオキサチオンにアルキニルリチウムやマグネシウムを作用させる場合と相当するイッテルビウムを作用させる場合で配位錯体中間体が制御され、高立体選択的炭素ー炭素結合形成が達成された。3.シリカ表面上にNbダイマ-を設計して触媒作用を調べ、Nb原子1個の制御によって、脱水素から脱水触媒作用へと触媒特性が180'転換される初めての例が見出された。すなわち、原子1個を付加することにより、そのサイトが塩基性から酸性へと転換される。4.主体反応制御系であるイオンチャンネルの化学構造を明らかにするために光アフィニティ-ラベル法を検討した。光ラベル用新規ジアジリンの合成し、これを用いて抗ペプチド抗体によるイオンチャンネル上のリガンド結合部位の解析を行い、テトラドトキシン誘導体を用いてNa^+チャンネルを、またジヒドロピリジン誘導体を用いてCa^<2+>チャンネルの解析を行った。さらに、ウサギ骨格筋Ca^<2+>チャンネルや電気ウナギ発電器官Na^+肱チャンネルについて検討した結果にもとづいてイオンチャンネルをモデル化して示した。5.ルテニウム触媒を用いてチトクロムPー450型酸化反応の開発を検討し、過酢酸を用いるオレフィンのαーケト-ルへの変換反応を見出した。特に、ステロイド側鎖の官能基導入反応として極めて有用で、コルテゾンアセテ-トやアドリアマイシンアセテ-トの立体選択的合成法を示した。以上、有機金属錯体複合系や生体反応複合系を新規に構築し、それを利用して高選択的有機反応を開発した。, 03215103
    研究期間 1991年 - 1991年
  • 固体表面上の準安定反応中間体の構造と素反応過程の研究
    岩澤 康裕; 大西 洋; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 一般研究(B), 次世代機能素子や高度表面機能材料の作製には、分子線エピタキシ-(MBE)、X線・荷電粒子線リソグラフィ等の極先端技術の確立が重要となっている.そのためには、これらの表面プロセスを支配する化学現象、特に化学反応素過程を理解しなくてはならない.しかし、従来の表面研究手法の多くは、単に組成分析のためだけのものであったり、平衡状態にある安定な表面のみを対象としたものであるため、時々刻々進行する表面反応の素過程を分子レベルで明らかにしうるものではない.本研究では、固体表面上で進行する化学反応の準安定反応中間体を捉えうる新しい表面分光法の開拓をめざし、本研究者らが考案した飛行時間フ-リエ変換型イオン分光器に基づく、電子刺激脱離イオン分光法を開発した.飛行時間フ-リエ変換型イオン分光器は静電型分析器の低エネルギ-における分解能の悪さ、通常の飛行時間型の検出効率の低さを同時に克服するものである.飛行時間フ-リエ変換型イオン分光器および超高真空対応2軸回転機構を製作して、超高真空槽に設置した.この超高真空槽には、ほかに表面構造解析のための低速電子回折装置、昇温脱離測定のための四重極質量分析計、直視型電子刺激脱離装置などが設置されており、また、仕事関数測定装置も近く設置する予定である.予備実験として、Ru(001)上に吸着した一酸化炭素の電子刺激脱離の測定を行なった.酸素イオンと一酸化炭素イオンの脱離を検出し、その飛行時間スペクトルを得ることができた.このように本研究で製作した飛行時間フ-リエ変換型イオン分光器は、ほぼ所期の性能が得られた.また、さらに性能向上のために改良すべき点についての知見も得た., 02453007
    研究期間 1990年 - 1991年
  • 巧妙に設計された反応場のミクロダイナミクス
    市川 勝; 御園生 誠; 中村 晃; 諸岡 良彦; 干鯛 真信; 岩沢 康裕
    日本学術振興会, 科学研究費助成事業, 北海道大学, 総合研究(B), 本研究は均一系・不均一系触媒作用にまたがる基本的な研究テ-マ 1)巧妙に設計された表面反応場のミクロダイナミクス 2)錯体分子反応場のミクロダイナミクス 3)細孔内反応場のミクロダイナミクス 4)高分子反応場のミクロダイナミクス等を当面の重要テ-マとして取り上げ21世紀を目指した均一系・不均一系触媒作用の接点的研究領域の開発推進のための総合的検討を行った。具体的には平成4年春に国内開催を予定している“第7回均一系・不均一系触媒国際会護"に向けて本研究領域の研究成果、情報の交換、企画調査の為の研究集会(平成3年2月23日)、2回の全体会議及び少人数の班員相互の個別打ち合わせ等を実施した。これにより国際会議の研究課題、運営企画方針について、意見調整を行った。とりわけ海外20ヶ国の著名な研究者にこの研究領域の将来、重要性に関する意識調査行いそれを下地に国内における研究活動と比較検討し、国際会議の討論課題に反影させた。本研究課題の調査研究(添付研究集会要旨集参照)の結果奨励される研究方向として (1)有機金属錯体とりわけ金属クラスタ-錯体を用いた触媒設計とこれによる触媒活性中心の分子レベルでの構築 (2)分子ヘテロポリ酸などによるバルク型反応場の動的特性 (3)粘土層間の修飾と高機能触媒反応場の開発 (4)ゼオライトなど細孔反応場の解明と化学合成への応用 (5)修飾結晶表面のミクロダイナミクスの解明と表面分子設計 (6)錯体分子反応場の制御と不斉反応場の創出及び有機合成への応用 (7)生体反応系のモデル錯体合成と高機能錯体反応場の開発 (8)高効率、高規制のオレフィン重合における高分子反応場のミクロダイナミクスの解明と展開 等が挙げられた。以上の諸点に関して日本国内の等一線の均一系と不均一系触媒研究者が本総合研究を橋渡しに交流し、企画調査し、討論を行うことができ大変有意義であった。, 02353009
    研究期間 1990年 - 1990年
  • X線吸収微細構造の測定・解析方法の調査研究
    黒田 晴雄; 岩澤 康裕; 朝倉 清高; 宇田川 康夫; 太田 俊明
    日本学術振興会, 科学研究費助成事業, 東京大学, 総合研究(B), EXAFS(広域X線構造微細構造)やXANES(X線吸収端構造)の応用が近年急速に拡大されているが、それにしたがって、EXAFSやXANESの測定方法の標準化、EXAFSデ-タの解析方法の確立、EXAFSやXANESに関する理論の検討、さらには、EXAFやXANESに関するデ-タベ-スの作成等の必要性が高まり、数年前から世界各国の関連分野の研究者の協力のもとに「XAFS国際ワ-クショップ」が開かれて、その報告がまとめられた。また、1992年にわが国で第7回XAFS国際会議を開催することになっており、そこでも上記の問題が会議の重要な課題になる。このような状況を踏まえて本研究課題では、国際ワ-クショップの報告を研究分担者に配布するとともに、各分担者が国際ワ-クショップの報告に取り上げられている個々の課題を分担して検討し、また、EXAFSならびにXANESの解析のためのプログラムに整備を推進した。それらの結果を持ち寄った国内ワ-クショップを1回開催し、分担して検討してきた内容の報告を求めるとともに、国際ワ-クショップの勧告に関する総合討論を行なった。また、現在、EXAFS解析プログラムがいくつか国内で作成されていろいろな研究グル-プによって利用されているが、それらのプログラムの妥当性と各研究グル-プが採用している解析手順の妥当性の相互比較を行なうために、国際ワ-クショップで作成された標準デ-タ等を各分担者に配布して、各分担者にその解析を求めた。以上のような活動の他に、第7回XAFS国際会議の企画・立案のための会議を数回開催し、同国際会議の開催に向けての準備活動を推進した。, 02353001
    研究期間 1990年 - 1990年
  • 光刺激脱離と光電子分光による光励起選択エピタキシ-の機構解明
    岩澤 康裕; 大西 洋; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 光励起を利用した半導体成長初期過程を解明するため、以下の研究を行なった. 1.高圧キセノンランプ、石英レンズ、フィルタ-等からなる紫外光源を整備した.この光源では、光学素子の組合せにより200〜1000nmの範囲内の任意の波長において、50〜100nmの幅で光出力100〜1000mWの準単色光を得られるようにした.また、ICFー152真空フランジに直接搭載しうるようにしたので、複数の超高真空装置で共用することができる.これを設置する超高真空装置のひとつには、角度分解電子刺激脱離装置が設置される.光源系との接続により光刺激脱離の測定が可能となる.この装置は、本申請者らが開発した飛行時間フ-リエ変換型質量分析器を備えている.これは従来の質量分析器の10^3倍の検出効率を有し、また、パルス光源を用いず、安価な定常光源を用いて高い効率で飛行時間法による並進エネルギ-測定が行なえるものである. 2.表面光化学反応容器を直結した超高真空走査トンネル顕微鏡(STM)装置を開発した.これは、比較的高圧における光励起プロセスにより成長中の表面を直ちに超高真空槽に移送してSTM観察を可能とするものである.STMは、金蒸着膜等で原子レベル分解能が得られることを確認している.今後は、光励起による金属ー半導体界面形成の典型例として、Si(001)ー(2×1)表面上へのGa(CH_3)_3の光励起堆積過程についての検討を進める予定である., 02253203
    研究期間 1990年 - 1990年
  • 振動分光法によるレ-ザ-・デポジション素過程の解明
    岩澤 康裕; 大西 洋; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 半導体表面上への金属膜成長の初期過程の解明を目的として、以下の研究を行なった. 1.偏光全反射蛍光EXAFSー予備実験およびその場測定装置の開発. Si表面上へのCu(DPM)_2のCVD成長を行ない、高エネルギ-物理学研究所放射光実験施設において、偏光全反射蛍光EXAFSの測定をおこなった.充分なS/B比のスペクトルが得られ、偏光依存性による表面構造の解析が可能であることがわかった.この結果を受けて、界面形成過程のその場追跡が可能な偏光全反射蛍光EXAFS装置の開発を行なった.これは、CVD成長時の気相成分の質量分析と、成長表面の偏光全反射蛍光EXAFS測定が可能な装置である. 2.表面反応追跡用超高真空走査トンネル顕微鏡(STM)装置の開発. 表面光化学反応容器を直結した超高真空STM装置を開発した.これは、比較的高圧条件で成長中の表面を直ちに超高真空槽に移送してSTM観察を可能とするものである.成長中に紫外光を照射し、その効果を検討することも重要な目的の一つである.このSTM本体は、大気中で金蒸着膜等を試料として原子レベル分解能が得られることを確認している.今後は、光励起による金属ー半導体界面形成の典型例として、Si(001)ー(2×1)表面上へのGa(CH_3)_3の光励起堆積過程についての検討を進める予定である., 02232212
    研究期間 1990年 - 1990年
  • 複合系の反応制御
    伊藤 嘉彦; 村橋 俊一; 金岡 祐一; 内本 喜一朗; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 京都大学, 重点領域研究, 1。イオンチャンネルの化学構造に関して、Na^+チャンネル分子中のトキシン結合部位をイモ貝毒・μーコノトキシンなどをリガンドとする試薬でラベルすることに成功し、これに基づいて電気ウナギNa^+チャンネルの結合部位の構造が推定された。2。固体触媒の原子レベルでの設計と触媒反応の開発に関して、シリカジェル担体上に固体触媒の反応サイトを原子レベルでNb1個から2個に設計することにより、その反応性が酸性から塩基性に逆転する例を見出した。また、アルミナに固定した[Ca(II)]_4/Al_2O_3触媒の設計によりNOとCOの同時除去法を開発した。3。均一系遷移金属錯体触媒による選択的反応の開発(1)酵素Pー450の鉄ーオキソ中間体に対応する活性種をルテニウム錯体過酸化物複合系によりシミュレ-トすることに成功した。特に、生合成型のアミンのαー位酸化は有用である。βーラクタムの酸化でアセトキシ基が導入され、カルバペネムなど重要医薬品の合成に利用される。(2)イソニトリル錯体複合系の制御により、1,2ージイソシアノベンゼン類のリビング重合を見出した。複素芳香族キノキサリン骨格を形成しつつ重合し、生成するポリ(2,3ーキノキサリン)はヘリックス構造をとることが明らかにされた。(3)ランタナイド金属錯体による立体化学制御に関して、光学活性2ーアシルー1,3ーオキサチアンと有機金属化合物の相互作用を活用することにより、ランタナイド系イッテルビウム有機金属試薬では有機リチウムやマグネシウムの場合と全く逆の立体選択性を与えた, 02231104
    研究期間 1990年 - 1990年
  • 飛行時間フ-リエ変換型質量分析計とそれを用いた当的表面解析装置の開発
    岩澤 康裕; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 試験研究(B), 本年度の研究ではまず、従来のイオン分光器よりもはるかに高い検出効率を有する飛行時間フ-リエ変換型イオン分光器(TOFFTIS:Timeーof Flight FourierーTransform Ion Spectrometerの略)を試作し、10^<-11>Torrまで排気可能な超高真空装置に組込んだ。TOFFTISは2軸回転機構により、試料を中心とした半空間を自由に転できる。計算機シミュレ-ションによれば、数eV以下のエネルギ-の、10〜100amuのイオンに対し、0.1mの飛行管を持つTOFFTISにより、充分な分解能でエネルギ-分析が可能である。しかし、加速条件下での質量分析は、この長さの飛行管では困難であることがわかった。今後は、主にイオン分光器として、電子刺激脱離イオン分光法への適用可能性について検討を進める予定である。 本研究ではさらに、高分解能電子エネルギ-損失分光法(HREELS)による吸着分子の振動スペクトルの測定や、低速電子回折(LEED)による吸着構造の検討など、電子刺激脱離イオン分光法と相補的な情報を与える手法を利用することにより、表面吸着種の配向と結合状態に関する総合的な研究を推進した。具体的には、まず、Ru(001)表面上での(一酸化炭素+アンモニア)、(一酸化炭素+アセチレン)、(一酸化炭素+メチルアミン)などの共吸着系について、その短距離秩序構造と吸着分子の解離過程に関して、新しい知見を得た。また、Mo(112)表面を秩序吸着酸素により修飾し、その上での一酸化炭素、水素、メタノ-ル等の吸着、解離過程を検討し、酸素原子の立体的、電子的効果についての知見を得た。, 01840017
    研究期間 1989年 - 1990年
  • 振動分光法によるレ-ザ-・デポジション素過程の解明
    岩澤 康裕; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 金属カルボニル等の有機金属錯体を用いたレ-ザ-・デポジション法(あるいは、レ-ザ-CVD)は、レ-ザ-の高い集光性を利用し、半導体基板に直接サブミクロン・オ-ダ-の回路パタ-ンを作製しうることから、次世代極微細デバイス作製技術の一つとして多くの注目を集めている。このプロセスは本質的には表面が関与した光化学反応過程であり、高度に制御された金属-半導体界面を作製するためには、プロセスを支配している化学反応素過程を明らかにする必要がある。本研究は、表面での化学反応過程の解明にきわめて有効な高度感振動分光法(高分解能電子エネルギ-損失分光法:HREELS)を用いて、表面での金属カルボニルの光分解過程を追超し、光分解反応の素過程、光反応における表面の役割、分解後の金属と半導体基板との界面形成過程を解明しようとするものである。 本研究ではまず、強力紫外光源の製作をおこなった。これは、大出力水銀-キセノン・ア-クランプおよび石英レンズ、紫外フィルタ-等の光学系からなるもので、200〜1000nmの範囲内の任意の波長において幅50〜100nm、光出力100〜1000mWの準単色光が得られるものである。これは、連続光源であるが若干の改変により、容易にパルス化することもできる。 現在、この紫外光源を超高真空表面解析装置に接続し、表面光化学反応の実験を進めている。本研究における界面での反応現象のミクロ過程解析を通して、半導体マイクロエレクトロニクスの格段の発展の為の金属-半導体界面の化学的基礎知見が得られるものと期待される。, 01650513
    研究期間 1989年 - 1989年
  • 複合系の反応制御
    伊藤 嘉彦; 村橋 俊一; 岩澤 康裕; 内本 喜一朗; 金岡 祐一
    日本学術振興会, 科学研究費助成事業, 京都大学, 重点領域研究, 本研究では金属系からなる複合系および生体複合系を解析し、これに基づいて複合系を設計、構築して有機反応の高次制御を行うもので、次の研究を検討した。1.光学活性フェロセニルホスフィン配位子を分子修飾して導入したアルキルアミノ側鎖とイソシアノ酢酸エステルの相互作用をNMRスペクトルで詳細に調べ、それに基づいてイソシアノメチルスルホンとアルデヒドの不斉銀(I)触媒アルドールを見出した。2.生体系イオンチャンネルのトキシン結合部位を同定するため、Na^+チャンネルと特異的に作用する光反応性μーコノトキシン誘導体の合成を行った。Ca^<++>チャンネルの光ラベルについても検討している。3.金属とヘテロ原子の相互作用を作用する立体化学制御に関してCrCl_2を用いる1,1ージクロロー2ーアルケンとアルデヒドの炭素一炭素結合反応並びにランタナイド金属を用いるαーチオケトンの反応で高立体選択性が達成された。4.固体触媒表面の反応制御を検討するためNbをSiO_2やTiO_2表面にモノマーとして固定化することに成功し、それを用いてエタノールの脱水素反応を行い、温和な条件で脱水素反応する新しい反応pathを認めた。また、NbダイマーのSiO_2表面への固定化についても検討し、Nbモノマー触媒とは異った触媒反応を見出している。5.ニトリル官能基を選択的に活性化することが出来る新規な複合系金属錯体の開発を目ざし、低原子価ルテニウム錯体がニトリルと特異的に配位錯体を形成して、そのαー位CーH結合を強く活性化することを見出した。このルテニウム錯体を触媒を用いてニトリル類のマイケル反応やアルドール反応など有用反応の開発に成功した。, 01649005
    研究期間 1989年 - 1989年
  • EXAFSを用いた光学活性結晶における不斉導入反応の動的解析
    岩澤 康裕; 朝倉 清高
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 本研究はキラル結晶における不斉導入反応の反応機構を偏光EXAFS法を用いて検討し、その素過程を明かにすることが目的である。そこで、以下の手順に従い研究を進めた。 (1)反応条件下でin-situ偏光EXAFS測定システムの開発した。特に、EXAFSの入射X線の電場ベクトル依存性を利用し、反応場の立体局所構造解析を行える。ゴニオメ-タの設計製作を行った。これとあわせて、反応進行中のEXAFSが測定できるようなEXAFSin-situ測定セルの設計製作も行った。 (2)反応条件下でのin-situ EXAFSの有効性を評価するため、固体表面に固定化した活性点での反応条件下に置けるEXAFSの測定を行った。具体的にはシリカ表面にRhのダイマ-を固定化し、そのCO挿入条件下における活性点構造の変化から、金属結合補助型CO挿入メカニズムを提案した。 (3)本研究の助成金により購入した薬品を用いて、4,4′-dimethylchalconeを合成し、その単結晶を成長させた。また、EXAFSをもちいて、臭素化過程を行うことになっているが、予備実験として、IRにより速度論的な解討を加えた。 (4)文部省高エネルギ-物理学研究所にある放射光実験施設に対し、EXAFS測定のマシンタイムの申請を行い、現在、それが受理されマシンタイムの配分をまっている段階である。, 01628503
    研究期間 1989年 - 1989年
  • 表面新物質相としての反応性表面
    田中 虔一; 岩沢 康裕; 川合 知二; 津田 惟雄; 潮田 資勝
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 「表面新物質相としての反応性表面」を研究課題とする本計画研究班は当初の研究計画の主要設備としての「新物質相創製装置」及び「表面機能化装置」を最終年度である平成元年度までに完成した。「新物質相創製装置」は東北大学電気通信研究所(潮田資勝教授)において主として初年度及び2年度にわたって設計製作し完成した。また、「表面機能化装置」は東京大学物性研究所(田中虔一)において、2年度と最終年度にわたって設計製作し完成した。 「新物質相創製装置」(東北大通信研)は超高真空下で単結晶試料を劈開、加熱、烝着等の処理を行えかつ長距離移動用サンプル・トランスファーロッド備えた設計で、試料上への金属の烝着量を単原子層以下にコントロールできるよう設計されている。この装置を使いGaーAs(110)面にCsを烝着しそこへO_2を吸着させることにより生成するショトキーバリアーの高さをラマン散乱の強度からCs量の関数として求めた。 「表面機能化装置」(東大物性研)は独自の方式を開発し、気圧から超高真空までの広い範囲でWell Defined Surface上の吸着から反応まで自由に行えるようにした。さらに一気圧Ar雰囲気下でWell Defined Surfaceを使った電気化学反応を行える独自の方式とした。この装置の完成でWell Defined Surfaceを使って気相から液相までの実験が可能となった。この装置の気相反応セルを使ってこれまで見つかっていないRh(100),Pt-Rh(100)表面に準安定状態の表面化合物として窒素原子の配位した表面の合成とその反応性を調べることに成功した。さらに、反応進行中の表面をHREELS,LEED及びAESで調べる事によって、表面における触媒反応の中間体の検出に成功した。, 01609003
    研究期間 1989年 - 1989年
  • 炭素ー水素結合の活性化による分子変換
    谷口 宏; 吉田 郷弘; 山本 明夫; 村橋 俊一; 御園生 誠; 岩沢 康裕
    日本学術振興会, 科学研究費助成事業, 九州大学, 重点領域研究, 研究計画に従い、炭化水素のCーH結合を金属錯体あるいは金属担持触媒を用いて活性化し、これに官能基を導入することにより機能性物質に導く新反応の開発を行い、その触媒作用機構の追求による基礎化学への展開を行った。各分担者による主な成果を次に記す。 1.ベンゼンとO_2から直接フェノールを得ることがCO存在下のパラジウム触媒によって成しとげられ、条件検討の結果Pb基準1270%という液相反応では最高の収率に達することが出来て内外の注目を集めた。 2.第二アミンのα位CーH結合の活性化による脱水素イミン合成の新反応を低原子価ルテニウム触媒を用いて成功した。合成原料として重要な1ーアザジエンや、ジヒドロキノリン体の合成法として重要である。 3.パラジウム触媒を用いて複素環アリルエステルから縮合環複素芳香族化合物が高収率で得られることを見出した。本法は複素環の特定位置に酸素官能基を導入できる合成化学的に重要な反応である。 4.パラジウム錯体による芳香族アルデヒドのCーH結合を活性化反応を利用し、8ーキノリンアルデヒドがピペリジン、COと反応し、αーケトアミドを定量的に生成することを見出した。この高率反応の機構を解明し、αーケトアミドの選択的合成法に指針を得た。 5.アルカンのCーH結合をPbを用いて活性化し、COとの反応によって脂肪族カルビン酸を一段階で合成することに初めて成功した。これまで合成反応の原料として利用困難であった種々のアルカン類が工業的にも利用可能となるのでその意義はきわめて大きい。 6.Alーポルフィリン錯体による非対称ケトンのジアステレオ選択的還元、ケトンのメタル化、非ヘム鉄錯体による芳香族CーH結合活性化反応によるヒドロキシル化、ロジウム錯体によるエチニルシラン類のCーH結合の活性化をへる二量化反応等の新反応の開発に成功した。, 01607006
    研究期間 1989年 - 1989年
  • 固体表面の吸着分子の配向状態及び素反応過程の時間分解観察
    岩澤 康裕; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 一般研究(C), 本研究は,固体表面における化学反応過程の微視的機構を理解する基礎として,吸着分子や反応中間体の結合と配向状態及びそれら吸着種と表面との相互作用を明らかにする新しい実験手法を開拓することを目的としている。その実現のために,全く新しい原理に基づく超高検出効率分析器(飛行時間フ-リエ変換型質量分析計)を考案し,これを用いた時間分解電子刺激脱離法の確立を目指した。電子刺激脱離法は,電子刺激により表面から脱離する化学種の角度分布,エネルギ-分布を測定するもので,分子線エピタキシ-のような動的成長過程の追跡に威力を発揮すると期待されている手法である。 本研究では,上記の目的を達成するために,まず既存の超高真空槽を改造,整備して,電子刺激脱離装置を設置しうるようにした。また,飛行時間フ-リエ変換型質量分析計のイオン化室,静電シャッタ-,超高真空内2軸精密回転機構等の構成部分の設計,製作をおこなった。さらに,これらと並行して,低速電子解析/オ-ジェ電子分光装置,昇温脱離測定システム,仕事関数精密測定装置などの補助的表面分析機器,試料マニピュレ-タ,試料清浄化システム,試料温度制御機構等の開発,製作をも行なった。現在,飛行時間フ-リエ変換型質量分析計を超高真空槽内に組込み,調整を行なっている。今後は,固体結晶表面上での吸着種の配向状態の研究を進める予定である。, 01540359
    研究期間 1989年 - 1989年
  • 有機典型元素化合物の異常原子価に関する総合研究
    秋葉 欣哉; 吉藤 正明; 古川 尚道; 中村 晃; 諸熊 奎治; 岩沢 康裕
    日本学術振興会, 科学研究費助成事業, 広島大学, 総合研究(B), 1.平成2年度に発足するべく採択された重点領域研究「有機典型元素化合物の異常原子価」(略称:有機異常原子価)を実行するために、研究計画・計画班員等を見なし、再検討・確認するための研究連絡会を研究代表者を中心に班長予定者である石川満夫(広島大工)・中村晃(阪大理)・古川尚道(筑波大化)の4人が広島・東京・大阪で行った。その結果、研究計画の骨子は申請計画通りに行うのが適当であるとし、計画班員について多少の手直しをして原案を作製した。総括班の評価グル-プの先生方にも御意見を伺いさらに改良を重ねた。 その結果以下の研究組織案を作製した:総括班(i)評価グル-プ 7名(ii)実施グル-プ 5名、第1班 高配位有機典型金属化合物の異常原子価 7名、第2班 高配位有機ヘテロ元素化合物と異常原子価 8名、第3班低配位および高歪有機典型元素化合物の特徴と異常性 7名、第4班 有機典型元素化合物および遷移金属化合物の接点 8名。 さらに、上記計画研究を補うと同時に新規な研究課題として、どのような傾向・内容の研究を必要とするかについても検討した。 2.平成2年1月6・7・8日に広島において本班の全体会議を行い、上記にて作製した「有機異常原子価」の計画案を説明し、詳細にわたり検討した。班員の意見をふまえて原案を多少改良し、第2年度・第3年度の発展方向および公募研究の内容に期待する点などについても種々討論した。さらに広報のやり方・担当者をきめ、本重点領域研究の盛り上げ方についても意見の交換をした。, 01307016
    研究期間 1989年 - 1989年
  • 反応性固体表面の設計と吸着分子の配向、結合状態に関する研究
    岩澤 康裕; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 超高真空技術の進歩やさまざまな表面解析機器の開発により、清浄結晶表面上の原子や吸着分子の構造、電子状態及び挙動が捉えられるようになり、固体表面が持つ高い反応性や特異な物性が具体的に認識されるようになってきた。最近では次のステップとして積極的に個体表面を修飾し、特異な表面物資相や新しい機能表面を作製する研究が始まっている。本研究者らは62年度の本重点領域研究の下で、Ru(001)表面をFe原子により修飾することにより、Ru表面ともFe表面とも異なる反応性の高い表面を得て、新しい反応性表面における吸着COの解離素過程を高分解能電子エネルギー損失分光法(HREELS)により解明した。本研究では、最外層がMo原子の一次元鎖状構造をとるMo(211)表面上に、酸素原子を規則的に配列した表面を作製して、表面の化学的環境と気体分子の吸着配向及び結合状態との対応を明らかにし、新しい反応性表面作製に関する研究を行った。従来、Mo単結晶表面に関しては余り研究が行われていないため、まずMo(211)面をMo単結晶ロッドから切り出し、機械的研磨を行った後、Ar^+スパッタリング、酸素処理、電子加熱アニール、Ar^+スパッタリングの繰り返しでMo(211)面の清浄化を行った。清浄Mo(211)面に基づくLEED(低速電子回析)の(1×1)構造を確認の後、酸素を吸着させると(2×1)構造の新しいサブスポットが観察され、吸着酸素原子はMo(211)表面で周期構造を作って存在していることが確認された。さらに、角度分解型紫外光電子分光法(ARUPS)を製作し、異方性を持つMo(211)面に吸着した原子・分子の電子状態及び配向状態を調べ、それらの対応を試みている。, 63609507
    研究期間 1988年 - 1988年
  • 固体表面の吸着分子の配向状態及び素反応過程の研究
    岩澤 康裕; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 一般研究(B), 超高真空技術の進歩やさまざまな表面解析機器の開発により、清浄結晶表面上の原子や吸着分子の構造、電子状態及び挙動が把えられるようになり、固体表面が持つ高い反応性や特異な物性が具体的に認識されるようになってきた。最近では、次のステップとして積極的に固体表面を修飾し、特異な表面物質相や新しい機能表面を作製する研究が始まっている。また一方で、これら素性の分かった表面上での吸着分子の挙動や表面反応の素過程に関する研究が、特に触媒作用や機能性材料作製のための表面反応などとの関連で、大きな注目を集め、また必要性が指摘されている。固体表面における化学反応過程を理解するためには、吸着分子や反応中間体の結合方向と配置及びそれら吸着種と表面との相互作用を明らかにする必要がある。本研究では、高分解能電子エネルギー損失分光法(HREELS)により吸着種の結合状態と結合の解離過程に関する研究を行った。また、新たに角度分析型飛行時間フーリエ変換質量分析計(FT-TOFMS)を設計、製作した。FT-TOFMSは、電子刺激脱離イオン角度分布(ESDIAD)測定法と飛行時間質量分析計の両方から得られる情報を抽出、解析することができる高効率の分析法である。これにより、反応中の吸着分子の結合サイトと吸着構造及び反応中間体のエネルギー状態と表面との相互作用に関する研究を行うことが可能である。HREELSを用いた研究では、Ru(001)表面に吸着したCOとNH_3が新しい(2×2)共吸着構造を形成し、その周期構造の場の中でNH_3が解離していくことが見いだされた。反応が実際に起こるためにはどのような構造と電子的相を作用が必要なのかを始めて明らかにした例といえる。, 63470002
    研究期間 1988年 - 1988年
  • 小分子の効率的な活性化とそれを利用した新規な有機合成反応の開発
    干鯛 眞信; 村井 真二; 生越 久靖; 岩澤 康裕; 井上 祥平
    日本学術振興会, 科学研究費助成事業, 東京大学, 総合研究(B), 化学は多種多様な機能と物性を有する物質を提供することにより、人類の複祉と社会の発展に多大の貢献をしてきた。その物質のうちで、特に有機化合物はその数と機能の多様性において圧倒的である。窒素分子(N_2)、二酸化炭素(CO_2)、一酸化炭素(CO)、メタン(CH_4)、および酸素分子(O_2)は、地球上あるいは大気中に豊富に存在する、あるいは他の資源から容易に変換できる単純な小分子である。これら小分子を出発原料として、有用な有機化合物の構成元素である炭素、水素、酸素および窒素を効率よく供給する物質変換法、言葉を変えれば、資源の種類に依存しない究極の化学工業プロセスを確立することは学術的にも社会的にもきわめて重要な課題である。本総合研究(B)は上記のような主旨の重点領域研究「小分子の活性化」を申請するための準備研究、調査を目的として行った。昭和63年10月24日および25日には東京にて公開シンポジウムが開催され、約100名のさまざまな領域の研究者が集まり活発な討論がなされた(講演、25件)。原始地球上で上記のような小分子からなる大気から生命の源となる物質が出現し、ついには生命が誕生したという説はよく知られている。また、現在も生物は光合成や窒素固定を通して二酸化炭素と窒素分子を効率よく固定している。自然が行ってきたであろう原理を人工的に発現させること、および自然を超えた手法の開発によりこれら小分子の効率的な活性化と反応を実現させることは、化学の最も挑戦的な研究課題の一つといえる。, 63307008
    研究期間 1988年 - 1988年
  • 反応性表面の設計と吸着分子の配向, 結合状態の研究
    岩澤 康裕; 有賀 哲也
    日本学術振興会, 科学研究費助成事業, 東京大学, 重点領域研究, 近年、清浄表面上の吸着原子や分子の構造、電子状態、挙動が捉えられるようになり、固体表面が持つ高い反応性や特異な物性が具体的に認識されるようになってきた。最近では、次のステップとして積極的に団体表面を修飾し、特異な表面物質相や新しい機能表面を作製しようとする研究が始まっている。本研究者らはこれまでに、(1)Mo、Co、Ru、Nbなどの有機金属化合物を用いてシリカ表面に一定の構造を持つ金属サイトを作製できること、(2)Ru(001)表面をFeで修飾するとRu表面ともFe表面とも異なる高反応性表面が得られること、(3)MgO(111)マイクロファセット表面にNgを吸着させると強塩基性表面が形成されること、などを見いだし、原子、分子レベルで固体表面の設計、修飾が可能であることを実証してきた。本研究では、Fe/Ru(001)バイメタル接合相と、触媒作用の面で特異な金属であるMoをとりあげ、それらの化学修飾した新しい反応性表面上での分子の吸着と配向状態及び結合状態を調べる。Mo(211)表面は、最外層でMo原子が一次元鎖状に配列した構造だが、この列間にO、S、Se原子を吸着させることにより、Mo原子が露出したままでその電子状態を制御できると考えられる。新しい反応性表面上での分子の吸着状態と電子状態を明らかにする為に高分解能電子エネルギ-損失分光法に紫外光電子分光法を組合わせて、角度分解の価電子帯を測定し、同時に振動結合構造を調べた。Fe/Ru(001)表面で2種類のCo吸着状態を捉え、その解離過程を観察することに成功した。また、ND_2の吸着状態にも2種類あることを見いだし、Fe/Ru(001)バイメタル接合表面に特有のものであることを明らかにした。さらに、N、C、Oからなる特異な超周期表面構造が形成されることを見いだした。このように金属単原子層の特性を明らかにした。, 62609510
    研究期間 1987年 - 1987年
  • 炭素-炭素結合の活性化による分子変換
    谷口 宏; 吉田 郷弘; 山本 明夫; 御園生 誠; 岩澤 康裕
    日本学術振興会, 科学研究費助成事業, 九州大学, 重点領域研究, 研究計画に従い, 炭水水素のC-H結合を金属錯体あるいは金属担持触媒を用いて活性化し, 官能基を導入することにより新しい合成反応の開発及びその触媒作用機構の解明を目指して研究を行い, 各分担者により次にあげる成果を得ることができた. 1.ベンゼンとO_2よりパラジウム触媒によりフェノールの一段階合成に成功. ベンゼンを酢酸パラジウム, フェナントロリン, 酢酸の存在下O_2及びCO加圧下(30気圧)で180°C, 24時間反応させるとフェノールが選択的に生成しその触媒効率は約15であり, これまでの液相反応での最高の値が得られた. 重酸素を用いる実験によりフェノールのOは定量的にO_2からきていることも確認した. 2.芳香族アルデヒドのC-H結合の活性化によるα-ケトアミドの合成に成功. パラジウム錯体存在下8-キノリンアルデヒド, ピペリジン及びCOを反応させると定量的にα-ケトアミドが得られることを見いだした. また, α-ケトアミドはN-アセチルアニリン等の芳香族C-H結合をPdで活性化し, アミンの存在下COと反応させダブルカルボニル化を行う方法でも合成できることも明かにした. 3.ポリマー担持酵素モデル鉄錯体によるカテコール類の選択的酸化反応の開発. 3価鉄塩をスチレン/ビニールピリジン共重合体等のポリマーに担持して, 3,5-t-ブチルカテコールの酸化を検討し, 均一系では酸化が殆んど起こらない場合でもポリマー担持鉄錯体を用いると酸化が進行することを見出した. 4.V-P複合酸化物によるブタン酸化及びシリカ担持N6触媒によるエタノールの脱水反応の機構的考察, 前者では(VO)_2P_2O_7が, また後者ではN6モノマー構造が活性を示すことがわかった., 62607006
    研究期間 1987年 - 1987年
  • 表面における化学反応のダイナミックス分光法による研究
    大西 孝治; 岩澤 康裕; 山添 昇; 吉田 郷弘; 田隅 三生; 秋鹿 研一
    日本学術振興会, 科学研究費助成事業, 東京工業大学, 総合研究(B), 表面が機能している状態やその上で化学反応を行っている状態を分光学的に明らかにすること, 即ちダイナミックな状態の表面を種々の分光法によって研究した. 各々の研究者により分担して行われた成果の概要を以下に記す. (1)振動分光法・磁気共鳴法を主とする研究. フーリエ変換赤外分光光度計を用いて, 近赤外レーザー光を光源とするラマン散乱の測定を行った. 偏光変調赤外分光法を用い, 光CVDによるシリコン薄膜の成長課程を研究した. ZrO_2上に解離吸着した原子状水素種の赤外スペクトルを明らかにした. 活性酸素ラジカル種をESRで観測した. (2)X線・電子線をプローブとする分光法による研究. 高感度のEXAFS用2結晶分光器を製作し, 金属超微粒子触媒を観測した. Moダイマー触媒やCoクラスター触媒を設計し, 触媒作用中の構造変化をEXAFSで観測した. アモルファス合金の表面局所構造の変化をEXAFSにより解析し, 表面活性との関連を検討した. 走査トンネル顕微鏡(STM)用の画像処理技術の向上を計るため超高真空仕様の装置開発に着手した. (3)機能性表面の創製課程の観察と表面機能の作用状能下における分光. 金属硝酸塩, エチレン,グリコール,硅酸エチルの系から調製した触媒は金属超微粒子を有することを見出し, 超微粒子生成課程を検討した. 精浄なCo表面と炭水素との相互作用をオージェ電子分光などを用いて明らかにした. Ph/SiO_2触媒にNb_2O_5を添加した系でRhとNb_2O_5との強い相互作用を研究した. ZnO上の表面ギ酸イオンは気相のギ酸を相互作用することにより分解することを見出した. 酸化スズに貴金属を少量添加することによるセンサーの増感作用をXPS等を用いて調べた., 62307001
    研究期間 1987年 - 1987年
  • 有機金属化合物を用いた活性表面の設計と触媒作用に関する研究
    岩澤 康裕; 朝倉 清高
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定研究, 本研究者らはこれまで, Mo, Cr, Fe, Co, Ru, Rhなどの有機錯体を用いて一定の構造を持つ金属サイトをシリカやアルミナ表面に設計し, その触媒機能と触媒作用機構を明らかにしてきた. これらの研究を通じて(1)従来困難であった触媒表面の分子設計が有機金属化合物を利用することにより可能なこと, (2)均一系とは異なった機能と物性が作れること, (3)固体触媒の触媒作用の研究に大きな障壁となっていた表面状態の複雑さと不明確さなどの問題を解決する方法となり得ること, を見いだしてきた. 61年度の本特定研究のもとでの研究により, Nbのπアリル錯体を用いてシリカやチタニア表面に新しいNbモノマー構造を作ることに成功した. モノマー構造を持つ初めての固体Nb触媒であり, 高い脱水素活性を示すことも従来の固体Nb触媒には見られない特質である. 本研究では, 選択的に進行するエタノールの脱水素反応の機構を研究し, 新しいタイプの反応分子間の共同触媒作用機構を見いだし, 自己幇助型脱水素反応機構と名づけた. すなわち, まずエタノールはNbモノマー上で解離吸着し, エトキシル基と水酸基となるが, 気相にエタノールが存在しない場合には673Kではじめてエチレンと水とに分解される. ところが気相のエタノールがさらに1分子吸着すると, エトキシル基が活性化され, 400Kでさえ脱水素が起こりアセトアルデヒドと水素が等量生成される. 第一に吸着するエタノールから生成するエトキシル基はそれ自体はα位のC-H結合で切断が起こりエチレンに転換されるが, そこに第二のエタノール分子が吸着するとβ位でC-H結合の切断が起こるようになる. しかも遥かに低い反応温度で脱水素生成物であるアセトアルデヒドが生成する. これは対称性の変化というよりもむしろ電子的供与効果と関連づけれら, Nbの4d軌道を通してエトキシル基のβ水素が活性化されている. この機構は触媒作用のひとつの概念を提供する., 62215005
    研究期間 1987年 - 1987年
  • 英国における有機金属化学及び触媒化学研究動向調査
    山本 明夫; 岩沢 康裕; 渡部 良久; 市川 勝; 田中 虔一; 宮下 晃; 吉田 寿勝; 伊藤 健兒; 辻 二郎; 中村 晃
    日本学術振興会, 科学研究費助成事業, 東京工業大学, 海外学術研究, 有機金属化学及び触媒化学は互いに密接に関連した重要な分野であり, 英国及びわが国では水準の高い研究が行なわれている. 今回の調査研究の目的はこの重要な領域の研究を促進するため, 英国における有機金属化学及び触媒化学の研究体制, 研究設備を含む研究動向に関して直接調査を行なうことにある. この調査により今後有機金属化学及び触媒化学の研究を推進する上で有意義な指針がえられるものと期待される. この調査期間中及び実地調査終了後の参加者のレポートに基づく意見を次にまとめる. 1)英国においては有機金属化学及び触媒化学における研究テーマの取り上げ方は, 非常に理学的であり, 応用への考慮はほとんど払われていないなど, 研究方針には日英の間にかなり違いが認められる. 有機金属化学においては金属クラスターを研究対象とする研究者が圧倒的に多く, 非常に多彩なクラスター錯体が合成されているが, 触媒反応に応用する研究はほとんど行なわていない. 一方, 我が国においてはかなり有機化学に偏っており, 無機化学的興味を追求する英国の研究者と対照的である. 触媒化学の研究においても, 似たような状況があり, ある程度応用を指向し, 意識する日本側研究者と異なり, 英国における研究は極度に表面化学に偏っており, 実際的応用とはほとんど無縁の研究が行なわれている. このような偏りは, ノーベル賞級研究を生みだす可能性を内蔵しているが, 全体的学問水準を上げるには多少問題があるように感じられた. 2)英国における研究は長い伝統に基づいて, 優れた環境の中でゆったりと行なわれており, 工作室等の研究補助システムも日本にくらべ充実している. 中でもオックスフォード大学Green教授の金属蒸気法を用いる錯体合成や, リバプール大学触媒研究所Heaton教授の高圧NMR分光法を用いる高圧触媒反応活性種の研究など, 他の追随を許さないような高度のテクニックを要する研究が印象的であった. 以上を総括すると, 英国の研究の進め方には見習うべき点も多いが, テーマが偏りすぎている傾向がある. 一方日本の研究者は概して応用に敏感であるため, 今後一層研究補助システムの充実を図る等, 研究環境を整えさえすれば, ある程度自然にバランスのとれた研究成果が生まれてくるであろうというのが調査研究参加者の一致した意見であった., 62041031
    研究期間 1987年 - 1987年
  • 有機金属化合物を用いた触媒設計と触媒作用の研究
    岩沢 康裕
    日本学術振興会, 科学研究費助成事業, 東京大学, 特定研究, 本研究では、新しい素材としてニオブ触媒を設計する目的で、ニオブのπ-アリル錯体を用いて新しいニオブ固定化触媒と、また、ニオブのエトキシド錯体を用いて超薄層ニオブ固定化触媒を設計した。さらに、得られたニオブ触媒の触媒機能を見い出すと共に、EXAFS分光法により決定されるニオブ活性構造との対応を明らかにした。 従来の塩化ニオブなどの無機化合物を用いた方法では、Nbの縮合物がもっぱらできてしまい、しかも不均一な表面状態を持ったニオブ担持触媒しか得ることはできない。従って、本計画ではニオブのπ-アリル錯体を用い、素性の明らかな単核ニオブ触媒を合成した。この調製手法により、さまざまなニオブの単核構造をシリカ,アルミナ及びチタニア表面に作ることができた。σ-アリル配位子を持つニオブ単核構造を上記無機酸化物上に固定化すると、プロペンのメタセシス反応に極めて高い活性を持つ新しいニオブ触媒が得られた。これまで活性なニオブ触媒は知られていない。アリル配位子を水素還元で除去して得られる低原子価ニオブ構造は一酸化炭素を水素化して種々の炭化水素を合成することを見い出した。通常のニオブ固体触媒ではこのような触媒作用を全く示さない。得られる炭化水素は【C_2】から【C_4】の炭化水素が81〜86%の高い選択性であった。さらに、低原子価ニオブを酸素で酸化して得られる酸化型のニオブ単核構造は、エタノールの脱水素反応に対し高い触媒作用を示すことが分かった。従来の担持ニオブ触媒は主に脱水反応型であり、はじめての脱水素機能型のニオブ触媒である。 一方、ニオブのエトキシド錯体を用いると、シリカ表面上に単原子層ニオブ酸化物を固定化することができた。この超薄層触媒は、単核触媒と全く異なり、エタノールの分子内脱水反応に対し高い触媒活性を持つことが見い出された。, 61225003
    研究期間 1986年 - 1986年
  • 触媒作用下の活性点構造の分光学的研究
    岩沢 康裕
    日本学術振興会, 科学研究費助成事業, 横浜国立大学, 一般研究(C), 59540254
    研究期間 1984年 - 1984年
  • クラスター固定化による新しい固体触媒の開発と触媒作用の研究
    岩沢 康裕
    日本学術振興会, 科学研究費助成事業, 横浜国立大学, 一般研究(C), 58550517
    研究期間 1983年 - 1983年

産業財産権

  • 燃料電池用電極及びその製造方法
    特許権, 岩澤康裕, 吉田祐介, 趙暁, 濵村寛, 特願2020-007560, 出願日: 2020年01月21日, 株式会社ニコン、国立大学法人電気通信大学
  • 芳香族ニトリル化合物の製造方法、及び芳香族ニトリル化合物合成用触媒
    特許権, 岩澤康裕, シルピ ゴーシュ, シャンカ シュブラ アチャリヤ, 吉田祐介, 特願2019-199748, 出願日: 2019年11月01日, 国立大学法人電気通信大学
  • 固体高分子形燃料電池及びケーブル供給機構
    特許権, 関澤央輝, 宇留賀朋哉, 唯 美津木, 岩澤康裕, 2015-90104, 出願日: 2015年04月27日, 国立大学法人 電池通信大学 国立大学法人 名古屋大学, 2016-207556, 公開日: 2016年12月08日
  • 固体高分子形燃料電池並びに計測装置及び方法
    特許権, 関澤央輝, 宇留賀朋哉, 岩澤康裕, 特願2015-040105, 出願日: 2015年03月02日, 国立大学法人電気通信大学, 特開2016-162587, 公開日: 2016年09月05日
  • 固体高分子形燃料電池カソード用の触媒およびそのような触媒の製造方法
    特許権, 岩澤康裕, 鷹尾忍, 特願2013-41734, 出願日: 2013年03月04日, 国立大学法人電気通信大学, 特開2014-168747, 公開日: 2014年09月
  • ベンゼンからフェノール合成用触媒
    特許権, 岩澤, 唯, 王, 及川, 特願2009-55354, 出願日: 2009年, 三井化学、東大TLO、 分子研TLO, 特許第5258356, 発行日: 2013年05月02日

学術貢献活動

  • 学術雑誌関係(編集委員長) 材料表面
    その他, 実施期間 2016年03月 - 2024年03月, ウエブジャーナル刊行

その他

  • 第4回CSJ化学フェスタ2014優秀ポスター発表賞
    堀田洸
    「固体高分子形燃料電池カソード触媒の形状制御と電気化学的活性評価}
    2014年 - 2014年
  • 第90回日本化学会春...
    第90回日本化学会春季年会、学生講演賞(2010年3月)
    上村洋平
    「PtSn合金ナノ粒子の時間分解XAFS解析」
    2010年 - 2010年