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研究者情報

マスター

アカウント（マスター）

  • 氏名

    髙草木　達(タカクサギ　サトル), タカクサギ　サトル

所属（マスター）

  • 触媒科学研究所　触媒構造研究部門

所属（マスター）

  • 触媒科学研究所　触媒構造研究部門

独自項目

syllabus

  • 2021, 表面ナノ材料科学特論, Surface Nanomaterials' Sciences, 修士課程, 工学院, 表面、ナノ材料、リソグラフィー炭素材料、表面物性、触媒
  • 2021, 表面ナノ解析科学特論, Surface Nano Analyses, 修士課程, 工学院, 表面、触媒、ナノ材料、量子ビーム、STMなど
  • 2021, 表面ナノ材料科学特論, Surface Nanomaterials' Sciences, 博士後期課程, 工学院, 表面、ナノ材料、リソグラフィー炭素材料、表面物性、触媒
  • 2021, 表面ナノ解析科学特論, Surface Nano Analyses, 博士後期課程, 工学院, 表面、触媒、ナノ材料、量子ビーム、STMなど
  • 2021, 環境と人間, Environment and People, 学士課程, 全学教育, 触媒、化学物質、環境とエネルギー、持続的な社会発展
  • 2021, 物理化学, Physical Chemistry, 学士課程, 工学部, 原子の構造、化学結合、分子軌道法
  • 2021, 一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), Freshman Seminar, 学士課程, 全学教育, 量子ビーム、プラズマ、触媒、ナノ材料

researchmap

プロフィール情報

所属

  • 大学院 環境科学院 環境物質科学専攻, 教授

学位

  • 博士（理学）（東京大学）

プロフィール情報

  • 姓

    高草木, タカクサギ

  • 名

    達, サトル

  • ID各種

    200901030607620959

通称等の別名

    北海道大学

対象リソース

所属

  • 大学院 環境科学院 環境物質科学専攻, 教授

業績リスト

研究キーワード

  • その場/オペランド計測   X線吸収分光法   表面X線散乱   走査プローブ顕微鏡   電極表面科学   触媒表面科学   

研究分野

  • 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
  • ナノテク・材料 / 薄膜、表面界面物性
  • ナノテク・材料 / 機能物性化学
  • ナノテク・材料 / 基礎物理化学

経歴

  • 2023年04月 - 現在 北海道大学 触媒科学研究所 教授
  • 2015年10月 - 2023年03月 北海道大学 触媒科学研究所 准教授
  • 2008年04月 - 2015年09月 北海道大学 触媒化学研究センター 准教授
  • 2007年04月 - 2008年03月 北海道大学 大学院理学研究科 助教
  • 2002年09月 - 2007年03月 北海道大学 大学院理学研究科 助手
  • 2001年04月 - 2002年09月 日本学術振興会特別研究員（DC2）

学歴

  • 2000年04月 - 2002年09月   東京大学大学院   理学系研究科   化学専攻（博士）
  • 1998年04月 - 2000年03月   東京大学大学院   理学系研究科   化学専攻（修士）
  • 1994年04月 - 1998年03月   東京大学   理学部   化学科

委員歴

  • 2024年04月 - 現在   日本表面真空学会   協議員
  • 2023年05月 - 現在   触媒学会   企画・教育委員会 委員
  • 2013年04月 - 現在   日本表面科学会（現 日本表面真空学会）東北・北海道支部会幹事
  • 2010年04月 - 現在   日本化学会正会員
  • 2003年04月 - 現在   電気化学会北海道支部幹事
  • 2022年03月 - 2024年03月   日本化学会北海道支部   庶務幹事
  • 2021年07月 - 2022年04月   触媒学会   次世代放射光ワーキンググループ委員
  • 2018年03月 - 2020年03月   電気化学会編集委員
  • 2015年04月 - 2018年03月   触媒学会北海道地区オーロラ委員
  • 2015年04月 - 2017年12月   日本XAFS研究会 企画幹事
  • 2015年04月 - 2017年03月   日本表面科学会（現 日本表面真空学会）東北・北海道支部会計幹事
  • 2013年04月 - 2014年05月   触媒学会総務委員会委員
  • 2012年04月 - 2014年05月   触媒学会討論会委員会委員

受賞

  • 2021年 日本表面真空学会 日本表面真空学会論文賞
     
    受賞者: 城戸大貴;上村洋平;三輪寛子;高草木達;朝倉清高
  • 2017年 American Vacuum Society VTD Shop Note Awards
     
    受賞者: Yoshihide Watanabe;Yusaku F. Nishimura;Ryo Suzuki;Hiromitsu Uehara;Tomoyuki Nimura;Atsushi Beniya;Noritake Isomura;Kiyotaka Asakura;Satoru Takakusagi
  • 2015年 BCSJ（日本化学会欧文誌）賞
     
    受賞者: Tao Ma;Kotaro Miyazaki;Hiroko Ariga;Satoru Takakusagi;Kiyotaka Asakura
  • 2015年 北海道大学研究総長賞奨励賞
     
    受賞者: 高草木 達
  • 2014年 日本化学会北海道支部奨励賞
     
    受賞者: 高草木 達
  • 2010年 日本化学会 第90春季年会 「若い世代の特別講演会」証
     
    受賞者: 高草木 達
  • 2008年 The Best Poster Prize (ISSS-5)
  • 2008年 日本化学会 第88春季年会優秀講演賞（学術）
  • 2000年 Student Poster Award（PACIFICHEM 2000）

論文

  • 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 2024年02月15日 [査読有り]
  • Takahiro Wada, Upendar Kashaboina, Yuta Nishikawa, Yuki Wakisaka, Deling Bao, Satoru Takakusagi, Yuta Inami, Fumiya Kuriyama, Arnoldus Lambertus Dipu, Hitoshi Ogihara, Shoji Iguchi, Ichiro Yamanaka, Daiki Kido, Masao Kimura, Motohiro Uo, Kiyotaka Asakura
    The Journal of Physical Chemistry C 2023年12月12日 [査読有り]
  • Cho Rong Kim, Honoka Maeda, Bang Lu, Yuto Nakamura, Yunli Lin, Yuki Wakisaka, Daiki Kido, Kiyotaka Asakura, Satoru Takakusagi
    Chemistry Letters 2023年12月 [査読有り]
  • Can Liu, Bang Lu, Hiroko Ariga-Miwa, Shohei Ogura, Takahiro Ozawa, Katsuyuki Fukutani, Min Gao, Jun-ya Hasegawa, Ken-ichi Shimizu, Kiyotaka Asakura, Satoru Takakusagi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 145 36 19953 - 19960 2023年08月 [査読有り][通常論文]
     
    Dynamic behavior of intermediate adsorbates, such as diffusion, spillover, and reverse spillover, has a strong influence on the catalytic performance in oxide-supported metal catalysts. However, it is challenging to elucidate how the intermediate adsorbates move on the catalyst surface and find active sites to give the corresponding products. In this study, the effect of the dynamic behavior of methoxy intermediate on methanol decomposition on a Pt/TiO2(110) surface has been clarified by combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. The methoxy intermediates were formed by the dissociative adsorption of methanol molecules on Pt nanoparticles at room temperature followed by spillover to the TiO2(110) support surface. TPD results showed that the methoxy intermediates were thermally decomposed at >350 K on the Pt sites to produce CO (dehydrogenation) and CH4 (C-O bond scission). A decrease of the Pt nanoparticle density lowered the activity for the decomposition reaction and increased the selectivity toward CH4, which indicates that the reaction is controlled by diffusion and reverse spillover of the methoxy intermediates. Time-lapse STM imaging and DFT calculations revealed that the methoxy intermediates migrate on the five-fold coordinated Ti (Ti-5c) sites along the [001] or [1 (1) over bar 0] direction with the aid of hydrogen adatoms bonded to the bridging oxygens (O-br) and can move over the entire surface to seek and find active Pt sites. This work offers an in-depth understanding of the important role of intermediate adsorbate migration in the control of the catalytic performance in oxide-supported metal catalysts.
  • Yasuyuki Yamada, Kentaro Morita, Takuya Sugiura, Yuka Toyoda, Nozomi Mihara, Masanari Nagasaka, Hikaru Takaya, Kiyohisa Tanaka, Takanori Koitaya, Naoki Nakatani, Hiroko Ariga-Miwa, Satoru Takakusagi, Yutaka Hitomi, Toshiji Kudo, Yuta Tsuji, Kazunari Yoshizawa, Kentaro Tanaka
    JACS Au 3 3 823 - 833 2023年01月10日 [査読有り]
  • Daiki Kido, Yohei Uemura, Yuki Wakisaka, Akihiro Koide, Hiromitsu Uehara, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Tokushi Sato, Harry Jenkins, Toshihiko Yokoyama, Satoru Takakusagi, Jun-ya Hasegawa, Kiyotaka Asakura
    Chemistry Letters 51 11 1083 - 1086 2022年11月05日 [査読有り][通常論文]
  • Yuki Nakaya, Eigo Hayashida, Hiroyuki Asakura, Satoru Takakusagi, Shunsaku Yasumura, Ken-ichi Shimizu, Shinya Furukawa
    Journal of the American Chemical Society 144 35 15944 - 15953 2022年09月07日 [査読有り]
  • Dae-Yeong Kim, Hyungwon Ham, Xiaozhong Chen, Shuai Liu, Haoran Xu, Bang Lu, Shinya Furukawa, Hyun-Ha Kim, Satoru Takakusagi, Koichi Sasaki, Tomohiro Nozaki
    Journal of the American Chemical Society 144 31 14140 - 14149 2022年08月10日 [査読有り]
     
    Using nonthermal plasma (NTP) to promote CO2 hydrogenation is one of the most promising approaches that overcome the limitations of conventional thermal catalysis. However, the catalytic surface reaction dynamics of NTP-activated species are still under debate. The NTP-activated CO2 hydrogenation was investigated in Pd2Ga/SiO2 alloy catalysts and compared to thermal conditions. Although both thermal and NTP conditions showed close to 100% CO selectivity, it is worth emphasizing that when activated by NTP, CO2 conversion not only improves more than 2-fold under thermal conditions but also breaks the thermodynamic equilibrium limitation. Mechanistic insights into NTP-activated species and alloy catalyst surface were investigated by using in situ transmission infrared spectroscopy, where catalyst surface species were identified during NTP irradiation. Moreover, in in situ X-ray absorption fine-structure analysis under reaction conditions, the catalyst under NTP conditions not only did not undergo restructuring affecting CO2 hydrogenation but also could clearly rule out catalyst activation by heating. In situ characterizations of the catalysts during CO2 hydrogenation depict that vibrationally excited CO2 significantly enhances the catalytic reaction. The agreement of approaches combining experimental studies and density functional theory (DFT) calculations substantiates that vibrationally excited CO2 reacts directly with hydrogen adsorbed on Pd sites while accelerating formate formation due to neighboring Ga sites. Moreover, DFT analysis deduces the key reaction pathway that the decomposition of monodentate formate is promoted by plasma-activated hydrogen species. This work enables the high designability of CO2 hydrogenation catalysts toward value-added chemicals based on the electrification of chemical processes via NTP.
  • 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 126 2 1006 - 1016 2022年01月20日 [査読有り][通常論文]
  • Shinya Mine, Motoshi Takao, Taichi Yamaguchi, Takashi Toyao, Zen Maeno, S. M. A. Hakim Siddiki, Satoru Takakusagi, Ken‐ichi Shimizu, Ichigaku Takigawa
    ChemCatChem 13 16 3636 - 3655 2021年08月20日 [査読有り]
  • Bang Lu, Daiki Kido, Yuta Sato, Haoran Xu, Wang-Jae Chun, Kiyotaka Asakura, Satoru Takakusagi
    The Journal of Physical Chemistry C 125 22 12424 - 12432 2021年06月10日 [査読有り][招待有り]
  • Yasuyuki Yamada, Kentaro Morita, Takuya Sugiura, Yuka Toyoda, Nozomi Mihara, Masanari Nagasaka, Hikaru Takaya, Kiyohisa Tanaka, Takanori Koitaya, Naoki Nakatani, Hiroko Ariga-Miwa, Satoru Takakusagi, Yutaka Hitomi, Toshiji Kudo, Yuta Tsuji, Kazunari Yoshizawa, Kentaro Tanaka
    2021年06月04日 
    <div><div><div><p>Herein, we report that the close-stacking of a double-decker-type dinuclear iron phthalocyanine complex on a graphite surface is effective for achieving high methane oxidation activity, comparable to those of certain MMOs, in an aqueous solution. </p></div></div></div>
  • Yuki Wakisaka, Hiromitsu Uehara, Qiuyi Yuan, Daiki Kido, Takahiro Wada, Motohiro Uo, Yohei Uemura, Toshihiko Yokoyama, Yutaro Kamei, Seiichi Kuroda, Akihiro Ohira, Satoru Takakusagi, Kiyotaka Asakura
    Electronic Structure 2 4 044003 - 044003 2021年01月23日 [査読有り][招待有り]
  • Yuki Wakisaka, Bing Hu, Daiki Kido, Md. Harun Al Rashid, Wenhan Chen, Kaiyue Dong, Takahiro Wada, Bapurao Bharate, Quiyi Yuan, Shingo Mukai, Yasuo Takeichi, Satoru Takakusagi, Kiyotaka Asakura
    Journal of Synchrotron Radiation 27 6 1618 - 1625 2020年11月01日 [査読有り]
     
    A bent crystal Laue analyser (BCLA) is an X-ray energy analyser used for fluorescence X-ray absorption fine-structure (XAFS) spectroscopy to separate the fluorescence X-ray emission line of a target atom from the elastic scattering X-rays and other fluorescence emission lines. Here, the feasibility of the BCLA for total reflection fluorescence XAFS (TRF-XAFS), which has a long X-ray footprint on the substrate surface owing to grazing incidence, was tested. The focal line of the BCLA was adjusted on the X-ray footprint and the XAFS signal for one monolayer of Pt deposited on a 60 nm Au film with high sensitivity was obtained. Although range-extended XAFS was expected by the rejection of Au fluorescence arising from the Au substrate, a small glitch was found in the Au L 3 edge because of the sudden change of the complex refraction index of the Au substrate at the Au edge. This abnormal spectrum feature can be removed by reflectivity correction using Au foil absorption data. BCLA combined with TRF-XAFS spectroscopy (BCLA + TRF-XAFS) is a new technique for the in situ surface analysis of highly dispersed systems even in the presence of a liquid overlayer.
  • F. Mauriello, H. Ariga-Miwa, E. Paone, R. Pietropaolo, S. Takakusagi, K. Asakura
    Catalysis Today 357 511 - 517 2020年11月 [査読有り]
  • Shun Tsunekawa, Futaba Yamamoto, Ke-Hsuan Wang, Masanari Nagasaka, Hayato Yuzawa, Satoru Takakusagi, Hiroshi Kondoh, Kiyotaka Asakura, Takeshi Kawai, Masaaki Yoshida
    The Journal of Physical Chemistry C 2020年10月20日 [査読有り]
  • Daiki Kido, Yohei Uemura, Yuki Wakisaka, Hiroko Ariga-Miwa, Satoru Takakuasgi, Kiyotaka Asakura
    e-Journal of Surface Science and Nanotechnology 18 0 249 - 261 2020年08月01日 [査読有り][通常論文]
     
    Extended X-ray absorption fine structure (EXAFS) plays an important role in the surface science and nanotechnology to characterize the non-crystalline materials using the curve fitting (CF) analysis. However, the CF has problems such as correlation between the structural parameters, the dependence on initial parameters, and the limitation of degree of freedom when EXAFS is applied to the complex system. In this paper, we propose a thorough search (TS) method to solve these problems. We analyzed EXAFS data for molybdenum oxide (alpha-MoO3) using the TS method. MO3 possesses a well-defined but complex local structure in which a central molybdenum (Mo) atom is surrounded by six oxygen (0) atoms. In CF analysis, the correlations of these six Mo-O bonds make it very difficult to derive reliable structural parameters from EXAFS data. In the TS analysis, the structural parameters regarded as a point (P) were surveyed thoroughly over a certain range. The goodness of fit was evaluated by R-factor. All P with R-factors less than a certain value were accepted. The accepted points P made a domain in which it was assumed that all points P in the domain should occur with equal probability and consequently their averages were used as representative structural parameters. If multiple independent domains were obtained, they were all regarded as possible candidates and the TS analysis provided possible structural parameters. The feasibility and advantages of the TS method were compared with the CF analysis and the micro reverse Monte Carlo method.
  • Takashi Toyao, Zen Maeno, Satoru Takakusagi, Takashi Kamachi, Ichigaku Takigawa, Ken-ichi Shimizu
    ACS Catalysis 10 3 2260 - 2297 2020年02月07日 [査読有り][招待有り]
     
    The discovery and development of catalysts and catalytic processes are essential components to maintaining an ecological balance in the future. Recent revolutions made in data science could have a great impact on traditional catalysis research in both industry and academia and could accelerate the development of catalysts. Machine learning (ML), a subfield of data science, can play a central role in this paradigm shift away from the use of traditional approaches. In this review, we present a user's guide for ML that we believe will be helpful for scientists performing research in the field of catalysis and summarize recent progress that has been made in utilizing ML to create homogeneous and heterogeneous catalysts. The focus of the review is on the design, synthesis, and characterization of catalytic materials/compounds as well as their applications to catalyzed processes. The ML technique not only enhances ways to discover catalysts but also serves as a powerful tool to establish a deeper understanding of relationships between the properties of materials/compounds and their catalytic activities, selectivities, and stabilities. This knowledge facilitates the establishment of principles employed to design catalysts and to enhance their efficiencies. Despite such advantages of ML, it is noteworthly that the current ML-assisted development of real catalysts remains in its infancy, mainly because of the complexity of catalysis associated with the fact that catalysis is a time dependent dynamic event. In this review, we discuss how seamless integration of experiment, theory, and data science can be used to accelerate catalyst development and to guide future studies aimed at applications that will impact society's need to produce energy, materials, and chemicals. Moreover, the limitations and difficulties of ML in catalysis research originating from the complex nature of catalysis are discussed in order to make the catalysis community aware of challenges that need to be addressed for effective and practical use of ML in the field.
  • Akihiro Koide, Yohei Uemura, Daiki Kido, Yuki Wakisaka, Satoru Takakusagi, Bunsho Ohtani, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Shigeki Owada, Makina Yabashi, Yusaku Yamamoto, Misaki Katayama, Keisuke Hatada, Toshihiko Yokoyama, Kiyotaka Asakura
    Physical Chemistry Chemical Physics 22 5 2615 - 2621 2020年 [査読有り]
     

    Ultrafast XANES spectra and full-potential multiple scattering reveal the anisotropic structure change of photoexcited WO3.

  • Suzuki Keisuke, Toyao Takashi, Maeno Zen, Takakusagi Satoru, Shimizu Ken-ichi, Takigawa Ichigaku
    CHEMCATCHEM 11 18 4537 - 4547 2019年09月19日 [査読有り][通常論文]
     
    The literature provides insights for catalyst design and discovery. Effective analysis of reported data using machine learning (ML) methods offers the ability to gain valuable information. However, utilizing the literature in this way has obstacles such as lack of compositional overlaps, bias from prior published data, and low sample counts for many elements. The present study describes an ML approach that considers elemental features as input representations instead of inputting catalyst compositions directly. This ML method has the potential for catalyst discovery, including catalytic reactions with limited catalyst composition overlap in the available data. Oxidative coupling of methane (OCM), water gas shift (WGS), and CO oxidation reactions were chosen to confirm the effectiveness of the proposed method by analysis using several state-of-the-art ML methods. Among the ML methods tested, gradient boosting regression with XGBoost (XGB) provided the best results, and prediction accuracy was improved by the proposed approach for all three reaction types. In addition, a quantitative value of "feature importance score" was calculated to evaluate the most influential input variables on catalyst performance. Finally, catalyst optimization was explored using ML as a "surrogate" model, and the top 20 promising candidate catalysts were identified for the OCM reaction based on the optimization. The advantages of ML in catalysis analysis as well as the difficulties and limitations originating from the complexity of heterogeneous catalysis were explored.
  • Kashaboina Upendar, Nishikawa Yuta, Wakisaka Yuki, Sirisit Natee, Nagamatsu Shin-ichi, Bao Deling, Ariga-Miwa Hiroko, Takakusagi Satoru, Inami Yuta, Kuriyama Fumiya, Dipu Arnoldus Lambertus, Ogihara Hitoshi, Iguchi Shoji, Yamanaka Ichiro, Wada Takahiro, Asakura Kiyotaka
    CHEMISTRY LETTERS 48 9 1145 - 1147 2019年09月 [査読有り][通常論文]
     
    The local structure of In/SiO2, which is a potential catalyst for the non-oxidative coupling of methane, was investigated by using in situ In K-edge X-ray absorption fine-structure analysis. During the activation process, the In/SiO2 catalyst underwent several metamorphosis-like transformations of its structure before final conversion to the active phase.
  • Kamachi Takashi, Tatsumi Toshinobu, Toyao Takashi, Hinuma Yoyo, Maeno Zen, Takakusagi Satoru, Furukawa Shinya, Takigawa Ichigaku, Shimizu Ken-ichi
    JOURNAL OF PHYSICAL CHEMISTRY C 123 34 20988 - 20997 2019年08月29日 [査読有り][通常論文]
     
    Adsorption is a fundamental step in catalysis on a solid surface, and therefore, its understanding is important for explaining its behavior. This work investigated the adsorption of various small molecules, including H-2, N-2, CO, CO2, CH4, NH3, H2O, H2S, dimethyl sulfoxide, alkanes, alkenes, alkynes, aromatic compounds, alcohols, aldehydes, ketones, nitriles, carboxylic acids, amides, and amines, on the anatase (101) and rutile (110) surfaces of TiO2, using periodic density functional theory calculations and statistical methods. Adsorption energies were computed at the same level of theory to obtain a clean and consistent data set. A linear relationship was observed between the adsorption energies of these molecules and their highest occupied molecular orbital (HOMO) levels, whereas no obvious correlation was evident for the lowest unoccupied molecular orbital levels. Improved correlations between the adsorption energies and HOMO levels were generated by dividing these, molecules into two subgroups: hydrocarbons and heteroatom- containing compounds. Interactions between frontier molecular orbitals and the surfaces were considered, to gain a better understanding of the significant correlations that were identified. The data show that these relationships can be primarily ascribed to the interactions between the HOMO of the small molecule and conduction state of the TiO2 surface. The statistical analysis using machine learning demonstrated that the HOMO and dipole moment are the first and second most important properties, respectively, in terms of rationalizing and predicting the adsorption energies.
  • Wakisaka Yuki, Kido Daiki, Uehara Hiromitsu, Yuan Qiuyi, Feiten Felix E, Mukai Shingo, Takakusagi Satoru, Uemura Yohei, Yokoyama Toshihiko, Wada Takahiro, Uo Motohiro, Sekizawa Oki, Uruga Tomoya, Iwasawa Yasuhiro, Asakura Kiyotaka
    CHEMICAL RECORD 19 7 1157 - 1165 2019年07月 [査読有り][通常論文]
  • Takakusagi Satoru, Asakura Kiyotaka, Iwasawa Yasuhiro
    CHEMICAL RECORD 19 7 1244 - 1255 2019年07月 [査読有り][招待有り]
  • Hinuma Yoyo, Toyao Takashi, Kamachi Takashi, Maeno Zen, Takakusagi Satoru, Furukawa Shinya, Takigawa Ichigaku, Shimizu Ken-ichi
    JOURNAL OF PHYSICAL CHEMISTRY C 122 51 29435 - 29444 2018年12月27日 [査読有り][通常論文]
     
    The surface oxygen vacancy formation energy (E-Ovac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine E-Ovac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence E-Ovac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O-2, NO, CO,CO2, and H-2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and E-Ovac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.
  • 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 16 387 - 390 2018年09月01日 [査読有り][通常論文]
  • Yuan Q, Wakisakai Y, Uemura Y, Wada T, Ariga-Miwa H, Takakusagi S, Asakura K, Brankovic S. R
    Journal of Physical Chemistry C 122 29 16664 - 16673 2018年07月26日 [査読有り][通常論文]
     
    The stoichiometry and reaction mechanism of Pt deposition via surface limited redox replacement (SLRR) of Cu underpotential-deposited (UPD) monolayer on Au(111) was studied using in situ polarization dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS), scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). We proposed that Pt deposition via SLRR of Cu UPD monolayer leads to formation/deposition of Pt-surface species mainly consisting of Pt(II) chloride with a square planar local structure [PtCl4] parallel to the Au surface (60%) which has a strong interaction of the Pt complex with the Au substrate. The rest (40%) was one-monolayer Pt metal cluster. This result provides a new understanding into the mechanism and stoichiometry of the SLRR reaction, which has a wide application for synthesis of monolayer catalysts.
  • Kato Masaru, Muto Marika, Matsubara Naohiro, Uemura Yohei, Wakisaka Yuki, Yoneuchi Tsubasa, Matsumura Daiju, Ishihara Tomoko, Tokushima Takashi, Noro Shin-ichiro, Takakusagi Satoru, Asakura Kiyotaka, Yagi Ichizo
    ACS APPLIED ENERGY MATERIALS 1 5 2358 - 2364 2018年05月 [査読有り][通常論文]
     
    Multinuclear metal active sites are widely used as catalytic reaction centers in metalloenzymes and generally show high catalytic activity. For example, laccases are known to catalyze the oxygen reduction reaction (ORR) to water at a multinuclear copper site with almost no energy loss. The ORR is an important reaction not only in oxygenic respiration but also in future energy generation devices such as polymer electrolyte fuel cells and metal-air batteries. For large-scale commercialization of these devices, there is a need to develop highly active ORR electrocatalysts based on nonprecious metals. Incorporation of multinuclear metal active sites in conductive materials such as carbon will allow us to develop highly active electrocatalysts like metalloenzymes. However, such methods had not been established yet. Herein, we report a copper-based ORR electrocatalyst with multinuclear copper active sites in nitrogen-doped graphene. The electrocatalyst was synthesized from the mixture of graphene oxide and a multinuclear copper complex in a short-period heating method. Electrochemical measurements revealed that the obtained electrocatalyst showed the highest electrocatalytic activity for the ORR in the Cu-based electrocatalysts in neutral aqueous solution. Physicochemical measurements including in situ X-ray absorption spectroscopy revealed the incorporation of multinuclear copper sites. Our synthetic approach will offer guidance for developing highly active electrocatalysts utilizing multinuclear metal sites not only for the ORR but also for other electrocatalytic reactions.
  • 高草木 達, 朝倉 清高
    表面と真空 61 5 309 - 314 2018年05月 [査読有り][招待有り]
  • 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 8 5 2018年05月01日 [査読有り][通常論文]
     
    Pt-Au nanostructures are important and well-studied fuel cell catalysts for their promising catalytic performance. However, a detailed quantitative local structure analysis, using extended X-ray absorption fine structure (EXAFS) spectroscopy, have been inhibited by interference between Pt and Au L3-edges. In this paper, Pt L3-edge XAFS analysis, free of Au L3 edge, is demonstrated for a Pt-Au reference sample using a low-cost log–spiral bent crystal Laue analyzer (BCLA). This method facilitates the EXAFS structural analysis of Pt-Au catalysts, which are important to improve fuel cell catalysts.
  • Takashi Toyao, Keisuke Suzuki, Shoma Kikuchi, Satoru Takakusagi, Ken-Ichi Shimizu, Ichigaku Takigawa
    Journal of Physical Chemistry C 122 15 8315 - 8326 2018年04月19日 [査読有り][通常論文]
     
    The process employed to discover new materials for specific applications typically utilizes screening of large compound libraries. In this approach, the performance of a compound is correlated to the properties of elements referred to as descriptors. In the effort described below, we developed a simple and efficient machine learning (ML) model for predicting adsorption energies of CH4 related species, namely, CH3, CH2, CH, C, and H on the Cu-based alloys. The developed ML model predicted the DFT-calculated adsorption energies with 12 descriptors, which are readily available values for the selected elements. The predictive accuracy of four regression methods (ordinary linear regression by least-squares (OLR), random forest regression (RFR), gradient boosting regression (GBR), and extra tree regression (ETR)) with different numbers of descriptors and different test-set/training-set ratios was quantitatively evaluated using statistical cross validations. Among four types of regression methods, we have found that ETR gave the best performance in predicting the adsorption energies with the average root mean squared errors (RMSEs) below 0.3 eV. Strikingly, despite its simplicity and low computational cost, this model can predict the adsorption energies on a range of Cu-based alloy models (46 in total number) as calculated by using DFT. In addition, we show the ML prediction for the differences in the adsorption energies of CH3 and CH2 on the same surface. This would be of great importance especially when designing the selective catalytic reaction processes to suppress the undesired over-reactions. The accuracy and simplicity of the developed system suggest that adsorption energies can be readily predicted without time-consuming DFT calculations, and eventually, this would allow us to predict the catalytic performances of the solid catalysts.
  • José Contreras-Mora, Hiroko Ariga-Miwa, Satoru Takakusagi, Christopher T. Williams, Kiyotaka Asakura
    Journal of Physical Chemistry C 122 11 6318 - 6322 2018年03月22日 [査読有り][通常論文]
     
    Phosphorous (P) diffusion in bulk Ni2P was investigated by the density functional theory (DFT) to find the origin of the lowerature P diffusion into the surface. The Ni2P bulk structure consists of two types of layers, Ni3P2 and Ni3P1, stacked along the [0001] direction. Two types of P vacancies in Ni2P were studied: V1 P (P deficient in N3P2) and V2 P (P deficient in N3P1). V1 P was a slightly more stable point defect than V2 P by 0.20 eV. The P diffusions to vacancies (V1 P and V2 P) had large diffusion barriers of more than 1 eV, except the P diffusion path along the [0001] direction through an interstitial site in Ni3P1 (I1→2 P) and then to V1 P, which showed the lowest energy barrier of about 0.18 eV. The DFT calculations suggested that the two adjacent vacancies (both V1 P) allow the local rearrangement of the structure to form a tetrahedral structure at the intermediate state. We have proposed a new diffusion mechanism in the intermetallic compound named the interstitial-vacancy diffusion mechanism.
  • Tao Ma, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    Thin Solid Films 646 12 - 16 2018年01月31日 [査読有り][通常論文]
     
    Graphene, a two-dimensional material, can be grown on a metal substrate using chemical vapor deposition — this growth process is notably influenced by the crystal orientation and the roughness of the substrate surface. We prepared epitaxial Cu(111) films on sapphire substrates using thermal evaporation at various substrate temperatures and studied their crystal orientation and roughness. The well crystallized Cu(111) film with a smooth surface was obtained when the substrate was maintained at 473 K during the deposition. High quality graphene with few intrinsic defects was grown on this Cu film.
  • 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, Yuan Qiuyi, 関澤 央輝, 宇留賀 朋哉, 岩澤 康裕, 朝倉 清高
    表面科学 38 8 378 - 383 公益社団法人 日本表面科学会 2017年09月 [査読有り][招待有り]
     

    A log-spirally bent crystal Laue analyzer has been investigated and developed for highly sensitive in situ surface X-ray absorption fine structure (XAFS) measurement. Both calculations and experiments were conducted to obtain its intensity distributions on the different positions of the analyzer. A home-made log-spirally bent crystal Laue analyzer was made and evaluated. It was revealed that higher XAFS signals were obtained with the home-made analyzer than with the commercial one.

  • Hua Huang, Takahiro Wada, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura, Yasuhiro Iwasawa
    CHEMICAL PHYSICS LETTERS 683 18 - 21 2017年09月 [査読有り][通常論文]
     
    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.
  • Qiuyi Yuan, Satoru Takakusagi, Yuki Wakisaka, Yohei Uemura, Takahiro Wada, Hiroko Ariga, Kiyotaka Asakura
    CHEMISTRY LETTERS 46 8 1250 - 1253 2017年08月 [査読有り][通常論文]
     
    We studied the initial stage of a Pt monolayer produced by surface-limited redox replacement (SLRR) using polarization-dependent total reflection fluorescence X-ray absorption fine structure (PTRF-XAFS). Different from the widely accepted understanding that metallic monolayer islands are formed, our XAFS showed that the Pt monolayer, initially present on the Au(111) substrate, was mainly in the form of a planar [PtCl4](2-) complex with its molecular plane parallel to Au(111). This result provides a new insight into the mechanism of SLRR.
  • Yohei Uemura, Daiki Kido, Akihiro Koide, Yuki Wakisaka, Yasuhiro Niwa, Shunsuke Nozawa, Kohei Ichiyanagi, Ryo Fukaya, Shin-Ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Shigeki Owada, Makina Yabashi, Keisuke Hatada, Akihide Iwase, Akihiko Kudo, Satoru Takakusagi, Toshihiko Yokoyama, Kiyotaka Asakura
    Chemical communications (Cambridge, England) 53 53 7314 - 7317 2017年06月29日 [査読有り][通常論文]
     
    Ultrafast excitation of photocatalytically active BiVO4 was characterized by femto- and picosecond transient X-ray absorption fine structure spectroscopy. An initial photoexcited state (≪500 fs) changed to a metastable state accompanied by a structural change with a time constant of ∼14 ps. The structural change might stabilize holes on oxygen atoms since the interaction between Bi and O increases.
  • Tadashi Ohba, Hitoshi Kubo, Yusuke Ohshima, Yuichi Makita, Noriaki Nakamura, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 90 6 720 - 727 2017年06月 [査読有り][通常論文]
     
    Noble metal nanoparticles always show bond length contraction with the decrease in particle size. PVP-protected small Pd metal nanoparticles (MNPs) were reported to have the unique characteristic of expanding Pd-Pd bond lengths with decreases in particle size. To investigate the origin of this phenomenon in more detail, this work examined Pd MNPs supported on SiO2 (Pd MNPs/SiO2) via extended X-ray absorption fine structure (EXAFS) analysis, where the SiO2 support was used to stabilize the MNPs to prevent unexpected aggregation at higher temperatures. EXAFS data showed that each sample had a face-centered cubic (fcc) structure and that the smallest particles had the longest Pd-Pd bonds. Temperature dependent EXAFS measurements also revealed significant static disorder in the bond-elongated Pd MNPs/SiO2 samples. The XAFS spectral features of these bond-elongated Pd MNPs on SiO2 are in good agreement with those for palladium carbide, and we conclude that the lattice expansion in Pd MNPs can be attributed to the formation of palladium carbide.
  • 鈴木 慶介, 瀧川 一学, 清水 研一, 高草木 達
    人工知能学会全国大会論文集 2017 4J13 - 4J13 一般社団法人 人工知能学会 2017年 

    メタンの酸化カップリング反応技術は,天然ガスを有効利用する手法の一つとして注目されており,機械学習を用いて反応量を予測する既存研究も存在する.本稿では既存研究に対して新たに,学習に用いるデータの形式(組成情報)と,特徴間の類似度を考慮したモデリングを行った結果を報告する.

  • Takuya Masuda, Yu Sun, Hitoshi Fukumitsu, Hiromitsu Uehara, Satoru Takakusagi, Wang-Jae Chun, Toshihiro Kondo, Kiyotaka Asakura, Kohei Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 16200 - 16210 2016年07月 [査読有り][通常論文]
     
    Organic molecular layers with viologen moieties as electron transfer mediators were constructed on hydrogen-terminated Si(111) surfaces, and metal catalysts for multielectron transfer reactions were incorporated into the molecular layers by immersing the viologen-modified Si(111) electrodes in aqueous solutions containing various metal complexes (K2PdCl4, NaAuCl4, and K2PtCl4). Significant enhancements were achieved for CO2 reduction at the Au-modified Si(111) electrode and for both hydrogen reaction (HER) and CO2 reduction at the Pd-modified Si(111) electrode. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) analysis showed that Au complexes were spontaneously reduced to metal nanoparticles during the metal insertion, and therefore, actual catalysts for CO2 reduction at the Au-modified Si(111) electrode were Au metal nanoparticles. In contrast, Pd complexes were inserted into the molecular layers and partly reduced during HER and CO2 reduction. Pd complexes and relatively small Pd nanoparticles (<2 nm) were considered to be actual catalysts for HER and CO2 reduction. Interestingly, at the Pt-modified Si(111) electrode, not only highly efficient HER but also highly selective CO2 reduction in preference to HER were achieved, despite the fact that HER is dominant at Pt pure metal electrodes even in CO2-saturated aqueous solutions. On the basis of XPS and XAFS analysis, Pt complexes were incorporated into the molecular layers and acted as confined molecular catalysts for both HER and CO2 reduction without being converted into Pt metal nanoparticles. This should be the major reason for the anomalously high selectivity of the Pt-modified Si(111) electrode for CO2 reduction, unlike pure Pt metal electrocatalysts.
  • 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 120 29 15785 - 15791 2016年07月 [査読有り][通常論文]
     
    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.
  • Takahiro Kaito, Hiroyuki Tanaka, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiroko Ariga, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 120 21 11519 - 11527 2016年06月 [査読有り][通常論文]
     
    In order to examine the relationship between the oxygen reduction reaction (ORR) activity of a fuel cell catalyst and its structure and/or electronic state, carbon-supported Pt and Pt alloys having various structures, compositions, and morphologies were studied. Regardless of the atomic ordering or morphology (core-shell or random alloy) of the catalyst, the ORR activity was primarily dependent on the Pt-Pt bond distance. Among these materials, Pt2Co, having the shortest Pt-Pt distance, exhibited the highest ORR activity. The activities of this catalyst per unit surface. area and per unit mass were approximately 10 times and 6 times higher than those of a commercially available carbon supported Pt electrocatalyst (Pt/C). This work also found a monotonic increase in catalytic activity with decreasing Pt-Pt distance.
  • Masaaki Yoshida, Takehiro Mineo, Yosuke Mitsutomi, Futaba Yamamoto, Hirokatsu Kurosu, Satoru Takakusagi, Kiyotaka Asakura, Hiroshi Kondoh
    CHEMISTRY LETTERS 45 3 277 - 279 2016年03月 [査読有り][通常論文]
     
    A cobalt-phosphate (Co-P-i) oxygen evolution cocatalyst on a SrTiO3 photoelectrode was investigated by Co and P K-edge X-ray absorption fine structure (XAFS) spectroscopy. Formation of an edge-sharing CoO6 octahedral structure nanocluster in the Co-P-i cocatalyst was verified by the Co K-edge XAFS spectra under the photoelectrochemical reaction. The P K-edge XAFS spectrum for the Co-P-i cocatalyst showed a pre-edge peak derived from the hybridization of Co(3d)-O(2p)-P(3p) valence orbitals. Therefore, it was spectroscopically demonstrated that a phosphate species binds to the Co edge of the CoO6 cluster in the Co-P-i cocatalyst. The phosphate species is likely to stabilize the CoO6 cluster for efficient oxygen evolution activity.
  • Yoshihide Watanabe, Yusaku F. Nishimura, Ryo Suzuki, Hiromitsu Uehara, Tomoyuki Nimura, Atsushi Beniya, Noritake Isomura, Kiyotaka Asakura, Satoru Takakusagi
    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A 34 2 2016年03月 [査読有り][通常論文]
     
    A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstrated by a successful PTRF-XAFS study of Pt-4 clusters deposited on a TiO2(110) surface. (C) 2015 American Vacuum Society.
  • 脇坂 祐輝, 城戸 大貴, 上原 広充, 上村 洋平, 高草木 達, 和田 敬広, Yuan Qiuyi, 朝倉 清高
    表面科学学術講演会要旨集 36 106 - 106 公益社団法人 日本表面科学会 2016年 
    広い立体角をもつ分光器Bent Crystal Laue Monochromator（ＢＣLA）は、高感度な蛍光XAFSを可能とし、表面への応用が期待されてきたが、未だに十分な感度が達成されていない。われわれはこの５年間BCLAの改良に取り組んできた。 本講演ではその取り組みを総括し、現状（表面感度について）を述べ、今後の展開について議論したい。特に、HOPGを基板としたモデル燃料電池Pt触媒へのこの手法の応用についても議論する。
  • Ichigaku Takigawa, Ken-ichi Shimizu, Koji Tsuda, Satoru Takakusagi
    RSC ADVANCES 6 58 52587 - 52595 2016年 [査読有り][通常論文]
     
    The d-band center for metals has been widely used in order to understand activity trends in metal-surface-catalyzed reactions in terms of the linear Bronsted-Evans-Polanyi relation and Hammer-Norskov d-band model. In this paper, the d-band centers for eleven metals (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, Au) and their pairwise bimetals for two different structures (1% metal doped- or overlayer-covered metal surfaces) are statistically predicted using machine learning methods from readily available values as descriptors for the target metals (such as the density and the enthalpy of fusion of each metal). The predictive accuracy of four regression methods with different numbers of descriptors and different test-set/training-set ratios are quantitatively evaluated using statistical cross validations. It is shown that the d-band centers are reasonably well predicted by the gradient boosting regression (GBR) method with only six descriptors, even when we predict 75% of the data from only 25% given for training (average root mean square error (RMSE) < 0.5 eV). This demonstrates a potential use of machine learning methods for predicting the activity trends of metal surfaces with a negligible CPU time compared to first-principles methods.
  • Yohei Uemura, Daiki Kido, Yuki Wakisaka, Hiromitsu Uehara, Tadashi Ohba, Yasuhiro Niwa, Shunsuke Nozawa, Tokushi Sato, Kohei Ichiyanagi, Ryo Fukaya, Shin-ichi Adachi, Tetsuo Katayama, Tadashi Togashi, Sigeki Owada, Kanade Ogawa, Makina Yabashi, Keisuke Hatada, Satoru Takakusagi, Toshihiko Yokoyama, Bunsho Ohtani, Kiyotaka Asakura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 4 1364 - 1367 2016年01月 [査読有り][通常論文]
     
    The dynamics of the local electronic and geometric structures of WO3 following photoexcitation were studied by femtosecond time-resolved X-ray absorption fine structure (XAFS) spectroscopy using an X-ray free electron laser (XFEL). We found that the electronic state was the first to change followed by the local structure, which was affected within 200 ps of photoexcitation.
  • Tao Ma, Kotaro Miyazaki, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 8 1029 - 1035 2015年08月 [査読有り][通常論文]
     
    The cleanliness of transferred graphene is of significant importance for its application as the window material in environmental cells used for electron microscopy and spectroscopy. We investigated the dependence of the cleanliness of graphene on transfer routes, including FeCl3 etching, (NH4)(2)S2O8 etching, electrochemical delamination, and O(2-)bubbling, by means of transmission electron microscopy and X-ray photoelectron spectroscopy. It was found that electrochemical delamination provided the cleanest graphene with only a small amount of poly(methyl methacrylate) (PMMA) residue existing on the surface.
  • Tadashi Ohba, Hitoshi Kubo, Yusuke Ohshima, Yuichi Makita, Noriaki Nakamura, Hiromitsu Uehara, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 44 6 803 - 805 2015年06月 [査読有り][通常論文]
     
    Pd nanoparticles exhibit the abnormal behavior of the Pd lattice expanding as the size of the Pd nanoparticles decreases. We measured extended X-ray absorption fine structure of poly(N-vinyl-2-pyrrolidone)-protected Pd nanoparticles and confirmed that the Pd Pd bond distance in small Pd nanoparticles with a diameter of less than 3 nm was elongated by 2% compared with that in Pd foil. The origin of the unusual bond elongation was discussed.
  • F. Mauriello, H. Ariga, M. G. Musolino, R. Pietropaolo, S. Takakusagi, K. Asakura
    APPLIED CATALYSIS B-ENVIRONMENTAL 166 121 - 131 2015年05月 [査読有り][通常論文]
     
    The transfer hydrogenolysis of glycerol promoted by supported palladium catalysts is reported. The reactions were carried out under mild conditions (453K and 5 bar of N-2) in absence of added hydrogen by using the reaction solvent, 2-propanol, as hydrogen source. The catalytic results are interpreted in terms of metal (Pd)-metal (Co or Fe) interaction that modifies the electronic properties of palladium and affords bimetallic PdM sites (M= Co or Fe), thus enhancing the catalytic properties of the systems in the conversion of glycerol as well as in the selectivity to 1,2-propanediol and 1-propanol. The transfer hydrogenolysis mechanism is here elucidated and involves the glycerol dehydration to 1-hydroxyacetone and the subsequent hydrogenation of 1-hydroxyacetone to propylene glycol. (C) 2014 Elsevier B.V. All rights reserved.
  • Naoyoshi Murata, Makoto Kobayashi, Yukari Okada, Takuya Suzuki, Hiroaki Nitani, Yasuhiro Niwa, Hitoshi Abe, Takahiro Wada, Shingo Mukai, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    REVIEW OF SCIENTIFIC INSTRUMENTS 86 3 034102  2015年03月 [査読有り][通常論文]
     
    We present the design and performance of a high-temperature in situ cell with a large solid angle for fluorescence X-ray absorption fine structure (XAFS) spectra. The cell has a large fluorescence XAFS window (116 mm(phi)) near the sample in the cell, realizing a large half-cone angle of 56 degrees. We use a small heater (25 x 35 mm(2)) to heat the sample locally to 873 K. We measured a Pt-SnO2 thin layer on a Si substrate at reaction conditions having a high activity. In situ measurement enables the analysis of the difference XAFS spectra between before and during the reaction to reveal the structure change during the operation. (C) 2015 AIP Publishing LLC.
  • 加藤 優, 君島 堅一, 柴田 真里, 野津 英男, 荻野 和也, 猪熊 喜芳, 太田 鳴海, 小柳津 暢久, 上原 広充, 大場 惟史, 上村 洋平, 高草木 達, 朝倉 清高, 八木 一三
    表面科学学術講演会要旨集 35 357 - 357 公益社団法人 日本表面科学会 2015年 
    固体高分子形燃料電池の酸素還元電極触媒としては主に白金系合金が用いられているが、埋蔵量やコスト面に問題を抱えているため、安価かつ高活性な非白金系酸素還元電極触媒の開発が近年盛んに行われている。本発表では、銅系酸素還元電極触媒の中で特に高い触媒活性を示す銅二核錯体触媒に着目し、その高い触媒活性を示す理由を解明するためにin situ XAFS測定を行ったので、その結果に関して報告する。
  • 朝倉 清高, 大場 惟史, 上原 広允, 高草木 達
    表面科学学術講演会要旨集 35 324 - 324 公益社団法人 日本表面科学会 2015年 
    Pdナノ粒子は脱硝触媒、部分水素化触媒等で広く用いられる。Pdナノ粒子において，ナノ粒子化すると格子が拡張するという奇妙な現象が報告されてきた．本研究では，この格子拡張をEXAFSで直接調べ，Pd-Pd結合の伸長に起因することを確認し，また水素吸蔵に伴う現象でないことをしめした．この奇妙なナノ粒子に関する現象について，可能性を議論したい．
  • Masaru Kato, Ken'ichi Kimijima, Mari Shibata, Hideo Notsu, Kazuya Ogino, Kiyoshi Inokuma, Narumi Ohta, Hiromitsu Uehara, Yohei Uemura, Nobuhisa Oyaizu, Tadashi Ohba, Satoru Takakusagi, Kiyotaka Asakura, Ichizo Yagi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 14 8638 - 8641 2015年 [査読有り][通常論文]
     
    A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.
  • Toshihiro Kondo, Joerg Zegenhagen, Satoru Takakusagi, Kohei Uosaki
    SURFACE SCIENCE 631 96 - 104 2015年01月 [査読有り][通常論文]
     
    Surface X-ray scattering (SXS) measurements were carried out to monitor the potential induced structure changes such as surface reconstruction lifting, adsorption of oxygen species, formation of surface oxide bilayer, reduction of surface oxide, and surface reconstruction at Au(111)/H2SO4 and Au(100)/H2SO4 interfaces in situ in real time using intense high energy X-ray. The phase transition of the reconstruction/lifting, adsorption of oxygen species, and surface oxide formation/reduction at the Au(100) electrode proceed much slower, slightly slower, and faster, respectively, than at the Au(111) electrode, (C) 2014 Elsevier B.V. All rights reserved.
  • Masaru Kato, Ken'ichi Kimijima, Mari Shibata, Hideo Notsu, Kazuya Ogino, Kiyoshi Inokuma, Narumi Ohta, Hiromitsu Uehara, Yohei Uemura, Nobuhisa Oyaizu, Tadashi Ohba, Satoru Takakusagi, Kiyotaka Asakura, Ichizo Yagi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 14 8638 - 8641 2015年 [査読有り][通常論文]
     
    A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.
  • Satoru Takakusagi, Takafumi Ogawa, Hiromitsu Uehara, Hiroko Ariga, Ken-ichi Shimizu, Kiyotaka Asakura
    CHEMISTRY LETTERS 43 11 1797 - 1799 2014年11月 [査読有り][通常論文]
     
    Pt was successfully electrodeposited on a Nb-doped TiO2(110) electrode from a solution of 1 mM K-2[PtCl4] and 50 mM H2SO4 using single-pulse chronoamperometry. The morphology of the deposited Pt nanoparticles was sensitive to the deposition potential and holding time. A novel method for the preparation of metal particles on a single-crystal TiO2 surface in a controlled manner has been proposed.
  • Masaaki Yoshida, Takumi Yomogida, Takehiro Mineo, Kiyofumi Nitta, Kazuo Kato, Takuya Masuda, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Tomoya Uruga, Kiyotaka Asakura, Kohei Uosaki, Hiroshi Kondoh
    JOURNAL OF PHYSICAL CHEMISTRY C 118 42 24302 - 24309 2014年10月 [査読有り][通常論文]
     
    Photoexcited hole transfer to MnOx cocatalysts on SrTiO3 photoelectrodes was examined under controlled potential conditions during UV irradiation using in situ Mn K-edge X-ray absorption fine structure (XAFS) spectroscopy. The absorption edges of spectra were found to shift to higher energies during irradiation, indicating that MnOx cocatalysts were oxidized by the migration of photoexcited holes accompanied by a positive potential shift of the MnOx cocatalysts. This oxidation process was promoted by the application of a positive applied potential, suggesting that the photoexcited hole transfer was enhanced by upward band bending at the cocatalystphotoelectrode interface. Structural changes of the MnOx cocatalyst were found to depend on the UV photon intensity; thus, the observations of photoexcited electron transfer by XAFS are associated with the photoelectrochemical activity during water splitting.
  • 鴻野健太郎, 有賀寛子, 高草木達, 大谷茂樹, 朝倉清高
    表面科学 35 8 415 - 419 2014年08月 [査読有り][招待有り]
  • Takahiro Kaito, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    REVIEW OF SCIENTIFIC INSTRUMENTS 85 8 084104  2014年08月 [査読有り][通常論文]
     
    A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge of Pt and Au and those with low absorption-edge energy such as Pt L-edge. (C) 2014 AIP Publishing LLC.
  • Yohei Uemura, Hiromitsu Uehara, Yasuhiro Niwa, Shunsuke Nozawa, Tokushi Sato, Shinichi Adachi, Bunsho Ohtani, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 43 7 977 - 979 2014年07月 [査読有り][通常論文]
     
    The electronic state modification and the decay process of WO3 after photoabsorption were followed using picosecond X-ray absorption fine structure (XAFS) spectroscopy. The W d(e(g)) orbital was filled by transition from the oxygen valence state. The decay process is explained mostly by a first-order process with a rate constant k = 0.5 +/- 0.1 ns(-1). The UV optical length is extremely important to follow the photoreduction process using XAFS spectroscopy.
  • K. Fujikawa, H. Ariga, S. Takakusagi, H. Uehara, T. Ohba, K. Asakura
    e-Journal of Surface Science and Nanotechnology 12 322 - 329 The Surface Science Society of Japan 2014年06月 [査読有り][通常論文]
     
    We have developed a new Reverse Monte Carlo code, called the micro Reverse Monte Carlo (m-RMC), which is applicable to structure analysis of nanomaterials and surface species. In the m-RMC, Reverse Monte Carlo is applied to an ensemble of replica files, each of which contains one molecule or one small cluster, because the Extended X-ray Absorption Fine Structure (EXAFS) is sensitive to short-range structures and has negligible interaction between molecules or clusters. We apply the m-RMC to face-centered cubic metals (Cu, Pd, and Pt) and discuss the advantages, validation, and problems of the m-RMC. The bond distance and some cumulant coefficients can be determined from the EXAFS using m-RMC. Some 50-100 replica files are sufficient to reproduce the EXAFS oscillations and radial distributions. The bond distance can be determined, including the asymmetric distributions,by m-RMC. We also apply m-RMC to α-MoO3 and Au clusters. The m-RMC analysis of MoO3 shows that three radial distribution peaks appear corresponding to three types of Mo–O bonds. The m-RMC analysis of Au cluster indicates the presence of Au55 cuboctahedral structure with Au-Au distance at 0.288 nm. We obtain a 3 D image of Au55 nanocluster from the unified file. The m-RMC method can be applied to the analysis of the EXAFS for chemical systems with appropriate care. [DOI: 10.1380/ejssnt.2014.322]
  • Takahiro Kaito, Hisashi Mitsumoto, Seiho Sugawara, Kazuhiko Shinohara, Hiromitsu Uehara, Hiroko Ariga, Satoru Takakusagi, Yoshikiyo Hatakeyama, Keiko Nishikawa, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 118 16 8481 - 8490 2014年04月 [査読有り][通常論文]
     
    A carbon-supported Pt-shell Au-core electrocatalyst (Pt/Au/C) was prepared by sequential deposition of Pt ions on the surface of Au nanoparticles supported on carbon. The area-specific activity of the oxygen reduction reaction (ORR) for the prepared Pt/Au/C in 0.1 M HClO4, aqueous solution was approximately 2 times higher than that for a commercial carbon-supported Pt electrocatalyst (Pt/C). The core-shell structure was confirmed using electrochemical methods and Pt and Au K-edge X-ray absorption fine structure (XAFS) analysis. XAFS analyses indicated that the Pt-Pt bond distance for the Pt/Au/C catalyst was shorter than that for Pt foil and the Pt/C catalyst. In addition, the Au Au distance was much shorter than that for Au foil. The reason for the high ORR activity of Pt/Au/C is considered to be shorter Pt-Pt bond distance as compared to that of Pt/C.
  • 藤川 圭介, 高草木 達, 朝倉 清高
    表面科学学術講演会要旨集 34 34 - 34 公益社団法人 日本表面科学会 2014年 
    MRMC(Micro Reverse Monte Carlo〕法は，非対称分布を考慮して，XAFSを解析できる手法である．この手法を用いて，AuおよびIナノ粒子の構造解析を行った． 解が一意的であるかということに関して問題はあるものの，熱振動の分布や動径分布関数を求めることができ，ナノ粒子の構造解析に有力な手法となる．
  • 酸化物単結晶上金属ナノ構造の反応特性と制御
    高草木達, 朝倉清高
    触媒誌 56 306  2014年 [査読有り][招待有り]
  • Kenichi Kon, Wataru Onodera, Satoru Takakusagi, Ken-ichi Shimizu
    CATALYSIS SCIENCE & TECHNOLOGY 4 10 3705 - 3712 2014年 [査読有り][通常論文]
     
    Platinum nanoparticles loaded onto various supports have been studied for the selective hydrogenation of lauric acid to n-dodecane. The activity depends on the support material and pre-reduction temperature. Pt/Nb2O5 reduced at 300 degrees C gives the highest activity. Pt/Nb2O5 shows higher activity than various Nb2O5-supported transition metals (Ir, Re, Ru, Pd, Cu, Ni). Under solvent-free conditions Pt/Nb2O5 is effective for the hydrodeoxygenation of lauric, capric, palmitic, myristic, oleic, and stearic acids under 8 bar H-2 at 180-250 degrees C, which gives high yields (88-100%) of linear alkanes with the same chain length as the starting compound. Tristearin is also converted to give 93% yield of n-octadecane. Pt/Nb2O5 shows more than 60 times higher turnover number (TON) than the previously reported catalysts for the hydrogenation of stearic acid to n-octadecane. Mechanistic study shows a consecutive reaction pathway in which lauric acid is hydrogenated to 1-dodecanol, which undergoes esterification with lauric acid as well as hydrogenation to n-dodecane. The ester undergoes hydrogenolysis to give the alcohol, which is hydrogenated to the alkane. Infrared (IR) study of acetic acid adsorption on Nb2O5 indicates that Lewis acid-base interaction of Nb cation and carbonyl oxygen, which suggests a possible role of Nb2O5 as an activation site of carbonyl groups during hydrodeoxygenation.
  • Hiromitsu Uehara, Yohei Uemura, Takafumi Ogawa, Kentaro Kono, Ryoichi Ueno, Yasuhiro Niwa, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 16 27 13748 - 13754 2014年 [査読有り][通常論文]
     
    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.
  • Satoru Takakusagi, Wang-Jae Chun, Hiromitsu Uehara, Kiyotaka Asakura, Yasuhiro Iwasawa
    TOPICS IN CATALYSIS 56 15-17 1477 - 1487 2013年11月 [査読有り][通常論文]
     
    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.
  • 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 570 64 - 69 2013年05月 [査読有り][通常論文]
     
    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.
  • Wang-Jae Chun, Kotaro Miyazaki, Naoki Watanabe, Yuichiro Koike, Satoru Takakusagi, Keisuke Fujikawa, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakura
    JOURNAL OF PHYSICAL CHEMISTRY C 117 1 252 - 257 2013年01月 [査読有り][通常論文]
     
    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.
  • Hiroko Ariga, Mayumi Kawashima, Satoru Takakusagi, Kiyotaka Asakura
    Chemistry Letters 42 12 1481 - 1483 2013年 [査読有り][通常論文]
  • Ying Huang, Hiroko Ariga, Xinlei Zheng, Xinping Duan, Satoru Takakusagi, Kiyotaka Asakura, Youzhu Yuan
    Journal of Catalysis 307 74 - 83 2013年 [査読有り][通常論文]
     
    We present the application of a one-step urea-assisted gelation method to prepare a SiO2-supported bimetallic catalyst composed of copper (Cu) and silver (Ag). Results show the remarkably enhanced performance of the catalyst for selective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). Coupled with a series of characterization and kinetic studies, the improved activity is attributed to the formation of Cu nanoparticles containing Ag nanoclusters on the SiO2 surface. The coherent interactions between the Cu and Ag species help create the active Cu+/Cu 0 species in a suitable proportion and prevent the transmigration of bimetallic nanoparticles during the hydrogenation process. The optimized CuAg/SiO2 catalyst with an Ag/Cu atomic ratio of 0.05 has a balanced Cu+/Cu0 ratio and highly dispersed bimetal particles, which account for its high turnover frequency, EG selectivity of 97.0%, and excellent catalytic stability during the hydrogenation of DMO to EG for longer than 150 h. © 2013 Elsevier Inc. All rights reserved.
  • Satoru Takakusagi, Hirotaka Nojima, Hiroko Ariga, Hiromitsu Uehara, Kotaro Miyazaki, Wang-Jae Chun, Yasuhiro Iwasawa, Kiyotaka Asakura
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 33 14080 - 14088 2013年 [査読有り][通常論文]
     
    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.
  • Masaaki Yoshida, Takumi Yomogida, Takehiro Mineo, Kiyofumi Nitta, Kazuo Kato, Takuya Masuda, Hiroaki Nitani, Hitoshi Abe, Satoru Takakusagi, Tomoya Uruga, Kiyotaka Asakura, Kohei Uosaki, Hiroshi Kondoh
    CHEMICAL COMMUNICATIONS 49 71 7848 - 7850 2013年 [査読有り][通常論文]
     
    The Mn-oxide/Nb:SrTiO3 photoelectrode for oxygen evolution reaction was investigated by in situ Mn K-edge XAFS spectroscopy under UV irradiation. The oxidization of the Mn oxide was observed via photoexcited carrier transfer, which results in the positive potential shift of the Mn oxide cocatalyst toward oxygen evolution reaction.
  • Kiyotaka Asakura, Satoru Takakusagi, Hiroko Ariga, Wang-Jae Chun, Shushi Suzuki, Yuichiro Koike, Hiromitsu Uehara, Kotaro Miyazaki, Yasuhiro Iwasawa
    FARADAY DISCUSSIONS 162 165 - 177 2013年 [査読有り][通常論文]
     
    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.
  • Takahiro Wada, Kyoko K. Bando, S. Ted Oyama, Takeshi Miyamoto, Satoru Takakusagi, Kiyotaka Asakura
    CHEMISTRY LETTERS 41 10 1238 - 1240 2012年10月 [査読有り][通常論文]
     
    In situ X-ray absorption spectroscopy was used to study the effect of H2S pretreatment on the activation of Ni2P catalysts for the thiophene hydrodesulfurization (HDS) reaction. It was found that H2S treatment produced Ni-S bonds that were slightly longer and that had higher coordination numbers than those formed during reaction. The longer Ni-S bonds formed by H2S treatment were changed to the shorter Ni-S bonds by the catalytic reaction, and these shorter bonds were associated with high activity. The work provides evidence that a NiPS phase is active in the HDS reaction.
  • Takahiro Wada, Kyoko K. Bando, Takeshi Miyamoto, Satoru Takakusagi, S. Ted Oyama, Kiyotaka Asakura
    JOURNAL OF SYNCHROTRON RADIATION 19 205 - 209 2012年03月 [査読有り][通常論文]
     
    Structural changes in Ni2P/MCM-41 were followed by quick extended X-ray absorption fine structure (QEXAFS) and were directly related to changes in X-ray absorption near-edge structure (XANES) which had been used earlier for the study of the active catalyst phase. An equation is proposed to correct the transient QEXAFS spectra up to second-order in time to remove spectral distortions induced by structural changes occurring during measurements. A good correlation between the corrected QEXAFS and the XANES spectral changes was found, giving support to the conclusions derived from the XANES in the previous work, namely that the formation of a Ni-S bond in a surface NiPS phase is involved in the active site for the hydrodesulfurization reaction.
  • Kyoko K. Bando, Takahiro Wada, Takeshi Miyamoto, Kotaro Miyazaki, Satoru Takakusagi, Yuichiro Koike, Yasuhiro Inada, Masaharu Nomura, Aritomo Yamaguchi, Travis Gott, S. Ted Oyama, Kiyotaka Asakura
    JOURNAL OF CATALYSIS 286 165 - 171 2012年02月 [査読有り][通常論文]
     
    Supported Ni2P catalysts are active for hydrodesulfurization (HDS) of petroleum feedstocks and have attracted considerable attention. In order to find out the structure of the active catalyst and to obtain insight into the reaction mechanism of thiophene HDS over Ni2P/MCM-41, we conducted a simultaneous time-resolved (STR) study with in situ X-ray absorption fine structure (XAFS) spectroscopy and Fourier transform infrared (FTIR) spectroscopy together with time-resolved product analysis. At 513 K. adsorbed tetrahydrothiophene (THT) was observed by RIR, following the formation of a nickel phosphosulfide phase (NiPS). Detection of the HDS products coincided with the THT formation. All these experimental data indicated that NiPS worked as the active phase and identified THT as a reaction intermediate for the HDS reaction. The STR study proved to be a powerful tool for the precise study of reaction intermediates and the catalytic reaction path. (C) 2011 Elsevier Inc. All rights reserved.
  • Ya-nan Wang, Xinping Duan, Jianwei Zheng, Haiqiang Lin, Youzhu Yuan, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    CATALYSIS SCIENCE & TECHNOLOGY 2 8 1637 - 1639 2012年 [査読有り][通常論文]
     
    The performance of an SBA-15-supported Cu catalyst for hydrogenation of dimethyl oxalate to ethylene glycol is markedly promoted with Au. A key genesis of the high activity of the catalyst is ascribed to the formation of Cu-Au alloy nanoparticles which stabilize the active species and retard their agglomeration during the hydrogenation process.
  • Takuya Masuda, Hitoshi Fukumitsu, Satoru Takakusagi, Wang-Jae Chun, Toshihiro Kondo, Kiyotaka Asakura, Kohei Uosaki
    ADVANCED MATERIALS 24 2 268 - 272 2012年01月 [査読有り][通常論文]
  • 黄 華, 原口 惟, 和田 敬広, 有賀 寛子, 高草木 達, 朝倉 清高
    表面科学学術講演会要旨集 32 113 - 113 公益社団法人 日本表面科学会 2012年 
    電子線リソグラフィー法を用いてSb2O4の線幅や間隔を変化させた不均一規制αーSb2O4/VSbO4 触媒を調製し，プロピレンの部分酸化反応を調べた．アクロレンへの選択性がSb2O4のミクロレベルの構造により変化することを見出した．これをリモートコントロール機構で説明した．
  • 原口惟, 和田敬広, 大南祐介, 松平宣明, 有賀寛子, 高草木達, 朝倉清高
    表面科学 33 8 426 - 430 The Surface Science Society of Japan 2012年 [査読有り][通常論文]
     
    Well-defined inhomogeneous α-Sb2O4/VSbO4 catalysts were prepared using an electron lithography method to investigate the effects of µm order structures on an atomic scale catalytic reaction. X-ray photoelectron spectroscopy (XPS) and laser microscopy revealed that µm order structures were successfully developed on a Si substrate where an α-Sb2O4 micro line with a controlled width was deposited on VSbO4. We carried out a propene partial oxidation reaction on this surface and found that the acrolein formation rate was significantly influenced by the width and interval of the α-Sb2O4 µm line. The results of this study indicate the possibility of controlling the surface reaction by the inhomogeneity of the surface structure in the µm order.
  • Bodong Li, Juan Wang, Youzhu Yuan, Hiroko Ariga, Satoru Takakusagi, Kiyotaka Asakura
    ACS CATALYSIS 1 11 1521 - 1528 2011年11月 [査読有り][通常論文]
     
    Carbon nanotube-supported RuFe bimetallic catalysts (RuFe/CNT) were prepared through a coimpregnation method for the selective hydrogenolysis of 20 wt % glycerol aqueous solution to produce glycols (1,2-propanediol and ethylene glycol). The Ru/CNT catalyst with smaller Ru nanoparticles (NPs) was significantly active for C-C bond cleavage, giving a considerable amount of CH(4) in the hydrogenolysis product. The RuFe/CNT catalyst with bimetallic NPs having an average size similar to Ru/CNT was more efficient for C-O bond cleavage, affording higher selectivity to glycols. Almost 100% glycerol conversion and over 75% selectivity to glycol could be obtained using the optimized RuFe/CNT catalyst under relatively mild conditions. The bimetallic RuFe/CNT catalyst was structurally robust and showed excellent reusability. Transmission electron microscopic images revealed that, when an appropriate amount of Fe entity was added, the RuFe bimetallic NPs were uniformly dispersed on the CNT surfaces and had an average size of similar to 3 nm. X-ray photoelectron spectroscopy indicated that a portion of the Fe species were interacted with Ru moieties, forming Ru-Fe alloys on the Ru domain, whereas other Fe species were in the forms of iron oxides, likely FeO and FeO(1+x) (0 < x < 0.5), mostly presenting on the periphery of RuFe bimetallic NPs. The occurrence of iron oxide species is crucial for the stability of RuFe bimetallic NPs during catalytic runs; but excess iron oxides block the surfaces of RuFe bimetallic NPs, resulting in a decrease in catalytic activity. Higher performance of the RuFe/CNT catalyst is attributed to the synergistic effects of the formation of Ru-Fe alloys and the interactions between the RuFe bimetallic NPs and iron oxides on CNT surfaces.
  • Wang-Jae Chun, Kotaro Miyazaki, Naoki Watanabe, Yuichiro Koike, Satoru Takakusagi, Keisuke Fujikawa, Masaharu Nomura, Kiyotaka Asakura
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 119 1395 890 - 893 2011年11月 [査読有り][通常論文]
     
    The bonding features and three dimensional structures of metal clusters on single crystal oxide surfaces can be determined by the polarization dependent total reflection fluorescence XAFS (PTRF-XAFS) method. K-edge XAFS has a cos(2) theta polarizationdependence to give successfully three dimensional structure while L-3 edge XAFS has a weaker polarization dependence though the L-3 edge is suitable for Au and Pt samples. In order to overcome this issue, we have developed an angle-resolved total reflection fluorescence XAFS (ARTRF-XAFS) method to determine more precise three dimensional structures of Au clusters using the L-3 edge by increase the number of data points. In this paper we described the methodologies of the ARTRF-XAFS and the results of Au clusters on the TiO2(110) surface. (C) 2011 The Ceramic Society of Japan. All rights reserved.
  • Alvin B. Hernandez, Hiroko Ariga, Satoru Takakusagi, Kumiko Kinoshita, Shushi Suzuki, Shigeki Otani, S. Ted Oyama, Kiyotaka Asakura
    CHEMICAL PHYSICS LETTERS 513 1-3 48 - 52 2011年09月 [査読有り][通常論文]
     
    Nickel phosphide (Ni2P) is an emerging catalyst for hydrodesulfurization and other important environment- and energy-related catalytic reactions. To understand its high performance, the surface structure of a Ni2P (0 0 0 1) single crystal surface was investigated using dynamical LEED analysis. The obtained surface structure for Ni2P (0 0 0 1)-1 x 1 is a P-covered Ni3P2 structure (Ni3P_P structure) as opposed to the expected bulk terminated surface structures. This Letter discusses the driving force for the formation of the Ni3P_P surface, which involves the minimization of dangling bonds. (C) 2011 Elsevier B. V. All rights reserved.
  • Motoko Harada, Hidenori Noguchi, Nikolas Zanetakis, Satoru Takakusagi, Wenbo Song, Kohei Uosaki
    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 12 4 44606  2011年08月 [査読有り][通常論文]
     
    Multilayers of gold nanoclusters (GNCs) coated with a thin Pd layer were constructed using GNCs modified with self-assembled monolayers (SAMs) of mercaptoundecanoic acid and a polyallylamine hydrochloride (PAH) multilayer assembly, which has been reported to act as a three-dimensional electrode. SAMs were removed from GNCs by electrochemical anodic decomposition and then a small amount of Pd was electrochemically deposited on the GNCs. The kinetics of the oxygen reduction reaction (ORR) on the Pd modified GNC/PAH multilayer assembly was studied using a rotating disk electrode, and a significant increase in the ORR rate was observed after Pd deposition. Electrocatalytic activities in alkaline and acidic solutions were compared both for the GNC multilayer electrode and Pd modified GNC electrode.
  • Kohei Uosaki, Jun Morita, Tomoko Katsuzaki, Satoru Takakusagi, Kazuhisa Tamura, Masamitu Takahasi, Jun'ichiro Mizuki, Toshihiro Kondo
    JOURNAL OF PHYSICAL CHEMISTRY C 115 25 12471 - 12482 2011年06月 [査読有り][通常論文]
     
    Ag/AgCl reaction at the Ag bilayer, which was under-potentially prepared on a Au(111) surface, was investigated using electrochemical quartz crystal microbalance (EQCM), scanning tunneling microscopy (STM), surface X-ray scattering (SXS), and electrochemical techniques. When the potential was scanned positively from -200 mV, the Cl(-) ion was adsorbed on the Au(111) electrode surface around 0 mV, and then the phase transition of the adsorbed Cl(-) ion layer from random orientation to (root 3 x root 3) structure took place at around +130 mV. The Ag bilayer and Cl(-) ions were oxidatively reacted to form the AgCl monolayer with (root 13 x root 13)R13.9 degrees structure around +200 mV, accompanied with the formation of AgCl monocrystalline clusters on the AgCl monolayer surface. The structure of the AgCl monolayer on the Au(111) surface was changed from (root 13 x root 13)R13.9 degrees structure to (4 x 4) structure around +500 mV. When the potential was scanned back negatively, the AgCl monolayer was electrochemically reduced, and a Ag monolayer, not a bilayer, was formed on the Au(111) surface. In the subsequent potential cycles, the structural change between the Ag monolayer and the AgCl monolayer was reversibly observed. All oxidative structural changes were much slower than the reductive ones.
  • Toshihiro Kondo, Masayo Shibata, Naoko Hayashi, Hitoshi Fukumitsu, Takuya Masuda, Satoru Takakusagi, Kohei Uosaki
    ELECTROCHIMICA ACTA 55 27 8302 - 8306 2010年11月 [査読有り][通常論文]
     
    It is demonstrated that resonance surface X-ray scattering (RSXS) in which incident X-ray energy close to the Pt L(III) absorption edge (11 55 keV) is used is very useful for the determination of the structure of electrodeposited Pt thin layers on a Au(1 1 1) surface This technique was applied to characterize the structure of electrodeposited Pt layers on Au(1 1 1) substrates prepared under two extreme conditions which are known to provide rough and atomically fiat layers Detailed structural information was obtained by RSXS measurements and it was confirmed that the structures of the Pt layers were as reported Pt atoms of the atomically flat monolayer were found to be situated at the threefold hollow cubic closest packing (ccp) sites of the Au(1 1 1)-(1 x 1) surface (C) 2010 Elsevier Ltd All rights reserved
  • Satoru Takakusagi, Ken-ichi Fukui, Ryugo Tero, Kiyotaka Asakura, Yasuhiro Iwasawa
    LANGMUIR 26 21 16392 - 16396 2010年11月 [査読有り][通常論文]
     
    We studied the methanol adsorption behavior of Pt nanoparticles that were vacuum-deposited on a TiO(2)(110) surface at room temperature by using an ultrahigh vacuum (UHV) scanning tunneling microscope (STM). A large number of bright spots were observed on fivefold-coordinated Ti (Ti(5c)) rows of the TiO(2)(110) surface after exposure of the Pt/TiO(2)(110) to methanol vapor. We assigned the bright spots to methoxy species. These were mobile and were found to hop along the Ti(5c) rows. In situ time-resolved STM observations of the formation and migration of the bright spots on the Pt/TiO(2)(110) were carried out in the presence of methanol. The bright spots were produced at the periphery of the Pt nanoparticles and migrated to the substrate Ti(5c) rows. We discuss the spillover process and behavior of the methoxy species on the Pt/TiO(2)(110).
  • 高草木 達
    化学と工業 63 9 741 - 741 2010年09月 [査読無し][通常論文]
  • Donghui Guo, Yuta Nakagawa, Hiroko Ariga, Shushi Suzuki, Kumiko Kinoshita, Takeshi Miyamoto, Satoru Takakusagi, Kiyotaka Asakura, Shigeki Otani, S. Ted Oyama
    SURFACE SCIENCE 604 17-18 1347 - 1352 2010年08月 [査読有り][通常論文]
     
    The surface structure of Ni2P (10 (1) over bar0), a model for highly active hydrodesulfurization catalysts, was studied using scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) in order to understand the reconstruction of the surface layers. Annealing at 573 K revealed a (1 x 1) LEED pattern which changed to a c(2 x 4) arrangement by further heating to 723 K. Atomic scale STM images were obtained for both the (1 x 1) and c(2 x 4) structures. Bright spots observed in the STM images were interpreted to be due to surface phosphorus atoms and this was supported by a density functional theory (INT) simulation. Several possible models for the c(2 x 4) reconstructed structures were proposed including a P-dimer defect model, a missing-row model and a missing-row + added-row model. The last model gave the best explanation for the c(2 x 4) structure. The mechanism for the c(2 x 4) reconstruction on the Ni2P (10 (1) over bar0) surface is discussed. (C) 2010 Elsevier B.V. All rights reserved.
  • S. Ted Oyama, Travis Gott, Kiyotaka Asakura, Satoru Takakusagi, Kotaro Miyazaki, Yuichiro Koike, Kyoko K. Bando
    JOURNAL OF CATALYSIS 268 2 209 - 222 2009年12月 [査読有り][通常論文]
     
    The hydrodesulfurization (HDS) of thiophene was studied over Ni2P/MCM-41 by in situ Fourier transform infrared (FTIR) spectroscopy and X-ray absorption near-edge structure (XANES) measurements at atmospheric pressure and 393-723 K (120-450 degrees C). FTIR showed the presence of adsorbed molecular thiophene principally on the MCM-41 support. In the presence of hydrogen new bands in the aliphatic CH stretching region (2953, 2918, and 2876 cm(-1)) and the CH2 scissoring region (1464 cm(-1)) appeared and grew with temperature up to 553 K (280 degrees C). These were assigned to a tetrahydrothiophene surface intermediate, whose presence is consistent with the high hydrogenation activity of nickel phosphide. XANES measurements between 353 and 573 K (180-300 degrees C) also showed growth of a signal (8330.9 eV) attributed to Ni-S interactions of either the adsorbed tetrahydrothiophene or a surface phosphosulfide. Transient XANES measurements showed that the sulfur species responded dynamically at the same rate as the steady-state rate, indicating that it was associated with an intermediate in the reaction. (c) 2009 Elsevier Inc. All rights reserved.
  • Satoru Takakusagi, Ken Kitamura, Kohei Uosaki
    ELECTROCHIMICA ACTA 54 22 5137 - 5141 2009年09月 [査読有り][通常論文]
     
    Electrochemical deposition of Ag and potential-induced structural change of the deposited Ag layer on a 23 x root 3 reconstructed surface of Au(1 1 1) electrode were followed by in situ scanning tunneling microscope (STM). A uniform Ag monolayer was formed on a reconstructed Au(1 1 1) surface in a 50-mM H(2)SO(4) solution at +0.3 V (vs. Ag/AgCl) after adding a solution containing Ag(2)SO(4) so that the concentration of Ag(+) in the STM cell became ca. 2 mu M. No characteristic height corrugation such as the Au reconstruction was observed on the surface, indicating that the lifting of the substrate Au reconstruction occurred by Ag deposition. The formed Ag monolayer was converted to a net-like shaped Ag nano-pattern of biatomic height when the potential was stepped from +0.3 to -0.2 V in the solution containing 2 mu M Ag(+). This result indicates that the substrate Au(1 1 1)-(1 x 1) surface was converted to the reconstructed surface even in the presence of Ag adlayer. Quite different structure was observed for I'd deposition on a reconstructed surface of Au(1 1 1) electrode at +0.3 V and the origin for this difference between Ag and I'd deposition is discussed. (C) 2009 Elsevier Ltd. All rights reserved
  • Takuya Masuda, Hideo Naohara, Satoru Takakusagi, Pankaj R. Singh, Kohei Uosaki
    CHEMISTRY LETTERS 38 9 884 - 885 2009年09月 [査読有り][通常論文]
     
    Adsorption process and structure of perfluorosulfonated acid (PFSA) polymer on a highly oriented pyrolytic graphite (HOPG) surface were elucidated by an in situ tapping mode atomic force microscope (AFM). Micellar aggregates of PFSA polymers first randomly adsorbed on a bare HOPG surface, and then the adsorbed aggregates extended under the influence of atomic arrangement of HOPG Surface, to form two-dimensionally ordered domains.
  • Toshihiro Kondo, Kazuhisa Tamura, Satoru Takakusagi, Ken Kitamura, Masamitu Takahasi, Jun'ichiro Mizuki, Kohei Uosaki
    JOURNAL OF SOLID STATE ELECTROCHEMISTRY 13 7 1141 - 1145 2009年07月 [査読有り][通常論文]
     
    The interfacial structures of Ag bilayer prepared by underpotential deposition on Au(111) (Ag(2ML)/Au(111)) were determined by ex situ scanning tunneling microscopy and in situ surface X-ray scattering measurements before and after oxidative adsorption and after reductive desorption of a self-assembled monolayer (SAM) of hexanethiol (C(6)SH) in alkaline ethanol solution. While no structural change was observed after oxidative formation of C(6)SH SAM on the Ag(2ML)/Au(111) in an ethanol solution containing 20 mM KOH and 0.1 mM C(6)SH, some of the Ag atoms in the bilayer were stripped when the SAM was reductively desorbed.
  • Toshihiro Kondo, Satoru Takakusagi, Kohei Uosaki
    ELECTROCHEMISTRY COMMUNICATIONS 11 4 804 - 807 2009年04月 [査読有り][通常論文]
     
    Stability of underpotentially deposited (upd) Ag layers on Au(111) surface was investigated by surface X-ray scattering (SXS). While the complete pseudomorphic Ag bilayer on Au(111) surface obtained by upd at 10 mV (vs. Ag/Ag(+)) was maintained its structure even after the circuit was disconnected and the surface was exposed to ambient atmosphere, the pseudomorphic Ag monolayer obtained by upd at 50 mV was converted to a partial bilayer with the coverage of 0.66 and 0.46 ML for the 1st and 2nd layer, respectively. These results show that Ag bilayer is structurally more stable than Ag monolayer on Au(111) and Ag atoms of the upd monolayer move around on the Au(111) surface without potential control. (C) 2009 Elsevier B.V. All rights reserved.
  • Kumiko Kinoshita, Shushi Suzuki, Wang-Jae Chun, Satoru Takakusagi, Kiyotaka Asakura
    SURFACE SCIENCE 603 3 552 - 557 2009年02月 [査読有り][通常論文]
     
    The carboxylic acids are stably adsorbed on TiO2(110) surfaces at room temperature. To demonstrate the neutralization mechanism proposed by Ashima et al. [H. Ashima, W.-J. Chun, K. Asakura, Surf Sci. 601 (2007) 1822.] that explains the stable adsorption of carboxylic acids, we studied the full-coverage adsorption structure of acetic anhydride on a TiO2(110) surface by STM (scanning tunneling microscopy). We directly observed three postulated species on the TiO2(110) surface; normal acetates (termed acetate A) forming a (2 x 1) ordered structure, a minor acetate species (termed acetate B) which was present between the bridging oxygen and the 5-fold Ti, and the oxygen vacancies. We determined the ratio of these three species. This ratio was in good agreement with the postulated conversion reaction of acetate B to A. (C) 2009 Elsevier B.V. All rights reserved.
  • Ambient Pressure(AP) XPSによる触媒表面のin situ評価
    高草木 達
    触媒 51 5 367 - 367 2009年 [査読無し][通常論文]
  • Daniel C. Hennessy, Michael Pierce, Kee-Chul Chang, Satoru Takakusagi, Hoydoo You, Kohei Uosaki
    ELECTROCHIMICA ACTA 53 21 6173 - 6177 2008年09月 [査読有り][通常論文]
     
    We present contact angle measurements of water on single-crystal rutile TiO(2) 0 10) surfaces, exposed to ambient air, or protected in dry air. Our measurements indicate that the surfaces exposed to ambient air are hydrophobic, with a contact angle of theta = 61(5)degrees. However, the well-protected dry surface also exhibits some hydrophobic tendency, with theta = 32(5)degrees. It is known that UV irradiation transforms both surfaces superhydrophilic, with theta=0 degrees IR. Wang, K. Hashimoto, A. Fujishima, M. Chikuni, E. Kojima, A. Kitamura, M. Shimohigoshi, T. Watanabe, Nature 388 (1997) 431-432]. We also present preliminary X-ray crystal truncation rod measurements on the hydrophobic TiO(2) (110) surface, and of the effect of UV illumination on the surface. Published by Elsevier Ltd.
  • Takayuki Michi, Masaaki Abe, Satoru Takakusagi, Masako Kato, Kohei Uosaki, Yoichi Sasaki
    CHEMISTRY LETTERS 37 6 576 - 577 2008年06月 [査読有り][通常論文]
     
    An in situ approach for rapid growth of multilayers of redox-active triruthenium cluster complexes has been developed under electrochemical potential control of the gold electrode, the formation process being successfully probed by cyclic voltammetry and AFM images.
  • Satoru Takakusagi, Ken Kitamura, Kohei Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY C 112 8 3073 - 3077 2008年02月 [査読有り][通常論文]
     
    Electrochemical deposition of Ag on a 23 x root 3 reconstructed surface of Au(111) electrode at various potentials was followed by scanning tunneling microscopy (STM) in situ in real time. At -0.2 V (vs Ag/AgCl), line shaped Ag deposits with the height of 0.46 +/- 0.03 nm, which is equivalent to 2 atomic height, were observed. The center of each Ag line was located in the hcp domain of the reconstructed structure. They then grew two-dimensionally so that the other regions, i.e., bridge and fcc domains, of the reconstructed Au surface were gradually covered with the Ag bilayer. As the deposition proceeded, another Ag layer started to nucleate and grow on the Ag bilayer. This layer was one atomic height and grew not linearly but two-dimensionally from the beginning. At 0.3 V, the monatomic layer of Ag was formed preferentially in the hcp domain and the Ag growth stopped at ca. 1 ML. The potential dependent stabilities of the deposited bi- and mono-atomic Ag layers were confirmed by the potential step measurements. The structural conversion from the bi- to mono-atomic layer of Ag was observed when the potential was stepped from -0.2 to +0.3 V. At 0 V, an intermediate potential, both the bi- and mono-atomic Ag layers were observed at the initial stage of Ag deposition. These results revealed that the biatomic Ag layer was more favored at more negative potentials in the range of -0.2 to +0.3 V. The growth mode of the potentiostatic electrochemical deposition of Ag on the reconstructed Au (111) electrode surface observed in this study is quite different from those previously reported for the electrochemical deposition on the reconstruction-lifted Au(111) electrode surface and deposition under ultrahigh vacuum (UHV) condition on the reconstructed Au(111) surface, showing the importance of structure of substrate surface and electrode potential on the growth mode.
  • 高草木 達, 北村 健, 魚崎 浩平
    表面科学 29 10 621 - 628 日本表面科学会 2008年 [査読無し][通常論文]
  • Kenji Hara, Ryuto Akiyama, Satoru Takakusagi, Kohei Uosaki, Toru Yoshino, Hiroyuki Kagi, Masaya Sawamura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 47 30 5627 - 5630 2008年 [査読有り][通常論文]
  • Kenji Hara, Keiji Iwahashi, Satoru Takakusagi, Kohei Uosaki, Masaya Sawamura
    SURFACE SCIENCE 601 22 5127 - 5132 2007年11月 [査読有り][通常論文]
     
    Functionalization of self-assembled monolayer (SAM) of alkanethiolate with metal containing unit is one of the versatile methods to obtain functional surfaces such as heterogeneous catalysts. However, organic molecules that strongly bind to transition metals at SAM terminal are limited. Recently N-heterocyclic carbenes (NHCs) such as cyclic diaminocarbenes have emerged as strongly a-donating ligands forming a robust bond with broad spectrum of transition metals. In the present study, for the purpose of establishment of a new robust basement for heterogeneous metal catalysts, a SAM of the alkanethiolate terminated with NHC-rhodium(I) complex moiety was prepared by utilizing a newly designed disulfide molecule bearing NHC-metal complex terminals. X-ray photoelectron spectroscopy (XPS) analysis and angle resolved XPS measurement revealed successful formation of the Rh-complex-terminated SAM on a gold substrate. Infrared reflection absorption spectroscopy (IRRAS) analysis suggested that the linker methylene chains connecting the rhodium complex moiety and the gold surface are in a loosely packed structure. This unique chemical species, NHC, would be a promising candidate as a basement for the construction of functional surface. (C) 2007 Elsevier B.V. All rights reserved.
  • Toshihiro Kondo, Jun Morita, Kazuya Hanaoka, Satoru Takakusagi, Kazuhisa Tamura, Masamitu Takahasi, Jun'ichiro Mizuki, Kohei Uosaki
    JOURNAL OF PHYSICAL CHEMISTRY C 111 35 13197 - 13204 2007年09月 [査読有り][通常論文]
     
    Potential-dependent surface structures of Au(111) and Au(100) single-crystal electrodes in a 50 mM H(2)SO(4) solution were investigated at an atomic level using in situ surface X-ray scattering (SXS) techniques. It was confirmed that both the Au(111) and Au(100) surfaces were reconstructed with an attached submonolayer of an oxygen species, most probably water, at 0 V (vs Ag/AgCl). Results at +0.95 V supported a previously suggested model for both the Au(111) and the Au(100) electrodes that, based on infrared and scanning tunneling microscopy measurements, the surfaces were a (1 x 1) structure with the coadsorbed sulfate anion and hydronium cation (H(3)O(+)). At +1.05 V, where a small amount of an anodic current flowed, adsorption of a monolayer of oxygen species was observed on both surfaces. When the single-crystal gold electrodes were electrochemically oxidized at +1.40 V, the expansion of the gold surface by about one monolayer of Au atoms was observed, suggesting the penetration of oxygen into the surface gold layers (i.e., the formation of two layers of surface oxide). When the surface oxide was reduced at +0.65 V, the surface structure returned back to the structure observed at +0.95 V before the oxide formation (i.e., a (1 x 1) structure with coadsorbed sulfate anion and H(3)O(+)). When the potential was reduced to 0 V, the surfaces were reconstructed again but with slightly more random structures than those before the potential cycle.
  • Takakusagi Satoru, Miyasaka Toyomitsu, Uosaki Kohei
    Journal of Electroanalytical Chemistry 599 2 344 - 348 Elsevier 2007年01月15日 [査読有り][通常論文]
     
    Alkyl monolayer (octadecyl) was formed on a hydrogen-terminated Si(1 1 1) (H–Si(1 1 1)) electrode via Si–C covalent bond by photoanodic reaction with C18H37MgCl in THF solution. The formation of the organic monolayer was confirmed by attenuated total reflection (ATR) FT-IR spectroscopy. This process was applied to a one-step patterning of an organic monolayer on a H–Si(1 1 1) by illuminating the H–Si(1 1 1) electrode through photomask in a C18H37MgCl/THF solution at positive potential. The formation of the pattern reflecting the shape of the photomask was confirmed by SEM observations.
  • Kenji Hara, Shinobu Tayama, Hidekazu Kano, Takuya Masuda, Satoru Takakusagi, Toshihiro Kondo, Kohei Uosaki, Masaya Sawamura
    CHEMICAL COMMUNICATIONS 41 4280 - 4282 2007年 [査読有り][通常論文]
     
    A single-crystal silicon surface was modified with a bisoxazoline-Pd molecular layer and utilized as a highly efficient (catalyst turnover number up to 780 000, 110 degrees C, 72 h) and recyclable catalyst in the aerobic oxidation of benzylic alcohols.
  • Satoru Takakusagi, Toyomitsu Miyasaka, Kohei Uosaki
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 599 2 344 - 348 2007年01月 [査読有り][通常論文]
     
    Alkyl monolayer (octadecyl) was formed on a hydrogen-terminated Si(111) (H-Si(111)) electrode via Si-C covalent bond by photoanodic reaction with C18H37MgCl in THF solution. The formation of the organic monolayer was confirmed by attenuated total reflection (ATR) FT-IR spectroscopy. This process was applied to a one-step patterning of an organic monolayer on a H-Si(111) by illuminating the H-Si(111) electrode through photomask in a C18H37MgCI/THF solution at positive potential. The formation of the pattern reflecting the shape of the photomask was confirmed by SEM observations. (c) 2006 Elsevier B.V. All rights reserved.
  • Satoru Takakusagi, Kohei Uosaki
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 45 11 8961 - 8966 2006年11月 [査読有り][通常論文]
     
    We demonstrate that photopatterning of an octadecyl monolayer, which was covalently attached to a Si(I 11) surface via Si-C bond [C18H37-Si(111)], is possible just by irradiating the monolayer surface with UV light (254 nm + 185 nm) in an atmospheric Ar environment through Cu microgrid patterns. The grid patterns were successfully transferred to the surface without detectable damage in the non-irradiated region. The patterned monotayer was further used as a template for metal pattern formation by electroless Cu deposition. The organic monolayer effectively worked as an efficient insulating mask for the electroless deposition of Cu, which was selectively deposited on the UV irradiated region. This approach is simple and convenient for fabricating microstructures of various molecules and metals on a Si surface.
  • Kenji Hara, Keiji Iwahashi, Yoshikazu Kanamori, Satoshi Naito, Satoru Takakusagi, Kohei Uosaki, Masaya Sawamura
    CHEMISTRY LETTERS 35 8 870 - 871 2006年08月 [査読有り][通常論文]
     
    A dimeric N-heterocyclic carbene (NHC)-rhodium(I) complex connected with a long chain dialkyl disulfide linker was synthesized, and used for the preparation of a Rh-modified alkane thiolate monolayer on a gold surface.
  • Y Higashimoto, Y Asanomi, S Takakusagi, MS Lewis, K Uosaki, Durell, SR, CW Anderson, E Appella, K Sakaguchi
    BIOCHEMISTRY 45 6 1608 - 1619 2006年02月 [査読有り][通常論文]
     
    The p53 tumor suppressor is a tetrameric transcriptional enhancer, and its activity is compromised by mutations that cause amino acid substitutions in its tetramerization domain. Here we analyze the biochemical and biophysical properties of peptides corresponding to amino acids 319-358 of wild-type human p53, which includes the tetramerization domain, and that of a cancer-derived mutant with valine substituted for glycine 334. Unlike the wild-type peptide, the G334V peptide forms amyloid fibrils by a two-step process under physiological conditions of temperature and pH. Nevertheless, the G334V peptide is capable of forming heterooligomers with a wild-type peptide. Computational modeling of the G334V peptide structure suggests that substitution of valine for glycine 334 causes a local distortion that contributes to a P-dominated structural transition leading to amyloid formation. Since the distortion is mostly on the surface, the mutant peptide is still able to form a pseudonative tetramer complex at higher concentrations and/or lower temperatures. Our study suggests a new potential mechanism by which mutations that compromise tetramer formation inactivate p53 as a tumor suppressor.
  • 自己組織化単分子層を用いた単一分子の電気伝導測定
    高草木達
    ぶんせき 9 451  2006年 [査読無し][通常論文]
  • ASANOMI Yuya, TAKAKUSAGI Satoru, CHUMAN Yoshiro, KAYA Shunji, IMAGAWA Toshiaki, UOSAKI Kohei, SAKAGUCHI Kazuyasu
    Peptide science : proceedings of the ... Japanese Peptide Symposium 2004 0 313 - 316 2005年03月 [査読無し][通常論文]
  • Yagi, I, T Awatani, T Kondo, K Hanaoka, J Morita, S Takakusagi, K Tamura, M Takahasi, J Mizuki, K Uosaki
    SURFACE OXIDE FILMS 2003 25 143 - 150 2004年 [査読有り][通常論文]
     
    Electrochemical oxide layer formation and reduction processes at single crystalline Au(100) and Au(111) surfaces were investigated by optical second harmonic generation (SHG) and surface X-ray scattering (SXS) techniques. SH signal response under 600 nm excitation wavelength at highly ordered Au(100) and Au(111) single crystalline surfaces were totally different. At the Au(100) electrode, the SH signal under 600 nm excitations increased upon the formation of highly oxidized surface. This response was essentially the same as those at polycrystalline Au electrode surfaces. At the Au(111) electrode, however, the SH signal excited by 600 nm showed essentially no change within the oxide formation/reduction region. On the other hand, the SXS results have indicated that the rate of incorporation of oxygen species into the low-lying Au layers was higher at the Au(100) than at the Au(111) surfaces. These results were explained in terms of the kinetically controlled formations of different kinds of Au oxides at each surface.
  • K Fukui, S Takakusagi, R Tero, M Aizawa, Y Namai, Y Iwasawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 5 24 5349 - 5359 2003年12月 [査読無し][通常論文]
     
    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.
  • S Takakusagi, K Fukui, R Tero, F Nariyuki, Y Iwasawa
    PHYSICAL REVIEW LETTERS 91 6 066102  2003年08月 [査読有り][通常論文]
     
    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.
  • S Takakusagi, K Fukui, F Nariyuki, Y Iwasawa
    SURFACE SCIENCE 523 1-2 L41 - L46 2003年01月 [査読無し][通常論文]
     
    Structures of two kinds of wide strands with different height formed on nonstoichiometric TiO2-x(1 1 0) surfaces are discussed based on atom-resolved STM images. Bright strands, which form linked (1 x 2) structure with single links and cross-links, consist of double strands of Ti2O3 added rows. A structural model of the linked (1 x 2) structure as well as its formation mechanism are discussed. Dark strands (DS) consist of triple strands, whose center row shows unique bias dependency on STM images. A structural model is proposed for the DS. (C) 2002 Elsevier Science B.V. All rights reserved.
  • S Takakusagi, M Kato, Y Sakai, K Fukui, K Asakura, Y Iwasawa
    JOURNAL OF MICROSCOPY-OXFORD 200 3 240 - 250 2000年12月 [査読有り][通常論文]
     
    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.
  • Y Yamaguchi, S Takakusagi, Y Sakai, M Kato, K Asakura, Y Iwasawa
    JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 141 1-3 129 - 137 1999年05月 [査読有り][通常論文]
     
    We have developed a XPEEM (X-ray photoemission electron microscopy) for a new surface imaging. XPEEM is a PEEM using X-ray as an excitation source and installed with an energy filter to select an X-ray photoelectron peak specific to the target atoms. XPEEM can image the distribution of elements, chemical states and chemical species at the working surface in a mesoscopic scale. (C) 1999 Elsevier Science B.V. All rights reserved.
  • 山口良隆, 高草木達, 嘉藤誠, 境悠治, 朝倉清高, 岩澤康裕
    表面科学 19 8 498 - 502 日本表面科学会 1998年08月10日 [査読無し][通常論文]
  • 山口良隆, 朝倉清高, 高草木達, 岩澤康裕
    表面 35 12 621 - 628 広信社 1997年 [査読無し][通常論文]

MISC

書籍等出版物

  • 高草木達 (担当:分担執筆範囲:4-26 走査型トンネル顕微鏡（STM）・原子間力顕微鏡（AFM）)
    朝倉書店 2023年02月 (ISBN: 9784254252743) xiv, 530p, 図版 [4] p
  • Nanoinformatics
    Ichigaku Takigawa, Ken-ichi Shimizu, Koji Tsuda, Satoru Takakusagi (担当:分担執筆範囲:Machine Learning Predictions of Factors Affecting the Activity of Heterogeneous Metal Catalysts)
    Springer Singapore 2018年
  • XAFSの基礎と応用
    高草木 達, 朝倉 清高 (担当:分担執筆範囲:4.7.1 全反射XAFS)
    講談社サイエンテフィク 2017年07月
  • X-ray and Neutron Techniques for Nanomaterials Characterization
    Wang-Jae Chun, Satoru Takakusagi, Yohei Uemura, Kyoko Bando, Kiyotaka Asakura (担当:共著範囲:X-Ray Absorption Fine Structure Analysis of Catalytic Nanomaterials,pp 609-664)
    Springer Berlin Heidelberg 2015年12月
  • 現代界面コロイド科学の事典
    高草木 達 (担当:分担執筆範囲:界面の一分子計測)
    丸善 2010年05月
  • 翻訳 応用界面・コロイド化学ハンドブック
    高草木 達, 魚崎 浩平 (担当:分担執筆範囲:第6章 自己組織化単分子層－金上のアルカンチオール)
    （株）エヌ・ティー・エス 2006年

講演・口頭発表等

  • 単結晶モデル表面を用いた触媒反応プロセスの原子レベル可視化  [招待講演]
    高草木達
    ナノ学会第22回大会 2024年05月 口頭発表（招待・特別）
  • 触媒材料開発における先端計測とマテリアルズ・インフォマティクス：現状と課題  [招待講演]
    高草木達
    NIFS研究会「数理科学・プラズマ科学・物質科学の共通研究拠点形成 」 2024年05月 シンポジウム・ワークショップパネル（指名）
  • 不均一な構造を有する触媒材料における構造・活性相関の評価：単結晶モデル触媒を用いたアプローチ  [招待講演]
    高草木達
    2023年度量子ビームサイエンスフェスタ 2024年03月 口頭発表（招待・特別）
  • 放射光と表面科学を用いた触媒活性点の原子レベル構造解析  [招待講演]
    高草木達
    北海道大学触媒科学研究所・立命館大学SRセンター共催シンポジウム「触媒科学と放射光－Soft～Tender X線の新たな展開」 2024年01月 シンポジウム・ワークショップパネル（指名）
  • Development of synchrotron X-ray and surface science techniques for characterizing plasma catalysis  [招待講演]
    Satoru Takakusagi
    2023 Australia-Japan Symposium on Plasma Catalysis 2023年11月 シンポジウム・ワークショップパネル（指名）
  • Dynamic Behavior of Intermediate Adsorbates to Control Activity and Product Selectivity in Heterogeneous Catalysis: Methanol Decomposition on Pt/TiO2(110)  [招待講演]
    Satoru Takakusagi
    MIRAI 2.0（日本・スウェーデンMIRAIプロジェクト） Research and Innovation Week 2023 Materials Science TEG 2023年11月 口頭発表（招待・特別）
  • 不均一な構造を有する固体触媒の放射光を用いた構造解析：不均一性への挑戦  [招待講演]
    高草木達
    第132回触媒討論会 2023年09月 口頭発表（招待・特別）
  • Atomic-level visualization of surface catalytic reactions by in situ/operando surface science techniques  [招待講演]
    Satoru Takakusagi
    ICAT-FHI Symposium: Approaching to the Catalysis Reality 2023年09月 口頭発表（招待・特別）
  • その場/オペランド表面科学計測による触媒反応の原子レベル可視化  [招待講演]
    高草木達
    第452回触媒科学研究所コロキウム 2023年06月 口頭発表（招待・特別）
  • 圧力ギャップフリー触媒表面科学を目指して：現状と課題  [招待講演]
    高草木達
    触媒科学計測共同研究拠点ミニシンポジウム「超高速データ駆動科学と先端計測技術の融合による触媒科学イノベーション」 2023年03月 シンポジウム・ワークショップパネル（指名）
    ダウンロード
  • オペランド偏光全反射蛍光XAFS法による触媒動作中の活性点三次元構造解析  [招待講演]
    高草木達
    第12 回 岩澤コンファレンス「 サステナブル社会のための触媒化学・表面科学の最前線 」 2023年03月 シンポジウム・ワークショップパネル（指名）
  • 偏光XAFSと単結晶モデル表面を用いた触媒活性点のオペランド三次元構造解析  [招待講演]
    高草木達
    触媒学会界面分子変換研究会ワークショップ『固体触媒の活性構造を知る』 2022年11月 口頭発表（招待・特別）
  • Unraveling 3D structure of active metal sites on catalyst surfaces under working conditions by operando PTRF-XAFS technique  [招待講演]
    Satoru Takakusagi
    MIRAI 2.0（日本・スウェーデンMIRAIプロジェクト） Research and Innovation Week 2022 Materials Science TEG 2022年11月 口頭発表（基調）
  • Elucidation of Precise 3D Structure-Activity Relationship in Heterogeneous Catalysis by Operando PTRF-XAFS Technique  [招待講演]
    Satoru Takakusagi
    IMS-ICAT Joint Symposium: Surface Science for Catalysis 2022年10月 口頭発表（招待・特別）
  • Operando PTRF-XAFS technique for precise 3D structure determination of active metal sites in heterogeneous catalysis  [招待講演]
    Satoru Takakusagi
    ICAT-FHI Symposium: New Dimension of Catalytic Surface Study 2022年09月 口頭発表（招待・特別）
  • Development of operando PTRF-XAFS technique for precise 3D structure determination of active metal sites in heterogeneous catalysis  [招待講演]
    Satoru Takakusagi
    International Symposium on Next Generation Synchrotron Radiation Facility Utilization for Catalysts Characterization as Post Symposium of TOCAT9 2022年07月 口頭発表（基調）
  • Operando PTRF-XAFS technique for elucidating relationship between 3D structure of active metal sites and catalytic properties under working conditions  [招待講演]
    Satoru Takakusagi, Lu Bang, Daiki Kido, Yuta Sato, Kiyotaka Asakura
    The 2021 International Chemical Congress of Pacific Basin Societies (Pacifichem2021) 2021年12月 口頭発表（招待・特別）
  • オペランド偏光全反射蛍光XAFS法の開発による動作中触媒表面の三次元構造解析  [招待講演]
    高草木達
    令和２年度日本表面真空学会東北・北海道支部学術講演会 2021年03月
  • 単結晶モデル表面を用いた触媒反応プロセスの原子レベル可視化  [招待講演]
    高草木達
    2020年度 触媒学会北海道支部 札幌講演会 2020年12月 口頭発表（招待・特別）
  • Atomic-level visualization of surface catalytic reactions by in-situ/operando XAFS and STM  [招待講演]
    Satoru Takakusagi
    International Joint Symposium On-Line: Cutting Edge of Surface Science For Atomic Scale Approach to Catalyst 2020年11月 シンポジウム・ワークショップパネル（指名）
  • Operando PTRF-XAFS technique for elucidating 3D structure-activity relationship in heterogeneous catalysis  [招待講演]
    Satoru Takakusagi, Lu Bang, Daiki Kido, Yuta Sato, Kiyotaka Asakura
    The 2nd Workshop of Reaction Infography / The 3rd IRCCS International Symposium 2020年01月 口頭発表（招待・特別）
  • 高草木達，魯邦，城戸大貴，佐藤優太，朝倉清高,  [招待講演]
    触媒動作中の活性点三次元構造決定のためのオペランド偏光全反射蛍光XAFS法の開発
    PF研究会「XAFS・X線顕微鏡分光分析分野でのIMSS，PF戦略的利用に関する研究会」 2019年12月 口頭発表（招待・特別）
  • Development of operando PTRF-XAFS technique for determining 3D structure of active sites in heterogeneous catalysis  [招待講演]
    Satoru Takakusagi
    Okazaki Conference “Forefront of Measurement Technologies for Surface Chemistry and Physics in Real-Space, k-Space, and Real-Time” 2019年12月 口頭発表（招待・特別）
  • 触媒動作中の活性点立体構造決定のためのオペランド偏光全反射蛍光XAFS法の開発と触媒インフォマティクス  [招待講演]
    高草木 達
    第17回SPring-8ユーザー協同体顕微ナノ材料科学研究会・第14回日本表面科学会放射光表面科学研究部会・第3回プローブ顕微鏡研究部会合同シンポジウム 2019年03月 口頭発表（招待・特別）
  • 偏光全反射蛍光XAFS法を用いた固気及び固液界面における表面金属ナノ構造の三次元構造解析  [招待講演]
    高草木 達
    日本表面真空学会学術講演会 2018年11月 口頭発表（招待・特別）
  • 担持金属モデル触媒表面の原子レベル構造解析と反応計測  [招待講演]
    高草木 達
    第122回触媒討論会 2018年09月 口頭発表（招待・特別）
  • Atomic-level structure and reactivity on well-defined model catalysts surfaces studied by STM and XAFS  [招待講演]
    Satoru Takausagi, Kiyotaka Asakura
    International Symposium on Advancement and Prospect of Catalysis Science & Technology 2018年07月
  • Structure and reactivity on well-defined model catalyst surfaces studied by STM and XAFS  [招待講演]
    Satoru Takakusagi, Kiyotaka Asakura
    Symposium on Nanomaterials for Environmental Purification and Energy Conversion 2018年02月 口頭発表（招待・特別）
  • 酸化物単結晶表面におけるAuナノ構造の原子レベル評価と制御  [招待講演]
    高草木 達, 朝倉 清高
    2017年日本金属学会秋期講演大会 2017年09月
  • Oxygen plasma treatment of ligand-protected Au clusters on TiO2(110) :unusual loading-dependence of Au nanoparticle size  [招待講演]
    S. Takakusagi, K. Asakura
    International Symposium on Pure and Applied Chemistry (ISPAC) 2017 2017年06月
  • Single metal dispersion on an oxide single crystal surface: effect of premodification with a mercapto compound on metal dispersion  [招待講演]
    S. Takakusagi, K.Asakura
    International Symposium on Pure and Applied Chemistry (ISPAC) 2016 2016年08月 口頭発表（招待・特別）
  • 3D structure analysis of atomically dispersed metal species on an oxide single crystal surface by polarization-dependent total-reflection fluorescence XAFS  [招待講演]
    Satoru Takakusagi
    The 74th Okazaki Conference “Frontier of X-ray Absorption Spectroscopy and Molecular Science” 2015年02月 口頭発表（招待・特別）
  • 3D structural determination of atomically dispersed metals on a TiO2(110) surface premodified with functional organic molecules  [招待講演]
    S. Takakusagi, H. Nojima, H. Ariga, H. Uehara, K. Miyazaki, W.-J. Chun, Y. Iwasawa, K. Asakura
    Vietnam Malaysia International Chemical Congress (VMICC) 2014 2014年11月 口頭発表（招待・特別）
  • 酸化物単結晶上金属ナノ構造の反応特性と構造制御  [招待講演]
    高草木 達
    2014年日本金属学会秋期講演大会 2014年09月 口頭発表（招待・特別）
  • Preparation and 3D structure analysis of atomically dispersed metal species on a TiO2(110) single crystal surface premodified with functional organic molecules  [招待講演]
    Satoru Takakusagi
    The 6th IEEE International Nanoelectronics Conference (IEEE INEC 2014) 2014年06月 口頭発表（招待・特別）
  • 酸化物単結晶表面上に高分散した金属種の構造と反応特性  [招待講演]
    高草木 達
    日本表面科学会触媒表面科学研究部会ワークショップ「表面化学の新展開」 2014年03月 口頭発表（招待・特別）
  • Dynamic Behavior of Intermediate Adsorbates to Control Activity and Product Selectivity in Heterogeneous Catalysis: Methanol Decomposition on Pt/TiO2(110)  [招待講演]
    Satoru Takakusagi
    MIRAI 2.0（日本・スウェーデンMIRAIプロジェクト） Research and Innovation Week 2023 Materials Science TEG 2023 2013年11月 口頭発表（招待・特別）
  • Preparation of monomeric metal species on a TiO2 single crystal surface premodified with with functional organic molecules  [招待講演]
    Satoru Takakusagi, Hirotaka Nojima, Kotaro Miyazaki, Takahiro Wada, Hiroko Ariga, Wang-Jae Chun, Masaharu Nomura, Yasuhiro Iwasawa, Kiyotaka Asakua
    17th Malaysian Chemical Congress (17 MCC) 2012年10月 口頭発表（招待・特別）
  • Atomically Dispersed Metal Species Formed on TiO2(110) Surfaces Premodified with Functional Organic Molecules  [招待講演]
    TAKAKUSAGI Satoru
    CRC-FHI Joint Meeting“Complex Surfaces in Material Science” 2012年09月 シンポジウム・ワークショップパネル（指名）
  • Formation of Atomically Dispersed Cu on a TiO2(110) Surface Precovered with Functional Organic  [招待講演]
    S. Takakusagi, H. Nojima, K. Miyazaki, T. Wada, H. Ariga, W.-J. Chun, M. Nomura, Y. Iwasawa, K. Asakura
    International Symposium and the Third Iwasawa Conference on Catalysis and Surface Science for Utilization of Carbon Resources and Related Topoics 2011年12月 シンポジウム・ワークショップパネル（指名）
  • Direct STM Visualization of Spillover Adsorbates on a Pt/TiO2(110) surface  [招待講演]
    Satoru Takakusagi, Ken-ichi Fukui, Kiyotaka Asakua, Yasuhiro Iwasawa
    14th Asian Chemical Congress 2011 (14 ACC) 2011年09月 口頭発表（招待・特別）
  • In-situ STM Observation of Spillover Process on a Pt/TiO2(110) Model Catalyst Surface  [招待講演]
    TAKAKUSAGI Satoru
    The Third Joint Symposium of CRC-Hokkaido Univ. and Xiarmen Univ. 2011年04月 シンポジウム・ワークショップパネル（指名）
  • 酸化物表面上金属ナノ構造の機能性有機分子による構造制御  [招待講演]
    高草木 達
    第6回放射光表面科学部会顕微ナノ材料科学研究会合同シンポジウム 2010年12月 シンポジウム・ワークショップパネル（指名）
  • 偏光全反射蛍光XAFS 法による固体表面上に形成した金属ナノ構造の精密解析  [招待講演]
    高草木 達, 朝倉 清高
    筑波大学-KEK第三回連携ミニ研究会-XAFSと機能性物質 2009年12月 シンポジウム・ワークショップパネル（指名）

担当経験のある科目（授業）

  • 表面量子ナノ材料科学・解析科学北海道大学
  • 化学購読（物理化学演習）北海道大学
  • 化学実験Ⅲ（物理化学実験）北海道大学
  • テクニカルイングリッシュI, II北海道大学
  • 触媒化学のフロンティア北海道大学
  • 物理化学北海道大学

所属学協会

  • 触媒学会   電気化学会   日本表面真空学会   日本化学会   日本XAFS研究会   アメリカ化学会   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2024年04月 -2027年03月 
    代表者 : 高草木 達
  • 科学技術振興機構（JST）：戦略的創造研究推進事業（CREST）
    研究期間 : 2019年10月 -2025年03月 
    代表者 : 野崎 智洋
  • 活性点立体構造と表面吸着種のオペランド複合計測による触媒反応機構の原子レベル解明
    日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 高草木 達
  • オペランド偏光全反射蛍光XAFS法の開発による触媒動作中の活性点三次元構造解析
    日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 高草木 達
     
    本年度は、まず、昨年度設計・製作を行ったオペランド偏光全反射蛍光XAFS装置の性能向上及び最適化に向けた試みを行った。真空度改善のため、真空排気ラインのコンダクタンスを大きくするとともに、排気に使用しているターボ分子ポンプを、より排気速度の大きいポンプへと変更した。こうした試みにより、真空度は2桁程度改善した。また、装置に取付けられている蛍光取り出し用のBe窓（ICF70規格のフランジ中央部にBe薄膜をろう付け）の有効径を可能な限り大きくし、試料と半導体検出器（19素子solid state detector）との距離及び立体角の最適化を行うことで、スペクトルのS/N比向上を実現した。 続いて、アルミナ単結晶表面上に白金ナノ粒子を担持したモデル触媒表面（Pt/α-Al2O3(0001)）でのCO酸化反応中のPt活性点電子状態及び3次元構造について、昨年度得られた結果の再現性もかねて、再度オペランド偏光全反射蛍光XAFS測定（Pt L3吸収端）を行った。反応ガス（CO、O2及び濃度補正用Arを含む混合ガス）雰囲気下で試料を加熱し、各温度で反応進行状況を確認しながらXANES測定を行ったところ、温度の上昇に伴ってスペクトルのwhite line強度は減少した。このことは温度上昇により、Ptが徐々に還元されたことを示している。活性は>473 Kで顕著になることがわかった。さらに、493 KでCO酸化反応が進行中のEXAFS測定にも成功し、スペクトルは三次元構造解析に十分なS/N比であった。予備的な解析から1 nm程度のナノ粒子が活性点であることを見出し、FEFFコードを用いた三次元構造決定を開始した。
  • 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)
    研究期間 : 2013年06月 -2018年03月 
    代表者 : 高草木 達, 原 賢二, 清水 研一, 松本 祐司, 瀧川 一学
     
    本研究では、表面金属ナノクラスター触媒（酸化物担持金属触媒）と固定化金属錯体触媒を用いた環境浄化及びグリーン有機合成反応をターゲットとし、単結晶モデル表面を始めとした規整ナノ反応場の原子レベル構造評価と実触媒の開発を並行して行った。担持金属触媒では、特に金属/酸化物界面に形成される特異なナノ構造による分子活性化に着目し、固定化金属錯体触媒では錯体の空間的配列や配向などの局所構造が触媒活性に与える影響を検討した。また、情報学的手法を用いた新規触媒物質の高速かつ高精度探索法の開拓を行った。
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2011年 -2013年 
    代表者 : 高草木 達, 角山 寛規, 朝倉 清高, 有賀 寛子
     
    実用上重要な酸化物担持金属触媒の特性（活性・選択性）は、金属クラスターのサイズや酸化物担体担体との相互作用に強く依存する。本研究では、単原子から10 nmまでのサイズの金クラスターを、サイズ分布の小さな状態で二酸化チタン単結晶表面へ担持するための方法論の開発を試み、担持後のクラスターに関してSTM/AFMや偏光全反射蛍光XAFS等の表面科学的手法を適用して、原子レベルの構造評価を行った。また構造と活性の相関を得るために、単結晶表面での触媒反応測定のための超高真空装置を開発した。

産業財産権

  • 有機単分子層の形成方法および機能素子の製造方法
    2004-319487
  • 分子デバイスとその製造方法
    2003-309431

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