Memoirs of the SR Center Ritsumeikan University
Online ISSN : 2435-7634
Print ISSN : 1345-1650
Volume 21
Showing 1-7 articles out of 7 articles from the selected issue
  • Naoki Takada, Tomoki Uchiyama, Yoshiharu Uchimoto, Hirona Yamagishi, T ...
    2019 Volume 21 Pages 3-5
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    Water electrolysis system for hydrogen production utilizing renewable energy is required to operate stably over a long period and in unstable energy supplying condition. Analysis of degradation mechanism of catalysis under electrochemical potential cycling will be useful for stable operation of water electrolysis. In this study, soft X-ray absorption spectroscopy (XAS) was utilized for the analysis of nickel catalyst used in a conventional alkaline water electrolysis system. Ni L-edge and O K-edge XAS were measured for the initial and electrochemical cycled nickel metal. In the initial state, the nickel(Ⅱ) oxide phase was present on the nickel metal surface. The electrochemical cycling caused the formation of nickel(Ⅲ) oxyhydroxide on the surface of the nickel metal. It was shown that the degradation mechanism can be analyzed at various depths by using XAS method for the catalyst of water electrolysis.
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  • Shintaro Tachibana, Hirona Yamagishi, Yuki Orikasa
    2019 Volume 21 Pages 7-9
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    Materials using multiple anion compounds are expected to be a new direction for realizing functional materials. In this study, compounds using fluoride and sulfide ions as anions were synthesized, and the electronic structures were analyzed by F K-edge and O K-edge X-ray absorption spectra. The analytical results of the spectra with the total electron yield mode providing the surface information and the fluorescence mode providing the bulk information show the difficulty for the removal of oxygen sources contained in the starting material during the synthesis process and uniformly distribution internally by a calcination process.
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  • Yuki Orikasa, Junya Furutani, Keisuke Yamanaka, Toshiaki Ohta
    2019 Volume 21 Pages 11-14
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    Cathode materials for lithium-ion batteries utilize oxidation/reduction reaction of metal-ion for charge storage. However, little analysis of the electronic state of lithium carrier ions has been performed. This is because there are not many methods for observing the light element lithium, and some surface films on active materials deposited after charging and discharging make the analysis of bulk structure difficult. In this study, the electronic structure change of lithium was analyzed by soft X-ray absorption spectroscopy which can directly observe the electronic state of lithium. To prevent the surface film formation, lithium was chemically extracted from LiCoO2, LiMn2O4, Li1.2Ni0.13Co0.13Mn0.53O2 of representative electrode materials.
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  • Shinji Okamoto, Yusaku Yamamoto, Hirokazu Kitazawa, Misaki Katayama, Y ...
    2019 Volume 21 Pages 15-18
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    The effect of the calcination and reduction treatment on the chemical state of the Ni species supported on TiO2 was revealed by the XRD and XAFS method. The TiO2-supported Ni catalyst calcined at various temperatures was characterized by the XRD measurements. It is revealed that the NiO species was incorporated into TiO2 support as the species of NiTiO3, when the calcination temperature was higher than 600 °C. The chemical state conversion of the Ni species during the temperature programmed reduction process was investigated by in situ XAFS measurements. The reduction of NiTiO3 proceeded below 700 °C, and the metallic Ni(0) species was generated on TiO2. The reduction temperature was higher than that of NiO on TiO2.
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  • Shunsuke Osaka, Yusaku Yamamoto, Hirokazu Kitazawa, Misaki Katayama, Y ...
    2019 Volume 21 Pages 19-22
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    The chemical state conversion of the Ni species supported on SiO2 has been analyzed by in situ XAFS measurements. The composition change by the gas switch from H2 to O2 for the partially reduced NiO particles indicates that the metallic Ni(0) species exists at both the particle surface and the inner core. In addition, the analysis on the reduction property suggests that the oxidized Ni species is located at the adjacent place to the metallic Ni(0) species. It is concluded that the metallic Ni(0) and NiO species are heterogeneously distributed in the Ni particle under the reaction condition. The reduction of the NiO particle was initiated at the highly reactive spots and was expanded peripherally. This study achieved to find out the detailed reduction mechanism of the NiO particle supported on SiO2.
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  • Takuya Tsuji, Yusaku Yamamoto, Hirona Yamagishi, Misaki Katayama, Yasu ...
    2019 Volume 21 Pages 23-26
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    Conversion reaction for NiO nanoparticles supported on acetylene black (AB) was analyzed using an in situ XAFS technique. The NiO particle supported on AB was synthesized by the impregnation method. For the first discharge process for a test cell of an NiO/AB cathode with a Li anode, it was revealed that the reactions of the Ni species proceeded at two different potentials. This indicates that the reactions in the surface layer and the bulk of the NiO particle have different reduction potentials. In addition, it was clarified that the Ni particles became smaller after the first discharge process and the fine size was kept in the following cycles.
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  • Misaki Katayama, Yasuhiro Inada
    2019 Volume 21 Pages 27-30
    Published: 2019
    Released: October 22, 2020
    JOURNALS FREE ACCESS
    Three geometrical factors, a tilt angle of the first crystal, an offset distance of the crystal surface, and a tilt angle of the horizontal guide rail, cause the drift of the exit beam height of the monochromatic X-ray for the Golovchenko-type monochromator. We have formulated the geometrical factors and established the technique to adjust the alignment of the monochromator to restrain the beam drift.
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