藤村 樹 (フジムラ タツキ)

写真a

所属

研究院(研究機関) ナノ・ライフ創新研究機構

職名

次席研究員(研究院講師)

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  • 2016年04月
    -
    2021年03月

    早稲田大学   大学院先進理工学研究科   先進理工学専攻  

学位 【 表示 / 非表示

  • 2021年03月   早稲田大学   博士(工学)

所属学協会 【 表示 / 非表示

  • 2016年03月
    -
    継続中

    電気化学会

 

研究分野 【 表示 / 非表示

  • 複合材料、界面

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  • Direct formation of metal layer on anion exchange membrane using electroless deposition process

    Tatsuki Fujimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Hiroshi Ito, Takayuki Homma

    Electrochemistry   89 ( 2 ) 192 - 196  2021年03月

     概要を見る

    In this work, a novel electroless deposition process on the anion exchange membrane (AEM) is proposed. AEM surface has a positively charged functional group, which in general does not allow the catalyst particle, such as Pd, to be formed on the surface. Hence, a different strategy from the conventional catalyzation process was required. We found that the sensitization process using Sn-containing solution, which is widely applied in the electroless plating on nonconductive substrates, hindered the Pd particle modification, which hence inhibited the following deposition reaction. Our several experiments and density functional theory analyses suggest that for Pd particle modification, anion in the bath turned out to play a key role. In particular, Cl provides the sufficiently strong connection between the precursor Pd and positive functional group of the substrate. This leads to favorable deposition of Pd catalyst particles and metal layer formation on the AEM. Therefore, we conclude that just a single pre-treatment to immerse the AEM films into PdCl /HCl solution is capable to perform electroless plating on it. We applied the novel process to the electrode formation, such as Pt and Ni-P, on the AEM for hydrogen evolution reaction (HER) as a case study. Both Pt and Ni-P was successfully formed on the AEM. The electrochemical measurements show that those electrodes are able to serve as the catalytic electrode for HER. The electroless process proposed here opens possibility of the direct metal fabrication on ion exchange membrane surface. − 2+ 2

    DOI

  • Analysis of the hydrogen evolution reaction at Ni micro-patterned electrodes

    Tatsuki Fujimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Takayuki Homma

    Electrochimica Acta   368  2021年02月

     概要を見る

    The behavior of bubbles generated by the hydrogen evolution reaction (HER) and the effect of these bubbles on HER performance were investigated using Ni micro-patterned electrodes. This study focused on the correlation between bubble behaviors affecting potential increase of HER and the surface microstructures of micro-patterned Ni cathode. Ni microdot array structures with diameters of approximately 5–10 μm, pitch of approximately 5–10 μm, and various dot heights were fabricated for alkaline water electrolysis measurements. The Ni micro-patterned structures controlled the surface wettability of the electrode. The change in the wettability influenced the HER efficiency during galvanostatic electrolysis at –20 mA cm . Moreover, in situ observation of the evolved bubbles on the electrode surface revealed that bubbles with larger diameters evolved on the electrode surface with lower wettability, and bubbles tended to detach from the electrode surface by decreasing the contact area between the bubbles and the electrode. It was also observed that bubbles evolved more easily on the sidewall of Ni microdots and that generated bubbles moved onto the surface of the microdots in high-aspect Ni micro-patterned electrodes, indicating that an increase in the overpotential can be suppressed by different bubble nucleation behaviors. Therefore, the micro-patterned surface texture affected the bubble nucleation and growth behaviors, which would suppress the decrease in HER efficiency. These results can provide insights for fabricating highly efficient surfaces for HER catalytic electrodes. –2

    DOI

  • Analysis of the effect of surface wettability on hydrogen evolution reaction in water electrolysis using micro-patterned electrodes

    Tatsuki Fujimura, Wakana Hikima, Yasuhiro Fukunaka, Takayuki Homma

    Electrochemistry Communications   101   43 - 46  2019年04月

     概要を見る

    The hydrogen evolution reaction (HER) was investigated using Ni catalytic electrodes with micro-patterned surfaces. The present aim was to correlate HER efficiency with the surface wettability of Ni cathodes produced with different micropatterns. Regular Ni microdot arrays, 5–10 μm in diameter, 5–10 μm in pitch were fabricated on a 7 mm diameter Cu substrate and tested in alkaline water electrolysis (AWE) experiments. Using electrodes of this design, it may be possible to relate the electrochemical reaction kinetics to the electrolyte wettability localized to the microdot surface area. The surface microstructures of the electrode considerably influenced the reaction efficiency of the HER during alkaline water electrolysis at −20 mA cm . Furthermore, in situ video observations of the electrode surface during the HER revealed that the bubble size increased when the surface wettability of the electrodes was decreased. That is, the surface texture (micro-patterns) affected the HER efficiency by influencing bubble evolution and aggregation behavior. This observation may aid in the design of highly efficient HER catalytic electrodes. −2

    DOI

  • Experimental measurement of overpotential sources during anodic gas evolution in aqueous and molten salt systems

    Brian Chmielowiec, Tatsuki Fujimura, Tomohiro Otani, Kiego Aoyama, Toshiyuki Nohira, Takayuki Homma, Yasuhiro Fukunaka, Antoine Allanore

    Journal of the Electrochemical Society   166 ( 10 ) E323 - E329  2019年

     概要を見る

    Current interrupt and galvanostatic EIS techniques were utilized in a complementary fashion to characterize the different sources of overpotential during anodic gas evolution. Room temperature anodic evolution of oxygen at a nickel working electrode in aqueous potassium hydroxide and the high temperature (348°C) anodic evolution of chlorine at a glassy carbon working electrode in molten (LiCl) -(KCl)13.3-(CsCl) where investigatd. Combining of the two techniques enables to separate the total measured overpotential into its ohmic, charge transfer, and mass transfer components. Potential decay curves indicated that natural convection (due to both bubble evolution and density driven flow) was a major driving force in reestablishing equilibrium conditions at the working electrode surface. During oxygen evolution, charge transfer resistance dominated the total overpotential at low current densities, but as the current density approached ∼100mA/cm , mass transfer overpotentials and ohmic overpotential became non-negligible. The mass transfer overpotential during chlorine evolution was found to be half that found during oxygen evolution. 57.5 29.2 2

    DOI

  • Analysis of cathodic reaction process of SiCl<inf>4</inf> during Si electrodeposition in ionic liquids

    Yasuhiro Tsuyuki, Tatsuki Fujimura, Masahiro Kunimoto, Yasuhiro Fukunaka, Piero Pianetta, Takayuki Homma

    Journal of the Electrochemical Society   164 ( 14 ) D994 - D998  2017年

     概要を見る

    Elementary steps in the electrochemical reduction process of SiCl in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) was investigated, focusing on molecular level behavior of the reactants at solid-liquid interface. Electrochemical measurements using an electrochemical quartz crystal microbalance (EQCM) identified a reduction peak corresponding to Si electrodeposition and several elementary steps with stable intermediates forming prior to the deposition. For detailed analysis, X-ray reflectivity (XRR) measurements with synchrotron radiation were applied in situ. The change in reflectivity of the electrode surface during the deposition was found to be due to the formation of a polymer-like Si such as Si Cl , which is an intermediate layer during the deposition process. These results were theoretically supported by density functional theory (DFT) calculations: after an electron transfers from the electrode, the Si in SiCl forms the bond with another SiCl , rather than the Si of the substrate, resulting in the formation of the intermediate structure. These data suggest an elementary step in the SiCl reduction process which can be described as follows; when SiCl is reduced, a polymer-like Si form such as Si Cl is generated. This intermediate species further reacts with other Si reactants after receiving additional electrons, which then finally deposits as Si on the substrate. 4 2 6 4 4 4 4 2 6

    DOI