yrammuS 要概片山 祐41Yu KATAYAMA山田 幾也超高圧合成法を活用した新しい蓄熱材料の創製42Ikuya YAMADAナノ空間での反応中間体吸着形態の制御による高選択的二酸化炭素電解触媒の創成(2021採択)Highly selective electrocatalyst for carbon dioxide conversion: precise tuning of the adsorption morphology of reaction intermediates in confined space (Project 2021)(2021採択)High-pressure synthesis of novel thermal-storage materials(Project 2021)43Rep. Grant. Res., Asahi Glass Foundation (2022)二酸化炭素削減が地球規模の課題となっている．これまで，電気化学的に二酸化炭素を資源化するプロセスの研究開発は盛んに行われてきたが，その低い反応選択性が実用化を阻んでいる．私たちはこれまでに，オペランド分光測定により複雑な二酸化炭素電解反応プロセスを可視化してきた．その中で，従来から知られていた反応中間体の吸着強度に加えて，反応中間体の吸着形態が反応選択性に大きな影響を与えることを明らかにした．しかしながら，現時点で反応中間体の吸着形態を有意に制御する方法は存在しない．そこで本研究では，二酸化炭素電解プロセス反応中間体の吸着形態を均一に制御する方法を確立し，その反応経路をコントロールすることで，高選択的な二酸化炭素電解触媒の開発を目指した．The past few decades of research have focused on developing the electrochemical process for recycling car-bon dioxide, but their low reaction selectivity hinders their practical application. We have visualized a com-plex reaction pathway for carbon dioxide electrolysis by the operando spectroscopic technique. We success-fully clarified that the adsorption morphology of the reaction intermediate has a significant influence on the reaction selectivity in addition to the adsorption strength of the reaction intermediate, which has been known for a while. However, there is no method for effectively controlling the adsorption morphology of the reac-tion intermediates. Therefore, in this study, we aimed to develop a highly selective carbon dioxide electrocat-alyst by establishing a method to control the adsorption morphology of the reaction intermediates, enabling the precise control of the reaction pathway for carbon dioxide electrolysis.本研究では，四重ペロブスカイト酸化物 ACu3Fe4O12 （A: アルカリ土類金属，希土類金属）とその関連化合物を対象とした材料探索を行い，結晶構造・電子状態・蓄熱性能等の評価を行った．既存のACu3Fe4O12化合物の微量元素置換によって蓄熱特性を劇的に向上させるのは困難であることが明らかになった一方，超高圧条件で新物質CeMn3Rh4O12を合成することに成功し，室温以下で低対称相への構造相転移が生じることが明らかになった．また，CaCu3Fe4O12におけるFeの一部をMnで置換したCaCu3Fe4-xMnxO12を合成し，室温以下において負の熱膨張が生じることが明らかになった．In this study, the crystal structure, electronic structure, and thermal storage properties were evaluated for the quadruple perovskite oxides ACu3Fe4O12 and related materials, which exhibit structural and electronic phase transitions with large latent heats. Although it was difficult to achieve dramatic improvement on the heat stor-age properties by chemical substitution in the known ACu3Fe4O12, a new compound CeMn3Rh4O12 was successfully synthesized under ultrahigh pressure conditions. CeMn3Rh4O12 exhibited structural phase tran-sition to a low-symmetry phase below room temperature. In addition, the Mn-doped oxide CaCu3Fe4-xMnxO12 was found to display negative and zero thermal expansion near room temperature.
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