「作れない」はずの合金材料を合成—CO₂を資源に変える新触媒の可能性

2026-07-02 東京都立大学

図1.電気化学的な非平衡構造再編成を利用した準安定な金属間化合物CuIn₂を含むナノ粒子の合成。相図は、物質・材料研究機構（NIMS）のデータ中核拠点が提供するMatNaviから、Okamoto, H.; Massalski, T. Binary Alloy Phase Diagrams; ASM 617 International :1990; Vol. 12 , pp 3528−3531.に記載のデータを用いた図を引用。

＜関連情報＞

• https://www.tmu.ac.jp/news/topics/38734.html
• https://pubs.acs.org/doi/10.1021/acs.jpclett.6c01116

選択的CO2還元のためのCu-In金属間化合物ナノ粒子の非平衡電気化学合成 Nonequilibrium Electrochemical Synthesis of Cu–In Intermetallic Compound Nanoparticles for Selective CO2 Reduction

Soichi Kikkawa,Tatsuya Koubayashi,Toshiaki Oka,Ray Miyazaki,Jun-ya Hasegawa,Hideyuki Kawasoko,and Seiji Yamazoe
The Journal of Physical Chemistry Letters  Published June 30, 2026
DOI:https://doi.org/10.1021/acs.jpclett.6c01116

Abstract

An In-rich Cu–In intermetallic compound (IMC), CuIn₂, was accessed through an electrochemical nonequilibrium pathway and obtained as bulk Cu₂In core/CuIn₂ shell nanoparticles. CuIn₂ is thermodynamically metastable in the Cu–In binary phase diagram and has previously been observed only at Cu/In interfaces in sputtered thin films. Here, electrochemical reduction of a mixed metal oxide precursor (Cu₂In₂O₅) under aqueous CO₂ reduction conditions enables the formation of a metastable CuIn₂ shell encapsulating a Cu₂In core. The resulting biphasic IMC particles exhibit characteristic CO₂ reduction selectivity with strongly suppressed competing H₂ evolution. Density functional theory calculations suggested that CO adsorption at Cu bridge sites on the In-rich CuIn₂(121) surface competitively inhibits H adsorption, which may contribute to the suppressed H₂ evolution. This work demonstrates a nonequilibrium electrochemical route for accessing metastable IMC phase through oxygen-elimination-induced restructuring of a mixed metal oxide precursor.