[Title] "Nonequilibrium Electrochemical Synthesis of Cu–In Intermetallic Compound Nanoparticles for Selective CO2 Reduction"
[Authors] S. Kikkawa, T. Koubayashi, T. Oka, R. Miyazaki, J. Hasegawa, H. Kawasoko, S. Yamazoe
[Journal] J. Phys. Chem. Lett. 17, 8000–8007 (2026)
[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.