Nonequilibrium Electrochemical Synthesis of Cu–In Intermetallic Compound Nanoparticles for Selective CO ₂ Reduction

High Resolution Image Download MS PowerPoint Slide An In-rich Cu–In intermetallic compound (IMC), CuIn 2, was accessed through an electrochemical nonequilibrium pathway and obtained as bulk Cu 2 In core/CuIn 2 shell nanoparticles. CuIn 2 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 (Cu 2 In 2 O 5 ) under aqueous CO 2 reduction conditions enables the formation of a metastable CuIn 2 shell encapsulating a Cu 2 In core. The resulting biphasic IMC particles exhibit characteristic CO 2 reduction selectivity with strongly suppressed competing H 2 evolution. Density functional theory calculations suggested that CO adsorption at Cu bridge sites on the In-rich CuIn 2 (121) surface competitively inhibits H adsorption, which may contribute to the suppressed H 2 evolution. This work demonstrates a nonequilibrium electrochemical route for accessing metastable IMC phase through oxygen-elimination-induced restructuring of a mixed metal oxide precursor.