Probing the Roles of Indium Oxides on Copper Catalysts for Enhanced Selectivity during CO2‑to-CO Electrochemical Reduction

The electrochemical CO2 reduction reaction (CO2RR) provides an alternative protocol to producing industrial chemicals with renewable electricity sources, and the highly selective, durable, and economic catalysts should expedite CO2RR applications. Here, we demonstrate a composite Cu–In2O3 catalyst in which a trace amount of In2O3 decorated on Cu surface greatly improves the selectivity and stability for CO2-to-CO reduction as compared to the counterparts (Cu or In2O3), realizing a CO faradaic efficiency (FECO) of 95% at −0.7 V (vs RHE) and no obvious degradation within 7 h. In situ X-ray absorption spectroscopy reveals that In2O3 undergoes the redox reaction and preserves the metallic state of Cu during the CO2RR process. Strong electronic interaction and coupling occur at the Cu/In2O3 interface which serves as the active site for selective CO2RR. Theoretical calculation confirms the roles of In2O3 in preventing oxidation and altering the electronic structure of Cu to assist COOH* formation and demote CO* adsorption at the Cu/In2O3 interface.