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 (FE_CO) 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.