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

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