Probing the Roles of Indium Oxides on Copper Catalysts for Enhanced Selectivity during CO 2 -to-CO Electrochemical Reduction.

The electrochemical CO 2 reduction reaction (CO 2 RR) provides an alternative protocol to producing industrial chemicals with renewable electricity sources, and the highly selective, durable, and economic catalysts should expedite CO 2 RR applications. Here, we demonstrate a composite Cu-In 2 O 3 catalyst in which a trace amount of In 2 O 3 decorated on Cu surface greatly improves the selectivity and stability for CO 2 -to-CO reduction as compared to the counterparts (Cu or In 2 O 3 ), 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 In 2 O 3 undergoes the redox reaction and preserves the metallic state of Cu during the CO 2 RR process. Strong electronic interaction and coupling occur at the Cu/In 2 O 3 interface which serves as the active site for selective CO 2 RR. Theoretical calculation confirms the roles of In 2 O 3 in preventing oxidation and altering the electronic structure of Cu to assist COOH* formation and demote CO* adsorption at the Cu/In 2 O 3 interface.