Solar‐Driven Sulfide Oxidation Paired With CO2 Reduction Based on Vacancies Engineering of Copper Selenide

Abstract Photovoltaic‐driven electrochemical (PV‐EC) carbon dioxide reduction (CO2R) coupled with sulfide oxidation (SOR) can efficiently convert the solar energy into chemical energy, expanding its applications. However, developing low‐cost electrocatalysts that exhibit high selectivity and efficiency for both CO2R and SOR remains a challenge. Herein, a bifunctional copper selenide catalyst is developed with copper vacancies (v‐CuSe2) for the CO2R‐SOR. The Faradaic efficiency (FE) of 62.4% for methane at −200 mA cm−2 is achieved in the cathodic CO2R. In a two‐electrode CO2R‐SOR system with 16 h of long‐term operation at a current density of 200 mA cm−2, an average Faradaic efficiency of 57.2% for methane and 97.7% for sulfur powder generation is achieved at cathode and anode, respectively. Compared to the coupling of CO2R with oxygen evolution reaction (OER), the energy efficiency (EE) of the CO2R‐SOR system can be increased to 22.9%. The mechanism study has found that the synergistic effect of copper vacancies and introduced Se significantly enhances the selectivity toward methane. Driven by silicon solar cells, a solar‐to‐methane conversion efficiency of 2% is achieved.