SnO₂-Doped CuO Nanosheets for Enhanced CO Selectivity in Electrochemical CO₂ Reduction

The electrocatalytic reduction of carbon dioxide (CO2) to carbon monoxide (CO) on CuO-based catalysts garnered significant attention due to their promising commercial potential. However, further catalyst design is required to enhance the catalytic selectivity of the CuO catalyst for CO. This work presents a simple method to fabricate oxygen vacancy defects in CuO nanosheets for enhanced CO selectivity. Bimetallic CuO–SnO2 catalysts with varying oxygen vacancy concentrations are obtained via a coprecipitation method. The concentration of oxygen vacancies is controlled by the molar ratio of copper to tin. At a copper–tin molar ratio of 30:1, the catalyst exhibits the highest concentration of oxygen vacancies and shows the best catalytic performance. At −0.5 V (versus RHE), the Faraday efficiency (FE) of CO reaches 87% and maintains stability for about 1 day. In situ electrochemical Fourier transform infrared (FTIR) spectroscopy directly demonstrated that oxygen vacancies facilitate the formation of the key intermediate *COOH and suppress the dimerization of *CO, thereby promoting CO production. The methodology for preparing the catalyst in this study is relatively simple and suggests a promising strategy for efficiently reducing CO2 to CO.