Cu₂S Nanoparticle-Modified Copper Hydroxide Nanowire Arrays for Optimized Electrochemical CO₂ Reduction Selectivity

A copper-based catalyst exhibits a wide distribution of catalytic products in electrochemical CO 2 reduction. However, it faces a grand challenge in reaction selectivity. A deeper understanding is needed regarding the mechanism of its diversified product selectivity. Herein, we design a cuprous sulfide nanoparticle-modified copper hydroxide nanowire array precatalyst by a simple solvothermal method for revealing the catalytic mechanism of copper-based catalysts in electrochemical CO 2 reduction. The role of cuprous sulfide nanoparticle modification in copper hydroxide nanowires on formate formation during CO 2 reduction is investigated. The intermediate during CO 2 reduction is altered by sulfur modification, resulting in improvement in formate selectivity. Density functional theory is used to investigate the effect of trace sulfur modification in copper on activity and selectivity toward formate formation. Compared with a pure copper surface, sulfur modification in copper can promote the formation of *OCHO, a key intermediate along the formate pathway.