Cu₂O/CuS Nanocomposites Show Excellent Selectivity and Stability for Formate Generation via Electrochemical Reduction of Carbon Dioxide

Formate is an important value-added chemical that can be produced via electrochemical CO2 reduction reactions (CO2RR). Cu2O-based catalysts have previously demonstrated decent activity for formate generation; however, they often suffer from poor electrochemical stability under reductive conditions. Here, we report a new Cu2O/CuS composite catalyst that simultaneously achieves an excellent faradaic efficiency of 67.6% and a large partial current density of 15.3 mA/cm2 at −0.9 V vs RHE for formate. Importantly, it maintains an average faradaic efficiency of 62.9% for at least 30 h at the same potential. The catalytic selectivity and stability for formate production outperform other Cu, CuS, and Cu2O catalysts.