Electro-reduced copper on polymeric C₃N₄ for photocatalytic reduction of CO₂

Coupling light absorber with an efficient cocatalyst is the most common way to fabricate composite photocatalyst. The light absorber supplies electrons and holes, while the cocatalyst domains chemical reactions. Inspired by the results from electrochemical CO₂ reduction, Cu-based materials are the most promising cocatalysts for photocatalytic CO₂ reduction. However, oxide-derived copper (OD-Cu) hasn't been introduced into photocatalytic systems yet, due to easily undergoing valence changes once exposed to air. Herein, we find that OD-Cu could be decorated on photocatalyst, polymeric C₃N₄ (PCN), by a self-designed in-situ electroreduction method. The as-prepared OD-Cu/PCN presents better visible light absorption than the one without in-situ electroreduction and prefers multi-carbon products. According to CO₂RR measurements, the highest selectivity to C₂H₅OH is 58%. Density functional theory calculation further indicates that the unique structure between OD-Cu and PCN leads to a low energy barrier of C–C coupling due to the enhanced *CO dimerization and thus promotes the production of C₂H₅OH. Moreover, this optimized sample achieves a solar-to-fuel efficiency, of up to 0.94%, which is 1.69 times the pristine PCN.