Effect of Charge on Carbon Support on the Catalytic Activity of Cu₂O toward CO₂ Reduction to C₂ Products

Electrochemical carbon dioxide (CO 2 ) reduction for C 2 products has been studied on a series of supported Cu-based catalysts; however, the charge-promotion effects from the substrates for the selectivity of CO 2 reduction are still unclear. Here we localize nanosized Cu 2 O on three carbon-based substrates that provide different charge-promotion effects: positively charged boron-doped graphene (BG), negatively charged nitrogen-doped graphene (NG), and weak negatively charged reduced graphene oxide (rGO). We demonstrate that the charge-promotion effects lead to an increase in faradaic efficiency (FE) for C 2 products with an order of rGO/Cu < BG/Cu < pure Cu < NG/Cu and an FE C 2 /FE C 1 ratio from 0.2 to 7.1. By performing in situ characterization, electrokinetic investigations, and density functional theory (DFT) calculations, we reveal that the negatively charged NG is favorable for stabilizing Cu + species under CO 2 reduction, which strengthens CO* adsorption to further boost C–C coupling for C 2 products. As a result, we achieve a high C 2+ FE of ∼68% at high current densities of 100–250 mA cm –2 .