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

Electrochemical carbon dioxide (CO2) reduction for C2 products has been studied on a series of supported Cu-based catalysts; however, the charge-promotion effects from the substrates for the selectivity of CO2 reduction are still unclear. Here we localize nanosized Cu2O 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 C2 products with an order of rGO/Cu < BG/Cu < pure Cu < NG/Cu and an FEC2/FEC1 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 CO2 reduction, which strengthens CO* adsorption to further boost C-C coupling for C2 products. As a result, we achieve a high C2+ FE of ∼68% at high current densities of 100-250 mA cm-2.