Switching CO2 Electroreduction Selectivity Between C-1 and C-2 Hydrocarbons on Cu Gas-Diffusion Electrodes

Regulating the selectivity toward a target hydrocarbon product is still the focus of CO2 electroreduction. Here, we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness, local pH, and facet in governing the selectivity toward C-1 or C-2 hydrocarbons. The selectivity toward C2H4 progressively increases, while CH4 decreases steadily upon lowering the Cu oxidation species fraction. At a relatively low electrodeposition voltage of 1.5 V, the Cu gas-diffusion electrode with the highest Cu delta+/Cu-0 ratio favors the pathways of *CO hydrogenation to form CH4 with maximum Faradaic efficiency of 65.4% and partial current density of 228 mA cm(-2) at -0.83 V vs RHE. At 2.0 V, the Cu gas-diffusion electrode with the lowest Cu delta+/Cu-0 ratio prefers C-C coupling to form C2+ products with Faradaic efficiency topping 80.1% at -0.75 V vs RHE, where the Faradaic efficiency of C2H4 accounts for 46.4% and the partial current density of C2H4 achieves 279 mA cm(-2). This work demonstrates that the selectivity from CH4 to C2H4 is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.