Additive-Assisted Electrodeposition of Cu on Gas Diffusion Electrodes Enables Selective CO2 Reduction to Multicarbon Products

Incorporating electrocatalysts for CO2 reduction (CO2R) into practically relevant reactor architectures, i.e., gas diffusion electrodes (GDEs), is crucial for the development of future CO2 electrolyzers. In this work, we investigated the additive effects of Cu electrodeposition onto GDEs and achieved improved performance in the conversion of CO2 to multicarbon (C2+) products compared to the conventional GDE preparation methods, such as spray coating of Cu nanoparticles onto GDEs. Specifically, we prepared GDEs based on polycrystalline copper (ED Cu), acetic acid (AA)-derived Cu2O, and lactic acid (LA)-derived Cu2O via direct electrodeposition. We compared the CO2R of these GDEs with that of a GDE prepared via spray coating of Cu2O nanocubes. Under the same testing conditions, LA Cu2O demonstrated the highest selectivity toward ethylene (similar to 60%) and overall C2+ products (>80%) in a flow cell, outperforming the state-of-the-art Cu2O nanocubes. Additionally, LA Cu2O also exhibited improved stability at a high current density of 300 mA cm(-2). Experimental results indicate that the enhanced CO2R performance is due to the optimized electrochemically active surface area, abundance of grain boundaries/defects, etc., on the electrodeposited Cu surface. We believe that the electrodeposition method developed in this study could be a cost-effective alternative to the expensive sputtering and complicated spray coating processes for practical CO2R applications in the future.