Cu(I) Reducibility Controls Ethylene vs Ethanol Selectivity on (100)-Textured Copper during Pulsed CO₂ Reduction

The electrochemical CO₂ reduction reaction (CO₂RR) can convert widely available CO₂ into value-added C₂ products, such as ethylene and ethanol. However, low selectivity toward either compound limits the effectiveness of current CO₂RR electrocatalysts. Here, we report the use of pulsed overpotentials to improve the ethylene selectivity to 67% with >75% overall C₂ selectivity on (100)-textured polycrystalline Cu foil. The pulsed CO₂RR can be made selective to either ethylene or ethanol by controlling the reaction temperature. We attribute the enhanced C₂ selectivity to the improved CO dimerization kinetics on the active Cu surface on predominately (100)-textured Cu grains with the reduced hydrogen adsorption coverage during the pulsed CO₂RR. The ethylene vs ethanol selectivity can be explained by the reducibility of the Cu(I) species during the cathodic potential cycle. Our work demonstrates a simple route to improve the ethylene vs ethanol selectivity and identifies Cu(I) as the species responsible for ethanol production.