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

The electrochemical CO reduction reaction (CORR) can convert widely available CO into value-added C products, such as ethylene and ethanol. However, low selectivity toward either compound limits the effectiveness of current CORR electrocatalysts. Here, we report the use of pulsed overpotentials to improve the ethylene selectivity to 67% with >75% overall C selectivity on (100)-textured polycrystalline Cu foil. The pulsed CORR can be made selective to either ethylene or ethanol by controlling the reaction temperature. We attribute the enhanced C 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 CORR. 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.