Electroreduction of Carbon Monoxide Over a Copper Nanocube Catalyst: Surface Structure and pH Dependence on Selectivity

The activity and selectivity for CO2/CO reduction over Cu electrodes is strongly dependent on the local surface structure of the catalyst and the pH of the electrolyte. Here we investigate a unique, Cu nanocube surface (CuCube) as a CO reduction electrode under neutral and basic pH by using online electrochemical mass spectroscopy (OLEMS) to determine the onset potentials and relative intensities of methane and ethylene production. To relate the unique selectivity to the surface structure, the CuCube surface reactivity is compared to polycrystalline Cu and three single crystals under the same reaction conditions. We find that the high selectivity for ethylene over the CuCube surface is most comparable to the Cu(100) surface, which has a cubic unit cell. However, the suppression of methane production over CuCube is unique to that particular surface. A basic pH is shown to enhance ethylene selectivity on all surfaces, and again the CuCube surface is unique.