Controllable Hydrocarbon Formation from the Electrochemical Reduction of CO₂ over Cu Nanowire Arrays

In this work, the effect of Cu nanowire morphology on the selective electrocatalytic reduction of CO₂ is presented. Cu nanowire arrays were prepared through a two-step synthesis of Cu(OH)₂ and CuO nanowire arrays on Cu foil substrates and a subsequent electrochemical reduction of the CuO nanowire arrays to Cu nanowire arrays. By this simple synthesis method, Cu nanowire array electrodes with different length and density were able to be controllably synthesized. We show that the selectivity for hydrocarbons (ethylene, n-propanol, ethane, and ethanol) on Cu nanowire array electrodes at a fixed potential can be tuned by systematically altering the Cu nanowire length and density. The nanowire morphology effect is linked to the increased local pH in the Cu nanowire arrays and a reaction scheme detailing the local pH-induced formation of C₂ products is also presented by a preferred CO dimerization pathway. Catalytic activity: A Cu nanowire array for CO₂ reduction was developed. The length and density of the Cu nanowire array could be altered by a simple electroetching method. With varying length and density of the nanowire the chemical selectivity for CO₂ reduction could be systematically tuned. The results provide experimental evidence for a nanostructure-dependent catalytic activity.