Electrochemical Reduction of CO₂at Cu Nanocluster / (101̅0) ZnO Electrodes

The electrochemical reduction of CO 2 in aqueous bicarbonate electrolytes is studied using Cu nanoclusters on single crystal 10 0 ZnO electrodes. Cu is known to generate methane as a primary product in electrochemical reduction reactions while the combination of Cu and ZnO produces methanol in gas-phase synthesis reactions. In reduction experiments at −1.4 V versus Ag/AgCl, gas phase products include hydrogen, carbon monoxide, methane and ethylene and liquid phase products include methanol, ethanol, formate, methyl formate and trace levels of propanol. faradaic efficiencies of Cu/ZnO electrodes are similar relative to Cu electrodes with the exception of alcohols where selectivity is improved by an order or magnitude. In-situ FTIR analysis shows several liquid-phase products along with methoxy and formate adsorbates. The nature of the improved alcohol selectivity and intermediates are considered relative to proposed mechanisms and results from this work.