Oxygen plasma induced hierarchically structured gold electrocatalyst for selective reduction of carbon dioxide to carbon monoxide

Electrochemical reduction of CO₂ into C1 products with high energy density has attracted attention due to the demands for renewable energy sources. Herein, we demonstrate a selective electrocatalytic CO₂ reduction system where the cathode consists of hierarchically structured Au islands catalysts. To be more specific, the Au islands were prepared by oxygen plasma treatment on the Au foil to increase the current density for the selective production of carbon monoxide with over 95% of faradaic efficiency. Faradaic efficiency, production rate, and the onset potential for CO₂ reduction were significantly improved by the expanded surface area compared with a polycrystalline Au electrode. Furthermore, the performance of CO₂ reduction to CO was enhanced by adding ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) which has high CO₂-capture ability and catalytic activity. On the other hand, the rate-determining step of the Au electrode for the CO production determined by Tafel plots was found to be consistent with the initial one electron transfer step to form the surface-adsorbed CO₂•^- intermediates regardless of the application of hierarchically structured catalyst and ionic liquid in the CO₂ reduction system.