Production of C4 Species from the Electrochemical Reduction of CO on Nanostructured Cu/CuO_x Catalyst

The electrolytic conversion of CO2 to useful fuels and chemicals is a promising technology for greenhouse gas reduction and waste utilization, but converting CO2 to larger multicarbon products with any selectivity is a major challenge. However, commercial electrolyzers for the conversion of CO2 to CO at high current density and high yield are in development. Subsequent electrochemical reduction of carbon monoxide affords the possibility of promoting a different reaction pathway for higher multicarbon product selectivity. The reaction conditions for the aqueous conversion of CO on Cu/CuOx catalyst have been explored including applied bias, gas flow rate, and oxide thickness. Significant faradaic efficiencies for C4 products (> 5% FE), including gamma-hydroxybutryic acid and succinic acid, were observed and quantified via NMR. The gas flow rate and resulting hydrodynamics of CO near the catalyst surface play a crucial role, with little C4 species observed at lower flow rates. A proposed reaction pathway for the formation of these C4 products will be presented as well.