Electrochemical Carbon Monoxide Reduction on Polycrystalline Copper: Effects of Potential, Pressure, and pH on Selectivity toward Multicarbon and Oxygenated Products

Understanding the surface reactivity of CO, which is a key intermediate during electrochemical CO2 reduction, is crucial for the development of catalysts that selectively target desired products for the conversion of CO2 to fuels and chemicals. In this study, a custom-designed electrochemical cell is utilized to investigate planar polycrystalline copper as an electrocatalyst for CO reduction under alkaline conditions. Seven major CO reduction products have been observed including various hydrocarbons and oxygenates which are also common CO2 reduction products, strongly indicating that CO is a key reaction intermediate for these further-reduced products. A comparison of CO and CO2 reduction demonstrates that there is a large decrease in the overpotential for C–C coupled products under CO reduction conditions. The effects of CO partial pressure and electrolyte pH are investigated; we conclude that the aforementioned large potential shift is primarily a pH effect. Thus, alkaline conditions can be used to inc...