Influence CO2 partial pressure and the supporting electrolyte cation on the product distribution in CO2 electroreduction

This paper reports a study of the influence of CO2 partial pressure and the cation of the supporting electrolyte on the electrochemical reduction of CO2 at copper electrodes in aqueous solution at 25°C. Both current efficiency (CE) and the rates of formation of the reduction products diminish linearly with decreasing CO2 pressure, while evolution of hydrogen increases. The product distribution was greatly influenced by the supporting electrolyte cation. The CE for the formation of C2H4 increased with cation in the order Cs+≈ K+ > Na+ > Li+, apparently in a manner related to the size of the cation radius. The non-metallic cation NH+4 allowed only hydrogen evolution with a CE of about 92%.