Efficiency and selectivity of CO2 reduction to CO on gold gas diffusion electrodes in acidic media

Abstract The electrochemical reduction of CO 2 to CO is a promising technology for replacing production processes employing fossil fuels. Still, low energy efficiencies hinder the production of CO at commercial scale. CO 2 electrolysis has mainly been performed in neutral or alkaline media, but recent fundamental work shows that high selectivities for CO can also be achieved in acidic media. Therefore, we investigate the feasibility of CO 2 electrolysis at pH 2–4 at indrustrially relevant conditions, using 10 cm 2 gold gas diffusion electrodes. Operating at current densities up to 200 mA cm −2 , we obtain CO faradaic efficiencies between 80–90% in sulfate electrolyte, with a 30% improvement of the overall process energy efficiency, in comparison with neutral media. Additionally, we find that weakly hydrated cations are crucial for accomplishing high reaction rates and enabling CO 2 electrolysis in acidic media. This study represents a step towards the application of acidic electrolyzers for CO 2 electroreduction.