Cation Effect on the Dynamics of Intermediates in Electroreduction of Carbon Dioxide in Acids

In the electrochemical reduction of CO₂, the employment of an acidic electrolyte with an alkali metal cation could reduce carbon loss. However, how the alkali metal cation activates CO₂and promotes the following proton-coupled electron transfer steps remains ambiguous. Here, from a rigorous analysis of CO₂reduction and CO reduction, we reveal that the kinetics of the CO₂electro-activation step and the following C–C coupling step both correlate positively with the concentration of K⁺, except that the promotion effect of K⁺on the CO₂-to-*CO step reaches a plateau when the concentration of K⁺is ≥0.7 M under a high overpotential. The activity toward multicarbon products is determined by the dual cationic effect of K⁺on the two steps, as evidenced in in situ Raman spectroscopy. The spectroscopic investigation shows that the adsorption of *CO shifts from atop configuration to bridge configuration as a net result of the dual cation effect, and the amount of adsorbed *OH increases with the rise of K⁺concentration.