Cation Effect on Interfacial CO₂ Concentration in the Electrochemical CO₂ Reduction Reaction

The capacity of larger alkali metal cations to maintain the interfacial CO 2 concentration by buffering the interfacial pH has been proposed to enhance the electrochemical CO 2 reduction reaction (CO 2 RR). In-situ spectroscopy is employed to determine the trend of interfacial CO 2 concentration with different alkali metal cations. Contradictory to the cation buffering hypothesis, the interfacial CO 2 concentration decreases with increasing size of alkali metal cations at CO 2 RR conditions on Au. The interfacial CO 2 concentration is largely dependent on the rate of CO 2 depletion by reduction or reaction with OH − generated at the electrode, and not on the proposed buffering effect.