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

The capacity of larger alkali metal cations to maintain the interfacial CO2 concentration by buffering the interfacial pH has been proposed to enhance the electrochemical CO2 reduction reaction (CO2RR). In-situ spectroscopy is employed to determine the trend of interfacial CO2 concentration with different alkali metal cations. Contradictory to the cation buffering hypothesis, the interfacial CO2 concentration decreases with increasing size of alkali metal cations at CO2RR conditions on Au. The interfacial CO2 concentration is largely dependent on the rate of CO2 depletion by reduction or reaction with OH- generated at the electrode, and not on the proposed buffering effect.