Unveiling the effects of ions in the electric double layer on the carbon dioxide reduction reaction

As a potential approach to minimize carbon emissions, the electrocatalytic transfer of carbon dioxide (CO2) to valuable chemicals has attracted great attention. Since such a process takes place at the liquid/solid interface, the electrolyte plays a vital role in determining the catalytic performance. Particularly, the cations including alkali metal cations and organic cations, and/or anions of the electrolyte can greatly change the activity and selectivity of the CO2 reduction reaction (CO2RR). Here, we review the development of the electric double layer and recent advances in the understanding of cation effects and anion effects on their electrocatalytic mechanisms and performance. Insights into the behavior of cations and anions in the electric double layer and their various mechanistic impacts on the electrochemical reduction of CO2 are of critical importance in optimizing reaction conditions and designing reactors for the efficient conversion of CO2. Finally, several challenges and outlook for better understanding and utilizing the electric double layer in the enhancement of the CO2RR are proposed, and we hope that this review can provide guidance for the design of more efficient CO2RR electrocatalysts.