Specific Cation Adsorption: Exploring Synergistic Effects on CO2 Electroreduction in Ionic Liquids

Abstract Ionic liquids (ILs) have gained attention as promising solvents as reaction media for the electrochemical conversion of CO 2 into valued‐added products. ILs can co‐catalyze the CO 2 reduction reaction (CO 2 RR), in particular, when Ag is applied as the primary metallic electrocatalyst. To broaden this co‐catalysis concept, we conducted a comprehensive study of a range of electrode materials exposed to three ILs, which differed in the chemical nature of their anions and cations. Here, we examine the activity of the electrode/IL combinations toward the CO 2 RR based on cyclic voltammetry data. The voltammetric experiments are complemented by gas chromatography analysis of the products, demonstrating that CO is the main product for most of the electrode/IL combinations. Our results demonstrate that the specific adsorption of the IL cation on the electrode plays a crucial role in the co‐catalytic effect of the ILs. Based on our analysis, we identify three classes of electrode materials, which differ in their synergistic interaction with the IL cations and their resulting CO 2 RR activity. The key criterion for this classification is the extent to which the CO 2 RR is superimposed on the reductive decomposition of the ILs.