Insight into the role of imidazolium cations in regulating Ag electrode interface for enhancing electrochemical CO2 reduction

Imidazolium-based ionic liquids (ILs) exhibit great potential in promoting electrochemical CO 2 reduction reaction (CO 2 RR) by reducing overpotential reduction and enhancing catalytic efficiency. However, the regulatory role of ILs structure in the local physicochemical region at the electrode/electrolyte interface and in reaction kinetics remain unclear. In this study, we designed imidazolium-based ILs with tunable cation alkyl chain length and systematically revealed the dynamic interfacial regulation mechanism controlled by cation structure, based on in-situ infrared spectroscopy and molecular dynamics simulations. The commercial Ag electrodes in electrolytes with critical chain length exhibit nearly 100% Faradaic efficiency for CO production while maintaining high current density. Imidazolium cations with critical chain length effectively regulate the electric double layer at the Ag electrode/electrolyte interface: they notably balance a range of positive and negative factors, including hydrophobicity, CO 2 absorption, conductivity, viscosity, and hydrogen evolution reaction, etc . Collectively, these effects synergistically shape an optimized interfacial local physicochemical region, enhancing the rate of CO 2 catalytic reactions. This work elucidates the mechanistic framework of interfacial regulation in CO 2 RR and delivers molecular design principles for engineering IL-based electrolytes toward enhanced catalytic selectivity.