Desolvated cations promote CO electroreduction through partial covalent interactions

Cations play a critical role in electrochemical CO₂ reduction, yet the mechanisms underlying their influence remain poorly understood due to limited knowledge of their solvation structures and interfacial interactions under operating conditions.Here, we combine surface-sensitive total electron yield X-ray absorption spectroscopy (TEY-XAS), surfaceenhanced infrared absorption spectroscopy (SEIRAS), and density functional theory (DFT) calculations to determine the solvation environment of cesium ions near a ligand-modified silver nanocatalyst under CO2-reducing conditions.We find that desolvated Cs⁺ ions, confined between a floating ligand layer and the silver surface, enable CO₂ activation at potentials as high as 0.4 V versus RHE-reducing the overpotential for CO₂-to-CO conversion by 250 mV compared to a bare Ag film.Our results further reveal a partial covalent character in Cs-intermediate interactions, which directly accounts for the enhanced catalytic activity.These findings provide multimodal spectroscopic evidence of desolvated cations and demonstrate their ability to interact with surface-bound species, engaging in partial charge transfer and thereby modulating reaction kinetics beyond purely electrostatic effects.This work offers a unified mechanism for cation-mediated catalysis and presents a promising strategy for designing next-generation electrochemical systems with reduced energy demands.