Atomic insights into how electrolyte concentration controls CO electroreduction to acetate

During the electrochemical conversion of CO to acetate on copper-based catalysts, the electrolyte concentration plays a crucial role in acetate selectivity. However, the correlation between the electrolyte concentration and the local microenvironment as well as the reaction kinetics remains unclear. In this work, we report for the first time the impact of KOH concentration on the solvent structure and reaction kinetics for CO reduction to acetate using advanced operando computational methods. With increasing KOH concentration, we find that the interfacial solvent structure becomes dense and the hydrogen bond network becomes more stable which benefits the directional transfer of protons/hydroxides. In terms of reaction kinetics, high-concentration KOH not only promotes the generation of *OH, but also accelerates its combination with surface *CO to form *COOH, a key step in the production of acetate. These insights offer a practical strategy for tuning electrolytes to boost catalyst performance.