The Effect of Electrolyte Alkali Cation on CO2 Electroreduction in Atomically Precise Ag25(SR)18 Nanoclusters

Abstract

Atomically precise metal nanoclusters (NCs) are promising electrocatalysts for the electrocatalytic carbon dioxide reduction reaction (eCO2RR), benefiting from their well-defined structures and unique physicochemical properties. Although surface engineering has been widely applied to tune eCO2RR activity and selectivity, the electrolyte composition—especially alkali metal cation identity—has emerged as a critical factor governing catalytic performance. However, the atomic-level mechanism by which alkali metal cations regulate eCO2RR on atomically precise silver NCs remains unclear. Herein, we combined first-principles simulations with electrochemical experiments to systematically investigate the cation effect on eCO2RR over thiolate-protected Ag25(SR)18 NCs. The simulation results show that the eCO2RR activity of Ag25 NCs follows the order of Li⁺ < Na⁺ < Cs⁺ ≤ K⁺ in alkali cation electrolytes. The stronger promoting effect of K⁺ is correlated to its more uniform interfacial water density. This cation-dependent activity trend, highlighting the pivotal role of cations in modulating electrocatalysis, is further verified by electrochemical measurements. Overall, this work provides atomic-scale insights into the cation-regulated eCO2RR mechanism and offers valuable guidance for designing high-efficiency electrocatalytic systems for CO2 reduction.