Accelerating the Reaction Kinetics of CO2 Reduction to Multi‐Carbon Products by Synergistic Effect between Cation and Aprotic Solvent on Copper Electrodes

Abstract Improving the selectivity of electrochemical CO 2 reduction to multi‐carbon products (C 2+ ) is an important and highly challenging topic. In this work, we propose and validate an effective strategy to improve C 2+ selectivity on Cu electrodes, by introducing a synergistic effect between cation (Na + ) and aprotic solvent (DMSO) to the electrolyte. Based on constant potential ab initio molecular dynamics simulations, we first revealed that Na + facilitates C−C coupling while inhibits CH 3 OH/CH 4 products via reducing the water network connectivity near the electrode. Furthermore, the water network connectivity was further decreased by introducing an aprotic solvent DMSO, leading to suppression of both C 1 production and hydrogen evolution reaction with minimal effect on *OCCO* hydrogenation. The synergistic effect enhancing C 2 selectivity was also experimentally verified through electrochemical measurements. The results showed that the Faradaic efficiency of C 2 increases from 9.3 % to 57 % at 50 mA/cm 2 under a mixed electrolyte of NaHCO 3 and DMSO compared to a pure NaHCO 3 , which can significantly enhance the selectivity of the C 2 product. Therefore, our discovery provides an effective electrolyte‐based strategy for tuning CO 2 RR selectivity through modulating the microenvironment at the electrode‐electrolyte interface.