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

Improving the selectivity of electrochemical CO2 reduction to multi-carbon products (C2+) is an important and highly challenging topic. In this work, we propose and validate an effective strategy to improve C2+ 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 CH3OH/CH4 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 NaHCO3 and DMSO compared to a pure NaHCO3, which can significantly enhance the selectivity of the C-2 product. Therefore, our discovery provides an effective electrolyte-based strategy for tuning CO2RR selectivity through modulating the microenvironment at the electrode-electrolyte interface.