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

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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 CH₃ OH/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 C₁ production and hydrogen evolution reaction with minimal effect on *OCCO* hydrogenation. The synergistic effect enhancing C₂ selectivity was also experimentally verified through electrochemical measurements. The results showed that the Faradaic efficiency of C₂ increases from 9.3 % to 57 % at 50 mA/cm² under a mixed electrolyte of NaHCO₃ and DMSO compared to a pure NaHCO₃ , which can significantly enhance the selectivity of the C₂ product. Therefore, our discovery provides an effective electrolyte-based strategy for tuning CO₂ RR selectivity through modulating the microenvironment at the electrode-electrolyte interface.