Solvent Mediated Interfacial Microenvironment Design for High‐Performance Electrochemical CO ₂ Reduction to C ₂₊ Products

Abstract Electrochemical CO ₂ reduction (CO ₂ RR) in membrane electrode assembly (MEA) represents a viable strategy for converting CO ₂ into value‐added multi‐carbon (C ₂₊ ) compounds. Therefore, the microstructure of the catalyst layer (CL) affects local gas transport, charge conduction, and proton supply at three‐phase interfaces, which is significantly determined by the solvent environment. However, the microenvironment of the CLs and the mechanism of the solvent effect on C ₂₊ selectivity remains elusive. Herein, a tailored interfacial structure is designed by introducing a solvent‐mediated catalyst‐ionomer‐solvent microenvironment. The acetone surface promotion strategy is beneficial for the unfolded ionomers to uniformly coat the catalysts, which contributes to enhancing interfacial hydrophobicity and inhibiting hydrogen evolution. Furthermore, molecular dynamics (MD) simulation and in situ ATR‐SEIRAS are employed to elucidate the appropriate interfacial network with a balanced distribution of CO ₂ and H ₂ O. The uniform and continuous network in acetone is advantageous for CO ₂ ‐to‐C ₂₊ . The optimized structure favors the production of C ₂₊ products in Cu‐based MEA, exhibiting a high C ₂₊ faradaic efficiency (FE) of 80.27% at 400 mA cm ⁻² .