Interfacial Water Tuning by Intermolecular Spacing for Stable CO₂ Electroreduction to C₂₊ Products

Electroreduction of CO₂ to multi-carbon (C₂₊ ) products is a promising approach for utilization of renewable energy, in which the interfacial water quantity is critical for both the C₂₊ product selectivity and the stability of Cu-based electrocatalytic sites. Functionalization of long-chain alkyl molecules on a catalyst surface can help to increase its stability, while it also tends to block the transport of water, thus inhibiting the C₂₊ product formation. Herein, we demonstrate the fine tuning of interfacial water by surface assembly of toluene on Cu nanosheets, allowing for sustained and enriched CO₂ supply but retarded water transfer to catalytic surface. Compared to bare Cu with fast cathodic corrosion and long-chain alkyl-modified Cu with main CO product, the toluene assembly on Cu nanosheet surface enabled a high Faradaic efficiency of 78 % for C₂₊ and a partial current density of 1.81 A cm^-2 . The toluene-modified Cu catalyst further exhibited highly stable CO₂ -to-C₂ H₄ conversion of 400 h in a membrane-electrode-assembly electrolyzer, suggesting the attractive feature for both efficient C₂₊ selectivity and excellent stability.