Interfacial Water Tuning by Intermolecular Spacing for Stable CO 2 Electroreduction to C 2+ Products

Electroreduction of CO 2 to multi‐carbon (C 2+ ) products is a promising approach for utilization of renewable energy, in which the interfacial water quantity is critical for both the C 2+ 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 C 2+ product formation. Herein, we demonstrate the fine tuning of interfacial water by surface assembly of toluene on Cu nanosheets, allowing for sustained and enriched CO 2 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 C 2+ and a partial current density of 1.81 A cm −2 . The toluene‐modified Cu catalyst further exhibited highly stable CO 2 ‐to‐C 2 H 4 conversion of 400 h in a membrane‐electrode‐assembly electrolyzer, suggesting the attractive feature for both efficient C 2+ selectivity and excellent stability.