Iodine‐Mediated C─C Coupling in Neutral Flow Cell for Electrochemical CO2 Reduction

Abstract Carbon utilization efficiency is of vital importance for electrochemical CO 2 reduction systems. Proton exchange membrane (PEM) electrolyzers using nonalkaline electrolytes can prevent CO 2 crossover and increase carbon utilization efficiency, yet they suffer from unfavored C─C coupling and severe hydrogen evolution. Herein, an iodine‐mediated approach to facilitate C─C coupling on Cu‐based catalysts toward multi‐carbon products in a neutral PEM electrolyzer is reported. By in situ constructing an I‐modified Cu surface, the hydrogenation of *CO is promoted and the C─C coupling process progresses through the *CO−*COH pathway with a low energy barrier. A high Faradaic efficiency of ≈72% and a high partial current density of 575 mA cm −2 are achieved for multi‐carbon products. The present study demonstrates an efficient approach to developing advanced CO 2 electrolyzers for high‐value products with high efficiency.