Abstract

Abstract Electrochemical carbon dioxide reduction (CO 2 ) is a promising technology to use renewable electricity to convert CO 2 into valuable carbon‐based products. For commercial‐scale applications, however, the productivity and selectivity toward multi‐carbon products must be enhanced. A facile surface reconstruction approach that enables tuning of CO 2 ‐reduction selectivity toward C 2+ products on a copper‐chloride (CuCl)‐derived catalyst is reported here. Using a novel wet‐oxidation process, both the oxidation state and morphology of Cu surface are controlled, providing uniformity of the electrode morphology and abundant surface active sites. The Cu surface is partially oxidized to form an initial Cu (I) chloride layer which is subsequently converted to a Cu (I) oxide surface. High C 2+ selectivity on these catalysts are demonstrated in an H‐cell configuration, in which 73% Faradaic efficiency (FE) for C 2+ products is reached with 56% FE for ethylene (C 2 H 4 ) and overall current density of 17 mA cm ‐2 . Thereafter, the method into a flow‐cell configuration is translated, which allows operation in a highly alkaline medium for complete suppression of CH 4 production. A record C 2+ FE of ≈84% and a half‐cell power conversion efficiency of 50% at a partial current density of 336 mA cm ‐2 using the reconstructed Cu catalyst are reported.