Localized Geometry Determined Selectivity of Iodide‐Derived Copper for Electrochemical CO2 Reduction

Abstract Two iodide‐derived copper (ID‐Cu) electrocatalysts (E‐ID‐Cu and W‐ID‐Cu) are prepared by electrochemical/wet chemical iodination of Cu foil and subsequent in situ electrochemical reduction reaction. In comparison to electropolished Cu (EP‐Cu), both E‐ID‐Cu and W‐ID‐Cu can produce multicarbon (C 2+ ) products with much‐improved selectivity, with Faradic efficiency (FE) reaching 64.39% for E‐ID‐Cu and 71.16% for W‐ID‐Cu at −1.1 V versus reversible hydrogen electrodes (RHE), which can be attributed to their localized geometry features with high defect density and high surface roughness. Given the well‐determined FEs towards C 2+ products, the partial current densities for C 2+ production can be estimated to be 251.8 mA cm −2 for E‐ID‐Cu and 290.0 mA cm −2 for W‐ID‐Cu at −1.2 V versus RHE in a flow cell. In situ characterizations and theoretical calculations reveal that the high‐density defects and high surface roughness can promote *CO adsorption by raising the d band center and then facilitate C–C coupling, contributing to the high selectivity of C 2+ products for ID‐Cu. Interestingly, the high surface roughness can increase the residence time of *C–H intermediates and decrease the formation energy of the *OCCO and*CH 3 CH 2 O intermediates, thus favoring C 2+ production, with a unique C 2 H 6 product observed over W‐ID‐Cu with FE of 10.14% at −0.7 V versus RHE.