Wurtzite CuGaS2 with an In‐Situ‐Formed CuO Layer Photocatalyzes CO2 Conversion to Ethylene with High Selectivity

Abstract We present surface reconstruction‐induced C−C coupling whereby CO2 is converted into ethylene. The wurtzite phase of CuGaS2. undergoes in situ surface reconstruction, leading to the formation of a thin CuO layer over the pristine catalyst, which facilitates selective conversion of CO2 to ethylene (C2H4). Upon illumination, the catalyst efficiently converts CO2 to C2H4 with 75.1 % selectivity (92.7 % selectivity in terms of Relectron) and a 20.6 μmol g−1 h−1 evolution rate. Subsequent spectroscopic and microscopic studies supported by theoretical analysis revealed operando‐generated Cu2+, with the assistance of existing Cu+, functioning as an anchor for the generated *CO and thereby facilitating C−C coupling. This study demonstrates strain‐induced in situ surface reconstruction leading to heterojunction formation, which finetunes the oxidation state of Cu and modulates the CO2 reduction reaction pathway to selective formation of ethylene.