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Abstract

The electrochemical reduction of CO2 is a promising route to convert waste products to valuable chemicals. Search for suitable and efficient CO2 reduction electrocatalysts with high C2:C1 selectivity holds great promise. Herein, for the first time we have developed a molten salt oxidized method to modify the morphology and oxidation state of a Cu-foam catalyst. The catalyst displayed a current density of 30 mA cm−2 (−1.4 V versus reversible hydrogen electrode) and an ethylene/methane ratio of 870. We provide insight into the improved performance of the catalysts by cross section scanning transmission electron microscopy and quasi in situ soft X-ray spectroscope, which show that copper oxides are surprisingly reconstructed with Cu (I) and Cu (0) on the surface during the reaction. First principle calculations also demonstrate that the partly reduced Cu2O (111) surface has a high reactivity and selectivity for C2+ products. Furthermore, the molten salt treated catalysts could be applied to the direct synthesis of multi-carbon fuels, including C3-C4 compounds in high CO2 pressure electrocatalytic reduction. Our results demonstrate that molten salt are both the oxidizing agent and reaction medium, which is a promising approach for synthesis of highly active CO2 electrocatalysts, which may open a new way for industrial application. © 2020 Wiley-VCH GmbH