Molten Salt Treated Cu Foam Catalyst for Selective Electrochemical CO 2 Reduction Reaction

Abstract The electrochemical reduction of CO 2 is a promising route to convert waste products to valuable chemicals. Search for suitable and efficient CO 2 reduction electrocatalysts with high C 2 :C 1 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 Cu 2 O (111) surface has a high reactivity and selectivity for C 2+ products. Furthermore, the molten salt treated catalysts could be applied to the direct synthesis of multi‐carbon fuels, including C 3 ‐C 4 compounds in high CO 2 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 CO 2 electrocatalysts, which may open a new way for industrial application.