Adjusting the Ratio of Oxidation States in a CuO@Cu2O for the Optimization of Electrocatalytic CO2 Conversion to Ethylene

Abstract Understanding the impact of surface copper valence states on the distribution of electrochemical carbon dioxide products is critical. Herein, CuO@Cu 2 O with a Cu 2+ /Cu + interface was fabricated using wet chemical etching approach. The hollow shape offered a large region for gas adsorption, while the interfacial mixed chemical state of Cu 2+ /Cu + with tunable control ratio raised the local density of CHO* and accelerated the carbon‐carbon coupling reaction. The H‐cell test results demonstrate that, as result of this precise structural design, the Faraday efficiency of ethylene is enhanced from 15.2 % to 43.5 %, and the service life is increased 4 times. In addition, its selectivity is almost 50 % and its partial current density in MEA is 93.2 mA cm −2 . In situ Raman and DFT data demonstrate that the Cu 2+ /Cu + interface effect enhances the concentration of COCHO intermediates and lowers the energy barrier for the conversion of CO* to COCHO* intermediates.