Controllable CO adsorption determines ethylene and methane productions from CO₂ electroreduction

Among all CO₂ electroreduction products, methane (CH₄) and ethylene (C₂H₄) are two typical and valuable hydrocarbon products which are formed in two different pathways: hydrogenation and dimerization reactions of the same CO intermediate. Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH₄/C₂H₄. However, it is challenging to experimentally control the CO adsorption configurations at the catalyst surface, and thus the hydrocarbon selectivity is still limited. Herein, we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures. The two model catalysts exhibit a high hydrocarbon selectivity toward either CH₄ (83%) or C₂H₄ (93%) under identical reduction conditions. Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu⁰ sites and local Cu⁰/Cu⁺ sites of the two catalysts, respectively. CO-temperature programed desorption, in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO (CO_B) on the low-coordination Cu⁰ sites is apt to be hydrogenated to CH₄, whereas the bridge-adsorbed CO plus linear-adsorbed CO (CO_B + CO_L) on the local Cu⁰/Cu⁺ sites are apt to be coupled to C₂H₄. Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity.