Among all CO2 electroreduction products,methane(CH4)and ethylene(C2H4)are two typical and valu-able 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 experi-mentally 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 con-trollable 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(COB)on the low-coordination Cu0 sites is apt to be hydrogenated to CH4,whereas the bridge-adsorbed CO plus linear-adsorbed CO(COB+COL)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.