Electrical anodization of Cu foil produces one-dimensional Cu nanowires of high surface areas, which turns to CuIn alloy nanowires by indium electrodeposition replacing edge site Cu atoms. An electrochemical pre-activation forms a highly conformal amorphous In(OH)3 overlayer with oxygen vacancy on the CuIn alloy that facilitates CO2 adsorption to promote selective CO formation suppressing competing H2 adsorption. Thus the activated CuIn alloy nanowires catalyse electrochemical CO2 conversion to CO with high CO selectivity (>68.2%) and high current density (ca. −3.9 mAcm−2) at −0.6 VRHE, which represents the higher partial CO current density (ca. −2.66 mAcm−2) than that of previously reported CuIn alloy powders without nanostructuring. The performance remains stable for more than 15 h without significant degradation.