Laser ablation in liquid was used to prepare homogeneous copper-zinc alloy catalysts that exhibited excellent selectivity for C2H4 in CO2 electroreduction, with faradaic efficiency values as high as 33.3% at a potential of -1.1 V (vs reversible hydrogen electrode). The high proximity of Cu and Zn atoms on the surface of the catalyst was found to facilitate both stabilization of the CO* intermediate and its transfer from Zn atoms to their Cu neighbors, where further dimerization and protonation occur to give rise to a large amount of ethylene product. The new homogeneous nanocatalyst, along with the mechanism proposed for its performance, may be very helpful for in-depth understanding of processes related to carbon dioxide electroreduction and conversion.