The electroreduction of CO2 to valuable chemicals and fuels offers an effective mean for energy storage.Although CO2 has been efficiently converted into C1 products (e.g.,carbon monoxide,formic acid,methane and methanol),its convention into high value-added multicarbon hydrocarbons with high selectivity and activity still remains challenging.Here we demonstrate the formation of multi-shelled CuO microboxes for the efficient and selective electrocatalytic CO2 reduction to C2H4.Such a structure favors the accessibility of catalytically active sites,improves adsorption of reaction intermediate (CO),inhibits the diffusion of produced OH-and promotes C-C coupling reaction.Owing to these unique advantages,the multi-shelled CuO microboxes can effectively convert CO2 into C2H4 with a maximum faradaic efficiency of 51.3％ in 0.1 M K2SO4.This work provides an effective way to improve CO2 reduction efficiency via constructing micro-and nanostructures of electrocatalysts.