High-rate electrolysis of CO2to C2+alcohols is of particular interest, but the performance remains far from the desired values to be economically feasible. Coupling gas diffusion electrode (GDE) and 3D nanostructured catalysts may improve the efficiency in a flow cell of CO2electrolysis. Herein, we propose a route to prepare 3D Cu-chitosan (CS)-GDL electrode. The CS acts as a “transition layer” between Cu catalyst and the GDL. The highly interconnected network induces growth of 3D Cu film, and the as-prepared integrated structure facilitates rapid electrons transport and mitigates mass diffusion limitations in the electrolysis. At optimum conditions, the C2+Faradaic efficiency (FE) can reach 88.2% with a current density (geometrically normalized) as high as 900 mA cm−2at the potential of −0.87 V vs. reversible hydrogen electrode (RHE), of which the C2+alcohols selectivity is 51.4% with a partial current density of 462.6 mA cm−2, which is very efficient for C2+alcohols production. Experimental and theoretical study indicates that CS induces growth of 3D hexagonal prismatic Cu microrods with abundant Cu (111)/Cu (200) crystal faces, which are favorable for the alcohol pathway. Our work represents a novel example to design efficient GDEs for electrocatalytic CO2reduction (CO2RR).