An intimate CuPd(100) interface was designed to lower the energy barriers of intermediate reaction (CO2 hydrogenation and C-C coupling) and improve the efficiency of C2 products. The optimal CuPd(100) interface catalyst exhibited a C2 Faradaic efficiency of 50.3%, which was 2.1 times higher than that of Cu catalyst (23.6%) at -1.4 VRHE in 0.1 M KHCO3