Fig. 2: Characterizations of 3D Cu–CS-GDL electrode.

a Schematic diagram of the process for preparation of the 3D Cu–CS-GDL electrode. b The SEM image and contact angle data of 3D Cu–CS-GDL electrode. c The side view of the SEM image of 3D Cu–CS-GDL electrode. d The TEM image of 3D Cu–CS-GDL electrode. e The HRTEM image of 3D Cu–CS-GDL electrode. f The EDS images of 3D Cu–CS-GDL electrode. g The XRD patterns of CP, 3D Cu–CS-GDL electrode with different in situ electroreduction times. h The normalized Cu K edge XANES spectra of 3D Cu–CS-GDL electrode.