(a) Schematic representation of the VG@GP fabrication process. (b) Top-view SEM image of the surface morphology of VG@GP. (c) The cross-sectional view SEM image of VG@GP. (d) Raman spectra of VG@GP. (e) XPS of the C1s spectrum of VG@GP. (f) The contact angles of electrolyte on Cu foil and VG@GP.