Figure 1

(a) XRD patterns of GO, RGO, GN2, GN6 and GN8.
Inset is the enlargement of the selective area for GN2. (b,c) SEM images of RGO (b) and GN6 composite (c). Inset of (c) is the schematic illustration of Ni NPs on the exposed RGO surface and in the sandwich structure.