Fig. 1.

Morphology of various graphene materials. A Classification grid for the categorization of different graphene types [43]. B TEM images of graphene nanoplates (1–5 nm), graphene nanoplates (5–20 nm), micro-graphite, and SEM image of natural graphite (top to bottom) [50]. C SEM images of GO (a) and ERGO (b) [118]