Fig. 2
a Model of a 3D-NG network, with periodic boundary conditions, composed of curved graphene nanoplatelets. The density is 0.5 g/cm 3. Pore size is of the order of 1–2 nm. Grey, orange, and magenta denote sp 2, sp 3, and sp 1 bonding, respectively. b Experimental model of 3D-NG derived from a polymer-based top-down approach [4]. c Experimental model of 3D-NG derived by assembly of GO sheets [6]