Figure 1. Schematic of the rGO formation.

Graphene oxide (GO) is used as a starting material for the preparation of reduced graphene oxide (rGO). Epoxy and hydroxyl functional groups are randomly distributed on both sides of the starting GO sheet. Via a thermal annealing process (that is, thermal reduction), some of atoms are removed, resulting in nanopores formed in rGO materials with a variety of sizes. All structures are represented as ball and stick with carbon, oxygen and hydrogen atoms in grey, red and white colour, respectively.