Fig. 1. (A) Schematic illustration of possible methods for the preparation of graphene, GO and rGO from graphite using mechanical cleavage, exfoliation, CVD and reduction methods including chemical, thermal and electrochemical methods. [Reprinted with permission from ref. 89, J. Filip and J. Tkac, Is Graphene Worth Using in Biofuel Cells?, Electrochim. Acta, 2014, 136, 340–354. Copyright© Elsevier.] (B) A schematic representation of the physical cracking of graphite-flake into functionalized graphene derivatives using a ball milling technique. [Reprinted with permission from ref. 90, J. Xu, J. Shui, J. Wang, M. Wang, H.-K. Liu, S. X. Dou, I.-Y. Jeon, J.-M. Seo, J.-B. Baek and L. Dai, Sulfur–Graphene Nanostructured Cathodes via Ball-Milling for High-Performance Lithium–Sulfur Batteries, ACS Nano, 2014, 8, 10920–10930. Copyright© American Chemical Society.].