Can closed shell graphitic materials be exfoliated? Defect induced porphyra-like graphene from the cooperation of activation and oxidation

Due to its inert closed-shell structure, the graphitic onion-like carbon (GOC) could not be exfoliated into a graphene-like structure by a simple Hummers' method even under rigorous conditions. Herein, we successfully exfoliated GOC into twisted graphene oxide nanosheets by the cooperation of chemical activation and Hummers' oxidation. Porphyra-like graphene nanosheets were further prepared from the twisted graphene oxide nanosheets by rapid thermal expansion. The defects introduced by activation were considered to play significant roles in the unfolding of GOC because they provide reactive sites for the oxidation. As an anode material for lithium ion batteries, the obtained porphyra-like graphene exhibited much better electrochemical properties than those of GOC. Our work can contribute to (1) deeply understand the exfoliation mechanism of graphitic materials by chemical oxidation especially the influence of defects during these steps; and (2) provide new strategies for designing functional graphene based materials from inert graphitic structures.