Synthesis and reduction of large sized graphene oxide sheets

Graphene oxide (GO) can be considered as one of the most visible outcomes of graphene research in terms of large scale production and commercialization prospects. Although GO can be easily prepared by oxidation-exfoliation of graphite in agitated solutions, the size of these sheets is generally limited due to fragmentation along fault lines during chemical oxidation and exfoliation in agitated solutions. In this account, we discuss recent strategies which have been developed for the preparation of large sized graphene oxide (LGO) sheets with lateral sizes >10 μm, using chemically expanded graphite as the starting material. LGO has a much lower density of defects than GO prepared using the conventional Hummers' method and can be readily transformed into graphene by chemical reduction. In addition, the unique advantages of using LGO sheets as a performance enhancer are discussed. Finally, this review also discusses recent advances in the chemical and electrochemical reduction of graphene oxide.