Microwave-induced preparation of porous graphene nanosheets derived from biomass for supercapacitors

Microwave radiation has attracted more attention because it can increase the degree of graphitization of carbon materials. In this study, the porous graphene nanosheets (PGNSs) derived from black sesame are prepared via microwave radiation. Compared with traditional carbonization, the PGNS-4 sample prepared via microwave radiation not only has a larger specific surface area (2414.5 m2 g−1), micropore with proper diameter, an appropriate number of mesopores and macropores, but also shows a higher degree of graphitization. Microwave radiation facilitated the transformation of the local carbon crystal structure of the material, resulting in locally highly graphitized. As an electric double-layer capacitor (EDLC) electrode material, the PGNS-4 exhibits a high specific capacitance of 369 F g−1 at 1.0 A g−1, and 320 F g−1 at 10.0 A g−1. The assembled symmetrical device fabricated has a maximum energy density of 25.2 W h kg−1. This study proposes microwave radiation is an ideal technique for synthesizing biomass-based porous graphene carbons, because of the high degree of graphitization, and the highly porous structure of the final product. [Display omitted] •Microwave radiation facilitates an orderly change in the carbon crystal structure.•The hexagonal lattice proves microwave radiation heightens the formation of graphene.•PGNS-4 shows high specific surface area with hierarchical porous structure.•PGNS-4 exhibits a high specific capacitance of 369 F g−1 at 1 A/g.