Hierarchical Porous Graphene Carbon-Based Supercapacitors

A high-rate graphene-based supercapacitor is very attractive for the practical application of graphene. Here, we first synthesized the films of the hybrids of biomass cellulose and large literal sheet sizes and weakly defective graphene flakes reaching high thermal conductivity and then converted them into hierarchical porous graphene carbon materials reaching superior supercapacity. The interconnected porous carbon framework, with macroporous walls sandwiched by micro/mesoporous activated carbon covering graphene flakes, was synthesized by template-free low-temperature activation of the cellulose/graphene hybrids at 650 °C. The graphene flakes could probably assist both the decrease in the temperature of the chemical activation of cellulose and the formation of the hierarchical carbon pores without destroying their sp2 bonds. The porous graphene carbon-based supercapacitors exhibit a reversible specific capacitance of ∼300 F/g and ultrahigh energy storage performance of 67 Wh/kg, 54 Wh/L, and 60 kW/kg over a 45 s discharge time.