Phenolic hydroxyl functionalized partially reduced graphene oxides for symmetric supercapacitors with significantly enhanced electrochemical performance

In this paper, three-dimensional phenolic hydroxyl functionalized partially reduced graphene oxides with high hydroxyl content and significantly enhanced electrochemical performance have been successfully prepared by a one-pot hydrothermal method from graphene oxide dispersions. A very small amount of 4-aminophenol is employed as reducing and N-doping agent, structure modifier and the phenolic hydroxyl source, at the same time. The electrochemical test results show that as binder-free electrode, the as-synthesized sample with high hydroxyl content (6.15 at%) exhibits an ultrahigh specific capacitance of 284.1 F g−1 at current density of 0.3 A g−1 in 6 M KOH electrolyte, and retains for 80.4% even at a current density of 10 A g−1. Above all, the as-assembled symmetric supercapacitor shows superior energy density of 9.9 Wh kg−1 at a power density of 75.0 W kg−1. The significantly enhanced electrochemical performance can be ascribed to the high hydroxyl content and other oxygen functional groups, N-doping, modified porous framework and the high specific surface area of the graphene. Those special characteristics suggest that the as-synthesized graphene materials may have potential applications in high performance supercapacitors.