Doping and controllable pore size enhanced electrochemical performance of free-standing 3D graphene films

High quality free-standing 3D nanoporous graphene (3DNG) films were fabricated using nanoporous nickel as template and catalyst. The effect of heteroatom doping and pore size on the electrochemical performance of the 3D graphene films as supercapacitor electrodes are systematically studied. Compared with macroporous graphene films, nanoporous graphene films exhibit an extraordinarily large operational window in neutral, acidic and alkaline aqueous electrolytes, as well as high packing density. Nitrogen and oxygen doping play different roles in different aqueous electrolytes on the electrical conductivity and pseudocapacitance of 3DNG. The realization of both high packing density, 3.65 mg/cm(2), and the maximum working window, as well as the synergistic effect between N and O doping, gives rise to a high areal capacitance of 435 mF/cm(2) in neutral electrolyte and excellent cycle stability up to 5000 cycles. The results provide a potential strategy to further increase the volumetric or areal energy density of carbon-based aqueous supercapacitor. (C) 2017 Elsevier B.V. All rights reserved.