Carbon Nanotube/Nitrogen-Doped Reduced Graphene Oxide Nanocomposites and Their Application in Supercapacitors

Electrodes of carbon-based nanocomposites with high specific surface areas and suitable pore sizes have high potential for improving power and energy densities of supercapacitors. In this study, nitrogen-doped reduced graphene oxide (NrGO) nanosheets were synthesized to increase the specific surface area of reduced graphene oxide (rGO). The specific surface area of NrGO was increased to 633 m²g^-1 compared to that of rGO, 450 m²g^-1. A series of NrGO/carbon nanotubes (CNTs) nanocomposites were prepared. By using NrGO/CNTs/polyvinylidene difluoride (PVDF)/carbon black/N-methyl-pyrrolidone (NMP) nanocomposites as both of anode and cathode into two electrodes, such symmetric supercapacitor in the 1 M KOH aqueous electrolyte exhibited high specific capacitance (227 F g^-1 at 20 mV s^-1), fast rate capability (83% capacitance of current density 1 mA cm^-2 at current density 5 mA cm^-2), low resistance (0.98 Ω), and excellent cycling stability (87% capacitance retention after 10,000 charge/discharge cycles). Moreover, the symmetric supercapacitor in the ionic liquid (BMIMTFSI) electrolyte possessed a wide operating voltage (3 V) and high energy density (89 Wh kg^-1 at 1 mA cm^-2). The carbon-based hybrid electrode has high potential for use in energy storage and conversion devices.