Functionalized three-dimensional graphene networks for high performance supercapacitors

Three-dimensional (3D) thermal reduced graphene network (TRGN) deposition on Ni foam without any conductive agents and polymer binders was successfully synthesized by dipping Ni foam into graphene oxide (GO) suspension and subsequent thermal reduction process. The direct and close contact between thermal reduced graphene and Ni foam is beneficial to the enhanced conductivity of the electrode, as well as the improvement of ion diffusion/transport into the electrode. Additionally, low-temperature reduction of GO possesses a large amount of stable oxygen-containing groups that can provide high pseudocapacitance. As a result, the TRGN electrode delivers a high specific capacitance of 442.8 F g−1 at 2 mV s−1 in 6 mol L−1 KOH. Moreover, symmetric supercapacitor based on TRGN exhibits a maximum energy density of 30.4 Wh kg−1 based on the total mass of the two electrodes in 1 mol L−1 Na2SO4 electrolyte, as well as excellent cycling stability with 118% of its initial capacitance after 5000 cycles.