Fabrication of functionalized nitrogen-doped graphene for supercapacitor electrodes

A unique and convenient one-step hydrothermal process for synthesizing functionalized nitrogen-doped graphene (FGN) via ethylenediamine, hydroquinone, and graphene oxide (GO) is described. The graphene sheets of FGN provide a large surface area for hydroquinone molecules to be anchored on, which can greatly enhance the contribution of pseudocapacitance. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and electrochemical workstation are used to characterize the materials. The nitrogen content exhibited in FGN can be up to 9.83 at.%, and the as-produced graphene material shows an impressive specific capacitance of 364.6 F g−1 at a scan rate of 10 mV s−1, almost triple that of the graphene (GN)-based one (127.5 F g−1). Furthermore, the FGN electrodes show excellent electrochemical cycle stability with 94.4 % of its initial capacitance retained after 500 charge/discharge cycles at the current density of 3 A g−1.