Chromium, fluorine and nitrogen tri-doped graphene sheets as an active electrode material for symmetric supercapacitors

The tri-doped (chromium, fluorine and nitrogen) graphene sheets (CFNG) have been prepared using quinolinium fluorochromate (QFC) as the single and novel source. Graphene oxide (GO) and CFNG were synthesized by modified Hummers method and simple hydrothermal method, respectively, and their electrochemical properties towards supercapacitor were studied. The HR-TEM images provide the crumpled sheet like morphology of CFNG. XPS reveals the presence of Cr, F and N in CFNG. The electrochemical studies such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD) were carried out using 1 M H2SO4 to evaluate the capacitive behaviour in three-electrode cells. A better storage capacitive behaviour of about 363 F/g at a current density of 0.5 A/g was achieved by CFNG. The capacitive performance of CFNG was also tested in two electrode cells, in which, a symmetric device was fabricated with CFNG, which exhibited specific capacitance of 160 F/g for 0.5 A/g. The symmetric CFNG supercapacitor device further delivers respective energy density and power density of 14.23 Wh/kg and 300 W/Kg with excellent capacitance retention of 98.8% and coulombic efficiency of 98.3% for over 1000 charge-discharge cycles. The electrochemical results were indicating that CFNG would be a potential candidate as an active electrode material for supercapacitors.