The Preparation And Capacitance Of Graphene Composite Materials

In this paper,GO was successfully obtained by modified Hummers method.A hydrothermal method is used to prepare rGO/CuO and rGO/CuO/Ni(OH)2 composites in the thesis.The structure of rGO/CuO and rGO/CuO/Ni(OH)2 materials are characterized by infrared and X-ray powder diffraction spectroscopy(XRD).The morphology of rGO/CuO and rGO/CuO/Ni(OH)2 composites is observed by scanning electron microscope(SEM).The capacitive properties of rGO/CuO and rGO/CuO/Ni(OH)2 composite materials are studied by cyclic voltammetry,chronopotentiometry technology,and electrochemical impedance spectroscopy in 6 M KOH solution.The FT-IR,XRD and SEM of rGO/CuO show that there are both graphene and CuO in composites.The capacitance analysis results indicate that the rGO/CuO composites has good performance when the hydrothermal time is 18 h,the hydrothermal temperature is 180?,the ratio of copper ions to graphene oxide is 1:4.In 6 M KOH solution and at current density of 10 mA/cm2,the specific capacitance of rGO/CuO is up to 277.8 F/g between 0-0.5 V.After 2000 times of charging and discharging,the capacitance remains 83.7%.The cycling property remains to be improved.The L16(45)orthogonal table is used to design the experiment in order to investigate the effect of hydrothermal time,temperature and the molar ratio of raw materials on the capacitance of rGO/CuO/Ni(OH)2 materials.The variance analysis results indicate that rGO/CuO/Ni(OH)2 composite has superior capacitance performance when the hydrothermal time is 9 h,the hydrothermal temperature is 180?,the ratio of copper to nickel ions is 2:1,the ratio of copper ions to hydroxide ions is 2:1 and the mass of graphene oxide is 1.2 milligrams.In 6 M KOH solution and at current density of 10 mA/cm2,the specific capacitance of rGO/CuO/Ni(OH)2 is up to 1363 F/g between 0-0.5 V.After 2000 times of charging and discharging,the capacitance remains 88.8%,which has superior cycling stability.An asymmetric capacitor is assembled by using rGO/CuO/Ni(OH)2 as positive electrode and rGO as negative electrode.Its specific capacitance is 64.5 F/g.The energy density and power density is 5.2 Wh/kg and 310.1 W/kg,separately.After 2000 times of charging and discharging,the capacitance remains 91.5%,which has superior cycling stability.