The Preparation And Capacitance Properties Of Graphene And Graphene/Nickel Hydroxide Composite Materials

Graphene (ERGO) was obtained by a rapid, effective and eco-friendly electrochemical method in 0.05 M potassium biphthalate solution. Graphene/Ni(OH)2 composite was prepared by hydrothermal method, which is signed as TRGO/Ni(OH)2. The structure characteristics of the reduced graphene oxide (ERGO) and TRGO/Ni(OH)2 composite were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetry and differential scanning calorimetry (TGA-DSC), X-ray diffraction spectroscopy (XRD). Transmission electron microscopy (TEM) was used to observe the morphology of ERGO and scanning electron microscope (SEM) was used to show the morphology of TRGO/Ni(OH)2 composite. Electrochemical studies of ERGO and TRGO/Ni(OH)2 composite are carried out using cyclic voltammetry, chronopotentiometry technology, and electrochemical impedance spectroscopy in pH=13 Na2SO4 solution and 1M KOH solution, separately.The FT-IR, XRD and TGA-DSC of graphene indicate that graphene was succesfully obtained by reducing graphene oxide. The results of capacitance ferformacce indicate graphene has good capacitance performance when the reduction time is 1 h and the electrode mass is 1.0 mg. In pH=13 Na2SO4 solution and at 0.65 A/g current density, the specific capacitance of ERGO is up to 254.9 F/g between-1-0.4 V. After 1000 times of charging and discharging, the specific capacitance remains 85%, which has superior cycling property. A symmetric capacitor was assembled by using graphene electrode. The specific capacitance is 46.6 F/g. The energy density and power density is 12.7 Wh/kg and 9211 W/kg, separately. After 1000 times of charging and discharging, the capacitance remains 77%. The cycling property remains to be improved.The FT-IR, XRD, TGA-DSC and SEM of TRGO/Ni(OH)2 indicate that composite contains Ni(OH)2 and graphene. The results of capacitance performance indicate TRGO/Ni(OH)2 composite has superior capacitance performance when the hydrothermal time is 10 h, the mass ratio of TRGO and Ni(OH)2 is 1:7 and the electrode mass is 2.6 mg. In 1 M KOH solution and at 3.8 A/g current density, the specific capacitance is up to 1488 F/g between 0-0.5V. After 2000 times of charging and discharging, the capacitance remains 72%, The cycling property remains to be improved. An asymmetric capacitor was assembled by using TRGO as positive electrode and TRGO/Ni(OH)2 as negative electrode. Its specific capacitance is 41.9 F/g. The energy density and power density is 3.7 Wh/kg and 220.9 W/kg, separately. After 1000 times of charging and discharging, the capacitance remains 95%, which has superior cycling property.