| As an energy storage and conversion device, the advantages of supercapacitors are high power density, long cycle life and extensive application. Therefore, developing supercapacitors is of great strategic significance. In a supercapacitor, electrode materials have a crucial impact on its integrated performance. Transition metal oxides/hydroxides electrode materials have attracted considerable interest due to their large capacitance and fast redox kinetics. Nickel hydroxide (Ni(OH)2) and manganese oxide (MnO2) are generally considered to be promising transition metal oxide/hydroxide for the next generation of supercapacitors due to their high theoretical capacitance, low cost, environmental friendliness, and natural abundance. Furthermore, carbon materials have received tremendous attention. For example, graphene is a newly reported carbon material that has been used as electrode material for supercapacitors considering its large surface area and excellent electronic conductivity. In order to make full use of their benefits, many researchers have attempted to develop hybrid electrode architecture incorporating Ni(OH)2 or MnO2 on the surface of carbon materials.Ni(OH)2/GO(Graphene Oxide) composite was prepared by chemical bath deposition from an aqueous solution composed of graphene oxide, nickel sulfate, ammonium persulfate, and ammonia at normal temperature and pressure. Through changing the experiment conditions, we got the optimized synthesis conditions:the amount of NiSO4·6H2O is 4mmol and the reaction time is 24h. The structure and morphology of the product were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM) and Fourier Transform-Infrared Spectroscopy(FT-IR). And its capacitive performance was studied by cyclic voltammetry(CV) and galvanostatic charge-discharge. The results showed that graphene oxide is coated by sheet-like Ni(OH)2·0.75H2O and its specific capacitance reaches up to 476F/g at 1A/g in 1mol/L KOH aqueous solution, which increases by 20% in comparison with pure Ni(OH)2 synthesized under the same conditions.. This method provides a straight forward and facile approach to distribute Ni(OH)2 on the surface of graphene oxide.MnO2/RGO(Reduced Graphene Oxide) composite was fabricated by precipitation method followed by calcination The influence of the amount of KMnO4, reaction time and temperature on the electrochemical properties of the product was discussed. The reaction procedures for MnO2/graphene are as follows:first, MnO2 is formed on GO in the solution which consists of 40ml graphene oxide,2mmol KMnO4 and 1mmol diammonium hydrogen citrate at 50℃ for 7h, then the obtained product is reduced to Mn02/RG0 through calcination at 350℃ for 2h in muffle furnace. The electrochemical properties of the MnO2/RGO electrode were explored by CV and galvanostatic charge-discharge. Its specific capacitance value is 112.9F/g at the current density of 0.3A/g in 0.5mol/L Na2SO4. Meanwhile, we investigated the effect of electrolyte solutions on the electrochemical performance of the prepared electrode. Its specific capacitance is as high as 441F/g in 1mol/L KOH alkaline solution, which is much higher than that in 0.5mol/L Na2SO4 neutral solution. So the composite displays higher specific capacitance in KOH alkaline solution. |
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