The Synthesis Of Mn₃O₄/graphene Material And Their Capacitive Performance Research

Abstract:Manganese oxide compounds (Mn3O4, MnO2, etc) have been widely used as supercapacitor electrode materials for a long time. However, their poor electronic conductivity greatly prohibit their further use in this field. Among these manganese oxide compounds, Mn3O4has won a great interest for it exists in a single hausmannite form under the room temperature and synthesizes easily. Recently, the primary strategy for enhancing the capacitive performance of Mn3O4is to mix it with those materials electronic conductive. In this work, Mn3O4/graphene materials are synthesized via choosing graphene as the matrix and their electrochemical properties are also investigated. The specific works are as follows:Firstly, Mn3O4is synthesized via a hydrothermal method under a fixed temperature with KMnO4and glycol. It exhibits a specific capacitance of150F g-1and120F g-1at the scan rate of5mV s-1and the current density of0.2A g-1, respectively. By contrast, in the second way, pure Mn3O4is obtained by a solvothermal route in the ethanol-water mixed solution with Mn(AC)2·4H2O as the reactant. While this time it exhibits a specific capacitance of205F g-1and150F g-1at5mV s-1and0.2A g-1, separately.In the second part, a series of Mn3O4/graphene materials are prepared through a solvothermal method. The phase and morphology of these as-prepared materials are characterized by various means like X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectra, etc. The electrochemical properties of these sample are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). In addition, the effects of graphene mass ratio and the solvothermal temperature on specific capacitance are also studied. The results show that a reasonable amount of graphene doped into Mn3O4can greatly enhance the electronic conductivity of Mn3O4. Then the rate capability and cycling stability of Mn3O4electrode is improved. In1.0mol L-1Na2SO4solution, the specific capacitance of Mn3O4/9.09wt.%grahene material is161.0F g-1and116.0F g-1at1A g-1and5A g-1, repectively. After1000cycles, its specific capacitance is230Fg-1at1Ag-1.