Improve the Supercapacity Performance of MnO2-Decorated Graphene by Controlling the Oxidization Extent of Graphene

Metal oxide decorated graphene nanocomposites have been explored as potential electrode materials for supercapacitors. In the present work, the effects of the oxidation degree of the graphene on the loading of needle-like nano-MnO2 and electrochemical performance of the MnO2-graphene composites were systemically investigated. MnO2-graphene composites were prepared for supercapacitor electrodes via hydrazine reduction of graphite oxide and a soft chemical precipitation route at relatively low temperature. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) characterizations confirm the decrease of oxygen-containing functional groups with the increase of reducing time. XRD, SEM, and TEM studies show the nanostructure and micromorphology of the prepared composites and indicate the crystallographic structures of alpha-MnO2. Cyclic voltammetry (CV) and galvanostatic charge discharge measurement were used to evaluate electrochemical properties of the composites, and the specific capacitance values were in the range of 74.8-124 F/g at 200 mA/g with 1 M Na2SO4 as the electrolyte. The oxygen-containing functional groups may increase the resistance of the composites, but benefits the dispersion of MnO2 on graphene and the infiltration of electrolyte. Therefore, controlling the oxygen content of graphene plays an important role in the fabrication of high energy-density graphene-based supercapacitor materials.