Solvothermal synthesis of graphene–MnO2 nanocomposites and their electrochemical behavior

Abstract

Well-crystallized Manganese Dioxide (MnO2) nanorods anchored on graphene sheets have been successfully synthesis via a facile, effective and scalable solvothermal process as electrode material for electrochemical capacitors. Highly pristine graphene synthesized from mild treatment of raw highly pyrolytic graphite in a proper ratio of ethanol and water was integrated with MnO2 resulting in a strong synergistic effect between the two materials which produced hybrid nanocomposites with better electrochemical properties. The results from X-ray diffraction (XRD) and Raman analysis revealed the formation of tetragonal α-MnO2 structure from the MnO2 precursors. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM) revealed the nanorods structure of MnO2 anchored on the graphene sheet. The electrochemical properties of graphene–MnO2 nanocomposites were investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Electrochemical measurements showed an improved specific capacitance of 380F/g at a scan rate of 5mV/s, an average energy density of 53Wh/kg and excellent cyclic performance. This enhanced energy storage ability and high rate capability can be attributed to the excellent pseudo-capacitance of MnO2 coupled with the high electrical conductivity of the synthesized graphene suggesting its potential as an electrode material for electrochemical capacitors.