Solvothermal synthesis of graphene–MnO2 nanocomposites and their electrochemical behavior

Abstract Well-crystallized Manganese Dioxide (MnO 2 ) 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 MnO 2 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-MnO 2 structure from the MnO 2 precursors. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM) revealed the nanorods structure of MnO 2 anchored on the graphene sheet. The electrochemical properties of graphene–MnO 2 nanocomposites were investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Electrochemical measurements showed an improved specific capacitance of 380 F/g at a scan rate of 5 mV/s, an average energy density of 53 Wh/kg and excellent cyclic performance. This enhanced energy storage ability and high rate capability can be attributed to the excellent pseudo-capacitance of MnO 2 coupled with the high electrical conductivity of the synthesized graphene suggesting its potential as an electrode material for electrochemical capacitors.