Graphene and Carbon Supported Manganese(IV)-Cobalt(II/III) Oxides Nanoparticles As High-Performance Electrochemical Supercapacitors

Abstract

The search for cleaner energy sources is required to shift focus to the generation of energy from electrochemical systems, batteries, fuel cells, solar cells, and super capacitors, among others. In this study we report a simple approach for preparation of the graphene (GR) and carbon (C) supported manganese(IV) and cobalt(II/III) oxides using microwave-assisted synthesis. The X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) methods were used for the characterization of morphology, structure and composition of the prepared the graphene and carbon supported MnO2-Co3O4 nanocomposites. Electrochemical performance of the MnO2-Co3O4/GR and MnO2-Co3O4/C nanocomposites was evaluated using long life cyclic voltammetry (CV) and galvanostatic charge-discharge. The MnO2-Co3O4/GR and MnO2-Co3O4/C nanocomposites which have different morphologies, have been prepared by microwave synthesis. It was found that the graphene supported MnO2-Co3O4 nanoparticles has significant influence on the electrochemical performance of composites electrodes compared with that of the carbon supported MnO2-Co3O4 nanoparticles. The maximum specific capacitance was achieved at the MnO2-Co3O4/GR electrode in the 1 M Na2SO4 aqueous solution at the scan rate of 10 mV s-1. After 1000 charge/discharge cycles at the scan rate 100 mV s-1 the capacitance of all the materials synthesized in this study remains over 94 %, suggesting great potential for supercapacitors.