Glycol assisted synthesis of graphene–MnO2–polyaniline ternary composites for high performance supercapacitor electrodes

The graphene-MnO2-polyaniline (rGO-MnO2-PAn) ternary composites were prepared via in situ chemical oxidative polymerization of polyaniline on the MnO2 decorated graphene sheets. The graphene sheets were treated with KMnO4 in a water-ethylene glycol system using the hydrothermal method to complete the loading of MnO2 on the graphene sheets, while the graphene oxide (GO) sheets were hydrothermally reduced to reduced graphene oxide (rGO). The glycol was introduced as a reductant to react with MnO4(-), and GO was protected from consumption in the process of deposition of MnO2. The structures and morphologies of the resulting ternary composites are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the composites as potential electrode materials for supercapacitors were investigated using different electrochemical techniques including cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS). The specific capacitance of a rGO-MnO2-PAn composite electrode was 395 F g(-1) at 10 mA cm(-2) in 1 M H2SO4 solution. The composites displayed good cycle stability retaining 92% of their original specific capacitance after 1200 cycles by continuous cyclic voltammetric scans at 100 mV s(-1).