Herein, reduced graphene oxide (rGO)/MnO2 hybrid materials were prepared via a direct redox reaction between MnCl2 and KMnO4 on reduced graphene oxide (rGO). A systematic study was carried out to understand the role of KMnO4. The morphology and microstructure of the as-prepared composite was characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman Spectroscopy. Results indicate that the concentrations of KMnO4 have a detrimental effect on the distribution of MnO2 nanoparticles on rGO sheets and hence on electrochemical properties. The electrochemical capacitive behavior of the as-prepared composite was investigated using cyclic voltammetry (CV), galvanostatic charge discharge, and electrochemical impedance spectroscopy (EIS) in 1 M Na2SO4 aqueous electrolyte solution. At the optimum concentration of KMnO4, the as-prepared rGM-1 composite shows a high specific capacitance of 366 F/g at a scan rate of 10 mV/s. The composite also exhibits good electrocatalytic activity towards the oxidation of dopamine (DA), exhibiting a low detection limit of 2.3 x 10(-7) M with a wide linear range between 2.5 x 10(-7) M and 2.30 x 10(-4) M. Hence, the use of rGO/MnO2 at an optimized concentration of KMnO4 is a potential competitive candidate in supercapacitor and biosensor applications. (C) 2016 Elsevier B.V. All rights reserved.