Graphene oxide (GO) is reduced by a rapid cathodic reduction at -1.1 V in 0.05 M potassium biphthalate buffer solution (C8H4O4H2/C8H4O4HK). Potassium biphthalate plays an important role in the reduction process and it is superior to sodium acetate buffer solution (HOAc/NaOAc). The possible reason for this dissimilarity is discussed in detail. The reduced graphene oxide (ERGO) is characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetty and differential scanning calorimetry (TGA/DSC), X-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). The results indicate that most of the oxygen functional groups in GO are successfully removed. Electrochemical studies are carried out using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. A maximum specific capacitance of 254.9 F g(-1) can be achieved in pH 13 Na2SO4 solution at current density of 1.14 A g(-1) within the potential window of 1.4 V. (C) 2014 Elsevier B.V. All rights reserved.