Improved electrochemical performances of reduced graphene oxide based supercapacitor using redox additive electrolyte

Reduced graphene oxide (rGO) is prepared by simple and eco-friendly hydrothermal reduction method. X-ray photoelectron spectroscopy and Ultraviolet-visible analysis corroborated the reduction of graphene oxide into rGO in basic medium. The flexibility of the prepared rGO is inferred from transmission electron micrographs. Further, the identification of suitable electrolyte is carried out using different anions (SO42-, Cl-, OH-) and cations (K+, Na+) for the superior performance of the rGO based supercapacitors. The electrochemical performance revealed that K+ and OH- ions are more active species in aqueous solutions. Subsequently, an effort was taken to improve the specific capacitance in the optimized 1 M KOH electrolyte by KI as redox additive at different concentrations (0.025, 0.05, 0.075 and 0.1 M). The calculated specific capacitance and energy density of rGO electrode in the optimized 1 M KOH + 0.05 M KI electrolyte is 500 F g(-1) and 44 Wh kg(-1), respectively. On the other hand, it exhibited the specific capacitance of 298 F g(-1) at 0.83 A g(-1) in non-aqueous polymer gel (PVA + KOH + KI) electrolyte. Finally, the charged aqueous device is utilized to glow the light emitting diode. (C) 2015 Elsevier Ltd. All rights reserved.