Hydrothermal fabrication of reduced graphene oxide/activated carbon/MnO2 hybrids with excellent electrochemical performance for supercapacitors

Abstract

A graphene/activated carbon/MnO2 (GAM) composite was synthesized by reacting in a hydrothermal synthesis reactor and maintaining at 140 °C for 2 h. MnO2 anchored on graphene/activated carbon (GR/AC) sheets and the activated carbon (AC) particles distributed on the graphene (GR) surface provided numerous meso/micropores that act as active sites for the discharge reaction. The GR forms a three-dimensional network with excellent electrical conductivity for application. In this study, we focus on the mass ratio of GR/AC and MnO2. The test outcome indicated that the GAM electrodes displayed exceptionable electrochemical performances especially when the mass ratio of GR/AC and MnO2 is 2:3. The specific capacitance of GAM has achieved 378 F g-1 at a constant current density of 50 mA g-1 in the 7 M KOH electrolytic solution. Beyond that, the GAM 2:3 electrodes have also shown splendid cyclic ability with a 91.58% capacitance retention over 3000 circles. The three dimensional network structure is expected to represent a thrilling orientation for heightening the electrochemical property of MnO2 and could be generalized for projecting next-generation superior supercapacitors.