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.