Bello, AbdulhakeemFashedemi, Omobosede O.Lekitima, Joel N.Fabiane, MopeliDodoo-Arhin, DavidOzoemena, Kenneth I.Gogotsi, YuryJohnson, Alan T. CharlieManyala, Ncholu I.2013-10-312013-10-312013Bello, A, Fashedemi, OO & Lekitima, JN ...et al, 2013, 'High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide', AIP Advances, vol. 3, no. 8.2158-3226 (print)10.1063/1.4819270http://hdl.handle.net/2263/32224We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF) with ~80 wt% of manganese oxide (MnO2) deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg-1 at a current density of 0.1 Ag-1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg-1 was obtained, with power density of 20 kWkg-1 and no capacitance loss after 1000 cycles. GF is an excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of doublelayer and redox capacitance mechanisms.en© 2013 Author(s).Symmetric electrochemical capacitorGraphene foamNanostructured manganese oxideCapacitorsGrapheneManganese oxidesNanostructuresPostprint Article