Facile Synthesis of Graphene-Wrapped Honeycomb MnO2 Nanospheres and Their Application in Supercapacitors

Graphene-wrapped MnO2 nanocomposites were first fabricated by coassembly between honeycomb MnO2 nanospheres and graphene sheets via electrostatic interaction. The materials were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and thermogravimetric analysis. The novel MnO2/graphene hybrid materials were used for investigation of electrochemical capacitive behaviors. The hybrid materials displayed enhanced capacitive performance (210 F/g at 0.5 A/g). Additionally, over 82.4% of the initial capacitance was retained after repeating the cyclic voltammetry test for 1000 cycles. The improved electrochemical performance might be attributed to the combination of the pesudocapacitance of MnO2 nanospheres with the honeycomb-like "opened" structure and good electrical conductivity of graphene sheets.