Synthesis and Capacitive Properties of Manganese Oxide Nanosheets Dispersed on Functionalized Graphene Sheets

Functionalized graphene was prepared by reducing functionalized graphene oxide with poly(diallyldimethylammonium chloride) (PDDA), transferring the surface charge of reduced graphene oxide (RGO) from negative to positive. A composite material of functionalized RGO with manganese dioxide (MnO2) nanosheets can be obtained by dispersing negatively charged MnO2 nanosheets on the functionalized RGO sheets via an electrostatic coprecipitation method. The structures of composites were investigated by high-resolution transmission electron microscopy (HRTEM), which indicated that the MnO2 nanosheets dispersed on functionalized RGO sheets, exhibiting a layered structure. The composite material exhibited enhanced capacitive performances than those of pure functionalized RGO and Na-typed birnessite (Na/MnO2) sheets, attributing to the synergic effect of both components. Additionally, over 89% of original capacitance was retained after 1000 cycles, indicating a good cycle stability of the composite materials.