The preparation of graphene decorated with manganese dioxide nanoparticles by electrostatic adsorption for use in supercapacitors

Graphene decorated with manganese dioxide nanoparticles are prepared by electrostatic adsorption. The manganese dioxide is synthesized by a microemulsion route using the cationic surfactant hexadecyltrimethyl ammonium bromide, which dispersed in water is converted to be positively charged. The surface charge of graphene in water is negative, allowing two forms of manganese dioxide-decorated graphene to be synthesized by electrostatic adsorption: (a) free in situ synthesis and (b) layer-by-layer self-assembly. By electrochemical analysis, the specific capacitances of two materials are found to be about 40% and 250% larger than that of manganese dioxide. The improvement is because of the tighter contact between graphene and manganese dioxide, and the higher conductive and capacitive characteristics of graphene.