Hollow spheres of nanocarbon and their manganese dioxide hybrids derived from soft template for supercapacitor application

A facile soft templating strategy has been developed for synthesizing hollow spheres of nanocarbon by hydrothermal process. In this soft templating strategy, poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) block co-polymers are used as the template while α-cyclodextrin are employed as the carbon precursor. After hydrothermal treatment, the soft templates can be easily removed by pyrolysis of the as-prepared hollow spheres in argon. The resultant hollow spheres of nanocarbon exhibit both micro- and meso-pores in carbon wall with a specific surface area of ∼380 m2 g−1. Upon incorporation of permanganate (MnO4−) into the hollow carbon spheres, nanocrystalline manganese dioxide (MnO2) is grown on the carbon surface, where the redox reaction between carbon and MnO4− takes place, giving rise to the formation of hollow carbon-MnO2 hybrid particles. An appropriate control in the diffusion of MnO4− into the core of hollow carbon spheres, nanocrystalline MnO2 can be successfully grown on both the external and internal surfaces of the hollow carbon structure. The carbon-MnO2 hybrid spheres are demonstrated as a promising candidate material for supercapacitor application.