N-doped ordered mesoporous carbon spheres derived by confined pyrolysis for high supercapacitor performance

Herein, we report a confined pyrolysis strategy to prepare mesoporous carbon nanospheres by which surface area of carbon spheres is increased, pore size is enlarged and effective N-doping is achieved. In this method, the mesoporous polymer sphere as carbon precursor and 2-methylimidazole as nitrogen precursor are encapsulated in a compact silica shell which provides a confined nano-space for the pyrolysis treatment. The in situ generated gases from mesoporous polymer sphere and 2-methylimidazole under pyrolysis diffuse into the pores of mesoporous polymer sphere in the confined compact silica shell, resulting in increased surface area, larger pore size and N-doping due to self-activation effect. As electrodes in supercapacitor, the N-doped mesoporous carbon nanospheres exhibit a significantly enhanced specific capacitance of 326 F g−1 at 0.5 A g−1, which is 2 times higher than that of mesoporous carbon spheres under unconfined pyrolysis condition, exhibiting its potential for electrode materials with high performance.