Fabrication of nitrogen-rich three-dimensional porous carbon composites with nanosheets and hollow spheres for efficient supercapacitor

N-doped carbon materials have shown great potential in energy-related areas, but well-controlled doping nitrogen content and components along with fine-constructing of multidimensional porous architectures remain great issues. Herein, we demonstrate a temperature-directed strategy to fabricate nitrogen-rich three-dimensional (3D) porous carbon composites with nanosheets and hollow spheres for efficient supercapacitors. Polydopamine@SiO2 core-shell spheres were first fabricated through a one-step synthesis method and followed by mixing with dicyandiamide and glucose to form a uniform precursor. After pyrolysis of the precursor at high temperature and etching of SiO2 cores, then the hollow carbon spheres were successfully inserted into the carbon sheets and finally obtained 3D porous hybrids. The nitrogen doping content and compositions of carbon hybrids can be controlled through adjusting the pyrolysis temperature. The as-prepared 3D carbon material with nitrogen content of 23.2 wt% and abundant mesopores exhibits a superior specific capacitance of 425 F g-1 at 1 A g-1 and remains 248 F g-1 even at a high current density of 80 A g-1 in 6 M KOH electrolyte. Our work provides a feasible and general approach to design and synthesize porous nitrogen-rich 3D carbon-based electrode materials for efficient supercapacitors.