Flower-like hierarchical porous nitrogen-doped carbon spheres from a facile one-step carbonization method for supercapacitors

A facile one-step carbonization method was developed to fabricate flower-like hierarchical porous nitrogen-doped carbon sphere (FHPNCS) from polyimide using polyurethane foam as macroporous scaffold. The FHPNCS possessed flower-like spherical morphology, well-developed hierarchical porous structure, high specific surface area and nitrogen-containing functional groups. These advantages led to excellent electrochemical performance. The FHPNCS electrode exhibited a high specific capacitance of 251.6 F g−1 at 1 A g−1, a high rate capability of 76% capacitance retention at 5 A g−1, and an outstanding cycling stability of only 4.4% loss in specific capacitance after 2000 cycles. Compared with previously reported multi-step templating methods, the present method only involves a facile thermal treatment procedure and avoids the use of hard templates and toxic raw materials, thus exhibiting great potential for large scale production of nitrogen-doped carbon materials for practical applications in supercapacitors.