Nitrogen/phosphorus co-doped porous carbon materials for supercapacitor electrodes

We demonstrate a facile and effective approach to prepare nitrogen/phosphorus co-doped porous carbon materials by means of carbonizing cyclomatrix polyphosphazene, which is synthesized by a polycondensation reaction of p-phenylenediamine and hexachlorocyclotriphosphazene. The samples prepared at different carbonization temperatures have a hierarchical porous structure, which provides channels for the transport and storage of electrons and ions. In addition, the specific surface area and the degree of graphitization increase with increasing carbonization temperature, while the content of nitrogen and phosphorus atoms decreases with the increasing carbonization temperature. The sample prepared at 1000 °C has the largest specific surface area of 1785 m2 g−1. The cyclic voltammetry and galvanostatic charge–discharge tests show that the sample prepared at 900 °C (NP-MCP-900) has the highest capacitance, 323 F g−1, at a current density of 1 A g−1, together with excellent rate performance and cycle stability.