Facile 3D Nitrogen‐Doped Hierarchical Porous Carbon for High‐Performance Supercapacitors

A novel activated nitrogen‐doped hierarchically porous carbon (ANPC) material has been synthesized using polyurethane foam as the supporting template, phenolic resin with a high carbonization ratio, and low‐cost ammonium polyphosphate as the carbon and nitrogen sources, respectively. The preparation process comprises curing and carbonization combined with KOH activation. Despite the simplicity of the process, the obtained ANPC‐4 exhibits a high specific surface area (1452 m 2 g −1 ), a well‐developed specific pore volume (0.799 cm 3 g −1 ), moderate mesoporous content (32.7%), good electrolyte ions transport property, and appropriate nitrogen dopant content. When used as a material for fabricating supercapacitor electrodes, the ANPC‐4 exhibits a significantly high capacitance value of 356 F g −1 at 0.2 A g −1 in a 6 M KOH electrolyte with outstanding rate performance. In addition, the symmetrical capacitors assembled by ANPC‐4 have good specific capacitance (175 F g −1 at 0.2 A g −1 ), high energy density up to 24.3 Wh kg −1 , and good cycling stability (94.5% capacitance retention after 10 000 cycles of testing).