Nitrogen-Doped Hierarchically Porous Carbons Derived from Polybenzoxazine for Enhanced Supercapacitor Performance

Nitrogen-doped hierarchically porous carbons (HPCs), which are synthesized from benzoxazine resins, were successfully prepared following the processes of polymerization, carbonization, and potassium hydroxide (KOH) activation. As the key factor, the KOH activation temperature influences the pore structure and surface functionality, which are crucial for the excellent performance. The HPC-800 material, with the highest activation temperature (800 °C), displays a hierarchical pore structure, a high specific surface area (1812.4 m²·g^-1), large total pore volume (0.98 cm³·g^-1), high nitrogen content (1.27%), and remarkable electrical conductivity. It has also presented an excellent electrochemical performance of high specific capacitance of 402.4 F·g^-1 at 0.1 A·g^-1, excellent rate capability of 248.6 F·g^-1 at 10 A·g^-1, and long-term cycling stability with >99.0% capacitance retention after 500 cycles at 1 A·g^-1 in 6 M KOH aqueous solution.