Nitrogen doped hierarchical porous carbon for supercapacitors and zinc ion hybrid capacitors†

Heteroatom-doped hierarchical porous carbon materials demonstrate significant promise for energy storage applications. In this paper, nitrogen-doped hierarchical porous carbon (NPC) materials were synthesized by one-step carbonization process using agar as the carbon precursor, urea as the nitrogen precursor, and KHCO₃ as the activating agent. Owing to the combined influence of substantial nitrogen and oxygen functional groups, interconnected hierarchical porous structure and large specific surface area, the NPC-600 electrode delivers a high specific capacitance of 450 F g⁻¹ and remarkable cyclic stability. Moreover, the NPC-600//NPC-600 symmetrical supercapacitor delivers an energy density of 29.41 Wh kg⁻¹ and good cyclic performance. More interestingly, a zinc ion hybrid capacitor (ZIHC) constructed with NPC-600 as the positive electrode achieves a capacitance of 368.78 F g⁻¹ (163.9 mAh g⁻¹), an energy density reaching 120.75 Wh kg⁻¹ and superior cyclic characteristics. The research affords a straightforward way for fabricating heteroatom-doped porous carbon as electrode for supercapacitor and ZIHCs.

Keywords: Hierarchical porous carbon; KHCO₃; Agar; Supercapacitor; Zinc ion hybrid capacitor.