Dual-Functional g-C₃N₄ Templated Synthesis of N-Doped Hierarchical Porous Carbon for High-Performance Zinc-Ion Hybrid...

The pursuit of high-performance cathode materials is essential for advancing aqueous zinc-ion hybrid capacitors (ZIHCs). However, conventional porous carbons often suffer from limited capacity and unsatisfactory rate capability due to insufficient active sites, mismatched pores, and low nitrogen-doping levels. Herein, we propose a novel strategy for synthesizing nitrogen-doped porous carbon (NPC) with a hierarchical pore structure using graphitic carbon nitride (g-C₃N₄) as a dual-function soft template and nitrogen source and potassium citrate as a combined carbon precursor and activating agent. The optimal material, NPC-0.5 (with a g-C₃N₄/potassium citrate mass ratio of 1:3), exhibits a high specific surface area (805 m² g^-1), a well-defined hierarchical pore network, and a nitrogen content of 7.94 at% dominated by graphitic-N species, which collectively enhance Zn²⁺ storage and facilitate rapid ion transport. When employed as a cathode for ZIHCs, the NPC-0.5 delivers a high specific capacity of 172 mAh g^-1 at 0.1 A g^-1, excellent rate capability (41% capacity retention at 20 A g^-1), and outstanding long-term cycling stability (86% capacity retention after 65,000 cycles at 10 A g^-1). This work provides an efficient and scalable approach for fabricating high-performance nitrogen-doped carbon cathodes for advanced ZIHCs.