N,P Dual-Doped Hierarchically Porous Carbon Derived from a Polyelectrolyte Complex as High-Performance Electrodes for Supercapacitors

Both the surface composition and the pore texture of electrode materials have a significant effect on their electrochemical performances. Herein, a new type of nitrogen and phosphorus dual-doped hierarchically porous carbon (NP-HPC), fabricated by simultaneous pyrolysis and activation of the polyelectrolyte complex with chitosan and polyphosphoric acid as the precursor, is demonstrated. The NP-HPC has a hierarchically interconnected porous structure, high surface area (2933 m 2 g −1 ), and doping of heteroatoms. Due to its unique features, the optimal NP-HPC-800 demonstrates a high specific capacitance (289 F g −1 at 0.5 A g −1 ), excellent rate performance (238 F g −1 at 10 A g −1 ), and superior cycling stability (96% retention after 5000 cycles at 5 A g −1 ) in 6 mol L −1 of KOH. Furthermore, NP-HPC-800 shows an excellent energy density of 22.5 Wh kg −1 at a power density of 183.3 W kg −1 . The low-cost and facile fabrication process provides a feasible approach to prepare heteroatom-doped carbon materials from a biomass precursor for energy-related applications.