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 m2 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.