Facile synthesis of chitosan derived heteroatoms-doped hierarchical porous carbon for supercapacitors

Carbon materials with hierarchical porous structure and heteroatom-doping have gained extensive attention as promising electrode for supercapacitors. In this study, we report a facile approach which involves only one step of calcination and washing treatment to prepare nitrogen-doped carbon material with tunable pore structure. This carbon material was derived from chitosan employing the blend of potassium nitrate and hexahydrate magnesium nitrate as the active agent. By adjusting the calcination temperature and active agents, the morphology and pore structure of the material can be effectively controlled. By means of this approach, the three-dimensional hierarchical porous carbon possesses a large specific surface area of 922 m2 g-1, and abundant nitrogen and oxygen functional groups. Benefiting from these advantages, the final product shows high specific capacitance of 225.3 F g-1 in a three-electrode system at 1 A g-1, good cycle stability with 88% capacity retention after 10000 cycles at 5 A g-1. Additionally, the constructed symmetric two-electrode supercapacitor shows remarkable specific energy of 10.46 Wh kg-1 with the specific power of 500.08 W kg-1. It also showed excellent electrochemical performance in PVA/KOH hydrogel electrolyte with 70.8 F g-1 at the current density of 1 A g- 1.