Nitrogen and phosphorus dual-doped hierarchical porous carbon with excellent supercapacitance performance

The incorporation of heteroatom into well-developed porous carbon materials can significantly improve the capacitive performance. We employ a facile route for the synthesis of nitrogen (N) and phosphorus (P) dually doped carbon materials via hydrothermal carbonization of nitrogen-containing biomass-derived compounds (chitosan) followed by phosphoric acid activation. The obtained carbon possesses well-defined hierarchical porosity (surface area: 639-1142 m(2) g(-1), pore volume: 0.48-0.76 cm(3) g(-1)) and large nitrogen and phosphorus content, depending on synthesis conditions. Due to heteroatom-doping and hierarchical pore size distribution, the specific capacitances of carbon materials reach 312.4 and 204.4 F g(-1) at 0.2 and 10 A g(-1) respectively. This excellent capacitive performance is ascribed to collaborative effect of electrical double layer capacitor and faradaic pseudocapacitor from the redox reactions of the nitrogen and phosphorus species. Moreover, the specific capacitance retains 97% after 2000 cycles indicating a good stability. (C) 2017 Elsevier Ltd. All rights reserved.