Microwave-assisted two-step pyrolysis of water hyacinth for the preparation of N-self-doped porous carbon

Biomass carbon, particularly heteroatom-doped porous carbon with additional pseudocapacitance, is widely used as an energy storage material. In this study, N-self-doped porous carbon enriched with hierarchical pore structures was prepared via microwave-assisted pyrolysis of water hyacinth. The porous carbon obtained at a heating power of 500 W and a final temperature of 700 °C (WPC-T7P5) has the highest specific surface area (SSA) of 2649 m2/g. In addition, WPC-T7P5 has abundant nitrogen-containing functional groups and a total N content of 2.73%. The carbon morphology and thermal stability show that the inorganic carbon content of WPC-T7P5 reaches 39.87% with a stable carbon structure. WPC-T7P5 possesses a specific capacitance of 374 F/g at 0.2 A/g and 254 F/g at 20 A/g, respectively, with a capacitance retention of 67.91%. A symmetrical supercapacitor based on WPC-T7P5 exhibits a maximum energy density of 8.09 Wh/kg at a power density of 50 W/kg. This study presents a novel microwave-assisted green technique to fabricate N-self-doped porous carbon.