N-doped porous carbon derived from different lignocellulosic biomass models for high-performance supercapacitors: the role of lignin, cellulose and hemicellulose.

Biomass-derived porous carbon (PC) has been widely studied in the field of supercapacitors due to its low cost, sustainability and developed pore structure, but how to screen the precursors of high-performance PC is still a major difficulty. Herein, six lignocellulosic biomass models based on different compositions were innovatively constructed and prepared into high-performance PC by a synergistic activation-doping strategy. The results show that the synergistic activation-doping strategy has a certain universality for biomass models. Meanwhile, cellulose and hemicellulose mainly contribute to the formation of micropores, resulting in high specific surface area (SSA), specific capacitance and energy density. While lignin provides some micropores and most mesopores for PC, which enables PC to exhibit excellent rate and cycling performance. Specifically, the MF prepared from the biomass model constructed based on wheat bran has the optimized specific capacitance (474 F g at 1 A g), due to its largest SSA (2773 m g) and high proportion of micropores (76.6%). At 5 A g, the coulombic efficiency during 5000 cycles is maintained at 98.8-99.4%, and the final capacity retention is 95.89%. Impressively, an aqueous symmetric supercapacitor based on MF assembled in 1 M NaSO electrolyte delivers an energy density of 27.66 Wh kg at a power density of 82.03 W kg. This study provides a reference for the precursor screening of high-performance PC at the composition level, and also contributes an operational idea for PC performance regulation.