In-situ template-assisted self-activation craft for direct preparing mesoporous-dominated N/S co-doped hierarchical porous carbon for supercapacitors.

Currently, it is a huge challenge to develop a rapid and sustainable approach to prepare N/S co-doped mesoporous-dominated hierarchical porous carbons (NSMHPC) for supercapacitors. Herein, we innovatively adopted an in-situ template-assisted self-activation strategy to exploit multiple X-NSMHPCs (X = A, M, N) from different sulfate (Al(SO)/MgSO/(NH)SO) precipitated kraft lignins (X-KLs, X = Al, Mg, NH). Compared with other X-NSMHPCs, N-NSMHPC delivered unique mesoporous-dominated hierarchical structures with excellent specific surface area (S) of 622.1 m/g, large pore volume (V) of 0.61 m/g, copious N/S content and high carbon yield of 32.8 %. Its unique tertiary pore structure and plentiful surface-exposed active sites facilitated rapid electrolyte penetration, and speedy ion insertion and extraction. As expected, N-NSMHPC delivered a superior specific capacitance of 226.6 F/g at 0.5 A/g, which was much higher than that of lignin-based or biomass-direct pyrolyzed-based PCs. When assembled as a symmetric supercapacitor, N-NSMHPC demonstrated a maximum energy density of 18.7 Wh/kg and a power density of 500 W/kg. Meanwhile, it only exhibited a 6.6 % specific capacitance drop at 20 A/g after 5000-cycle charge-discharge tests. This span-new strategy provides a green and efficient sight for designing high-yield-high performance NSMHPC for supercapacitors.