Three-dimensional nitrogen-doped hierarchical porous carbon derived from cross-linked lignin derivatives for high performance supercapacitors

Nitrogen-doped hierarchical porous carbons are prepared by hydrothermal crosslinking reaction and KOH activation using sodium lignosulfonate as carbon precursor, 1,6-hexanediamine as crosslinking agent and nitrogen source. As-prepared nitrogen-doped hierarchical porous carbon possesses a high specific surface area (1867.4 m2 g−1), moderate nitrogen-doped content (3.6 at.%) and presents a superior three-dimensional hierarchical porous structure with rich micropores, favorable mesopores and interconnected macropores. The nitrogen-doped hierarchical porous carbon electrode performs high specific capacitance (440 F g-1 at 0.5 A g−1) and excellent cycle stability (94.8% of its initial capacitance after 3000 cycles at 20 A g−1) in a three-electrode workstation using 6 M KOH electrolyte, while it shows a superior rate capability (80.4% from 331 F g-1 at 1 A g−1 to 266 F g-1 at 20 A g−1) in 1 M H2SO4. Furthermore, the nitrogen-doped hierarchical porous carbon assembled supercapacitor delivers a high specific capacitance (370 F g-1 at 0.5 A g−1) and remarkable energy density (18.5 Wh kg−1 at a power density of 300 W kg−1, 10.4 Wh kg−1 at high power density of 12 kW kg−1) in 6 M KOH electrolyte. The as-prepared nitrogen-doped hierarchical porous carbon with outstanding electrochemical performance is promising for applications in sustainable energy-storage devices.