Oxygen-enriched hierarchical porous carbons derived from lignite for high-performance supercapacitors

Functional coal-based carbon materials with reasonable pore structure and surface properties have attracted extensive attention for use in high-performance supercapacitors. Herein, a ball milling-assisted bimetallic salt catalytic pyrolysis strategy was developed to prepare oxygen-doped hierarchical porous carbon (OHPC) derived from lignite. The optimized OHPC-1 shows a large specific surface area (1638 m2/g), rational pore structure distribution (mesopores account for 71.3%), and suitable oxygen doping, which ensure sufficient charge storage, rapid electrolyte ions diffusion, as well as the contributed pseudocapacitance. The obtained OHPC-1 exhibits a high specific capacitance of 283 F/g at 0.5 A/g in 6.0 M KOH electrolyte (operating voltage 1.2 V). The assembled OHPC-1//OHPC-1 symmetrical capacitor delivers a high energy density of 16.5 Wh/kg at the power density of 300 W/kg with long cycling stability. In sum, the proposed facile route for high-value utilization of lignite looks promising for the preparation of cost-effective porous carbons for high-performance supercapacitors.