Lignin-derived heteroatom-doped porous carbons for supercapacitor and CO₂ capture applications

The present study reports the economic and sustainable syntheses of functional porous carbons for supercapacitor and CO₂ capture applications. Lignin, a byproduct of pulp and paper industry, was successfully converted into a series of heteroatom-doped porous carbons (LHPCs) through a hydrothermal carbonization followed by a chemical activating treatment. The prepared carbons include in the range of 2.5 to 5.6 wt% nitrogen and 54 wt% oxygen in its structure. All the prepared carbons exhibit micro- and mesoporous structures with a high surface area in the range of 1788 to 2957 m² g⁻¹. As-prepared LHPCs as an active electrode material and CO₂ adsorbents were investigated for supercapacitor and CO₂ capture applications. Lignin-derived heteroatom-doped porous carbon 850 shows an outstanding gravimetric specific capacitance of 372 F g⁻¹ and excellent cyclic stability over 30,000 cycles in 1 M KOH. Lignin-derived heteroatom-doped porous carbon 700 displays a remarkable CO₂ capture capacity of up to 4.8 mmol g⁻¹ (1 bar and 298 K). This study illustrates the effective transformation of a sustainable waste product into a highly functional carbon material for energy storage and CO₂ separation applications.