Nitrogen-modified biomass-derived cheese-like porous carbon for electric double layer capacitors

Abstract

Lignin, an abundant biomass constituent in nature, was modified by pyrrole to produce nitrogen-doped porous carbon. The porous carbon was efficiently activated through simultaneous chemical and physical reactions using potassium hydroxide as an activation agent during the heat treatment. Surface area analysis showed that the activated carbon possessed mesopores (∼15 nm) and a large specific surface area of 2661 m² g⁻¹, with a cheese-like morphology. Electrochemical double layer capacitors fabricated using the activated carbon as an electrode material showed a specific capacitance of 248 F g⁻¹ at a low current density of 0.1 A g⁻¹ and 211 F g⁻¹ at a high current density of 10 A g⁻¹ in 6 M KOH solution. Charge and discharge for 1000 cycles at different current densities ranging from 0.1 to 10 A g⁻¹ confirmed excellent specific capacitance retention and good cycling stability. This work demonstrates that the nitrogen-doped cheese-like porous activated carbon is a promising electrode material for electric double layer capacitors.