Deoxygenated lignin carbon aerogel with enhanced electrochemical performance in organic systems for supercapacitor...

Porous lignin carbon materials have attracted considerable attention for use as supercapacitor electrode materials. However, their electrochemical performances can be significantly affected by the presence of oxygen heteroatoms on their surfaces. In this study, oxygen heteroatoms were partially eliminated from a lignin-derived carbon aerogel through deoxygenation treatment using hydrazine hydrate. The relationship between the surface chemical composition and the textural structure of the carbon aerogel was examined, and the electrochemical behavior resulting from its use as a carbon electrode in a symmetric supercapacitor was evaluated, both before and after deoxygenation. Simple deoxygenation of the carbon aerogel reduced the surface oxygen content from 10.45 to 4.08 %, resulting in an ultrahigh specific surface area (3356.2 m² g^-1) and average pore size of 2.16 nm. In an organic electrolyte consisting of a 1 M Et₄NBF₄ acetonitrile solution, an exceptional specific capacitance (182.93 F g^-1 at a current density of 1 A g^-1) and excellent stability (capacitance retention of 96.63 % after 10,000 cycles) were achieved for the deoxygenated carbon aerogel. Additionally, at a high power density of 18,660 W kg^-1, the material demonstrated a high specific energy density of 40.66 Wh kg^-1. This remarkable energy-storage capability was attributed to deoxygenation, which resulted in an enhanced specific surface area, a suitable pore size distribution, and an excellent wettability toward the organic electrolyte. This study therefore offers a flexible technique for enhancing the functionality of lignin-based porous carbon materials, and paves the way for the high-value use of lignin in the new energy sector.