Structure-performance relationships in lignin-derived carbon aerogels: the role of subunit composition in electrochemical behavior.

Carbon aerogels have emerged as promising electrode materials for supercapacitors due to tunable porous structure and excellent electrochemical property. However, their performance highly depends on both biomass sources and preparation methods. In the present study, three distinct lignins extracted from pine (softwood), poplar (hardwood), and wheat straw (grass) were employed to fabricate lignin-resorcinol-formaldehyde carbon aerogels (LRFCs) via sol-gel polymerization under deep eutectic solvent (DES) system. The lignin chemical structure, molecular weight distribution, and monomeric composition (G/S/H subunits) influencing on both formation kinetics of LRF gels and physicochemical properties of resulting LRFCs were elucidated. Our findings reveal that pine lignin, with dominant G subunits, exhibits superior reaction kinetics for sol-gel processing and enhanced thermal stability compared to poplar (GS-rich) and wheat straw (GSH-containing) lignins. Furthermore, pine LRFC demonstrated exceptional electrochemical performance, achieving a high specific capacitance (197 F g-1 at 0.5 A g-1), outstanding rate capability, and charge transfer kinetics. This work establishes clear structure-property relationships between lignin subunit composition and resulting LRFC performance, highlighting the advantages of softwood lignin for rapid fabrication of advanced carbon materials with optimized electrochemical properties, and providing valuable guidelines for biomass aimed at high-performance supercapacitors.