Green reorganization of lignin aromatic units toward porous carbon for ultrahigh performance supercapacitors

Lignin, the most abundant aromatic biopolymer on Earth, serves as a sustainable but underutilized precursor for advanced carbon materials. Herein, we introduce a green hydrothermal reorganization strategy designed to direct the transformation of lignin into porous carbons with an ultrahigh specific surface area for advanced supercapacitors. The hydrothermal treatment effectively removes hydroxylated functional groups while preserving and enriching aromatized lignin units, resulting in a structurally optimized precursor for subsequent reorganization into porous carbon. The optimized carbon material (HEHLC-800) demonstrates an exceptionally high specific surface area of approximately ~3598 m² g^-1, accompanied by a well-balanced distribution of micropores and mesopores. In symmetric supercapacitor configurations, HEHLC-800 delivers significantly superior energy-power characteristics compared to commercial activated carbon (YP-80). Specifically, it achieves a high energy density of 91.9 Wh kg^-1 at a power density of 427.5 W kg^-1 and retains 70.2 Wh kg^-1 even at a high power density of 43.7 kW kg^-1 under a 3.5 V ionic liquid electrolyte. This work offers a sustainable, scalable route for producing biomass-derived carbons that exceed commercial benchmarks in high-energy supercapacitors.