Lignin fast pyrolysis for energy storage: Phenolic-rich oil coproduction and supercapacitor carbon from activation of the residual char

To develop high-performance carbon-based electrode materials for supercapacitors, this study establishes a complete conversion pathway from natural poplar wood to porous activated carbon. Lignin was rapidly extracted within 30 min using a deep eutectic solvent system composed of choline chloride, ethylene glycol, and various benzenesulfonic acids, serving as an intermediate precursor for subsequent carbon production. The extracted lignin, characterized by high thermal stability, abundant active functional groups, and uniform molecular weight, is subjected to fast pyrolysis. The resulting pyrolysis residue is activated via KOH to produce a porous carbon material featuring a high proportion of micropores and a specific surface area of 2353 m 2 /g. When employed as a supercapacitor electrode, this material delivers a specific capacitance of 340.4 F/g at 0.5 A/g in a three-electrode system. In a two-electrode symmetric configuration, it exhibits excellent rate performance and achieves an energy density of 15.19 Wh/kg. The study further links the phenolic-rich oil coproduct and gas evolution behavior to their roles in modulating carbon residue quality, thereby influencing overall storage performance. The advantages of the benzenesulfonic acid-based DES system and its effectiveness in rapid lignin extraction are demonstrated. By integrating lignin fractionation, fast pyrolysis, and porous carbon fabrication, this study establishes an efficient pathway for producing high-performance carbon electrodes for supercapacitor applications.