Abstract: Alkali lignin (AL) is extracted from eucalyptus wood via a geopolymer-assisted low-alkali hydrothermal method. Using AL as theprecursor, lignin-based porous carbon (LPC) is fabricated with three activators including KOH, NaOH,and ZnCl₂ to investigate the influences of activators on the structure and electrochemical properties of LPC. The results reveal that compared with commercial lignin, the as-extracted AL preserves the native aromatic skeleton and oxygen-containing functional groups of lignin more completely, which facilitates the generation of electrochemically active sites during the subsequent high-temperature carbonization and activation process. Among the three activators, KOH exhibits the strongest etching effect. The obtained LPC-KOH possesses abundant micropores, a large specific surface area and a high proportion of C=O bonds, delivering a specific capacitance up to 336 F/g at a current density of 0.1 A/g. NaOHcontributes to the construction of hierarchical micro-mesoporous channels, while ZnCl₂ can greatly increase the mesopore proportion within LPC. Accordingly, LPC-NaOH and LPC-ZnCl₂ display outstanding rate capability.

Key words: lignin, chemical activation, porous carbon, zinc ion hybrid capacitor, electrochemical performance