Construction of hierarchical porous carbon from softwood lignin extracted by deep eutectic solvent for high-performance supercapacitors

Lignin-derived porous carbon materials are promising electrode materials for supercapacitors owing to its tunable structure and excellent electrochemical properties. In this study, lignin (L EG and L PG ) was extracted using deep eutectic solvent (DES) and prepared into hierarchical porous carbon electrodes (CL EG and CL PG ) for supercapacitors. A systematic comparison of the structures and properties of both the lignins and the derived carbons was conducted. The results indicate that L EG , which has higher hydroxyl content, more abundant conjugated structure and β-O-4 linkage, was successfully converted into CL EG with an extremely high specific surface area (3096 m 2 ·g -1 ) and rich hierarchical porous structure under the synergistic effect of magnesium oxide as template agent and potassium acetate as chemical activator. Consequently, CL EG exhibits a high specific capacitance of 386.0 F·g -1 at 1 A·g -1 with excellent rate performance. The assembled symmetrical supercapacitor device achieved an energy density of 14.6 Wh·kg -1 at a power density of 250 W·kg -1 in 6 M KOH electrolyte solution, and maintained 88.3% capacitance after 12,000 cycles. This research provides a new strategy for designing high-performance carbon electrode materials from lignin.