Conversion of Lignin into Porous Carbons for High-Performance Supercapacitors via Spray Drying and KOH Activation: Structure-Properties Relationship and Reaction Mechanism

Lignin-derived porous carbons have emerged as promising electrode materials for supercapacitors. However, the challenge remains in designing and controlling their structure to achieve ideal electrochemical performance due to the complex molecular structure of lignin and its intricate chemical reactions during the activation process. In this study, three porous carbons were synthesized from lignin by spray drying and chemical activation with varying KOH ratios. The specific surface area and structural order of the prepared porous carbon continued to increase with the increase of the KOH ratio. Thermogravimetric-mass spectrometry (TG-MS) was employed to track the molecular fragments generated during the pyrolysis of KOH-activated lignin, and the mechanism of the thermochemical conversion was investigated. During the thermochemical conversion of lignin, KOH facili-tated the removal of H2 and CO, leading to the formation of not only more micropores and mesopores, but also more ordered carbon structures. The pore structure exhibited a greater impact than the carbon structure on the electrochemical performance of porous carbon. The optimized porous carbon exhibited a capacitance of 256 F g−1 at a current density of 0.2 A g−1, making it an ideal electrode material for high-performance supercapacitors. © 2024, Tech Science Press. All rights reserved.