Lignin-Derived Hierarchically Porous Carbon Nanofibers via Deep Eutectic Solvent Electrospinning and Silica-Templated Etching for High-Performance Supercapacitors

The valorization of lignin, an abundant and renewable resource, remains pivotal to advancing sustainable material innovation. Herein, we propose a green and cost-effective strategy for synthesizing lignin-derived hierarchically porous carbon nanofibers (HPCFs). This approach utilized choline chloride-lactic acid deep eutectic solvent (ChCl-LA DES) for lignin dissolution, followed by wet-electrospinning to fabricate lignin-based fiber aerogels. SiO₂ nanospheres were uniformly embedded within electrospun fibers as sacrificial templates to create macropores, and the lignin carbonization generated abundant mesopores and micropores, ultimately producing carbon nanofibers with multiscale pore architectures. Furthermore, the hierarchical pore distribution can be tuned by modulating the SiO₂ nanosphere content, which in turn optimized the textural properties and electrochemical performance of the carbon nanofibers. The optimized carbon nanofibers doped with 100 mg of SiO₂ nanospheres (100-HPCF) exhibited distinct improvement in specific surface area (779.515 m²/g) and specific capacitance (237.1 F/g at 0.5 A/g), representing a marked improvement over nontemplated lignin-derived electrospun carbon fibers (LESCFs). Moreover, 100-HPCF demonstrated exceptional cycling stability, retaining 97.7% of its peak capacitance after 15000 cycles. The integration of lignin valorization, DES-enabled processing, and hierarchical pore-structure optimization establishes a sustainable and viable pathway for developing advanced carbon materials with exceptional supercapacitor performance.