High-performance carbon nanofibers derived from polyazomethine and lignin: Structural and electrochemical insights for energy storage applications

Abstract

This study presents the fabrication and electrochemical evaluation of polyazomethine (PAM)/lignin-derived carbon nanofiber (CNFs) as free-standing, heteroatom self-doped electrodes optimized through iodine stabilization and high-temperature carbonization. PAM containing thiophene and ether linkages was electrospun with lignin into nanofibers, followed by thermal treatment at 700–900 °C to investigate the impact of structural modifications on electrochemical performance. Microstructural analyses confirmed that carbonization at 900 °C promoted graphitization, leading to an increase in electrical conductivity (11.38 S/cm) and the formation of a mesoporous structure with a high specific surface area (101.4 m²/g). Electrochemical characterization revealed that CNFs, which were carbonized at 900 °C, exhibited superior specific capacitance (165.2 F/g at 0.5 A/g), energy density (24.75 Wh/kg), and power density (250 W/kg). The CNF also demonstrated excellent stability, retaining 89.6 % of its initial capacitance after 4000 charge-discharge cycles. Electrochemical impedance spectroscopy confirmed that CNF-900 had the lowest charge transfer resistance and internal resistance, facilitating efficient ion and electron transport. The incorporation of lignin contributed to the formation of a hierarchical porous network, further improving electrochemical performance. These findings highlight the potential of PAM/lignin-derived CNFs as sustainable, high-performance electrode materials for next-generation energy storage applications.