Green self-assembly of digestate-derived humic acid/sulfonated polyaniline nanocomposites for high-performance...

Humic acid (HA) extracted from digested sludge offers a sustainable precursor for energy-storage electrodes but is limited by low intrinsic conductivity. Here, a mild anti-solvent self-assembly strategy is proposed to construct HA/sulfonated polyaniline (HA/SPANI) nanocomposites with a stable conductive interface and hierarchical porous structure. Strong π-π interactions and hydrogen bonding between HA and SPANI effectively enhance electron/ion transport and structural stability. The optimized HA/SPANI nanocomposite exhibits a high specific capacitance of 797 F g^-1 at 1 A g^-1 with improved rate performance and cycling stability compared with pristine PANI. A flexible symmetric supercapacitor assembled from this material achieves an energy density of 12.7 Wh kg^-1 at a power density of 200 W kg^-1 and stable operation in powering multicolor LEDs. This work provides a sustainable route for the high-value utilization of digested sludge and demonstrates an eco-friendly pathway toward high-performance electrode materials for next-generation flexible energy storage devices.