Hydrothermal-KOH activated expired TCM waste into porous carbon for All-Solid-State supercapacitors

This study presents a sustainable and scalable strategy to transform an expired traditional Chinese medicine (TCM) Ban Langen granules into high-performance porous carbon materials for advanced all-solid-state supercapacitors. Through a synergistic combination of hydrothermal carbonization and potassium hydroxide (KOH) activation, hierarchical porous carbons (PBCM-600-3) with a moderate specific surface area of 1,183 m²/g and optimized pore architecture (micropores:0.5-1 nm; mesopores: 2-3 nm) were synthesized. The activated carbon exhibited exceptional electrochemical performance, delivering a specific capacitance of 493F/g at 0.5 A/g and retaining 93 % capacitance retention after 10,000 cycles at 20 A/g in 6 M KOH. When integrated into solid-state devices with a neutral 1 M Na₂SO₄ electrolyte, the system achieved a high specific capacitance of 269F/g and stable operation at an expanded voltage window of 1.8 V achieves a far higher energy density of 30.26 Wh/kg at a power density of 444.6 W/kg. This work not only provides a facile route for TCM waste valorization but also establishes a paradigm for designing eco-friendly, high-performance energy storage materials through strategic pore engineering and electrolyte optimization. The findings highlight the transformative potential of circular economy principles in addressing pharmaceutical waste while advancing sustainable energy technologies.