Upcycling Waste Fruit Bags into Hierarchical Porous Carbon for High-Performance Zinc-Ion Hybrid Supercapacitors

Abstract The rational design of hierarchical porous heteroatom-doped carbon is critical for advancing the practical application of zinc-ion hybrid supercapacitors (ZIHSs). Herein, we propose a sustainable upcycling strategy to convert waste fruit bags into N/O-codoped porous carbon cathodes for ZIHSs, via synergistic regulation of the precarbonization temperature and KOH activation parameters. The optimized 500-WFBPC-4 sample exhibits a well-defined hierarchical pore structure, moderate defect density, and uniform N/O doping, which jointly accelerate ion/electron transport and expose abundant active sites. The as-fabricated cathode delivers a high specific capacity (228.2 mA h g–1 at 0.1 A g–1), excellent rate capability, and long-term cycling stability (only 13.2% capacity decay after 10 000 consecutive cycles). The assembled flexible all-solid-state ZIHS also exhibits an outstanding energy density (108.2 Wh kg–1) and maintains stable performance under bending conditions, showing great promise for flexible electronic applications. This work provides a scalable waste-to-value route and a referential design strategy for low-cost, high-performance carbon-based ZIHS cathodes.