Hierarchical Porous Activated Carbon Derived from Coconut Shell for Ultrahigh-Performance Supercapacitors

In this research, we successfully produced hierarchical porous activated carbon from biowaste employing one-step KOH activation and applied as ultrahigh-performance supercapacitor electrode materials. The coconut shell-derived activated carbon (CSAC) features a hierarchical porous structure in a honeycomb-like morphology, leading to a high specific surface area (2228 m(2) g(−1)) as well as a significant pore volume (1.07 cm(3) g(−1)). The initial test with the CSAC electrode, conducted in a 6 M KOH loaded symmetric supercapacitor, demonstrated an ultrahigh capacitance of 367 F g(−1) at a current density of 0.2 A g(−1) together with 92.09% retention after 10,000 cycles at 10 A g(−1). More impressively, the zinc–ion hybrid supercapacitor using CSAC as a cathode achieves a high-rate capability (153 mAh g(−1) at 0.2 A g(−1) and 75 mAh g(−1) at 10 A g(−1)), high energy density (134.9 Wh kg(−1) at 175 W kg(−1)), as well as exceptional cycling stability (93.81% capacity retention after 10,000 cycles at 10 A g(−1)). Such work thus illuminates a new pathway for converting biowaste-derived carbons into materials for ultrahigh-performance energy storge applications.