Bitter Apple Pulp‐Derived Porous Carbon with Rich Oxygen Functionalities for High‐Performance Zinc‐Ion Storage

Abstract Enhancement of the energy‐power performance of aqueous zinc‐ion hybrid supercapacitors (ZIHSCs) relies on the development of high‐performance carbon‐based cathode materials. Porous carbon derived from plant‐based biomasses is particularly attractive due to its rich surface functionalities, high specific surface area (SSA), tunable porosity, cost‐effectiveness, and environmental sustainability. Here, bitter apple pulp (BAP) is explored as a green precursor to realize a novel activated carbon for ZIHSC applications. KOH activation at 900 °C results in a carbon (BAPC1‐900) with an exceptionally high SSA of 3254 m² g⁻¹, pore volume of 1.8 cm³ g⁻¹, and rich oxygen functionalities (C─O, C─OH) significantly outperforming the non‐activated counterpart (64 m² g⁻¹, 0.016 cm³ g⁻¹). Raman spectroscopy reveals that the high SSA and oxygen content facilitate the simultaneous adsorption/desorption of Zn²⁺ and desorption/adsorption of SO₄^2‐ ions, ensuring an impressive Zn‐ion energy density of 162 Wh kg⁻¹ within a potential window of 0–1.8 V in an aqueous ZnSO₄ electrolyte for the optimized BAPC1‐900‐based cathode. Besides, the electrode demonstrates excellent reversibility over 50 000 cycles, retaining over 95% capacity retention. This study highlights the efficacy of pulp‐based biomass‐derived porous carbon and KOH‐activation chemistry in maximizing the zinc‐ion storage potential of carbon‐based cathodes for next‐generation energy storage.