Green Synthesis of Biomass-Derived Activated Carbon from Wood Apple Shell for Enhanced Electrochemical Energy Storage

In alignment with the recent sustainable development goals aimed at improving human life on Earth and minimizing carbon footprints, the utilization of natural and renewable resources for energy production presents a sustainable and forward-thinking approach to future energy needs. In this context, we report a biomass-waste-derived synthesis route for developing energy storage materials that support sustainable energy solutions. Specifically, wood apple shell (WAS), an underutilized agro-waste material, was employed as a sustainable carbon precursor for the fabrication of activated carbon electrodes suitable for electrochemical double-layer capacitors. Through chemical activation using sulfuric acid, a highly porous carbon structure was obtained. XRD analysis revealed broad (002) diffraction peaks, characteristic of an amorphous carbon framework. BET surface area analysis confirmed a high specific surface area of 590.65 m²/g, which enhances ion transport and accessibility within the electrode material. X-ray photoelectron spectroscopy and FT-IR analysis further indicated the presence of abundant oxygen-containing surface functional groups (such as CO and C-O), which are known to improve electrolyte wettability and facilitate efficient charge storage. Electrochemical performance was evaluated in KOH electrolytes with concentrations of 2, 4, and 6 M. Among these, the electrode demonstrated optimal performance in 4 M KOH, delivering a high energy density of 29 Wh/kg and a power density of 5512 W/kg. Furthermore, the electrode showed excellent cycling stability, retaining more than 96.8% of its initial capacitance after 10,000 charge-discharge cycles. To demonstrate the practical applicability of the fabricated device, we successfully powered a green LED, showcasing its real-world energy storage potential. These findings underscore the promise of WAS-derived activated carbon as a low-cost, eco-friendly electrode material for low-power electronic applications and next-generation sustainable energy storage technologies.