Zinc Oxide‐Enhanced Porous Activated Carbon From Waste Walnut Shells for Supercapacitor Electrodes

ABSTRACT This work shows the direct conversion of waste walnut shells into zinc oxide‐enriched porous activated carbon (ZnO‐AC w ) and focuses on its electrochemical performance analysis. The synthesis method consists of two steps: thermal carbonization and ZnCl 2 chemical activation. The XRD analysis revealed the presence of ZnO, graphitic carbon, and crystallinity of the synthesized composite material (ZnO‐AC w ). The as‐prepared ZnO‐AC w was found to have rod and 2 D plate‐like microstructures as observed in SEM images. The elemental composition confirmed the traces of Zn, O, Al, Si elements, and graphitic carbon. The BET analysis confirmed a high specific surface area of 756 m 2 g −1 and a mesoporous structure with an average pore radius of 16.3 Å. Electrochemical studies demonstrated a specific capacitance of 77.7 F g −1 at a high current density of 5 A g −1 . The capacitance retention was about 80% even after the 10,000 CV cycles. The experimental findings prove the high electrochemical performance of the ZnO‐enriched activated carbon, which was introduced. It also produced an energy density of 8.74 Wh kg −1 . This synthetic approach demonstrates the promising potential of walnut shells derived activated carbon as an electrode material for the supercapacitor.