Energy storage studies of a novel green route synthesized high-performance supercapacitor based on Fe₃O₄

This study reports the synthesis of magnetic iron oxide (Fe₃O₄) nanoparticles using Aegle marmelos pulp extract as a green reducing agent. The formation of Fe₃O₄ nanoparticle with a cubic crystal structure was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM), which indicated crystallite sizes in the 10–13 nm range. Magnetic property analysis through vibrating sample magnetometer (VSM) measurements revealed a superparamagnetic nature with a saturation magnetization (Ms) of 41.99 emu/g. The electrochemical performance of the synthesized electrode material was evaluated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a 1 M KOH electrolyte. The electrode exhibited a specific capacitance of 1348 F/g at a current density of 3 mA/cm², along with an energy density of 46.8 Wh/kg and a power density of 500 W/kg. Furthermore, the electrode demonstrated excellent stability, retaining over 93.34% of its initial capacitance after 3000 GCD cycles. These findings indicate that the green-synthesized Fe₃O₄ electrode is a promising candidate for high-performance supercapacitor applications.