Green synthesis of Mn3O4 nanomaterials by Cassia tora leaves extract for supercapacitor device with activated carbon

The sustainable and eco-friendly approach was employed for the synthesis of manganese oxide (Mn3O4) nanomaterials with Cassia tora leaf extract as a natural reducing and stabilizing agent. The green-synthesized Mn3O4 nanoparticles exhibited a spongy and granular morphology, as confirmed by SEM and TEM analyses, with an average particle size of 21 nm, promoting efficient electrolyte ion diffusion. The Mn3O4 electrode, tested in 1 M KOH electrolyte, delivered remarkable pseudocapacitive performance with a specific capacitance of 468 F/g at 5 mV/s from CV analysis and 249 F/g at 3 A/g from GCD measurements. The capacitive behavior was governed by a diffusion-controlled charge storage mechanism, as supported by kinetic separation studies. The asymmetric solid-state supercapacitor device (ASSD) (Mn3O4| |1M PVA-KOH| |AC) exhibited a high energy density of 98 Wh/kg and a power density of 2064 W/kg, with outstanding cyclic stability, retaining 97.6% of its capacitance after 10,000 cycles. Electrochemical impedance spectroscopy revealed a low equivalent series resistance (ESR) of 3.5 Ω, highlighting excellent conductivity and electrode-electrolyte compatibility. The successful fabrication and integration of green Mn3O4 nanomaterials into a high-performance supercapacitor device underscore their potential in next-generation, sustainable energy storage systems.