Highly Porous Carbon From Azadirachta Indica Leaves and Uio-66 Derived Metal Oxide for Asymmetrical Supercapacitors

Bio-wastes are a great source of carbon possessing good electrical conductivity and high specific surface area for non-faradic charge adsorption. Unlike, metal oxides provide faradic type charge storage due to their high redox activity. Herein, we have utilized the neem leaves (Azadirachta Indica) derived activated carbon (NDAC) and UiO-66 (Zr-based metal-organic framework) derived zirconium oxide ZrO ₂ (ZO) based electrodes for hybrid supercapacitors. In a three-electrode system, the NDAC as a negative electrode shows a high specific capacitance of 262 F/g at 1A/g using 1M Na ₂ SO ₄ electrolyte. Besides, ZO as a positive electrode material delivered a high specific capacitance of 337 F/g at a current density of 0.25 A/g using the same electrolyte. Furthermore, an asymmetrical supercapacitor is assembled using charged balanced NDAC and ZO electrodes using 1M Na ₂ SO ₄ electrolyte. The NDAC//ZO based asymmetrical device delivers a maximum energy density of 49.2 Wh/kg at a high-power density of 540 W/kg along with a long cycle life of ∼78% (after 5000 cycles). These results give new directions for the application of low-cost bio-wastes and MOF-derived metal oxides for next-generation high-energy-density hybrid supercapacitors.