Fuel‐Modulated Nickel Ferrite for Supercapacitor Application

ABSTRACT Energy storage systems are vital to meet the increasing demand for instant power sources for electric vehicles and portable electronics. This study examines how variations in the concentration of fuel and oxidizers used during synthesis affect the electrochemical performance of nickel ferrite as an electrode in supercapacitors. Three samples of nickel ferrite, NF1, NF2, and NF3, were prepared via the sol–gel auto‐combustion method using metal nitrate (oxidizers) to citric acid (fuel) ratios of 1:0.60, 1:0.73, and 1:1. Characterization techniques such as XRD, SEM, EDS, Raman, and FTIR were applied to analyze the structure, crystallite size, morphology, elemental composition, and metal‐oxygen bonding. All three samples exhibited a pure spinel phase with varying stoichiometry. Their electrochemical performance was assessed using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy in 1 and 3 M KOH electrolytes. The NF2 electrode demonstrated the highest specific capacitance among the three samples, achieving a value of 834.37 F/g at 1 A/g in 3 M KOH. A symmetric supercapacitor device was fabricated using this electrode, achieving an energy density of 19.26 Wh/kg and a power density of 600 W/kg, with excellent stability retaining 99.97% capacitance after 10 000 cycles. The electrode and electrolyte interaction was studied by density functional theory calculations, and it revealed adsorption energies of −2.22 and −2.38 eV for the OH molecule adsorbed on nickel and iron atoms in nickel ferrite. The results indicate that both fuel and electrolyte concentrations are crucial parameters that need to be optimized to achieve the best performance of the material.