Electrochemical performance of Sr-doped cobalt nickel ferrite ceramics for supercapacitor applications

This study explores the synthesis, structural characterization, and electrochemical performance of strontium-doped cobalt nickel ferrite nanoparticles, Co₀.₅Ni₀.₅₋ₓSrₓFe₂O₄ (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5), prepared via solution combustion synthesis for the first time. Powder X-ray diffraction (PXRD) confirmed the successful incorporation of Sr²⁺ ions into the ferrite lattice without impurity peaks. The crystallite size, internal strain, lattice parameter, cell volume, and density were systematically analyzed, revealing a decrease in crystallite size and an increase in internal strain and lattice parameter with higher Sr doping. SEM analysis revealed a porous structure in the synthesized ferrite nanoparticles, which contributed to enhanced electrolyte interaction and improved electrochemical properties. The porosity, attributed to gas evolution during combustion, enhances surface area and interaction with the electrolyte, critical for supercapacitor applications. Electrochemical measurements, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD), indicated superior capacitive behavior for Sr-doped samples, especially those prepared with gum arabic (GA) as a dispersant. The addition of GA significantly increased specific capacitance and reduced impedance by improving the dispersion and interaction of active materials. The capacitance values, determined from CV and GCD data, showed a trend of decreasing with increasing scan rates and current densities, but Sr-doped samples exhibited better retention of capacitance and reduced impedance. These findings suggest that Sr-doped Co₀.₅Ni₀.₅₋ₓSrₓFe₂O₄ ferrites, particularly those synthesized with GA, hold significant potential for high-performance supercapacitor and energy storage applications. The study highlights the importance of optimizing doping levels and employing effective dispersants to enhance the electrochemical properties of ferrite-based materials.