Hydrothermally engineered Ni,Zn (Fe2O4) spinel ferrite nanostructures for high-energy supercapacitors

Abstract

The work reported here involves the synthesis of Ni–Zn spinel ferrite nanoparticles for potential energy storage in supercapacitors. Structural and morphological analysis reveals that the highly crystalline phases exhibit average crystallite sizes of 41.8 nm (nickel ferrite) and 35.9 nm (zinc ferrite). The structure of the spinel ferrites is further confirmed through FT-IR and Raman spectroscopy. Field-emission SEM demonstrates a porous morphology, while EDS confirms the elemental composition. XPS analysis confirms the binding energy of each element. BET results confirm the high specific surface area of the synthesized materials, ranging from 28.04 to 31.83 m² g⁻¹. Electrochemical studies of nickel ferrite and zinc ferrite nanoparticles were performed in a 3 M KCL electrolyte. Among the investigated electrodes, the symmetric devices delivered specific capacitances for nickel ferrite (NF) and zinc ferrite (ZF) of 81.7 F g⁻¹ and 243.3 F g⁻¹, respectively, at a low current density of 0.9 A g⁻¹. Moreover, the ZF electrodes demonstrated a significantly higher energy density (27.37 Wh kg⁻¹) than NF (9.19 Wh kg⁻¹), while maintaining nearly identical power density (∼405 W kg⁻¹) at 0.9 A g⁻¹. An NF//ZF asymmetric supercapacitor demonstrated excellent electrochemical performance, achieving 385.67 F g⁻¹ specific capacitance, accompanied by 53.56 Wh kg⁻¹ energy density and a power density of 399.95 W kg⁻¹, all measured at 0.8 A g⁻¹.