Electrochemical charge storage properties of novel inverse spinel (CuNiZnAlFe)₃O₄ type high entropy oxide

Abstract

The novel (CuNiZnAlFe)3O4 type nanocrystalline High Entropy Oxide (HEO) was synthesized through the sol‐gel method with combustion at 350°C for 1 h duration. The XRD analysis reveals the formation of inverse spinel [B(AB)O4] type phase indexed with the space group of Fd‐3 m confirmed through the Rietveld Refinement of the XRD data. The lattice constant for the synthesized spinel phase was found to be 8.2453°A. The Scanning Electron Microscope of the synthesized HEO confirms the flakes‐like morphology with porous microstructure. The Energy Dispersive X‐ray (EDX) analysis and elemental mapping confirm the homogeneous distribution of the cations over the selected region. It was found that Fe and Ni are in the +3 and +2 states, other cations, Cu and Zn, are in the +2 states, and Al is in the +3 confirmed through the X‐ray photoelectron Spectroscopy. The electrochemical performance was studied in three electrodes in a 2 M KOH aqueous electrolyte. The specific capacitance value was 2.02, 1.58, 1.24, 1.06, 0.87, 0.71, and 0.65 F/g at scan rates of 5, 10, 20, 30, 50, 80, and 100 mV/s, respectively. The low value of specific capacitance was observed due to the stable ionic structure of the inverse spinel phase. The magnetization behavior of the sample is also investigated. The M‐H loop of the (CuNiZnAlFe)3O4 HEO sample exhibits a ferrimagnetic nature.