Design and multifunctional potential of Al3+, Er3+-substituted Ni0.2Cu0.8AlxErxFe2−2xO4 spinel ferrites for sustainable energy and environmental applications

Abstract

In the current work, Al³⁺ and Er³⁺-substituted nickel-copper spinel ferrites Ni_0.2Cu_0.8Al_xEr_xFe_2−2xO₄ (x = 0, 0.04, 0.08, 0.12, 0.16) are prepared using the sol–gel method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-VIS), and dielectric measurements were employed to examine the prepared nano ferrites. XRD confirms the production of spinel ferrites with a cubic structure. The crystal size of the ferrites ranges from 6.9 to 14.7 nm. The FTIR study confirmed the formation of spinel ferrites and showed that vibrational bands shifted to higher wavenumbers following substitution. UV-VIS spectroscopy revealed that the band gap increased after the substitution of Al³⁺ and Er³⁺ ions. Variations in dielectric properties with frequency were also examined. The synthesized ferrites showed a maximum degradation activity of 89% for crystal violet dye. The electrochemical performance of the fabricated ferrites was assessed using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The synthesized ferrites exhibit an excellent specific capacitance of 634 F g⁻¹. These ferrites possess multifunctional properties and can be used as catalysts for removing organic pollutants and as electrode materials for supercapacitor applications.