Multifunctional properties of NiFe₂O₄ nano-ferrites: Oxygen evolution reaction, photocatalytic performance and magnetic properties

In this study, NiFe 2 O 4 (NF) nano-ferrites were synthesized via a sol–gel route and calcined at 500 °C, 600 °C and 700 °C to investigate the influence of calcination temperature on their structural, morphological, magnetic, electrocatalytic, and photocatalytic properties. X-ray diffraction and Rietveld refinement analyses confirmed the formation of single-phase inverse spinel structures (space group of Fd-3 m) with lattice constants around 8.34 Å. The average particle size decreased from 118.67 nm (NF-500) to 67.95 nm (NF-700), indicating temperature-dependent grain refinement. Electrochemical investigations demonstrated that NF-600 exhibited the lowest onset potential (1.52 V vs. RHE) and overpotential (1.61 V at 50 mA cm −2 ) in 1 M KOH. Magnetization measurements confirmed soft ferrimagnetic behavior for all samples, with NF-500 showing the highest saturation magnetization (44.22 emu/g at 5 K) and NF-600 exhibiting the highest coercivity (337.46 Oe at 5 K), suggesting their suitability for magnetic separation and sensing applications. Furthermore, NF-600 achieved the highest photocatalytic efficiency (95 %) for methylene blue degradation under UV light and H 2 O 2 within 180 min, attributed to its optimal balance between crystallinity, particle size, and surface area. UV–Vis spectroscopy revealed that all NF samples possess narrow and nearly identical band gap energies (∼1.81–1.82 eV), indicating that the enhanced photocatalytic activity of NF-600 arises primarily from improved crystallinity and surface properties rather than significant changes in electronic structure. • Spinel form of NiFe 2 O 4 synthesized at different temperature via Sol-gel method. • NF-600 exhibited lowest onset potential of OER as 1.52 V vs. RHE • All samples exhibited soft ferrimagnetic properties due to M s around 40 emu/g. • NF-600 is degregated MB by 95 % MB under UV light in 180 min. • Removing NPs from water is possible with a small magnet at room temperature.