Magnetic and photocatalytic properties of Ni–Co ferrites

Abstract In this work, different compositions of NixCo1-xFe2O4 (x = 0, 0.2, 0.5, 0.8 and 1) spinel ferrites were prepared through the chemical co-precipitation technique by substitution of Co ions with Ni ions. Thermogravimetric analysis, differential thermal analysis, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infra-red, Raman spectroscopy, ultraviolet–visible, photoluminescence and vibrating sample magnetometer techniques were used to characterize the synthesized compounds. The obtained NixCo1-xFe2O4 nanoparticles with the average size in the range of ~17–~36 nm have single cubic structure. The crystal size and lattice parameter increase with the increase in nickel content. There are two major absorption bands on the FT-IR spectra: the high frequency bands ‘ν1’ is assigned to the tetrahedral while the low frequency bands ‘ν2’ is assigned to the octahedral complex. The nanoferrites have an optical band gap between 1.37 and 1.78 eV. The magnetic property such as saturation magnetization and coercivity of the compounds remarkably changes with the concentration of Ni2+. The photocatalytic activity of the compounds was further studied using methylene blue (MB) as model organic pollutants. It is found that an appropriate amount of nickel (Ni2+) can greatly increase the amount of hydroxyl radicals generated by the nanoferrite, leading to an obvious increase in the photocatalytic activity.