Design of visible light-assisted Fenton-like Ni-Fe oxide nanocomposites for photodegradation of rhodamine-B

This study deals with nickel oxide (NiO) incorporated into a Fe oxide catalyst, prevailing idea for improving the photodegradation activity of wastewater treatment. The standard sol-gel method was adopted to prepare pure Ni oxide, Fe oxides and mixed Ni-Fe Oxides. The synthesized materials were tested by photodegradation of water pollutant rhodamine B (RhB) under visible-light irradiation. From the XRD analysis, it was evidenced that all the synthesized samples showed nanocrystalline phases. The UV-vis absorption decreases the bandgap energy value from 2.16 to 1.80 eV for pure Fe oxides to 8 wt% Ni-Fe oxides (8NiFe), respectively. Field emission scanning electron microscope-EDS results revealed the uniform and fine distribution of the NiO species on the surface of the Fe oxides and strong interaction between the NiO and iron oxide species. From the M-H curves, the negative field shifting of the hysteresis loop was evidence of exchange coupling between the anti-ferromagnetic and ferromagnetic phases of Ni-Fe oxide materials. Thus, the NiO dopant played an exciting role in improving the morphological, structural, optical and ferroelectric properties of the Fe oxides and enhanced the dye photodegradation efficiency. Among various NiO loadings, the 8NiFe catalyst exhibited an enhanced visible-light absorption and superior photocatalytic degradation performance (similar to 90%) compared to other catalysts, which can explain the presence of major active species of the electron-hole pairs of the material. Finally, the prepared catalysts were highly efficient and more stable in the visible-light-driven degradation of the water pollutant RhB up to the 4th run.