Structural characteristics and visible-light-driven photocatalytic of ZnO@octahedral NiFe2O4 microcrystal prepared via thermal decomposition process.

Owing to the confinement of ZnO in the photocatalytic application: the wide bandgap, the rapid photogenerated carriers recombination, and the expensive cost for the catalyst separation from the wastewater, the p-n heterojunction of NiFe₂O₄ magnetic phase and ZnO is considered to improve the photocatalytic efficiency and the catalyst separation by the external magnetic. The NiFe₂O₄/ZnO composites with 0–12 wt% of NiFe₂O₄ were prepared by an ordinary process and characterized using XRD, Raman, SEM, EDS, TEM, HRTEM, UV–Vis spectroscopy, and PL techniques. The Raman spectra confirm the crystallinity of ZnO and NiFe₂O₄, including their defects. As increasing NiFe₂O₄ incorporation, the crystallite size of ZnO phase depicts a lower value with changing from 53.14 to 40.49 nm, whereas NiFe₂O₄ phase reveals a greater value of 60.61–141.55 nm. The dislocation density, lattice constants, and atomic coordinates are also discussed in terms of ion diffusion. The morphology analysis reveals ZnO particles on the surface of NiFe₂O₄ microcrystals, confirming the p-n heterojunction formation. The energy bandgap of the as-synthesized samples is in the range of 1.52–2.85 eV, suggesting to the visible light photocatalysis. The prominent PL spectrum indices the forming of Zn interstitial defect state. Under the visible light irradiation, the dye degradation was investigated as a result of the photoreduction percentage and catalyst dosage. With prepared by a facile process, 12 wt% NiFe₂O₄-loaded ZnO displayed the high methylene blue degradation of 96.96 % within 150 min under visible light irradiation, confirming an excellent photocatalyst. Due to the microstructural composite, the active surface site and the p-n heterojunction were elucidated as the principal mechanism for the difference in reaction time. The dye degradation was discussed in association with the structural constants, morphology, and defects. [ABSTRACT FROM AUTHOR]