Efficient NiO/F-TiO₂ nanocomposites for 4-chlorophenol photodegradation

This work aimed to study NiO/F-TiO₂ composites in the photocatalytic degradation of 4-chlorophenol. F-TiO₂ support was prepared by in-situ fluorination of TiO₂ using the sol-gel method. The heterostructured materials were prepared by wet impregnation method, varying NiO content (0.5, 1.0, and 2.0% wt). The solids were characterized by X-ray fluorescence, X-ray diffraction, nitrogen physisorption, diffuse reflectance UV-Vis spectrophotometry, infrared spectroscopy, and X-ray photoelectron spectroscopy. The characterization studies showed that the coupling of TiO₂ with fluoride ions promoted the generation of ≡Ti-F surface species that could be responsible for the decrease in the recombination frequency of charge carriers and the increased photoactivity. In addition, it was found that the coupling of NiO/F-TiO₂ semiconductors improved the photocatalytic properties of the fluorinated support, obtaining higher percentages of degradation and mineralization of the phenolic contaminant. These results are possibly a consequence of factors such as the formation of larger crystallites, lower band gap energies, and the generation of p-n type interfacial heterojunctions that potentiate the proper separation of electron-hole pairs. An effect of NiO content on photoactivity was observed, being a percentage of 1.0% wt the optimum in this photocatalytic treatment.