TiO₂ Phase Ratio's Contribution to the Photocatalytic Activity

Photocatalysis is one of the approaches for solving environmental issues derived from extremely harmful pollution caused by industrial dyes, medicine, and heavy metals. Titanium dioxide is among the most promising photocatalytic semiconductors; thus, in this work, TiO₂ powders were prepared by a hydrothermal synthesis using titanium tetrachloride TiCl₄ as a Ti source. The effect of the hydrochloric acid (HCl) concentration on TiO₂ formation was analyzed, in which a thorough morpho-structural analysis was performed employing different analysis methods like XRD, Raman spectroscopy, SEM/TEM, and N₂ physisorption. EPR spectroscopy was employed to characterize the paramagnetic defect centers and the photogeneration of reactive oxygen species. Photocatalytic properties were tested by photocatalytic degradation of the rhodamine B (RhB) dye under UV light irradiation and using a solar simulator. The pH value directly influenced the formation of the TiO₂ phases; for less acidic conditions, the anatase phase of TiO₂ crystallized, with a crystallite size of ≈9 nm. Promising results were observed for TiO₂, which contained 76% rutile, showing a 96% degradation of RhB under the solar simulator and 91% under UV light after 90 min irradiation, and the best result showed that the sample with 67% of the anatase phase after 60 min irradiation under the solar simulator had a 99% degradation efficiency.