Solar-driven active and reusable immobilized fluorine-doped ZrO2−x thin film photocatalyst for dye-contaminated water

Abstract

An immobilized fluorine-doped ZrO_2−x thin film photocatalyst was synthesized on glass substrates using the pulsed spray pyrolysis (PSP) technique for the first time. PSP is simple to control, capable of producing homogeneous thin films on a mass-production scale, and easy to use. Firstly, the fluorine-doped ZrO_2−x thin film was prepared at an optimum deposition temperature at 400 °C and 30 min spray time, and thoroughly characterized. Its performance was then evaluated for the photocatalytic degradation of the Remazol Red (RR) dye as a model organic water contaminant under solar light. The results revealed that the degradation kinetics of the RR dye were represented by pseudo-first-order, and the apparent rate of degradation increased fourfold, i.e., from 78.7 × 10⁻⁵ min⁻¹ for the ZrO₂ thin film at 400 °C/30 min to 339 × 10⁻⁵ min⁻¹ for the F-doped ZrO_2−x thin film at 400 °C/30 min. This is due to the presence of fluorine, which reduces the band gap of ZrO₂ and exhibits substantial absorption in the solar spectrum instead of the UV range, in addition to the reduction in the rate of electron–hole pair recombination. The study found that the most important role in the RR dye degradation was played by the oxidizing species order: ¹O₂ ≈ O₂˙⁻ > ˙OH. To sum up, the F-doped ZrO_2−x thin film is a promising immobilized photocatalyst for dye removal.