Preparation of platinum-and silver-incorporated TiO₂ coatings in thin-film photoreactor for the photocatalytic decomposition of o-cresol

Platinum-incorporated TiO₂ (Pt-TiO₂) and silver-incorporated TiO₂ (Ag-TiO₂) coatings on sapphire tubes of a thin-film photoreactor were prepared using a photoreduction process. Results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) revealed that the Ag-TiO₂ coatings consisted of a mixture of Ag ₂O, Ag and TiO₂ particles, owing to the partial oxidization of silver particles on the TiO₂ coatings, while the Pt-TiO₂ coating contained a mixture of Pt and TiO₂ particles. Diffuse reflectance UV-Vis spectra (DRS) showed that metal particles (Ag or Pt) incorporated into the TiO₂ coatings promoted optical absorption in the visible region and made it possible for the coatings to be excited by visible light. Photoluminescence (PL) spectra showed that the PL intensity of the Pt-TiO₂ coating was lower than that of the Ag-TiO₂ and TiO₂ coatings, indicating that the Pt-TiO ₂ coating had a higher efficiency of charge carrier trapping, immigration and transfer, which subsequently promoted the pseudo-first-order rate constants after the UV/TiO₂ process. The Pt-TiO₂ coatings for the photocatalytic decomposition of o-cresol under UV light irradiation corresponded to a higher pseudo-first-order rate constant (k) of 0.02min¹ when compared with the photocatalytic decomposition rates of pure TiO₂ coatings (k=0.0062min¹) and Ag-TiO₂ coatings (k=0.01min¹). The experimental results also indicated that the photodegradation rate of the Pt-TiO₂ coating under visible light irradiation was significantly higher than the photodegradation rates of the Ag-TiO₂ and pure TiO₂ coatings.