Analysis of silver particles incorporated on TiO2 coatings for the photodecomposition of o-cresol

Silver-modified TiO2 (Ag–TiO2) and pure TiO2 coatings were prepared on sapphire substrates by dip-coating process for the photodecomposition of o-cresol. In order to investigate the behaviors of silver incorporated on TiO2 surface coatings, Brunauer-Emmett-Teller (BET) surface area measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), diffuse reflectance UV–Vis spectra (DRS), and photoluminescence (PL) emission spectra were performed. Experimental results indicate that the silver on TiO2 surface coatings were easily oxidized into silver oxide (Ag2O), because of the existence of Ag2O crystal phase in XRD spectrum and Ag2+–O and O1s–Ag chemical bonding states in Ag 3d and O 1s narrow scans of XPS, respectively. PL spectra showed that as increasing the amount of silver incorporated, the PL intensity of Ag–TiO2 coatings evidently decrease, which means that the Ag–TiO2 coatings have higher efficiencies of charge carrier trapping, immigration and transferring, and subsequently promote the photodecomposition rate constants after the UV/TiO2 process. An optimal composition of 0.50 wt.% Ag–TiO2 coating for the photodecomposition of o-cresol correspond to a maximum photodecomposition rate constant (k value) of 0.01 min− 1 as compared to that of the pure TiO2 coatings (k = 0.0062 min− 1).