CdS/TiO2 composite films for methylene blue photodecomposition under visible light irradiation and non-photocorrosion of cadmium sulfide

Abstract

AbstractCadmium sulfide/titanium dioxide (CdS/TiO2) composite films were grown on glass by the chemical bath deposition (DBQ) and sol-gel/dip coating methods, respectively, in order to increase the photocatalytic activity of TiO2 in photodegradation processes. The influence of the CdS deposition time on the morphology, optical absorption, and phononic modes of the composites were examined. Scanning electron microscopy (SEM) images showed clearly the CdS deposit on the TiO2 surface. The absorbance spectra indicated that the absorption of composites depends on the CdS deposition time and the absorption edges are shifted to the visible range. Micro Raman spectra exhibited the phonons associated with the TiO2 anatase and the longitudinal optic (LO) phonon of CdS whose intensity increases with the CdS deposition time. Photodegradation of methylene blue (MB) under visible light irradiation was observed in all films and the results were compared with those obtained with TiO2 films. The decomposition is higher for the composite with the CdS deposition time of 15 min. This optimal deposition time allows maximal enhancement of the charge carriers transfer to TiO2 involved in the photocatalysis. No signal associated with cadmium was detected by the atomic absorption spectroscopy (AAS), which means that the CdS photocorrosion does not occur since trap centers such as OH-Cd-S and Cl−, which trap holes and inhibit the photocorrosion, are produced during the growth process.