Visible light active CdS@TiO₂ core-shell nanostructures for the photodegradation of chlorophenols

The presence of chlorophenols in various environmental media has become a human health concern. In this study, homogeneous cadmium sulfide (CdS) sub-microspheres were prepared through a solution phase and hydrothermal method, form cadmium acetate dihydrate and thiourea. CdS@TiO₂ core-shell nanostructures were synthesized using the as prepared CdS (1:4), through two steps including the solution phase and hydrothermal methods. The prepared CdS sub-microspheres and CdS@TiO₂ were characterized using a number of physico-chemical techniques such as X-ray diffraction (XRD), RAMAN spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–vis Diffuse Reflectance Spectroscopy (UV–vis DRS), Scanning Electron Microscopy (SEM), Transmission Electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). The experimental results demonstrated that the morphology of the CdS sub-microspheres can be easily controlled by changing the ratio of cadmium acetate/thiourea. The SEM analysis revealed that the CdS sub-microspheres prepared by solution phase and hydrothermal methods possess an average size of around 149 and 470 nm respectively. The CdS sub-microspheres and CdS@TiO₂ core-shell materials were evaluated for the visible light photocatalytic degradation of 2,4-dichlorophenol and 2,4,6-trichlorophenol. CdS@TiO₂ showed up to 20% enhanced photocatalytic activity for the degradation of 2,4-DCP and 2,4,6-TCP compared to pure CdS. Up to 70% of 2,4-DCP and 2,4,6-TCP were removed in 6 h. The enhanced photoactivity can be attributed to the longer lifetime of photo-generated electron − hole pairs from the CdS@TiO₂ compared to the pure CdS material.