Photocatalytic Performance And Photocorrosion Properties Of CdS/ZnO/TiO₂ Composites

The CdS with a band gap of 2.4 eV has excellent photoelectric properties is considered to be a narrow band gap semiconductor material with high photocatalytic activity in the visible range,which is widely used in the field of photoelectric detection and photocatalysis.However,its own characteristics of metal sulfides lead to the occurrence of photocorrosion,which restricting its practical application.Therefore,it is extremely important to find a simple and low-cost method to improve the stability of CdS.In this paper,the combination of ZnO,TiO₂ and CdS materials is studied by means of hydrothermal method and liquid phase deposition.By controlling the composition of the structure and optimizing the reaction conditions,the stability of the catalyst is improved while the photcatalytic properties of CdS show no attenuation.In this paper,the morphological changes and crystal structures of the samples were studied by scanning electron microscopy?SEM?,X-ray diffraction?XRD?and transmission electron microscopy?TEM?.The photocatalytic performance was studied by the degradation of organic dyes.The catalytic performance of the ZnO arrays was greatly improved by CdS quantum dots,but due to the strong photocorrosion of the CdS materials,the performance of the catalyst was rapidly attenuated.After cycles test,it can not detect the Cd and S element in the sample with energy dispersive X-ray spectrometry?EDS?,which indicate most of CdS were corroded during the photocatalytic process.By coating a layer of TiO₂ on the surface of the prepared CdS-sensitized ZnO arrays with liquid phase deposition,the photocatalytic activity of the sample was greatly enhanced.The composite structure greatly enhanced the catalytic stability and show no attenuate in the catalytic performance.The catalytic stability of the catalyst was studied by morphology and elemental change,and the catalytic mechanism was also investigated.Further,using CdS as a substrate and coating a layer of TiO₂ by liquid phase deposition,the ZnO arrays were secondary growing on TiO₂ layer.This structure can greatly enhance catalytic performance of the sample,and the proportion of CdS in the catalyst has also been increased,which leads to the enhancement of visible light absorption.Moreover,the catalytic degradation for different organic dyes was studied.It was found that the composite was suitable for most of the dye pollutants.And this structure could improve the contact area for the pollutants and greatly enhance the stability of the catalyst.