Electrodeposited ZnIn2S4 onto TiO2 thin films for semiconductor-sensitized photocatalytic and photoelectrochemical applications

Abstract

In this study, ZnIn2S4/TiO2 heterostructure was successfully synthesized on ITO-coated glass substrates via a facile two-step process from aqueous solution. First, TiO2 thin film was prepared by sol–gel and deposited onto ITO coated glass substrate by spin-coating method. Then the zinc indium sulfide semiconductor was fabricated via electrodeposition technique onto TiO2/ITO coated glass electrode. The X-ray diffraction patterns confirm that the heterostructure is mixed of both Anatase TiO2 and Rhombohedric ZnIn2S4. The scanning electron microscopy (SEM) images show that the morphology change with the deposition of ZnIn2S4 over TiO2 thin film and a total coverage of the electrode surface was obtained. Optical absorption spectroscopy study of ZnIn2S4/TiO2 heterostructure exhibits a remarkable red-shift compared to the TiO2 and ZnIn2S4 achieve the best efficiency of visible light absorption. Therefore, it is expected to apply to visible-light photocatalysis and solar cells. To investigate the effect of the heterojunction on the photocatalytic activity of ZnIn2S4/TiO2 thin films, photodegradation of methylene blue in the presence of ZnIn2S4 was performed. ZnIn2S4/TiO2 heterostructure exhibited strong photocatalytic activity, and the degradation of methylene blue eached 91% after irradiation only for 4h. Also, the study of the photocurrent density produced by ZnIn2S4/TiO2 thin film electrode reached 0.8mAcm−2, about four times higher than that measured on TiO2 thin film. These results indicate that the heterojunction have a better photo-electrochemical performance than the pure TiO2 thin films under illumination. As a result, the obtained ZnIn2S4/TiO2 heterostructure would have great potential in photocatalytic and Photoelectrochemical devices.