Paper TF-ThP12
Fabrication of CdS-based Visible Light Photocatalyst by the Use of Ammonia-Free Chemical Bath Deposition Technique

Thursday, October 18, 2007, 5:30 pm, Room 4C

In the recent years, utilization of a second semiconductor of lower band-gap as a sensitizer to TiO ₂ attracted lot of attention as an emerging technique for preparation of visible light photocatalyst. CdS is one of the effective low band semiconductors which can be used as a sensitizer to TiO₂. However, the preparation of CdS layer by popular conventional chemical bath deposition (CBD) technique with ammonia as a complexing agent create environmental problem as large scale production causes employment of large amounts of ammonia, which is toxic, highly volatile and harmful for the environment. In this present study CdS thin films were deposited on glass substrate by ammonia free chemical bath deposition technique with Sodium citrate as a substitute to ammonia. After deposition, all the samples were annealed at 400 °C in high vacuum of 5 x 10 ^-5 Pa for 30 min. On the top of CdS layers TiO₂ thin films were deposited by dc magnetron sputtering technique with using a mask to leave exposed CdS surface. Different samples were prepared with various amount of thiouria content for the preparation of CdS layer. The CdS thin film prepared by ammonia free recipe shows highly oriented crystallographic structure. The optical property of the CdS thin film exhibits higher red shift in compare to CdS prepared by conventional technique. Different amount of red shift has been observed with different thiouria concentrations. The photocatalytic activity was measured by decomposition of Methanol separately in UV-Vis and visible light. The surface morphology of the CdS and TiO₂ surface was studied by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM). The result is attributed to the crystallographic structure and microstructure of both CdS and TiO₂ layers.