The effect of number of SILAR cycles on morphological, optical and photo catalytic properties of cadmium sulfide–titania films

Abstract

In this paper, cadmium sulfide–titania nanocomposites were successfully synthesized by electrochemical anodizing and successive ionic layer adsorption and reaction (SILAR) methods. Cadmium sulfide was successfully deposited on titania nanotubes with tunable loading amounts by controlling deposition cycles of SILAR. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by FE-SEM, XRD, EDX and UV–Vis methods. Titania nanotubes with 90–220 nm in diameter and 15–30 nm in wall thickness were prepared by one-step anodizing method and then cadmium sulfide deposited onto titania to form cadmium sulfide–titania heterostructure. Characterization of the cadmium sulfide–titania sample indicated that the number of SILAR cycles significantly influenced the morphology and photo catalytic activity of fabricated films. Rh B and MO were adopted as the model dyes and the photo catalytic tests were carried out in detail. Results showed that the photo catalytic activity of cadmium sulfide–titania samples is higher than that with bare titania sample. The incorporation of cadmium sulfide on titania improves the photo catalytic activity due to the synergetic effect. The photo catalytic activity increase with the proper increase of cadmium sulfide amount; however, the activity decreases when the amount of cadmium sulfide is further increased which may result in the formation of the compact films on the surface and a decrease in surface area of samples. Cadmium sulfide–titania sample prepared by SILAR deposition with 5 cycles gives the highest degrading rate, which can be attributed to appropriate cadmium sulfide content. Cadmium sulfide–titania is easy to be recycled and has good stability for repeated use. A mechanism is also studied and an electron transfer route is provided and accounts for the enhanced photo catalytic activity. With the improved visible light degradation performance, cadmium sulfide–titania samples would be expected to be used in water purification.