Effect of silver sulfide decorating on structural, optical and photo catalytic properties of iron-doped titanium dioxide nanotubes films

Iron-doped titanium dioxide nanotubes (FeTiO₂ NTs) decorated with Ag₂S with good photo catalytic performance were prepared by anodization and successive ionic layer adsorption and reaction (SILAR) methods. The morphology, crystal structure, elemental composition and light absorption capability of prepared samples were characterized by FE-SEM, XRD, EDX and UV–Vis methods. SEM results show that prepared FeTiO₂ NTs have tube diameter in the range of 50–90 nm. Characterization of the Ag₂S/FeTiO₂ NTs samples indicated that Ag₂S was deposited on the surface of FeTiO₂ NTs nanotubes and also the number of SILAR cycles significantly influenced the morphology of prepared samples. The effect of the SILAR cycles on the optical and photo catalytic properties of the hybrids were studied. Results showed that the photo catalytic activity of Ag₂S/FeTiO₂ NTs samples is higher that bare FeTiO₂ NTs sample. The high photo catalytic activity of the hybrids were mainly ascribed to the narrow band gap, large specific surface area and effective heterojunction. The photo catalytic activity increase with the proper increase of Ag₂S amount; however, the activity decreases when the amount of Ag₂S is further increased which may result in the formation of the compact films on the surface and a decrease in surface area of samples. Ag₂S/FeTiO₂ NTs 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, Ag₂S/FeTiO₂ NTs samples would be expected to be used in water purification.