Studies On Fabrication Of Visible Light Sensitive Nano-TiO₂Materials And Application In Photocatalysis

Titanium dioxide nano-materials as one kind of new photocatalytic materials have broad applications in photocatalytic degradation. In this paper, the magnetic core-shell structure Fe3O4/TiO2and TiO2nanotube arrays (TINT) were prepared. These structures can solve the recycling problems of TiO2nanomaterial during photocatalysis. In addition to modificate the TiNTs wall with metal nanoparticles or other semiconductor with narrow band gaps to expands the spectral response scope of TiO2and improve the utilization effeiciency of visible light. The main contents for the thesis are as follows:(1) Fabrication, characterization and photocatalytic properties study of the photocatalytic materials—magnetic core-shell Fe3O4/TiO2hybrids:The magnetic core of Fe3O4nanoparticles (10～20nm) were synthesized by reduction-precipitation method, and then coated with a TiO2shell to form the core-shell structure (60～70nm) by homogeneous precipitation method. Pt nanoparticles were deposited on Fe3O4/TiO2surface by a2-step photo-platinization method. The hybrids can be fast collected by an additional magnetic field. The resulted composite nanomaterials were characterized by TEM, EDS, XRD and FT-IR. In this study, he composite nanomaterials were used as photocatalyst for the degradation of AO7dye under ultraviolet and visible light conditions, the influence of Pt quantity on photocatalytic degradation of AO7was studied. The results show that Fe3O4/TiO2/215Pt has an excellent photocatalytic activity. Compared to TiO2, Fe3O4/TiO2/215Pt could completly degrade AO7within50min under ultraviolet light, and the photocatalytic efficiency improved to2.0times. On other hand, under visible light,59.0%of AO7was degraded within60min by Fe3O4/TiO2/215Pt, which is2.4times than TiO2.(2) The preparation of TiNT for photocatalysis:TiNT was fabricated by anodization of a piece of pure titanium foil in two different electrolytes (A and B). TiNT-B diameter is about130～150nm, wall thickness is～8nm, with the length of～1.4μm. TiNT-B is more suitable for the the photocatalytic degradation AO7under UV illumination. Investigate the affecting factor of the light Intensity was also carried out. The light utilization efficiency is highest when the light intensity is31mW/cm2. (3) Decoration and photocatalytic applications of TiNT:Ag nanoparticles were deposited on the TiNT by chemical reduction method; CdS/TiNT was prepared by sequential chemical bath deposition. Ag/CdS/TiNT and Pt/CdS/TiNT were prepared. The samples were characterized by SEM, XRD, DRS and XPS. The study for influence of layer number and calcination conditions on crystal structure and photocatalytic of TiNT hybrids, the optimized condition for preparing TiNT based photocatalyst as following:assembly of5layers CdS, and then annealing at200℃for1h. Investigation of the influence on quantity of Pt nanoparticles on photocatalytic degradation of AO7was studied. The result shows that under visible light the photocatalytic efficiency of215Pt/5CdS/TiNT is2.9times than the unmodified, and Pt nanoparticles play an important role in prevent of the CdS photocorrosion.