Study On Preparation And Photocatalysis Of The Sol-gel-derived TiO₂ Nano-scaled Materials

Nano-scaled TiO2 materials, which have many good characteristics such as powerful oxidation strength, high photocatalytic activity, high chemical stability, nontoxicity and so on, have been widely used in the field of environmental protection, construction and agriculture. In this study, sol-gel method was employed to prepare three different forms of TiO2 nano-scaled materials, including TiO2 nanopowder, TiO2 thin films and TiO2 fibers.At first, the TiO2 nano-scaled materials and the photocatalysis mechanism of TiO2 were introduced. Then the absolute advantage of the TiO2 nanocrystallines in the photocatalysis filed was highlighted. The study of sol-gel-derived TiO2-based nanocrystallines under low temperature was carried. Then the TiO2 thin films were prepared by adding different organic film-forming agent, in order to fix the TiO2. However, because the photocatalytic activity of thin films was far worse than the powder sample, we had prepared TiO2 fibers which not only had high photocatalytic properties, but also fixed the TiO2 through sol-gel method. Furthermore, the incorporation of Au could greatly enhance the photocatalytic activity of TiO2 fibers. X-ray diffraction (XRD), transmission electron microscopy (TEM), High resolution transmission electron microscopy (HRTEM), Energy Dispersive X-ray Detector (EDS), UV-Vis Absorption Spectra(UV-Vis Abs), Atomic Force Microscope (AFM) and water contact angle were used to understand the crystallization property, microstructure, optical property, hydrophilicity and photocatalytic property of the prepared TiO2 nano-scaled materials. The main research results were as follows:Tetrabutyl titanate was chosen as titanium precursor. TiO2 nanocrystallines were prepared by sol method under room temperature. The crystal size was 3-4 nm, and the size was well-distributed. The results demonstrated that as the water amount (n) increased, the crystal size increased, the photocatalytic activity increased first and then decreased. The TiO2 nanocrystallines had the highest photocatalytic activity when n=120. In addition, this paper researched the photodegradation of different TiO2 nanocrystallines to methyl orange, methyl ene blue and rhodamine B. It was found that rhodamine B was easy to degrade, methylene blue was the next, and methyl orange was difficult to degrade.The TiO2 thin films were obtained by adding organic film-forming agent (PVP, PEG) into water-based TiO2 sol. The research results showed that the surface of PVP-TiO2 thin films was smooth, and the thickness was about 600 nm. The surface of PEG-T1O2 thin films was rough, and the thickness was about 300 nm. And the addition of PVP and PEG was favourable to improve the performance of film hydrophilic. When the agent was PVP or small molecular weight of PEG, the photocatalytic of TiO2 film was low, and when the agent was large molecular weight PEG, the TiO2 film showed better photocatalytic properties. The TiO2 thin films showed the best properties when the molecular weight of PEG was 6000, and the addition of PEG were 10%.TiO2 fibers and Au/TiO2 composite fibers were developed via sol-gel approach. The results demonstrated that TiO2 was anatase after the heat treatment, and the size of Au particles was 7-15 nm. The incorporation of Au could greatly enhance the photocatalytic activity of TiO2, which increased with the addition of Au incorporation.