Titanium Dioxide Nanomaterials Synthesis, Characterization And Photocatalytic Performance Study

As world wide environment pollution and energy resource crisis are graving gradually today, effective utilization of solar energy to solve pollution problems and others has became a great interest in many countries. The synthesis and applications of photocatalyst with high quantum-efficiency and high activity, in which solar energy can be utilized efficiently, have attracted much attention in the field of material, chemistry, environment science and energy sources science. Titania, as a semiconductor material, is one of the most important photocatalysis due to it is relatively inexpensive, highly stable chemically, and the photogenerated holes are highly oxidizing. In addition, reducing ability of the photogenerated electrons is high enough to produce superoxide from dioxygen. Here, a series of titania nanoparticles with different morphologies and its composite have been prepared by the solution route, whose phase structure, microstructure, and photocatalysis properties are also investigated.(1) Titania nanorods have been hydrothermally prepared using Ti(SO₄)₂ as titanium source, and the different pH values of Ti(SO₄)₂ aqueous solution were adjusted by adding ammonia dropwise at room temperature. Nanoparticles with different phase structure and morphologies can be obtained by simply changing the pH adjusted reagent (NaOH, N₂H₄·H₂O), which also indicates that the presence of amidos favors the formation of the anatase. Based on the experiments, the formation of the nanorods through a nucleation, crystal growth and oriented aggregated growth process is proposed.(2) The anatase nanoribbons with a width of tens of nanometers and a length of 10-20μm have been synthesized through a sol-gel combined hydrothermal route using Ti(SO₄)₂ as titanium source. The product was characterized with TEM, HRTEM, XRD, TG techniques in detail, and the photocatalytic properties were also investigated. It is indicated that different from the TiO₂ nanoribbons previous reported, the as-prepared nanoribbons exhibit polycrystalline nature, and anatase, rutile and brookites phases coexist in a single nanoribbon. The synthesis of the nanrribon with this new microstructure might provide a novel route to the nanomaterials. (3) The use of titania in the photocatalytic degradation technique in pollution organics and sterilization, has increased steadily in recent years as the photocatalytic degradation technique exhibits an attractive combination of high chemically stablility, simplicities and economic advantages, but the wide band gap and high probabilities of electron-hole recombination make the use of titania limited. So improving the activity of photocatalyst becomes an important field of research. The results of many studies indicated that deposition of noble metals (such as Ag,Pt,Au) on the photocatalayst surface increases the electron-transfer rate to oxygen and thereby the quantum yield.Here, Ag/TiO₂ nanorod composite was synthesized by a simple solution route. In the synthesis process, AgNO₃ was used as Ag source, pH values of suspension were adjusted by ammonia, glucose was used as reducing agent to deoxidize Ag⁺ to Ag. The product was characterized by XRD, TEM, SEM and UV-vis techniques, and the Ag nanoparticles with sizes of 3-4nm to ca.20nm can be controlled by adjusting the molar ratio of Ag to TiO₂. UV-vis spectra demonstrated the red shift of the absorption band of the composite comparing to the pure TiO2 nanorods. Furthermore, the composite exhibited excellent photocatalytic property upon the decomposition of phenol, which shows potential applications in the catalytic area.