Preparation, Characterization And Photocatalytic Properties Of Nanosized ZnTiO₃-TiO₂ Complex Materials

The application of titanium dioxide as a heterogeneous photocatalyst is attracting considerable attention for water and air purification and remediation. Unfortunately, because of its wide band gap of 3.2 eV, it can be activated only by the irradiation of UV light (wavelength < 387 nm), which constitutes only a small fraction (about 3-5 %) of the solar spectrum. Simultaneously, the nano-TiO₂ powder as a photocatalyst exists as the questions for recycles difficultly and difficult to be reused. So it will be very important to develop a TiO₂ photocatalyst with higher activity by shifting its optical response to the visible light and increasing the separation efficiency of photogenerated e--h⁺ pairs. In our study, a series of Nanosized ZnTiO₃-TiO₂ Complex Materials with good photocatalytic properties were successfully prepared using Sol-Gel method and template method.This thesis mainly consists of three major parts:Part one ZnTiO₃-TiO₂ nano-composite photocatalytic material was prepared via Sol-Gel method and characterized by transmission electron microscope (TEM), powder X-ray diffractometry (PXRD), UV-Vis spectrum and zeta (ζ) potential. The influences of light source,calcination temperature and calcination time on the photocatalytic property of the nano-composite materials was investigated by using the decolorizing degradation of methylene blue (MB) solution as the model reaction. The results exhibit that the catalytic activity of material is related to its size and properties of dispersion and superficial charge. On the surface of the ZnTiO₃-TiO₂ material with a average size of 60 nm and good dispersion and the highest negative charge, obtained by calcining at 600 oC for 3 h. Decolorizing efficiency of methylene blue (MB) solution is up to 93 % under 7 h of the solar light radiation while the efficiency is 82 % under 7 h of ultraviolet light radiation , so the nano-composite material shows higher photocatalytic activity than pure TiO₂ and ZnO and the activity was closely related with the oxygen vacancy and ZnTiO₃-TiO₂ junction of the ZnTiO₃-TiO₂ photocatalyst; the efficiency can be maintained above 81 % when the catalyst is repeatedly used for 4 cycles and is easily removed from the system; so the material is no energy consumption, no pollution, good photocatalytic property and green environment-friendly catalytic material.Part two in this article, a novel ZnTiO₃-TiO₂ nanocomposite photocatalytic material was prepared via the citric acid-assisted sol-gel method, and characterized by transmission electron microscope (TEM), powder X-ray diffractometer (PXRD), UV-Vis spectrum and Zeta (ζ) potential. The influence of light source, molar ratios of citric acid to Zn²⁺, calcination temperature and calcination time on the photocatalytic property of the nanocomposite materials was investigated by using the decolorizing degradation of methylene blue (MB) solution as the model reaction. The results exhibits that the sample obtained at 700 oC for 3 h and n(citric acid):n(Zn²⁺) =1:1, showing the optimal photocatalytic property. Decolorizing efficiency of MB solution is up to above 98 % under 2.5 h of solar light radiation and the determined kinetic parameters k was 0.293 mg (L / h)^-1 that was 2.0 and 1.5 times of pure ZnO and TiO₂, respectively, while the efficiency is about 17.5 % under 2.5 h of ultraviolet light radiation; the material also shows good catalytic stability, the decolorizing efficiency of MB solution remains 80 % after 5 cycles; the activity was closely related with the oxygen vacancy.Part three a series of Sn⁴⁺/ZnTiO₃-TiO₂ photocatalytic materials with a hollow fiber structure were successfully prepared using cotton fiber as the template. By using thermo-gravimetric (TG), scanning electron microscopy (SEM), diffuse re?ection spectrum (UV–Vis), Fourier Transform Infrared Spectroscopy (FT-IR) and Zeta (ζ) potential measurement were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. Using the degradation of MB solution as the model reaction, the influence of amount of catalyst, calcining temperature, calcining time and amount of Sn⁴⁺-doped on the photocatalytic property of the Sn⁴⁺/ZnTiO₃-TiO₂ was investigated. The results show that adulteration is disadvantage for photocatalytic degradation reaction, and undoped the sample prepared by template method has good catalytic activity with 600 oC for 3 h of calcination and 40 mg of catalyst. Decolorizing efficiency of MB solution is up to 96 % under 4 h of the solar light irradiation, the material also shows good catalytic stability, the decolorizing efficiency of MB solution remains 83 % after 5 cycles.