Preparation, Characterization And Properties Of SO₄^2-/TiO₂、BiOI/TiO₂and La-SrTiO₃Photocatalysts

The excessive exploitation of resources and the serious pollution of nature have posed a great threat to our living environment. In recent years, photocatalysis technology has showed a broad application prospect in the field of environmental governance and attracted wide attention, even becoming the hot pot of great research. Photocatalytic materials are developed mainly in TiO2, ZnO and other metal oxides, these traditional semiconductor materials have the advantages of low cost, the mild reaction conditions, high chemical stability, higher UV photocatalytic efficiency and so on. However, the light the materials use are limited to ultraviolet light, lower solar energy conversion efficiency, which restricts its the application to a greatly. Thus how to modified nanomaterials to improve the performance and better apply to actual application, which become the focus of research.In this work, SO42-/TiO2, BiOI/TiO2and La-SrTiO3photocatalysts were prepared by sol-gel-impregnation, deposition and sol-gel method respectively, and characterized by various modern techniques, and the relation between the structure and photocatalytic performance of SO42-/TiO2, BiOI/TiO2and La-SrTiO3photocatalysts were studied. There are three sections of our researching work as follows:First, SO42-/TiO2nano-photocatalysts were prepared by sol-gel-impregnation method regarding tetrabutyl titanate as the titanium source and characterized by means of X-ray diffraction (XRD)、Brunauer-Emmett-Teller (BET) surface area measurements, photoluminescence (PL) spectra and transmission electron microscopy (TEM). The hydroxyl radical produced in the supernatant of the irradiated catalyst suspension containing terephthalic acid were also investigated by measuring the fluorescence derived by the reaction with terephthalic acid, the photocatalytic activities of as-prepared anatase SO42-/TiO2nano-photocatalysts were studied by methyl orange as mode compound under UV and visible light irradiation. The results show that, when SO42-was loaded on anatase TiO2catalyst, its BET surface area increased、adsorption quantity increased and photocatalytic activity enhanced. The formation rate of hydroxyl radical on the SO42-/TiO2catalyst is positively correlated with its photocatalytic activity.Second, BiOI/TiO2(A)(A:anatase) photocatalysts were prepared at room temperature by a deposition and sensitisized method at room temperature, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra and UV-vis diffuse reflection spectroscopy (UV-vis DRS). The photocatalytic activities have been evaluated by photodegradation experiments of rhodamine B (RhB). The absorption intensity of BiOI/TiO2(A) samples enhances in370-630nm with the increase of BiOI content, and the redshift of absorption band edges increase. When content of BiOI arrives1.7%, their UV and visible light photocatalytic activities reaching the maximums. Compared with TiO2(A), BiOI/TiO2(A) catalyst shows much higher UV and visible light photoactivity. Meanwhile, UV light photoactivity of1.7%BiOI/TiO2(A) is slightly higher than that of P25and its visible light photocatalytic activity is much higher than P25catalysts. It can be due to the stronger absorption in370-630nm, the obvious shift red of absorption band edge, and the effective transfer of the photogenerated electrons and holes, which reduce the recombination of electron-hole pairs.Third, La-doped SrTiO3catalysts with different La contents were prepared by a sol-gel method, and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurements, X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), scanning electron microscope (SEM), photoluminescence (PL) spectra and UV-vis diffuse reflection spectroscopy (UV-vis DRS). The UV and visible light photocatalytic activities of La-SrTiO3photocatalysts were investigated by using methyl orange as a model pollutant and the effects of La content and calcination temperature on methyl orange photocatalytic degradation were discussed. It has been shown that photocatalytic activities reaching the maximums around La content of0.5%and the calcination temperature of400℃, the La-doped SrTiO3still keeps a perovskite structure and there is no big difference between pure SrTiO3and0.5%La-SrTiO3samples in particle size and morphologies. But the absorption edge of La-SrTiO3sample is obviously red-shifted. Compared with pure SrTiO3, the La-SrTiO3sample obviously exhibits much higher UV and visible light photocatalytic activity. The enhanced photocatalytic activity can be mainly attributed to the increase of BET surface area, the enhancement in adsorption performance, the stronger absorption in250-650nm light region and the lower band-gap energy level.