| In recent years, semiconductor photocatalytic oxidation technology has attracted widely attentions mainly due to its characteristics such as strong oxidation capability, low energy consumption, moderate reaction conditions, quick degrading speed, no-secondly pollution and large application range, and is a new promising practical technology for degrading environmental pollutions. However, the practical application step of the semiconductor photocatalytic oxidation technology is held back to a certain extent by the some shortcoming like the low quantum efficiency of semiconductor material in itself and the lower efficiency for utilizing the solar light. Moreover, the involving the photocatalytic reaction, the relationships between structure and activity, the relationships between activity and interface-charge transferring, the modification mechanism, are not well understood up to date. These problems are needed to solve.In order to improve the photocatalytic activity under visible light and make full use of the solar light, the nano-sized titanium dioxide must be modified. With these in mind, the main purpose of the paper is to prepare nano-sized TiO2 modified with noble metal Ag and ABO3-type perovskite photocatalyst and improve the photocatalytic activity under visible light, and the interface-charge transferring mechanism and the photocatalytic activity of composite film photocatalysts were also principally investigated.TiO2 nanoparticles were prepared by a sol-hydrothermal process and by a sol-gel method and were characterized by several testing techniques. The photocatalytic activity was principally investigated. The results show that the stronger SPS response of T550 attributes to the efficient photoinduced electron transferring, the surface states related to oxygen vacancies can induce photocatalytic reactions under visible irradiation, especially in the resulting biphasic TiO2 due to the electron transfer from anatase surface states to rutile. Nanosized anatase TiO2 film on the ITO glass has been fabricated via spin coat process, with sodium dodecylbenzenesulfonate modified TiO2 nanoparticles, which is synthesized by a sol-hydrothermal method, and also characterized mainly by means of several testing techniques. It can be suggested that the superhydrophilic performance is mainly attributed to the high roughness resulting from hierarchical surface structure. The formation of characteristic surface structure is close related to the DBS addition. This will be useful to fabricate other newly nanostructured semiconductor film materials, and promote the practical application in the wetting areas of TiO2 films.Noble metal depositing has been considered as an effective method to hinder the photogenerated electron/hole pair recombination and accelerate the photoexcitation and formation of oxidizing species, consequently to enhance the photocatalytic activity. TiO2 nanoparticles and TiO2 film were prepared by a sol-hydrothermal process, and were characterized by several testing techniques. The photocatalytic activity for degrading Rhodamine B was principally investigated. Nano-sized TiO2 film deposited with the noble metal Ag was prepared by the sol-gel method. The influences of different Ag content on the TiO2 structure and properties were studied and the effect of Ag-depositing on photo-induced charge separation and photocatalytic activity were principally investigated. The results show that the appropriate Ag-depositing content can improve the photo-indcued charge separation and decrease the chance of the combination efficiencies of the photo-induced electrons and holes, which are responsible for the enhancement of TiO2 photocatalytic performance. The optimum silver nitrate concentration of was found to be 1×10?3 mol·L-1. Moreover, reproducibility tests proved that the photocatalytic activity of the silver-modified films remains intact even after eight consecutive experiments of new added pollutant quantities.ABO3-type perovskite LaFeO3 shows a variety of unusual and interesting structure and properties, which was applied in catalytic field. LaFeO3 nano-sized photocatalysts were synthesized by a sol-gel method, using citric acid as complexing reagent and La(NO3)3·6H2O and Fe(NO3)3·9H2O as raw materials. The as-prepared samples also were characterized by several testing techniques, the optimum preparation conditions and the photocatalytic activity for degrading Rhodamine B under visible irradation were principally investigated. The results show that the crystallite size becomes larger and the SPS response becomes much stronger of LaFeO3 nanoparticles with increasing calcination temperature. The LaFeO3 sample calcined at 500℃exhibits higher activity, and the activity decreases with increasing calcination temperature, which is in good agreement with the characterization results. According to the results of XRD characterization, the crystallite size increases, the energy band bending upward becomes large, the built-in electric field becomes strong, resulting in the SPS intensity increases as the calcination temperature rises. The crystallite size is large, the migrating time of photoinduced charge carriers from the inner to surface is long. Thus, the less photoinduced charge carriers can reach to surfaces in advance of recombination, to fewer be captured to initiate photochemical reactions, resulting in the decrease in the activity.The sol-gel method is an usual synthesized method. However, the practical application step of the method is hold back at a certain degree by the some shortcoming like small crystallite size and large surface area of the samples prepared by the sol-gel method. So it is necessary to explore new method. LaFeO3 nano-sized photocatalysts were synthesized by hard template method using SBA-16 as template and were characterized by several testing techniques such as nitrogen adsorption-desorption and surface photovoltage spectroscopy. The sample activity of LaFeO3 for degrading Methylene Blue solution under visible irradation was evaluated. We principally investigated the effects of the preparation method on the structure, the properties of LaFeO3. The results show that LaFeO3 prepared by hard template method is porous nano-materials and its surface area calcined at high temperature still becomes larger. Compared with the photocatalytic activity of LaFeO3 prepared by a sol-gel method, its photocatalytic activity increases.TiO2 is an untra-violet photocatalyst and LaFeO3 is a visible photocatalyst. If TiO2 was modified by LaFeO3, some properties would be gained. It will realize sensitized intention and improve the photocatalytic activity under visible light. It will happen coupling or inpouring of photo-induced electron and enhance photoinduced charage separation. A series of nano-structured film photocatalysts were prepared using TiO2 and LaFeO3 as semiconductor representatives, and were characterized by several testing techniques such as photoluminescence spectrum and surface photovoltage spectroscopy. The photocatalytic activity of LaFeO3 for degrading Methylene Blue solution under visible irradation was evaluated. The results show that the photocatalytic activity of the composite film increases. The coupling between LaFeO3 and TiO2 conduces the high photocatalytic activity of the LaFeO3-TiO2 film; the charge inpouring from TiO2 to LaFeO3 conduces the photoinduced charage separation.This paper could effectively supplement the basic theories of nano-sized semiconductor material, which would greatly speed up the practical process of nanomaterial in photocatalysis and would offer potent foundation in photoelectron conversion and photoinduced synthesis. |
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