Preparation And Photocatalytic Performance Study Of NaMO₃（M=Nb,Ta） Semiconductor Photocatalyst

In this new era, the science and technology were rapid developed,the social civilization was progressed quickly, the living standard was improved fast, while there were still many problems does not be solved for human. The energy shortage and environmental pollution were the most important problems among them as they spread to the whole world, the whole society and the whole of mankind. At present, the coal, oil and natural gas are the mainly sources of energy could be used directly for human, with the most exploitation of these sources, energy crisis is becoming more and more serious. With the heavy use of fossil energy resources, the environmental pollution will becoming another serious problem which could not be underestimated. Finding the sustainable, clean and efficient new energy resources and environmental governance are the significant and difficult problem for the scientists at present.Semiconductor photocatalytic is a hot technology which was emerging up in late twentieth century. This technology can produce clean and efficient new energy H2 from splitting water under the sun light irradiation with pholocatalyst. It can also purifying the environment by decomposing the organic pollutants and reducing CO2. This technology attracted much concern of many scientists because it can effectively solve the energy shortage and environmental pollution problems. During the past forty years of development, the technology both from the material research and development or performance have made breakthrough progress, But its quantum yield is still not reached production standards, there is still a big distance from the practical application.There are Many reasons affecting the semiconductor activity:(1) The width of semiconductor band gap is so wide that can absorb ultraviolet light only. But there were only 5% ultraviolet in the natural sunlight, for the majority of photocatalyst can only use this small part of the energy, for 45% of the visible light is not effectively used. So that, it is necessary to research and development new semiconductor photocatalytic materials with smaller band gap.(2) The photogeneration electron and hole can not be used effectively as its high recombination rate. Semiconductor can produce electron-hole pairs under the light irradiation, the electronic can carry photocatalytic reduction and hole can carry photocatalytic oxidation reaction. It can be promote the photocatalytic reaction while separating the electron and hole and carry out themselves’ reaction only. But these electrons and holes are getting recombination before they carry out the reaction, which greatly inhibit the photocatalytic reaction.(3) The particle size of semiconductor material is too big and the specific surface area is small. The photocatalytic reaction is carried out on the catalyst material surface, the material surface absorbs light energy and generating electrons and holes, and then transport to the surface to carry out the redox reaction. So that the material surface is closely related to the photocatalytic reaction. The smaller particle size, the bigger surface area, and it could absorb more energy to improve the photocatalytic performance.In this paper, there are some works have been done based on the defects of semiconductor photocatalysis, in order to improve the photocatalytic properties of photocatalytic materials. The main contents are as follows:(1) Fabricate Na Nb O3 single crystal films with different crystal orientation(100, 110, 111) on the La Al O3 single crystal substrate by high temperature solid phase method and hydrothermal method, and analyse the crystal structure, surface morphology, crystal, film growth, optical and electrical performance of these samples. The growth law of crystal and the growth pattern of single crystal films were investigated by changing the heating time in high temperature solid phase method. Finally, photocatalytic performance of these samples were evaluated. There were two methods were taken in this experiment, degradation of organic pollutants rhodamine B and hydrogen production from splitting methanol water solution.(2) Preparation of Na Nb O3 single crystal thin film(111) on La Al O3 substrates by pulsed laser deposition(PLD), and post treat the samples in different atmosphere(Air, H2/Ar). The crystal structure, surface morphology, growth conditions, the optical properties and the influence by post treat of obtained samples were detailed analysis. The relationship between photocatalytic oxidation performance and after treatment was study by degradation of organic pollutants rhodamine B.(3) Prepare La doped Na Ta O3 powder in different atmosphere by high temperature solid state method, then analysis their crystal structure, morphology and optical properties of surface. The photocatalytic properties were evaluate by organic pollutants rhodamine B degradation, pure water splitting and hydrogen production from splitting methanol water solution. At last, the effect of cocatalyst Ni O was investigated.