Of Wo <sub>, Functional Semiconductor 3 </ Sub> And Tio <sub> 2 </ Sub> Synthesis In Environmental Governance

For metal oxides which have adverse conditions for adsorption application, in this paper we set metal oxide WO₃ as an example to develop the adsorption ability. We have obtained hexagonal single crystal WO₃ nanorods growing along [110] axis by a simple hydrothermal method. And we use rhodamine B (RhB) and methylene blue (MB) as probes to character the adsorption capacity and to get saturated adsorptioncurves. In this part, we characterized the structures of WO₃ nanorods by XRD, TEM, HRTEM, ASED, FFT, XPS, UV-vis-DRS, nitrogen adsorption (BET), and then discussed the relationship beteen adsorption and structures of WO₃.There are some problems for development of the visible light photocatalysts. WO₃ as an important semiconductor material has the band gap 2.7 eV which could produce excited electrons under visible light. So WO₃ is one of good visible light catalysts. We synthesized the WO₃ nanosheets exposed (001) facets by hydrothermal method and then used the RhB as a probe to study its catalytic properties under visible light. And we characterized the structures of WO₃ by XRD, TEM, HRTEM, SAED, FFT, XPS, UV-vis-DRS, Raman, PL, nitrogen adsorption BET and so on, and then discussed the relationship between exposed (001) facets and photocatalytic activity.Owing to the limitations of TiO₂ catalyst under visible light, changing the morphology and structure of TiO₂ for visible light photocatalytic response is a very important aspect. In this part, we synthesize the single crystal TiO₂ nanoparticles with varieties of pore sizes, and then we used RhB, phenol, 4-chlorophenol as probes reaction to characherize their photocatalytic activities. And we also characherized the structure of TiO₂ by XRD, TEM, HRTEM, SAED, UV-vis-DRS, nitrogen adsorption(BET), ESR and so on and then the visible light photocatalytic mechanism has been discussed in depth.This paper mainly contains three specific parts as follows:1. Synthesis of hexagonal single crystal WO₃ nanorods and the research of adsorption ability First, we synthesized hexagonal single crystal WO₃ nanorods growing along [110] axis and esposed relatively more (001) facets by the hydrothermal method. These WO₃ nanorods have powerful adsorption for organic dyes, mainly owning to the hexagonal structure and exposed (001) facets. Synthesis of this structures by modulating the synthetic conditions as follows: (1) (NH₄)₁₀W₁₂O₄₁·5H₂O as tungsten source, samples WO₃ nanorods growing along [110] axis were obtained by adjusting acidity with HCl or H₂SO₄. These WO₃ samples exposed relatively more (001) facets performed strong adsorption capacity for RhB and MB. (2) Na₂WO₄·2H₂O as tungsten source, samples WO₃ nanorods growing along [110] axis were obtained by adjusting acidity with HCl or H2SO4. This prepared WO₃ samples exposed relatively much less (001) facets have not good for adsorption capacity for RhB and MB.Therefore, NH₄⁺ which was from (NH₄)₁₀W₁₂O₄₁·5H₂O adsorbed on the (001) facets, ignoring the [001] axis, so this WO₃ nanorods growing along [110] axis exposed more (001) facets which were acative facets for adsorption.2. Synthesis of orthorhombic WO₃ nano-crystal sheets exposed (001) facets and study of the photocatalytic acativity under visible lightThe WO₃ nano-crystal sheets exposing (001) facets were obtained by hydrothermal method. This material has excellent visible light photocatalytic activity under visible light, which was mainly contributed to the acative (001) facets exposed. F- ion from HBF₄ could be absorbed on the (001) facets, so we could get different exposure ratios of (001) facet by changing the amount of the HBF4. And through comparing the photocatalytic activities of different (001) facets exposed samples, it was found that the degradation of RhB under visible light became worse as the (001) facets exposure ratios become lower. So we could get the conclusion that (001) facets was powerful reactive acativity. This provided a good visible light photocatalysis for the future development.3. Synthesis of TiO₂ nanoparticles with multi-pore structure and the study of visible light photocatalytic activityTiO₂ nanoparticles with vaireties of proe sizes could be prepared by a solvothermal method. This material had powerful photocatalytic activity under visible light, owing to the multi-pore structure and oxygen vacancies. The oxygen vacancies of TiO₂ surface could generate·OH and O₂ -which were necessary for photocatalytic degradation of organic pollutants. Therefore, it was a good exploration for high visible light efficiency of TiO₂ photocatalysis.