Dissertation
Dissertation > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst

Synthesis of Molybdenum Titanium Oxides and the Photocatalytic Performance under Visible Light

Author YangHuaBo
Tutor WangAnJie
School Dalian University of Technology
Course Energy and chemical
Keywords Titanium dioxide Photocatalysis Modification molybdenum oxide X-rayphotoelectron spectroscopy
CLC O643.36
Type Master's thesis
Year 2013
Downloads 45
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The rapid development of the chemical industry led to the increasing industrial waste water, improper disposal of waste water and emissions can cause serious environmental pollution. As a new method of wastewater treatment, photocatalytic degradation method has advantages on stable operation, good effect, no secondary pollution. Photocatalytic materials, however, there has been the problems of low quantum efficiency and low light energy utilization. To improve the utilization of visible light and the quantum efficiency is the aim of the research of photocatalytic technology. This thesis modified the material (P25) and synthesized two new materials, reduced the band gap of the photocatalytic material and improved the absorption of visible light, to achieve the purpose of the photocatalytic activity.Molybdenum trioxide has been used by various researchers to modify the surface properties of TiO2or doped in the lattice of TiO2, due to its band gap is lower than that of TiO2and Mo6+and Ti4+have close ionic radii. This thesis modified P25by loading different quality MoO3in the incipient impregnation way. In addition, the author modified the MoO3modified P25with citric acid. The photodecomposition of methylene blue in aqueous solution by all the samples above was investigated respectively. The samples were also characterized by XRD. Raman, UV-Vis, etc. The results shows that with the increase of the mass ratio of MoO3and P25, the photocatalytic degradation activity of xMoO3/P25increased first and then decreased. The following factors were analyzed:particle size, the distribution of MoO3on the surface of P25and surface acidic. The photocatalytic degradation activity changed after the samples were modified by citric acid, the reasons included changes in particle size of the samples, the variation of the band gap and the increasing recombination of electron and hole.As a catalyst, molybdenum oxide material has excellent performance in many respects, nano-molybdenum oxide materials has attracted wide interest of researchers because of its small size effect, high reactivity and surface effect and other points. In this paper, the author synthesized Ti-doped MoO2in solvothermal. noted as Ti-MoO2. Ti-MoO2was characterized by XRD, XPS, UV-Vis, etc. The photocatalytic degradation was also investigated in the visible light. The XRD indicates that Ti-MoO2possessed a MoO2structure. As evidenced by XPS, the surface of Ti-MoO2contained Ti4+, Mo4+, Mo5+and Mo6+;then combining with the XRF data shows that Mo was the enrichment atom on the surface of Ti-MoO2. The UV-Vis shows that Ti-MoO2had a strong absorption of visible light, the band gap energy of Ti-MoO2was1.94eV. The pseudo first order reaction rate constant of the degradation of methylene blue over Ti-MoO2was almost2.5times higher than that of P25.The author synthesized Ti-doped Mo8O23in hydrothermal, noted as Ti-Mo8O23. Ti-Mo8o23was characterized by XRD, XPS, UV-Vis, etc. The photocatalytic degradation was also investigated in the visible light. The XRD indicates that Ti-Mo8O23possessed a Mo8O23structure. As evidenced by XPS, the surface of Ti-Mo8O23mainly contained Ti4+and Mo6+as well as small amount of low valent Ti species, then combining with the1CP data shows that Mo was the enrichment atom on the surface of Ti-Mo8O23. The UV-Vis shows that Ti-Mo8O23had a strong absorption of visible light, the band gap of Ti-Mo8O23was2.63eV. The pseudo first order reaction rate constant of the degradation of methylene blue over Ti-Mo8O23was almost two times higher than that of P25. The band gap of Ti-Mo8O23was hight and the quantum efficiency was low, which may cause the poor photocatalytic effect.

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