| TiO2, as one of the most welcome material in catalytic field, is concerned in the present research. In this paper, based on the density functional theory(DFT), the band gap, density of states of monoclinic TiO2(B) were simulated by using the calculation software CASTEP of first principles to discuss the relationship of the monoclinic phase TiO2 between its optical properties and catalytic activity. A noble and simple chemical peroxide-complex-hydrothermal method for the preparation of monoclinic TiO2(B) nanotubes from a precursor based on Ti(SO4)2, hydrogen peroxide and different base was reported. The influence of the H2O2/Ti molar ratio, the calcination temperature and acid treatment on structure and property of products were studied, and some excellent reference data were gained. The morphology, crystal structure, thermal stability, component and surface properties were intensively investigated by TEM, XRD, LRS, TG-DSC, XPS, BET and FT-IR techniques. And the catalytic degradation of methyl orange was used as model reaction to study the catalytic properties of monoclinic TiO2(B) nanotubes under different conditions. The effects of preparation and reaction conditions on the catalytic performances are studied. Meanwhile, nanostructure TiO2 with single crystal phase, anatase and rutile, were prepared by homogeneous precipitation and microemulsion-hydrothermal methods, and to study their catalytic activity. The following is the main aspects of the present research.In chapter 1, the research status of TiO2, photocatalytic principles, the main preparation methods of one-dimensional TiO2 nanotubes, the basic theory of first principles simulation, as well as significance and content of topics were introduced In chapter 2, with the density functional theory(DFT), the band gap, density of states of anatase TiO2 and monoclinic TiO2(B) were simulated by using the plane wave pseudo potentials(PWPP). The calculation showed that compared to anatase, Ti-O bonds of TiO2(B) have been changed by tomic population analysis; the band gap of monoclinic TiO2(B) was wider, which was smaller than the experimental result.The results of theoretical simulation were in accordance with experimental results.In chapter 3, the band gap, density of states, electron density of monoclinic Nao.2Ti02 were simulated by using the plane wave pseudo potentials (PWPP) based on the density functional theory (DFT). Calculated results show that Na0.2TiO2 is an indirect semiconductor with the band gap of 2.81 eV. The density of states is mainly made up of Ti 3d and O 2p. The material has strong broadband UV absorption, extends the range of spectral response and increases utilization rate of solar energy and photocatalytic efficiency. While the Na and O atoms is connected by a strong ionic and weak covalent mixed bond, the Ti-O bond is shorter and has more covlent component than Na-0 bond. This work may provides a theoretical guid for the molecular design and applications of Na0.2TiO2 and related materials. Therefore, the bond-characteristics and stability of Sodium Titanate can be changed by Cation-exchange.In chapter 4, a new approach, to synthesize TiO2(B) nanotubes by peroxide-complex-hydrothermal treatment in concentrated NaOH solution, was presented. The as-prepared nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption-desorption isotherm measurements (BET). The diameter of the nanotube was from 6 to 25 nm. In addition, the sodium ions covering the surface of the TiO2(B), were not presence after washing with the deionized water, repeated. It was suggested that the nanotubes TiO2(B) were formed during the hydrothermal process from the TEM, which two-dimensional thin layer fromTiO2 crystal and NaOH solution, generated one-dimensional TiO2(B) nanotube by the axis of crystal plane [200], with the whole process through 3-2-ID. In chapter 5, TiO2(B)has been used for the first time as a hydrogen peroxide catalyst and showed remarkable activity for the removal of MO in aqueous solution at darkness. The experiment compares the photocatalysts of monocline TiO2 (B) and anatase TiO2 in stationary MO solution both in absence and presence of H2O2 under Hg lamp, the results have shown that the presence of H2O2 obviously improved the activity of TiO2 catalyst(the degradation ratio 99%) and accelerated the decomposition of MO, and H2O2 must be necessary to achieve high MO decomposition especially for TiO2 (B). At the same time, we found that TiO2 (B) exhibited excellent repetitive-use performance; degradation reaction followed the first order kinetics; the better stability catalyst was conducive to strong practical applications value and Cutting down costs of wastewater treatment with repeated use. Therefore, the unique catalytic properties of nano-TiO2/H2O2 have opened up a new direction for conventional catalytic research, with a certain degree of academic values and application prospects. |
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