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Synthesis and Application of Visible Light Photocatalytic Materials of Bi Family

Author: NiQiuYang
Tutor: XuXiaoWen
School: Suzhou Institute of Technology
Course: Applied Chemistry
Keywords: Bismuth Molybdate Bismuth Vanadate Visible Light Photocatalytic Materials Zeolite
CLC: O643.32
Type: Master's thesis
Year: 2010
Downloads: 77
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Abstract

Recently, environmental pollution became increasingly serious, majority of which was chemical pollution. The critical of environmental protection is exploring practical technique of intoxication of chemical pollutants. Heterogeneous photocatalysis has now become one of the promising techniques of green-environmental treatment, which has the unprecedented advantage of conventional high-temperature and catalytic technique. The ideal photocatalyst should be possessed of high stability, low-cost, nontoxicity, high activity, and high adsorbtion of sunlight. Currently, TiO₂ has been the one of the most widely researched and applied semiconductor photocatalyst. However, the high probability of re-combination of electron and hole lead to the low efficiency of photo-quantum. In addition, the wide band gap lead to the light adsorbed only account for a small amount of sunlight, which consequently, results to inadequate usage of sunlight. The band gap of the TiO₂ is 3.2eV. It absorbs only the ultraviolet light （λ< 400 nm）, which accounts for about 4% of the sunlight. The research of novel photocatalyst fouce on binary or ternary oxides, People hope to find out a photocatalyst with high charge separation efficiency, wide photo response, working under visible irradiation,and high photocatalytic activity. In all of these compounds, Bi contained compounds has attracted much interests because of the ability of solving the energy and environmental problem. In this paper, we study the synthesis of Bi contained compounds and the photocatalytic activities.Nanoparticles of porous Bi₂MoO₆ were prepared by template-free co-precipitation method. XRD patterns of the Bi₂MoO₆ samples imply that Bi₂MoO₆-400 has the crystallinity. The TEM images show the as-prepared products are composed of porous structure. Photocatalytical activities under visible light irradiation of Bi₂MoO₆ were evaluated using methyl orange （MO） as model, and all samples were able to induce the oxidative photo-degradation of MO.Bismuth molybdate （Bi₂MoO₆） nanoparticles were prepared on NaY type zeolite by the impregnation with Bi（NO3）3 and （NH4）6Mo7O24 solution and subsequent calcination at different temperatures. XRD patterns of the Bi₂MoO₆/NaY（BM） samples imply the formation of Bi₂MoO₆ nanoparticles on NaY zeolite, and with increasing the calined temperature, the crystalline of Bi₂MoO₆ of BM become perfect and the bigger particle size. The TEM images show the Bi₂MoO₆ nanoparticles with the size of about 10 nm formed on the outer surface of NaY zeolite single crystallites. EDAX patterns show that the content of Bi atoms is higher than that of Mo atoms according to the molar ratio of Bi and Mo is 2:1. This phenomenon may be attributed to that some of the BiO+ or Bi³⁺ are in the channel of the zeolite, and do not integrate with MoO42- , resulting in the yield of BM below 100%. The antimicrobial properties can be researched by coating materials onto mildews and observed by photograph through microscope. It is showed that BM-400 has the best antimicrobial effect when exposing under the UV. The photocatalytic activities of the Bi₂MoO₆/NaY （BM） were evaluated by the degradation of methyl orange （MO） in aqueous solution under visible light irradiation.Bismuth vanadate （BiVO₄） nanoparticles were prepared on NaY type zeolite by the impregnation with Bi（NO3）3 and （NH4）6Mo7O24 solution and subsequent calcination at different temperatures. The XRD patterns of the BiVO₄/NaY （BV） calcined at different temperatures show that the characteristic peaks of NaY is relatively weak and absent of the characteristic peaks of BiVO₄. TEM micrographs clearly show BiVO₄ extremely high dispersed on the outer surface of NaY zeolite single crystallites. But for BV （high）, the characteristic peaks of BiVO₄ were obviously observed, but the characteristic peaks of NaY were relatively weak. TEM micrographs show BiVO₄ nanoparticles with the size of about 10 nm formed on the outer surface of NaY zeolite single crystallites, the particles of BiVO₄ on NaY type zeolite are composed of many smaller particles. EDAX patterns show that the content of Bi atoms is higher than that of V atoms according to the molar ratio of Bi and Mo is 1:1. This phenomenon may be attributed to that some of the BiO+ or Bi³⁺ are in the channel of the zeolite by ion exchange, and do not integrate with VO3-. The photocatalytic activities of the BV were evaluated by the degradation of methyl orange （MO） in aqueous solution under visible light irradiation. The BV-400 possessed a high photocatalytic activity under visible light irradiation.Nanoparticles of porous BiVO₄ were prepared by template-free co-precipitation method. XRD patterns of the samples show that the diffraction of BiVO₄ -400 is consistent to the JCPDS 83-1700 of BiVO₄. For the diffuse reflectance spectra, based on extrapolations of the straight portions of the absorption edge, it can be estimated that BV and BiVO₄ have a band gap of 2.4 eV, which can be ascribed to the characteristic absorption of monoclinic BiVO₄. Photocatalytical activities under visible light irradiation of BiVO₄ were evaluated using methyl orange （MO） as model, and all samples were able to induce the oxidative photo-degradation of MO.

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