【作者】 李昕；

【导师】 陶霞；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2012， 博士

【摘要】 光催化技术作为一种高效、清洁的高级氧化技术是近年来备受瞩目的一种水体污染物处理技术。在众多可用于光催化反应催化剂的半导体中，TiO₂纳米材料由于其无毒、催化活性高、化学性能稳定、价格低廉等优点成为最具工业化应用前景的光催化剂材料之一。然而，现在普遍研究的TiO₂悬浮体系存在催化剂分离困难、后处理费用高、难于回收使用等问题，限制了TiO₂光催化剂在工业上的应用。构建TiO₂膜作为催化剂的非均相降解体系则能有效的解决这些问题。但是，TiO₂的带隙能决定其仅能接受紫外光激发，对太阳光利用率低；并且，TiO₂固化成膜后存在比表面积小、薄膜容易脱落等缺点，严重影响钛基薄膜材料的光催化效率。如何提高钛基薄膜材料的可见光诱导的光催化效率以及探索一种简单的制备性能稳定的钛基薄膜的方法，仍是现在研究者亟待解决的问题。本文以提高钛基薄膜光催化效率为目的，一方面通过制备具有可见光响应的非金属掺杂的TiO₂颗粒，并采用简单的涂覆法制备了非金属掺杂的TiO₂薄膜电极，扩展钛基薄膜对可见光的响应；另一方面优化成膜工艺，如成膜过程中引入TiO₂纳米晶体制备不同粒径的微纳复合薄膜来促进光在薄膜内部的散射提高光利用效率，或者引入造孔剂增加薄膜比表面积；同时，构建光电催化反应体系和双染料协同敏化反应体系，通过提供适宜的外部环境，促进钛基薄膜的催化反应效率。围绕上述的内容，本论文主要开展了以下几个方面的工作:第一，通过溶胶-凝胶法制备包覆了碘单质的孔穴结构TiO₂微米颗粒（I₂-NVS TiO₂颗粒）。将I₂-NVS TiO₂颗粒与水热法制备的TiO₂纳米晶体混合构建了I₂-NVS TiO₂微米颗粒/TiO₂纳米晶微纳复合薄膜（I₂-TiO₂薄膜）。并创新性的将这种薄膜材料应用于光催化降解体系。为了增加薄膜的比表面积、薄膜与玻璃基底的粘附力，聚乙二醇（PEG）被引入到薄膜中做粘附剂和造孔剂。实验结果表明：制备的I₂-TiO₂薄膜光催化效率明显提高。可通过以下两方面解释这种性能的提高：一方面，包覆于薄膜中的碘能够被可见光激发并对TiO₂进行敏化，从而有效窄化了TiO₂的禁带宽度，使其能够被可见光激发，提高对太阳光的利用率；另一方面，不同粒径的颗粒使光在薄膜中发生了漫反射，延长光线传输路径，从而提高了TiO₂薄膜的光利用效率，进而提高光催化活性。第二，通过对孔穴结构TiO₂颗粒制备方法进行改进，创新性的制备了包覆了碳的TiO₂微米颗粒（C-NVS TiO₂颗粒）。采用上面介绍的方法构建了C-NVS TiO₂微米颗粒/TiO₂纳米晶体微纳复合薄膜（C-TiO₂薄膜），并将其应用在光催化降解领域。EDS、XPS、SEM、紫外-可见漫反射光谱等检测手段被用来对薄膜的构成、表面价态和形貌等性质进行表征。结果表明：碳元素并没有掺杂进TiO₂颗粒的晶格中，而是以胶囊结构的形式被包裹在TiO₂颗粒的孔穴中；C-TiO₂薄膜的光吸收带明显红移，具有可见光催化活性；引入碳之后，薄膜可见光诱导的光催化降解效率明显提高。第三，创新性的将I₂-TiO₂薄膜和C-TiO₂薄膜应用于光电催化降解体系中，并对薄膜光电转换效率、阻抗、带隙能等光电性能进行分析。结果表明：I₂-TiO₂薄膜和C-TiO₂薄膜在400-600nm的范围内光响应能力与纯TiO₂薄膜相比明显提高；引入非金属掺杂元素之后的薄膜拥有更低的电子传输阻力、更高的光响应能力和更负的导带电位，从而拥有更高的光电催化效率。第四，通过对TiO₂纳米晶制备过程的改进制备了碘掺杂的TiO₂纳米晶，构建了碘掺杂的TiO₂纳米晶薄膜（I-TiO₂薄膜），并将薄膜首次应用于双染料协同敏化反应体系中。结果表明，在罗丹明B/荧光素钠双元染料协同敏化下，I-TiO₂薄膜对罗丹明B的降解效率是单染料体系的8倍；在罗丹明B/茜素红双元染料协同敏化下，I-TiO₂纳晶薄膜对罗丹明B的降解效率是单染料体系的5倍。另外，我们对双染料协同降解反应机理也进行了讨论。这样一个融合了碘掺杂薄膜扩展的可见光响应能力、薄膜可循环使用以及双染料协同效应三重优势的反应体系为钛基薄膜的可见光催化处理废水的发展指明了一个新的研究方向。更多还原

【Abstract】 Photocatalysis has many merits in the terms of the removal ofharmful organic compounds, wastewater treatment and cleanup of pollutedair. This technology has been dramatically growing over the last decades.In recent years, TiO₂as an efficient photocatalysis has gained muchattention for its advantages of nontoxicity, photostability, andbiocompatibility as a highly efficient and promising photocatalyst.Generally, the degradation of organic pollutants is carried out insuspensions mediated by powder TiO₂. But in practical applications, thephotoactive flm is more viable due to its easy separation recovery andsimple post-treatment process. As for photoactive coating layer, largesurface area, sufficient mechanical/thermal stability and good adhesion to the substrates are the basic requirements.In this paper, we devote to search new methods to enhance theefficiency for photocatalytic reaction as well as to fabricate visible-lightresponse TiO₂films based on visible-light induced nanovoid-structuredTiO₂materials or iodine-doped TiO₂nanocrystals of the degradation ofpollutants. The main results and conclusions are summarized as follows:1) A visible-light response iodine-encapulated TiO₂film （I₂-TiO₂film）was prepared by packing the （I₂）n-encapsulated nanovoid-structured TiO₂particles and TiO₂nanocrystals （TNCs） via a doctor-blade method. Thevisible-reduced photocatalytic efficiency of the as prepared I₂-TiO₂filmwas measured by monitoring the decomposition of rhodamine B （RhB）Alizarin Red S （AR）, fluorescein sodium （Flu） and2,4-dichlorophenol（2,4-DCP）. The results showed that the degradation rate of the I₂-TiO₂filmwas significantly higher than pure TiO₂film. The improved photocatalyticperformance can be attributed to the present of （I₂）nencapsulated in TiO₂and work as photosensitizer to enlarge the spectral response and enhancethe visible-light utilization. Furthermore, the microparticles（I₂-TiO₂）/nanocrystals （TNCs） mixed structure, in which the I₂-TiO₂miroparticle worked as light scatterers, could be recognized as anotherfactor leading to an improved of light utilization of the film.2) A corbon-encapulated TiO₂film （C-TiO₂film） was prepared bypacing the corbon-encapulated TiO₂particles synthesized via sol-gel route using glucose as carbon source. The as-prepared films were characterizedby SEM, XRD, and diffuse reflectance spectra. With the analysis of EDSand XPS measurements we deduced that the carbon was encapsulated inthe nanocavities of TiO₂particles rather than doped in the lattice of it. Thedegradation efficiency of RhB, AR, Flu, and2,4-DCP under visible-lightirradiation was investigated. Compared with pure TiO₂film, the C-TiO₂film showed a higher photoreaction activity, which can be explained bythe banding shift causing by carbon modifying.3) The visible-light absorbing I₂-TiO₂and C-TiO₂film electrodeswere fabricated and studied as film electrodes for theirphotoelectrochemical and photoelectrocatalytic （PEC） properties. Thephotoelectrochemical property was evaluated by the incidentphoto-to-current conversion efficiency, electrochemical impedancespectroscopy and Mott-Schottky analysis data. The results showed thatI₂-TiO₂and C-TiO₂films exhibited stronger absorption in the400-550nmrange, lower electron transfer resistance and more negative fat bandpotentials comparing with pure TiO₂film. At a bias potential of0.5V, thevisible-light-induced PEC degradation ratios of RhB and tetracycline onI₂-TiO₂film or C-TiO₂film electrodes were significantly higher that onpure TiO₂electrode.4) An iodine-doped TiO₂nanocrystals film （I-TiO₂film） wasprepared and used as photocatalysis in Flu-sensitiezed and eosin Y （EO）-sensitized degradation of RhB under visible-light illumination. Thedegradation results showed that when Flu or EO was introduced to theI-TiO₂film/RhB system, the degradation ratio of RhB was significantlyenhanced, with an eight-fold or five-fold improvement compared with thatin the I-TiO₂film/RhB system free of sensitizer. In this degradationsystem the advantages of I-doping, inherent film characteristic andsynergistic degradation effect of binary dyes have been simultaneouslyachieved. This study could provide a feasible industrial route to designinghigh-performance visible light photocatalyst system.更多还原