二氧化钛光催化薄膜的结构调控及其性能研究

发布时间：2018-02-24 17:15

  本文关键词： 纳米材料 TiO_2 光催化 复合结构 异相结　出处：《浙江大学》2016年博士论文　论文类型：学位论文

【摘要】：过去几十年来,随着人类社会的发展,人口激增,全球化进程不断推进,伴随而来的环境污染与高能量消耗问题开始变得越来越突出。寻找治理污染的有效途径,实现清洁可持续发展模式成为现代社会的共识。二氧化钛(TiO_2)由于其稳定性高,成本较低,环境友好,用途广泛和优异的光催化性能而引起研究者的重视,在光催化环境治理等诸多领域得到广泛应用。TiO_2纳米粉体比表面积大,催化活性高,但容易团聚且难以完整回收,容易造成二次污染；TiO_2薄膜回收方便,可反复多次使用,无二次污染,但其制备工艺复杂,光催化性能不如粉体催化剂高,限制了其大规模产业化应用。因此,制备工艺简单、结合力好、光催化性能优异的TiO_2薄膜的研发具有重要的科学研究意义和工程应用价值。钛金属原位氧化工艺特点决定了金属钛基板与TiO_2薄膜之间的结合十分紧密,采用该技术已获得纳米管、纳米线、纳米棒、纳米花等一/三维纳米阵列TiO_2薄膜。本文致力于双氧水直接氧化钛金属基板制备TiO_2薄膜的相结构和纳米形貌调控,通过“异相结”和“一/三维纳米结构”的有机组合,协同优化TiO_2薄膜的光电催化性能,为TiO_2光催化在环境和能源领域的工程应用打下基础。本文首先总结了光催化工作原理,回顾了TiO_2作为光催化剂的研究现状、已有的制备工艺、掺杂技术、相结构调控、纳米形貌调控,以及相关理论。在此基础上,提出本文的研究背景,并阐述了本文主要研究思路。本文利用钛金属与特定双氧水溶液反应后得到的溶液作为前驱液,在钛金属基板上实现金红石相TiO_2纳米花单层膜的沉积,消除了薄膜与基板之间的TiO_2纳米颗粒阻挡层。TiO_2单层膜的纳米结构(纳米棒或者纳米花)的形成可用定向粘附理论解释,具体纳米形态与钛金属基板的预处理工艺密切相关。采用稀硝酸替代混合酸对钛基板进行清洗处理时,由于减少了混合酸酸洗导致的腐蚀点,TiO_2形核率下降,后续在已生长纳米棒缺陷位置形核概率上升,因而有利于纳米花而不是纳米棒阵列的形成。系统研究了沉积温度、时间,以及纳米花薄膜后续热处理对其光电性能的影响,结果表明,80℃沉积6h并经后续450℃热处理1h的纳米花薄膜的光电催化降解水中若丹明B染料的效率是一种商用金红石TiO_2纳米颗粒薄膜的4.9倍,是商用P25 TiO_2纳米颗粒薄膜的1.3倍。薄膜光电催化效率的提高可归因于中间阻挡层的消除、纳米花固有的高比表面积,以及单晶TiO_2纳米棒导致的外加偏电压作用下的高电子迁移率。本文使用钛基板在高温下原位真空热氧化,成功制得了钛基TiO_2纳米线薄膜,研究了纳米线阵列的生长过程及薄膜的结构参数,并探讨了纳米线的生长机理。通过降解水中染料罗丹明B的方式测试经不同时间热氧化处理后酸洗钛片的光催化性能。薄膜结构表征结果表明,一定真空条件下钛片在750℃热氧化5～10h后可以获得大量直径40～50 nm,长度3.0～5.0 μm的单晶金红石结构TiO_2纳米线；使用H2O_2氧化钛片表面预先获得一层多孔非晶TiO_2薄层,可显著影响纳米线的生长。光催化性能测试结果表明,真空热氧化处理1h获得的扁平片状纳米结构金红石薄膜具有最高的光催化降解罗丹明B的能力；热处理时间从5h延长到10h,得到的纳米线金红石薄膜的光催化性能有所提高。本文针对单位面积TiO_2有效担载量的问题,在钛基板上通过逐层沉积锐钛矿/金红石复合结构纳米棒、锐钛矿溶胶-凝胶层和金红石纳米花的方式,最终得到一种具有“三明治”结构的TiO_2复合薄膜。该复合薄膜总体相组成为79%锐钛矿和21%金红石,接近于商用P25 TiO_2；其禁带宽度为3.0 eV。紫外光照下降解罗丹明B染料时,复合薄膜的准一级反应速率为12.3×10-3 min-1,明显高于构成薄膜的锐钛矿/金红石纳米棒(3.9×10-3 min-1)、溶胶-凝胶锐钛矿(0.3×10-3min-1)和金红石纳米花(4.7×10-3 min-1)的降解速率。研究结果表明,不同相组成和纳米形貌的TiO_2薄膜的适当组合,是提高其光催化活性的有效手段。为充分利用纳米线薄膜中纳米线之间的空间,提高薄膜的TiO_2有效担载量,本文将纳米线阵列薄膜浸没于特定前驱液中,获得一种纳米分级结构薄膜。该薄膜表面由均匀分布的锐钛矿相TiO_2纳米线主干和金红石相TiO_2纳米分支构成。其中分支为单晶结构,随着二次沉积时间的延长而逐渐长大。由于其独特的形貌和相结构的复合,薄膜具有特定能带匹配的异相结结构,其高比表面积、独特的分支形貌和混晶效应使得薄膜的光能利用效率得到有效提升,光电响应性能和光催化降解水溶液中有机物的性能得以显著提高。为了进一步厘清异相结结构在分支TiO_2纳米薄膜中的作用,本文将锐钛矿相TiO_2纳米线薄膜分别置于一定浓度的TiCl4活TiF4溶液中，，成功制备了不同相组成的分级结构TiO_2纳米线薄膜。其中，TiCl4溶液体系中沉积得到的薄膜包含锐钛矿/金红石异相结复合结构；而TiF4溶液体系中沉积得到的薄膜不包含异相结结构。通过精确控制制备工艺,深入分析薄膜TiO_2担载量、相组成和纳米形态与光催化性能之间的关系,确认了分支结构TiO_2薄膜中“异相结”的重要作用。此外,还研究了阴离子掺杂的作用,复合薄膜在光催化应用中存在的“自然时效”现象,以及复合薄膜对不同有机物的光催化降解特性。
[Abstract]:Over the past few decades, with the development of human society, population growth, accelerating process of globalization, accompanied by environmental pollution and high energy consumption problem has become increasingly prominent. Finding effective ways to control pollution, to achieve the sustainable development mode of modern clean become social consensus. Titanium dioxide (TiO_2) due to its high stability. Low cost, friendly environment, wide application and excellent photocatalytic performance caused by the attention of researchers, in the photocatalytic environmental governance and many other fields have been widely used.TiO_2 nano powder specific surface area, high catalytic activity, but it is easy to aggregate and difficult to complete recovery, easy to cause two pollution; convenient TiO_2 recycling film that can be used repeatedly, no two pollution, but the complex preparation process, photocatalytic properties as powder catalyst, limit its large-scale industrial application. Therefore, the preparation process Simple process, good adhesion, developing excellent photocatalytic properties of TiO_2 thin films is of great significance in scientific research and engineering application value. The titanium in situ oxidation characteristics determine the combination between titanium substrate and TiO_2 thin film is very close, the technology has been the nanotubes, nanowires, nanorods, nano flowers etc. a 3D / nano array TiO_2 films. This paper focuses on the direct regulation of phase structure and hydrogen peroxide titanium oxide nano morphology of TiO_2 thin films prepared by metal substrate system, through the organic combination of heterogeneous nodes "and" A / three-dimensional nano structure, the photoelectrocatalytic properties of TiO_2 thin films for collaborative optimization, TiO_2 photocatalytic lay the foundation in the environment and the energy field of the engineering application. This paper summarizes the principle of photocatalysis, reviews the research status of TiO_2 as photocatalyst, the preparation process, the doping technology, phase structure regulation, Nano morphology controlling, and the related theory. On this basis, puts forward the research background, and expounds the main research method of this dissertation. The solution reaction of titanium with a specific hydrogen peroxide solution as the precursor solution, deposition on titanium substrate of rutile phase TiO_2 nanoflower solid monolayer, eliminating the nano structure TiO_2 nanoparticles between the film and the substrate of the barrier layer.TiO_2 layer (nanorods or nanoflowers) can be explained by the formation of directional adhesion theory, the pretreatment process and the specific form of nano titanium metal substrate is closely related. By using dilute nitric acid instead of mixed acid cleaning treatment on titanium substrate, due to the decrease of the corrosion point of mixed acid wash the lead, the nucleation rate of TiO_2 decreased in the subsequent growth position of defect nucleation nanorods has probability rise, which is conducive to nano flowers instead of nanorod array formation. The time of deposition temperature, and the nano flower film following heat treatment effect on the photoelectric performance results indicate that the deposition of 6h and the subsequent 80 degrees 450 degrees of heat treatment of photocatalytic degradation of 1H in nanometer film if the efficiency of rhodamine B dye is 4.9 times of a commercial rutile TiO_2 nanoparticles film that is 1.3 times that of commercial P25 TiO_2 nanoparticle film. The film photoelectrocatalytic efficiency can be attributed to the middle barrier layer to eliminate the inherent nanoflower high specific surface area, and the applied bias voltage under high electron mobility of single crystal TiO_2 nanorods. This leads to the use of titanium substrate at high temperature in vacuum thermal oxidation and successfully prepared titanium based TiO_2 Nanowire Films, structure parameters of thin film growth process and nanowire arrays, the growth mechanism of nanowires was discussed. The degradation of dye Luo Dan B The photocatalytic properties of titanium acid tablets with different time after thermal oxidation test. The film structure characterization results show that certain vacuum conditions of titanium at 750 DEG C thermal oxidation after 5 ~ 10h large diameter 40~50 nm, length 3 ~ 5 m single crystal Jin Hongshi TiO_2 nanowires using H2O_2 titanium plate surface; to obtain a layer of porous amorphous TiO_2 thin layer, can significantly affect the growth of nanowires. The test results show that the photocatalytic performance, processing ability of flat sheet-like nanostructure Jin Hongshi film obtained by 1H vacuum thermal oxidation has the highest photocatalytic degradation of rhodamine B; heat treatment time extended from 5h to 10h, the photocatalytic properties of nanowires Jin Hongshi thin films were improved. The unit area TiO_2 effective loading problem on the titanium substrate layer by layer deposition / Jin Hongshi composite structure of anatase nanorods, sharp Titanium sol gel layer and rutile nano flowers, finally get a TiO_2 composite film has a "sandwich" structure. The composite film is divided into 79% general 21% anatase and rutile, close to the commercial P25 TiO_2; the band gap of 3 eV. UV light degradation of rhodamine B dye, first-order reaction the rate of composite film is 12.3 x 10-3 min-1, which was significantly higher than that of thin films of anatase / rutile nanorods (3.9 x 10-3 min-1), sol-gel anatase and rutile (0.3 * 10-3min-1) nanoflower (4.7 x 10-3 min-1) degradation rate. The results show that the proper combination of TiO_2 films with different phase composition and morphology of nano that is an effective way to improve the photocatalytic activity. In order to make full use of nanowires between nanowires in the film space, improve film TiO_2 loading, the nanowire array film immersed in The specific precursor solution, obtain a nano hierarchical structure of thin film. The thin film surface by uniform distribution of anatase TiO_2 nanowires and nano rutile TiO_2 main branch. The branch is single crystal structure, along with the prolonging of deposition time two times and gradually grew up. Because of the composite microstructure and its unique morphology, film with a specific band, phase structure, its high surface area, unique morphology branch and the effect of the mixed crystal makes the film light use efficiency effectively, electro-optical properties of organic matter degradation in aqueous solution and the photocatalytic performance can be improved significantly. In order to further clarify the role of heterogeneous nodes in the branch of TiO_2 nano structure in the film, the anatase TiO_2 nanowires films were placed in a certain concentration of TiCl4 TiF4 solution, the hierarchical structure of TiO_2 nanowires with different phases were prepared. Thin film. The thin film deposition TiCl4 solution obtained contained anatase / rutile phase structure of composite structure; and thin film deposition system of TiF4 solution obtained does not contain a heterogeneous structure. The preparation process by accurately controlling the system, in-depth analysis of thin film TiO_2 loading, the relationship between the phase composition and morphology and photocatalytic properties of nano the confirmation of the branch structure in the TiO_2 film "out of phase" knot "of an important role. In addition, also studied the anion doping effect of composite film on photocatalytic application in the presence of" natural aging "phenomenon, and the composite film with photocatalytic degradation properties.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O643.36;TB383.2


本文编号：1531055