【作者】 申乾宏；

【导师】 杨辉；

【作者基本信息】 浙江大学 ， 材料学， 2008， 博士

【摘要】 TiO₂以其优异的光催化活性和物理化学特性,在环境污染治理方面已获得较为广泛的研究和应用。尤其在能源、环境问题日益突出的今天,TiO₂光催化材料的研究更具现实意义。薄膜是TiO₂的重要应用形式,能克服悬浮型粉体光利用效率低、易聚集、难回收等问题,并易于实现在玻璃、陶瓷及金属等不同基材上负载。近年来,随着TiO₂薄膜在太阳能电池柔性衬底、建筑物墙面、工程塑料等不耐热或难以加热材料表面应用需求的增加,其低温制备研究受到了关注,成为材料学、化学和环境科学等领域的研究热点。本文对TiO₂薄膜的低温制备及其光催化性能改善途径进行了研究。采用溶胶-凝胶方法,通过配方设计和工艺改进,合成出含有TiO₂晶粒的稳定溶胶（TiO₂纳米晶溶胶）。利用该溶胶在基材表面负载成膜,实现结晶TiO₂薄膜的低温制备。在此基础上,从构造多孔性结构、半导体复合、染料敏化等三方面,探索具有高光催化活性TiO₂薄膜的制备方法。论文主要研究内容及结论如下:（1）常温液相合成TiO₂纳米晶溶胶,实现结晶TiO₂薄膜低温制备。采用溶胶-凝胶方法,设计以水为主要溶剂的反应配方体系（钛酸丁酯:去离子水:无水乙醇:盐酸（摩尔比）=1:185:10:0.1）,改进传统控制工艺,合成TiO₂溶胶。通过¹³CNMR、XAFS等测试方法对钛酸丁酯的水解行为、溶胶粒子的物相结构等进行研究,结果表明在该配方体系下,钛酸丁酯充分水解,形成的水合钛离子缓慢聚合并自发定向排列,在液相中生长出锐钛矿型TiO₂晶粒,形成稳定的TiO₂纳米晶溶胶（平均粒径28.7 nm）。利用溶胶在基材表面负载成膜,在室温下制得具有良好光催化活性的结晶TiO₂薄膜。（2）低温下构造出多孔性TiO₂薄膜形貌,提高薄膜光催化活性。分别以球形苯丙乳液粒子和4,4’-二羟基二苯基丙烷（BPA）为模板,将其引入TiO₂纳米晶溶胶,待其负载成膜后,使用有机溶剂将薄膜中的模板选择性溶解去除,实现TiO₂多孔薄膜的低温制备（室温或60℃干燥）。详细考察了配方、工艺等因素对薄膜表面形貌的影响,探讨了多孔薄膜的制备机理,并对薄膜的吸附及光催化等性能进行了研究。结果表明:在使用结构刚性的苯丙乳液粒子硬质模板时,通过控制模板粒子与TiO₂胶粒间的异相凝聚,有利于促进苯丙乳液粒子在薄膜中分散,形成具有一定壁厚的多孔结构。TiO₂溶胶与苯丙乳液的比例是影响薄膜孔结构的关键因素,涂膜液的陈化时间决定了孔的密集程度,采用超声波振荡辅助溶解,能快速有效地去除苯丙乳液粒子。优化的制备条件为:15 g TiO₂溶胶,0.2 g苯丙乳液,10 g H₂O,涂膜液陈化15 d,薄膜浸入甲苯后,超声波振荡10 min。在使用结构柔性的BPA软质模板时,TiO₂胶粒与BPA构成了两相体系,通过调节涂膜液中各组分含量对TiO₂与BPA在薄膜内部的分相过程进行控制,制备出孔隙分布均匀的TiO₂多孔薄膜。BPA浓度决定了它对TiO₂薄膜表面形貌的影响区域,随BPA浓度的降低,其影响逐渐由薄膜内部转向于极其表面的区域。TiO₂胶粒浓度和乙醇含量是制备多孔薄膜的关键,低TiO₂胶粒浓度和高乙醇含量有利于获得良好多孔性薄膜。涂膜液的优化组成为:4 g TiO₂溶胶,0.07 g BPA,10 g无水乙醇。多孔性增强了薄膜的吸附性能,增加了TiO₂与有机污染物的接触,通过吸附和光催化氧化的协同作用,有效提高了薄膜光催化活性。（3）低温下实现TiO₂-PEDT/PSS、TiO₂-SnO₂叠层式半导体结构的有效复合,提高薄膜光催化活性。分别采用有机半导体（PEDT/PSS,聚乙撑二氧噻吩,其中掺杂聚苯乙烯磺酸盐）和无机半导体（SnO₂）与TiO₂复合,低温下（60或100℃干燥）制备出以相应半导体薄膜为底层,TiO₂薄膜为表层的双层复合半导体薄膜。研究表明底层半导体与表层TiO₂形成异质结,两者能带发生交迭,TiO₂层光生电子向底层半导体注入,有效抑制了TiO₂光生电子、空穴的复合,提高了量子效率,薄膜光催化活性因此得到显著增强,相对于单一TiO₂薄膜,最大提高了将近3倍。（4）建立稳定TiO₂-CuTsPc复合敏化体系,拓展薄膜光响应波长。将水溶性的四磺酸酞菁铜（CuTsPc）作为敏化剂引入TiO₂溶胶中,通过静电吸引作用促使CuTsPc分子与TiO₂胶粒发生结合,获得CuTsPc敏化的TiO₂溶胶（TiO₂-CuTsPc溶胶）。利用溶胶室温负载于基材表面制得TiO₂-CuTsPc薄膜。考察了TiO₂-CuTsPc溶胶合成的水浴加热时间以及CuTsPc浓度等条件对薄膜中CuTsPc负载量的影响,研究了CuTsPc负载量与薄膜光催化性能的关系,并探讨了CuTsPc的负载机理。研究发现CuTsPc的负载能将薄膜的光响应波长拓展至600-700 nm,有效提高了薄膜的可见光催化活性。UV-Vis吸收光谱表明水浴加热时间越长,溶胶中CuTsPc浓度越高,CuTsPc在薄膜中的负载量就越大。随着薄膜中CuTsPc负载量的增大,薄膜的可见光催化活性先提高、后降低,当CuTsPc在20 gTiO₂溶胶中的添加量为0.036 g,并在80℃水浴加热8 h时,所制薄膜的可见光催化活性最高。CuTsPc分子在TiO₂胶粒表面的附着,使CuTsPc随TiO₂胶粒成膜均匀、牢固地负载于薄膜中,因此有利于敏化效果的发挥和薄膜的循环使用,经2～3次循环后,薄膜的可见光催化活性趋于稳定。更多还原

【Abstract】 TiO₂ has been widely studied and applied in environment protection due to its excellent photocatalytic activity and physicochemical characteristics.Especially in the time when the pollution problem becomes more and more conspicuous,the study on TiO₂ catalyst has more practical significance.Film is an important application pattern of TiO₂ catalyst,which is more effectively to utilize light and easier to recycle compared with TiO₂ powder,and can be facilely deposited on a variety of substrates such as glass slide,porcelain bricks,metal panels,etc.Resently,in order to extend the application of TiO₂ film on heat-intolerant organic substrates and realize the large-area coating in the preparation of TiO₂ film,the research on its low-temperature preparation method has been attracting more and more attention and become a prosperous research area in the field of material,chemistry and environment science.In this paper,the low-temperature preparation of TiO₂ film and the approaches to improve its photocatalysis have been studied.By means of sol-gel method,TiO₂ sol containing nanometer crystal grains（called TiO₂ nano-crystal sol）was synthesized via improving formula and control process,and thus crystalline TiO₂ film could be prepared from the TiO₂ nano-crystal sol without any high-temperature treatment. Based on this,the preparation methods of TiO₂ film with higher photocatalysis were explored from three aspects such as constructing porous structure,coupled semiconductor and dye sensitization.The main research contents and results are as follows:（1）Synthesized TiO₂ nano-crystal sol in aqueous solution at room temperature, realized low-temperature preparation of crystalline TiO₂ film.The reaction formula with water as primary solvent was designed（where more ratio of Ti（OC₄H₉）₄:H₂O:C₂H₅OH:HCl=1:185:10:0.1）and suited control process was improved to synthesize TiO₂ nano-crystal sol through sol-gel method.¹³CNMR and XAFS were adopted to analyse the hydrolyzation behavior of Ti（OC₄H₉）₄ and the crystal structure of TiO₂ colloidal particle.The results showed that Ti（OC₄H₉）₄ hydrolyzes completely and no organic radicals were linked to Ti atoms in the final sol. Hydrate titanium ions polymerized slowly and bonded orientedly,and thus anatase TiO₂ crystal grains grew in the aqueous solution,and stable TiO₂ nano-crystal sol was formed subsequently（Mean particle diameter is 28.7 nm）.The resultant sol was coated on the substrate,and crystalline TiO₂ film with well photocatalytic activity was obtained at low temperature.（2）Fabricated porous surface morphology of crystalline TiO₂ film at low temperature,increased photocatalytic activity of the film.Styrene-acrylate spheres and 4,4’-isopropylidenediphenol（BPA）were used as templates to control the surface morphology of TiO₂ film and added into TiO₂ nano-crystal sol respectively.The film was prepared from resultant solution,and then the template was preferentially extracted by organic solvent.So the porous anatase TiO₂ film was obtained at low temperature（dried at room temperature or 60℃）.The influence of the formula and control process on the morphology of the film was investigated and the preparation mechanism of porous TiO₂ film was discussed.The adsorption properity as well as photocatalytic performance were also studied.Results are as follows:When rigid styrene-acrylate spheres was used as a template,suitable control of heterocoagulation between styrene-acrylate spheres and TiO₂ colloidal particle was favorable to the dispersion of styrene-acrylate spheres in the film as well as the formation of porous structure with certain wall thickness.The mass ratio of TiO₂ sol and styrene-acrylate emulsion affected the morphology of the pores;the aging time was a dominant factor for the formation of the dense pores on the surface; styrene-acrylate spheres could be eliminated effectively by the ultrasonic oscillation. The appropriate proportion was:15 g TiO₂ sol+0.2 g styrene-acrylate emulsion+10 g H₂O;the solutions are aged for 15 d,and the film was soaked into toluene and vibrated by ultrasonic for 10 min.When flexible BPA was used as a template,the resultant solution was a two phase mixture consisting of BPA and TiO₂ colloidal particles.The control of phase separation of these two substances in film could be achieved via adjusting the dosage of the components in the solution,and thus TiO₂ film with homogeneous and continuous porous structure was obtained.With the decrease of BPA concentration, the effect region of BPA was changed from the inside region of the film to the surface region of the film.Low concentration of TiO₂ colloidal particle and high content of ethanol was propitious to form porous structure.The appropriate proportion was:4 g TiO₂ sol+0.07 g BPA+10 g C₂H₅OH.The porosity enhanced the adsorption properity of the film,and more TiO₂ particles could contact with the pollutant molecule.So the photocatalytic activity was increased via the adsorption followed by photocatalytic oxidation.（3）Designed laminated coupled semiconductor at low temperature,increased photocatalytic activity of the film.Poly（3,4-ethylenedioxythiophene）/poly（styrenesulfonic acid）（PEDT/PSS,an organic semiconductor）and SnO₂ were used to increase the photocatalytic activity of TiO₂ film respectively.The dual-layer coupled semiconductor film was prepared at low temperature（dried at 60 or 100℃）,which used corresponding semiconductor film as an underlayer and TiO₂ film as a surface layer.The spectroscopy study on the film indicated that these dual-layer structure formed heterojunction,and there was an overlapping band in the coupled semiconductor film.The underlayer semiconductor induced a better charge separation due to electron transfer from TiO₂ layer to underlayer semiconductor,and thus the recombination of photon-generated electron-hole pair was suppressed.Hence,the photocatalytic activity of coupled semiconductor film was increased significantly compared with TiO₂ film,and the highest could increase about 3 times.（4）Established TiO₂-CuTsPc sensitizing system at low temperature,extended the light response region of the film.Copper（Ⅱ）phthalocyanine tetrasulfonic acid（CuPcTs）was added into TiO₂ sol, and phthalocyanine sensitized TiO₂ sol（TiO₂-CuTsPc sol）was synthesized via the adsorption of CuTsPc on the TiO₂ colloidal particles due to electrostatic attraction. TiO₂-CuTsPc film was then prepared by coating the resultant sol on the substrate at room temperature.The influence of water bath time and the CuTsPc concentration on the CuPcTs loading in the film were investigated,and the relationship between CuPcTs loading and photocatalysis was studied,Furthermore,the loading mechanism of CuTsPc was also discussed.The results showed that the sensitization of CuTsPc could extend the light response region of the film to 600-700 nm,and thus increase the visible-light photocatalytic activity of the film.UV-Vis absorption spectra indicated that prolonging the time in water bath or raising the CuPcTs concentration in TiO₂ sol were helpful for increasing the amount of CuPcTs supported in TiO₂ film.The visible-light photocatalytic activity of the film was increased with the amount of CuPcTs,but too much CuPcTs would decrease the photocatalytic activity.When 0.036 g CuPcTs was added into 20 g TiO₂ sol and the mixture was heated in the water bath at 80℃for 8 h,the photocatalytic activity could reach the highest.CuPcTs could be loaded in the film uniformly and firmly via adsorption on the TiO₂ colloidal particles,and this ensured the stability for repeated use of TiO₂-CuTsPc film.The photocatalytic activity of the film became stable after being used 2～3 times.更多还原