二氧化钛复合薄膜的制备及其光催化降解有机污染物

发布时间：2018-03-12 19:36

本文选题：TiO2-ZnO复合薄膜　切入点：离子掺杂　出处：《济南大学》2015年硕士论文　论文类型：学位论文

【摘要】：二氧化钛是一种催化活性高、无毒无污染、价格低廉、性质稳定的n型半导体光催化剂,然而,TiO2存在两大方面的缺陷:一是TiO2的禁带宽度比较大,带隙能为3.2eV,也就是说二氧化钛只有在受到波长小于387.5nm的紫外灯照射时才会激发产生光生电子和空穴,但是紫外光在太阳光中所占的比例还不足5%,这使二氧化钛在日常应用中对太阳光的利用率极低;二是光生电子和空穴很不稳定且非常容易发生复合,这严重降低了二氧化钛的光催化性能。从而,减小带隙能和降低电子空穴对的复合率成为了拓宽TiO2的应用领域及改善其光催化活性的重要突破口。为了实现上述突破,必然要对TiO2进行改性研究。迄今为止,研究者已经研制出许多应用于TiO2改性的方法,其中离子掺杂和半导体复合是我们在本研究中所采用的两种改性方法,改性处理不仅将TiO2的光响应范围拓宽到可见光区域,而且大大降低了光生电子-空穴对的复合率。本论文主要研究了以下几个方面:(1)TiO2薄膜及TiO2-ZnO复合薄膜的制备及性能测试该实验选用钛酸四正丁酯和二水合醋酸锌分别作为钛源和锌源,采用溶胶-凝胶法制备出TiO2胶体和ZnO胶体,将陈化好的胶体按一定体积混合搅拌得到TiO2-ZnO复合胶体,采用浸渍提拉法在洁净干燥的玻璃基体上拉制薄膜,待薄膜干燥后,采用外掺杂的方法在其表面掺杂离子Ce、F、Ca、Fe、La,待离子溶液自然风干后,将薄膜置于马弗炉中进行高温焙烧,通过对甲醛的降解性能测试来确定离子的最佳单双掺浓度。薄膜对有机污染物降解的实验结果表明了离子掺杂复合改性之后的TiO2薄膜光催化活性得到了显著的提高。(2)TiO2及TiO2-ZnO光催化剂的表征本研究通过使用紫外-可见分光光度计(UV-vis)、荧光光谱(PL)仪、场发射扫描电镜(FE-SEM)、差热-热重分析仪(DTA-TG)、X射线衍射仪(XRD)及氮气吸附-脱附仪(BET),对薄膜和粉体进行了一系列的光学性能及结构表征。红移及荧光光谱分析结果表明了:离子掺杂和复合改性不仅诱发了薄膜较强的可见光吸收,而且降低了电子-空穴对的复合率;DTA-TG及XRD结果显示了改性后的催化剂晶型主要维持在光催化性能最好的锐钛矿;FE-SEM及BET测试揭示了复合改性的薄膜是由较小的纳米粒子构成的,同时具有较大的比表面积。(3)光催化机理的探讨首先,ZnO与TiO2复合后会形成交错能级,经光照射时,ZnO导带上的电子会很容易地被激发到TiO2的导带上,相反,TiO2价带上产生的空穴会转移到ZnO的价带上,因此ZnO复合后大大降低了TiO2的带隙能及电子-空穴的复合率。其次,半径较小的离子掺杂后会与TiO2形成掺杂能级,从而进一步减小其带隙能;半径较大的镧系金属离子掺杂后会引起TiO2的晶格扭曲,使其能够接收更多的光生空穴并产生更多的自由基来氧化吸附的有机污染物分子。另外,掺杂的离子可以结合电子或空穴,阻止其复合的进行。(4)应用领域的拓展与以往研究不同,本研究将离子掺杂后的TiO2-ZnO复合薄膜主要应用于甲醛这一新兴污染物的降解,使其在实际生活中更加具有应用价值。
[Abstract]:Titanium dioxide is a high catalytic activity, non-toxic and pollution-free, low price, the N type semiconductor photocatalyst, stable however, defects of TiO2 in two aspects: one is the band gap of TiO2 is relatively large, the band gap energy of 3.2eV, that is to say only by TiO2 UV light wavelength is less than 387.5nm when irradiated to stimulate production of photogenerated electrons and holes, but the UV light accounted for in the light of the sun in the proportion of less than 5%, which makes the daily application of titanium dioxide in the sunlight utilization rate is extremely low; the two is the photogenerated electrons and holes are very unstable and very prone to complex, which greatly reduces the photocatalytic performance titanium dioxide. Thus, reducing the band gap energy and reduce the electron hole pair recombination rate is to widen the application fields of TiO2 and improve an important breakthrough in the photocatalytic activity. In order to realize the breakthrough, must be modified TiO2. Study. So far, the researchers have developed many applications on TiO2 modification methods, including ion doping and semiconductor composite is two kinds of modified methods we used in this study, the modification will not only widen the range to the visible light region in response to the TiO2 light, but also greatly reduces the photogenerated electrons hole pair recombination rate. This paper mainly studies the following aspects: (1) preparation and performance test of TiO2 film and TiO2-ZnO composite film of the experiment using butyl titanate four and two hydrated zinc acetate were used as titanium source and zinc source, using sol-gel method to prepare TiO2 and ZnO colloid. Chen Huahao colloid according to a certain volume mixing TiO2-ZnO Composite Colloid by dip coating method on glass substrate drawing clean dry film, the film after drying, using the method of doping on the surface of doped ion Ce, F, Ca Fe, La, for ion solution of natural dried, the film in the muffle furnace for high temperature roasting, the degradation of formaldehyde test to determine the optimal concentration of doped ions. Single and double film on degradation of organic pollutants and the experimental results show that the ion doped TiO2 thin film photocatalytic activity after greatly improved. (2) characterization of photocatalyst TiO2 and TiO2-ZnO in this study by using UV visible spectrophotometer (UV-vis), fluorescence spectroscopy (PL) spectrometer, field emission scanning electron microscopy (FE-SEM), thermogravimetric analyzer (DTA-TG), X ray diffraction (XRD) and nitrogen adsorption desorption instrument (BET), on thin films and powders were optical properties and structural characterization of a series of red shift and fluorescence spectra. The analysis results show: ion doping and composite modified films not only induced a strong absorption of visible light, but also reduce the electron hole pair complex Photosynthetic rate; DTA-TG and XRD results showed that the modified catalyst crystal after mainly maintained in the best photocatalytic activity of anatase; FE-SEM and BET test revealed a thin film composite modification is composed of smaller particles, and has a high surface area. (3) to investigate the photocatalytic mechanism of the first. ZnO and TiO2 compound will be formed after the level crossing, after light irradiation, ZnO electronic conduction band can be easily excited into the conduction band of TiO2, on the contrary, TiO2 will be transferred to the valence band holes on the valence band of ZnO, so the ZnO composite greatly reduces the recombination rate of TiO2 band gap energy and electron hole. Secondly, ion doping smaller radius will be formed after the doping level and TiO2, so as to further reduce its energy gap; the radius of lanthanide metal ions doping will lead to larger distortion of the crystal lattice of TiO2, so that it can receive more and more photohole Organic pollutants to free radical oxidation and adsorption. In addition, the doping ions with electrons or holes, prevent the composite. (4) the application development different from previous studies, this study will degrade TiO2-ZnO composite film after ion doping is mainly applied to formaldehyde this emerging pollutants, the it has more application value in real life.

【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2

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