【作者】 张瑜；

【导师】 梁伟；

【作者基本信息】 太原理工大学 ， 材料学， 2009， 硕士

【摘要】 随着全球环境污染和能源危机的日益严重,人们越来越关注环境和能源问题,迫切需要开发高效、低能耗、使用范围广的功能材料。TiO₂光催化氧化技术作为一种新的污染治理技术,因其具有能耗低、反应条件温和、催化活性高等优点引起了各国研究者的广泛关注。但是TiO₂作为一种宽禁带半导体（Eg=3.2eV）,只有在能量较高的紫外光照射下才能表现出光催化活性,而占太阳光大部分的可见光却不能被有效利用,同时产生的光生电子与空穴的再复合率高,量子产率低,TiO₂的上述缺陷极大地限制了该技术在实际中的应用。掺杂贵金属Pt制备改性纳米TiO₂光催化剂的思路引起了众多学者的关注:铂掺杂后,在Pt-TiO₂界面会形成能捕获电子的浅势阱—Schottky势垒,进一步抑制光生电子-空穴的复合;同时可以改变TiO₂的表面状态、对其表面活性基团的增减产生重要的作用。因此了解Pt掺杂对TiO₂表面性质和光催化活性的影响,有助于深入了解TiO₂光催化机理和指导高催化活性光催化剂的制备。本文另辟蹊径,通过传统的溶胶-凝胶法结合蒸涂法制备了纯TiO₂薄膜及掺杂铂改性的TiO₂薄膜。实验结果表明,500℃热处理后的TiO₂均为锐钛矿型。本文的实验结果如下:（1）薄膜的UV-VIS结果表明,喷铂不同时间后的改性TiO₂薄膜都具有不同程度的可见光响应性,其光吸收曲线都有一定程度的红移。尤其是TPT-180s薄膜的光吸收曲线红移了30nm,在λ<670nm的可见光范围内都有吸收。而且除位于紫外光区的本征吸收边外,还出现了一个新的吸收边650nm,对应带隙为1.91eV,而相同制备工艺下制得的其它薄膜仅显示出TiO₂半导体的本征吸收。（2） SEM结果表明各种薄膜中TiO₂颗粒形貌有所差异,纯TiO₂薄膜中颗粒的平均大小在40⁸0nm之间,呈多面体树叶状;而在TPT-180s复合薄膜中,颗粒尺寸较均匀,平均大小在20⁴0nm之间,TTP-180s薄膜表面出现龟裂现象,而PTT-180s薄膜中部分颗粒为多面体状,部分为球状,一些颗粒长大现象较严重。（3） TPT-180s薄膜的横截面图像表明该薄膜总厚度约为160nm,里外两层TiO₂层的厚度分别约为60nm和70nm,而位于中间的铂层厚度约为30nm,该层厚度与铂的蒸涂时间成正比关系。（4） TPT-180s薄膜的TEM结果表明,与基体尺寸相当的铂团簇（20⁴0 nm）弥散分布在TiO₂基体中;同时在Pt-TiO₂界面存在金属与基体的接触区。SADP表明,夹层式复合薄膜TPT-180s由金属铂和锐钛矿型TiO₂构成。（5） XPS结果表明,在TPT-180s薄膜表面,铂钛原子比Pt:Ti≈2.5%; TTP-180s薄膜表面,铂钛原子比为无穷大;而在T薄膜和PTT-180s薄膜表面,铂钛原子比为零。在TPT-180s薄膜表面,钛元素为Ti4+,氧元素为O2-,而铂元素为Pt0,即铂以铂单质的形式存在,表层的这部分铂原子是在热处理过程中由中间层扩散至薄膜表面的。（6）可见光照射下降解不同初始浓度的甲基蓝溶液的实验表明,TPT-180s薄膜的光催化活性明显优于纯TiO₂薄膜、TTP-180s和PTT-180s薄膜,TPT-180s薄膜对甲基蓝溶液的最佳降解工艺为:甲基蓝初始浓度为30mg/L,体积为100ml;在此工艺条件下,纯TiO₂薄膜对甲基蓝溶液的降解率为76.6%,TPT-180s的最终降解率为83.4%。（7）实验室条件下制备的TiO₂薄膜较稳定,反复进行6次降解实验后,纯TiO₂薄膜和TPT-180s薄膜对甲基蓝溶液的降解率分别仅下降了5%和3%,再继续进行降解实验,薄膜的光催化活性保持稳定。更多还原

【Abstract】 Since the appearance of global environment pollution and energy crisis, environment and energy problems have been the focus of people,s research all over the world. People have been cried for developing high efficiency, low energy consume, wide-use function materials. The photocatalytic oxidation technique of TiO₂ has been paid more and more attention for many advantages, such as low energy consumption, mild reaction condition,easy operation and so on. However, TiO₂ as a wide-gap semiconductor（Eg=3.2eV）, it shows photocatalytic activities only when illuminated by light with wavelength< 387nm, meanwhile, induced electron-hole pairs recombine easily, low quanta efficiency, which largely confine its application in practice.Considering the problems above, the method of doping Pt has been presented because it can form Schottky barrier to trap electrons and change the characters of surface of photocatalysts, promote induced electron-hole pairs to apart, change the quantity of active function groups, which much affect the efficiency of multi-phase reaction.Different Pt-modified TiO₂ thin films were prepared by traditional sol-gel method together with arc discharging. All Titania thin films turned into anatase when calcined at 500℃. Main results were shown as follows:（1） Absorbance properties of all films were examined by UV-vis spectrometer. Compared with pure TiO₂ film, all systems show some kinds of visible light response when Pt layer lies between two TiO₂ coatings. Especially, the absorbance curve of TPT-180s composite film has redshifted by 30 nm and expanded even up to 650nm, its corresponding bandgap energy is 1.91eV. whereas, other films made under the same conditions only show their characteristic absorbance in region of wavelength<400nm.（2） The SEM results show that morphologies and sizes of granules in all systems are different: In pure TiO₂ thin film, the average sizes are in the range of 40⁸0nm and polyhedral-like, while in TPT-180s composite film, the average sizes are in the range of 20⁴0nm, particles in TTP-180s film seemed to be aggregating, while in PTT-180s, some particles even grow heavily.（3） The cross-section morphology results show that the whole thickness of TPT-180s composite film is 160nm, the outer and inner TiO₂ coatings are 60nm and 70nm, respectively, while Pt layer between them are about 30nm, which may come from the middle layer to surface by diffusion.（4） The TEM bright-field results of TPT-180s film show that the deposited Pt granules aggregate into Pt clusters （20⁴0nm）. The selected-area electron diffraction analysis approves that TiO₂ is in the form of anatase phase in TPT-180s composite thin film after heat treatment.（5） XPS results show that Ti element is in the form of Ti4+, O in the form of O2- and Pt element in the form of Pt0 on surface of TPT-180s composite film. The atomic ratio of Pt to Ti element is about 2.5%, while for PTT-180s thin film and T （or PTT-180s film）, the value is infinite and zero, respectively.（6） The photocatalytic activities of all systems have been tested by photobleaching different concentrations of methyl blue solution. The results show that the activities of TPT-180s film excel that of other references. The prime bleaching techniques are: the beginning concentration of MB solution-30mg/L,100mL, the illuminating time 2h. The ultimate degradation rate of pure TiO₂ is 76.6%, while the degradation rate of TPT-180s is 83.4%.（7） The prepared films are stable that after using six times, the photocatalying rate of pure TiO₂ film and TPT-180s only decrease by 5% and 3% respectively.更多还原