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题名: 纳米TiO2的一步水热法可控制备及其光催化性能研究
作者: 张颖
答辩日期: 2014-05-26
导师: 王传义
专业: 材料物理与化学
授予单位: 中国科学院大学
授予地点: 北京
学位: 硕士
关键词: 二氧化钛 ; 水热法 ; 介孔结构 ; 异面结 ; 混晶结构 ; 光催化
摘要: 二氧化钛(TiO2)纳米材料具有光催化活性好、光电效应、耐光腐蚀能力强、本身稳定性高、环境友好、价格相对低廉及对人体无毒性等优点,TiO2已成为光催化降解污染物以及光解水制氢等领域人们最感兴趣、研究最深入的一种半导体材料。但是由于TiO2的能带间隙较宽,对太阳光的利用率很低,并且其光生电子-空穴对的复合率较高,光量子产率较低,因而限制了它在实际生活中的应用。
尽管传统的提高TiO2光催化活性的方法是对其进行修饰,例如贵金属沉积、离子掺杂以及半导体复合等,这些方法的确都能有效地拓宽TiO2的光谱响应范围并抑制其光生载流子的复合,从而提高其光催化活性,但是这些方法的制备工艺都比较复杂,并且不绿色环保。本文采取一步水热法,无需其他制备工艺,以水溶性钛源二(2-羟基丙酸)二氢氧化二铵合钛和无机酸为原料,可控合成出高活性纳米二氧化钛。对制备的纳米TiO2不进行任何再修饰,仅通过对其本征特性,例如比表面积大小、混晶结构等的控制来调控样品的光催化性能。本文的主要研究内容如下:
(1)利用浓盐酸为无机酸原料,无需模板制备了高比表面积的微/介孔孔径可调控的纳米锐钛矿TiO2微球,研究了水热反应的时间对生成的多孔材料孔径大小的影响,讨论了不同孔径TiO2样品一小时内紫外光催化降解2,4-二氯酚活性的大小,并与商用P25对比。结果表明,一步水热法生成的多孔TiO2微球随着其水热反应时间的延长,孔径的增大,对2,4-二氯酚的降解效率越来越高。在72h生成的介孔TiO2微球一小时内的降解率达到89.8%,高于P25对其74.3%的降解率。
(2)利用氢氟酸为无机酸原料,控制水热反应体系的时间,第一次制备出类似异质结的新型异面结结构,其由锐钛矿(101)面和(200)面构建而成,晶格失配率高达84%。讨论了锐钛矿二氧化钛在含有和不含有异面结的情况下,紫外光照下分解水制氢性能并与商用P25光解水制氢性能进行比较。结果表明:含有异面结的锐钛矿TiO2紫外光下分解水制氢性能是不含异面结的锐钛矿TiO2四倍,并且高于P25的光解水效率。
(3)利用浓硝酸和氨水调节水热体系,调控水热反应系统的pH,制备出锐钛矿-金红石混晶纳米TiO2。研究了锐钛矿和金红石在混晶结构中的比例对其粒径、比表面积大小及光催化活性的影响。结果表明:含有适当比例的混晶结构TiO2在紫外光下降解甲基橙溶液,其效率远大于锐钛矿TiO2和金红石TiO2。
英文摘要: Titanium dioxide (TiO2) has attracted much attention because of its specific properties: photocatalytic activity, photovoltaic effects, long-term stability, nontoxicity, and low cost. The photochemical reactivity, physicochemical properties and application for TiO2 strongly depends upon the crystal structure, morphology, size and microstructure of the particles. Therefore, it is of great important to develop an effective method to synthesize TiO2 with controllable phases and morphologies and it has been an important research focus in the field of materials and photocatalysis. However, its wide band gap reduces the utilization efficiency of sunlight; it enhances the recombination of photogenerated carriers and lowers quantum efficiency, thus limiting the application of it in life. As it can extend the scope of TiO2 spectrum and restrain the recombination of photogenerated electron-hole pairs to result in a drastic improvement of photocatalytic activity by means of decorating the TiO2 with such as metal deposition, ion doping and coupled semiconductor et al, it will pay much on the preparation technology and additional decorative materials. Herein we prepare TiO2 samples without decoration by a simple one-pot hydrothermal synthesis taking Titanium (IV) bis (ammonium lactate) dihydroxide as the precursor, which has great photocatalytic activity due to such as controllable large specific surface area and mixed crystal structure. Our main work is as follows: (1) We prepare adjustable micro/meso-porous anatase TiO2 with large specific surface area by a one-pot template-free synthesis using HCl. The size of pores can be adjusted by the reaction time and the photocatalytic activity changes as the porous size. We study the different degradation rates of 2,4-Dichloropheno using TiO2 samples with different porous sizes upon UV-light irradiation in one hour and compare them to Degussa P25. The results show that TiO2 samples prepared with 72 h can degrade the 2,4-Dichloropheno more quickly than P25, which the former and later degradation rates are 89.8% and 74.3, respectively. (2) A new kind of crystallographic plane junctions (CPJs) between (101) and (200) facets of anatase TiO2 has been fabricated by a simple one-pot hydrothermal method by controlling the reaction time using HF. The CPJs are featured with mismatch of as large as 84%. We study the photocatalytic water splitting upon UV-light irradiation to produce H2 using anatase TiO2 samples with CPJs or not. It demonstrates that photocatalytic H2 production with TiO2 samples containing CPJs is 4 time higher than that not containing CPJs, which is even higher compared to the H2 amount produced by P25. (3) The mixed crystal structure of anatase and rutile TiO2 samples are synthesized by adjusting the pH of reaction solution using HNO3 and NH3?H2O. We study the relation between the mass ratio of anatase to rutile and the particle size, specific surface area and photocatalytic activity of prepared TiO2 samples. The results indicate that the photocatalytic degradation efficency of methyl orange will higher than that of anatse TiO2 and rutile TiO2 samples when the mass ratio of anatase to rutile is in a specific range.
内容类型: 学位论文
URI标识: http://ir.xjipc.cas.cn/handle/365002/3446
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作者单位: 中国科学院新疆理化技术研究所

Recommended Citation:
张颖. 纳米TiO2的一步水热法可控制备及其光催化性能研究[D]. 北京. 中国科学院大学. 2014.
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