【作者】 谢超；

【导师】 徐自力；

【作者基本信息】 吉林大学 ， 环境科学， 2004， 硕士

【摘要】 1972年，Fujishima和Honda发现在TiO2电极上可光催化分解水。这一事件标志着复相光催化中一个新领域的开始。从那以后，化学家和物理学家对探讨光催化反应的主要过程及增强TiO2的光催化效率作了大量的研究。近年来，应用复相光催化净化环境已成为最活跃的研究领域之一。应用半导体金属氧化物或硫化物作光催化剂可完全消除大气和废水中的有机污染物。TiO2、ZnO、Fe2O3、WO3、CdS等都是半导体，也就是说，在它们的价带和导带之间有一适当的带隙（1-3eV）。在受到大于其带隙能的光照射时，价带电子被激发到导带上去，产生高反应活性的电子-空穴对，电子-空穴对迁移到固体表面以后，它们与具有适宜氧化还原潜势的吸附质发生电子转移过程，于是光催化降解过程就发生了。与光降解水中污染物相比，气—固复相光催化研究得较少，但由于其对受污染的大气环境如办公室、工厂等处进行污染控制有潜在的应用前景，气—固复相光催化已越来越引起了人们的关注。在适宜的条件下（室温、1大气压、氧气为氧化剂），用半导体作光催化剂可有效地使许多有机物转化为CO2和H2O。本论文中，我们首先选用不同的合成条件（合成路线，使用不同的醇作为溶剂，陈化时间，焙烧温度以及硅的含量）制备了TiO2-SiO2复合纳米粒子。不同合成路线所制备样品对庚烷的光催化能力所表现出的不同说明复合粒子的光催化活性是和催化剂中两种组分混合的均一程度有很大的关系。对于庚烷而言，使用乙醇合成的催化剂的光催化能力要高于使用甲醇，异丙醇和正丁醇作为溶剂所合成的催化剂。另外，陈化时间的延长有利于获得较高的光催化活性。对于庚烷和SO2, 均是当复合粒子含有大约9.1 mol% SiO2时光催化活性最高。以上样品使用多种现代技术手段如XRD、BET、FT-IR、SPS、XPS及UV-Vis等对它们的结构、性质进行了表征。通过以上表征发现，硅的加入可以显著地抑制所制备的催化剂的粒径的生长和晶型的转变，并且可以在催化剂的表<WP=76>面产生Br?nsted酸，所有这些均有利于光生电子和空穴在表面的分离，从而可以极大地提高光催化活性。本论文的第三章对庚烷和甲苯的光催化活性进行了比较。研究发现庚烷可以迅速的被完全降解成为CO2,因此在反应结束之后可以保持催化剂表面的洁净。而在降解甲苯的过程中，会生成反应活性很低的中间产物，这些中间产物覆盖在样品表面的活性中心，会影响其后进行的光催化反应。对于光催化降解庚烷，具有大的表面积的催化剂可以获得较高的催化活性，而对于甲苯，具有较小表面积的催化剂可以获得的催活活性。更多还原

【Abstract】 In 1972, Fujishima and Honda discovered the photocatalytic splitting of water on TiO2 electrodes. This event marked the beginning of a new era in heterogeneous photocatalysis. Since then, research efforts in understanding the fundamental processes and in enhancing the photocatalytic efficiency of TiO2 have come from extensive research performed by chemists and physicists. In recent years, applications to environmental cleanup have been one of the most active areas in heterogeneous photocatalysis. This is inspired by the potential application of semiconductor metal oxides and sulfides photocatalysts for the otal destruction of organic compounds in polluted air and wastewaters. TiO2, ZnO, Fe2O3, WO3, CdS, etc, are semiconductors, i.e. they have a moderate energy band-gap (1-3 eV) between their valence and conduction bands. Under illumination by photons of greater than band-gap energies, the valence band electrons can be excited to the conduction band, creating highly reactive electron-hole pairs. After migration to the solid surface, these may undergo electron-transfer processes with adsorbates of suitable redox potentials. Studies involving gas-solid heterogeneous photocatalysis are relatively few in number compared with the substantial literature on photocatalytic water treatment, but are now of growing interest because of the potential application to contaminant control in contained air atmospheres as found in aircraft and spacecraft, office buildings and factories. At moderate conditions (room temperature, one atmosphere pressure and with molecular oxygen as the only oxidant), the above mentioned semiconductors have proved to be effective photocatalysts for the thermodynamically favored transformations of many organics to CO2 and H2O. <WP=78>In this paper, firstly we selected different synthesis conditions (synthesis route, different alcohol, aging time, calcination temperature and Si concentration) to prepare TiO2-SiO2 mixed oxides. The different of the photocatalytic activity performance exhibited by the samples prepared via two different synthesis routes illustrates that the photocatalytic activity of mixed oxides is closely related with its degree of homogeneity. For heptane, the catalyst prepared by using ethanol as the solvent shows higher photocatalytic ability than those prepared by using methanol, i-propanol and n-butanol. In addition, longer aging time is beneficial for obtaining higher photocatalytic activity. In the case of heptane and SO2, the catalyst researches the highest photocatalytic activity when about 9.1 mol% SiO2 is added. The properties of the samples mentioned above are characterized by means of XRD, BET, FT-IR, SPS, XPS and UV-Vis. It was found that the addition of silica can effectively inhibit the growth of crystalline size and the phase transformation from anatase to rutile, moreover, promote the generation the Br?nsted acid.The comparison between the photocatalytic activity of heptane and toluene was made in the chapter three of this paper. It was found that the catalyst surface was kept clean after the photoreaction in that heptane can be rapidly and completely photodegraded into CO2. However, toluene can not be rapidly and completely photodegraded into CO2 and produce less-active intermediates adsorbed on the catalyst surface to block the active sites. Therefore, we suggest that for heptane larger surface area is beneficial for higher photocatalytic activity. On the contrary, smaller surface area may be good for photodegradation of toluene.更多还原