【作者】 俞娇仙；

【导师】 刘素文；

【作者基本信息】 山东轻工业学院 ， 材料学， 2008， 硕士

【摘要】 随着工业的迅速发展,能源危机和环境污染日益严重。如何节约能源,控制和处理环境污染已成为当前的重大课题。在众多纳米光催化材料中,TiO2因具有氧化性强、稳定性好、廉价无毒等优点,成为最有发展前景的纳米光催化剂。但TiO2的量子产率低,光催化性能不高;禁带能量较高(3.2ev),只能在紫外光下才有活性,耗费能源。因此,对TiO2进行改性以提高其光催化活性,拓展光谱响应范围是光催化发展进一步走向实用化的关键。本文在总结纳米TiO2光催化剂改性研究进展的基础上,重点进行了以下几个方面的研究。1.为了提高光催化剂的活性,用燃烧法制备了Bi离子掺杂TiO2和Eu离子掺杂TiO2纳米光催化剂。对掺杂机理进行了研究,并通过光降解实验确定了Bi离子、Eu离子的最佳掺杂浓度。结果表明:掺杂可以使晶格发生畸变,降低电子–空穴对的复合,提高量子产率,从而提高光催化效果。掺杂后的样品光催化活性得到明显提高,并且不同的掺杂离子存在着不同的最佳掺杂浓度,Bi离子的最佳掺杂浓度为3%, Eu离子的为0.5%。2.为了拓展TiO2的光响应波长范围并提高其光催化活性,采用非金属离子掺杂的方法对TiO2进行改性。分别用溶胶–凝胶法和溶剂热法制备了N掺杂TiO2和S掺杂TiO2。通过X射线衍射、透射电镜、比表面积测定仪、红外光谱、紫外–可见吸收光谱等对样品的晶相、形貌、比表面积、吸收边等进行了表征。与纯TiO2相比较,掺杂样品的粒径较小,比表面积较大,由于掺杂使价带上移,禁带宽度减小,或者形成杂质能级,使样品在可见光区的吸光强度明显增加。通过对硝基苯的降解表征了其可见光光催化活性,发现不同的非金属离子掺杂样品均表现出很好的可见光催化活性。3.通过溶胶–凝胶法制备了N–La共掺杂TiO2纳米晶。研究了掺杂浓度对光催化活性的影响。结果表明在N的掺杂浓度为5%、La的掺杂浓度为0.5%时,光催化效果最好。在此基础上,用溶胶–凝胶法制备了N–La共掺杂的纳米光催化薄膜,研究了离子掺杂、镀膜层数对光催化活性、晶格畸变等方面的影响。研究结果表明,半径较大的La3+取代半径较小的Ti4+形成新的结构缺陷,从而有益于表面粒子的羟基化,使薄膜的光催化能力明显增强。镀膜层数为四层的样品的光催化活性最强,在紫光灯下照射3h对甲基橙和硝基苯的降解率分别达到73.98%、96.29%;同时N掺杂可以使禁带宽度窄化,引起催化剂吸收边的红移,从而使可见光响应活性明显增加,在日光灯下照射3h对甲基橙和硝基苯的降解率可达到56.19%和87.86%。由此可见N–La共掺杂除了能将催化剂的光响应波长拓展至可见光区域外,还不降低样品在紫外光区的光催化活性,在利用太阳光光催化方面展现出广阔的应用前景。综上所述,本文通过不同离子的掺杂对TiO2进行改性,在改性TiO2的离子掺杂浓度、制备方法、降解效果、光催化剂的作用机理等方面获得了一些有意义的结果,具有一定的创新性,为纳米光催化材料的进一步研究和实际应用奠定了基础。更多还原

【Abstract】 With the rapid development of industry, energy crisis and environment pollution become more and more serious. So how to save energy, how to control and deal with the enviroment pollution have been the most important thing nowadays. Among all the nano-photocatalytic materials, TiO2 become a most promising photocatalyst for its strong oxidation activity, stability and nontoxic. However, TiO2 has two main disadvantages: Firstly, low quantum yield and low photocatalytic activity. Secondly, large band gap energy (3.2ev) which is only active to ultraviolet light and thus waste energy source. Therefore, how to modify TiO2 in order to increase its photocatalytic activity and extend its range of photo-response spectrum is the key to further utilize in photocatalysis. In this paper, on the foundation of summarizing the development of the modification of nano-scaled TiO2 photocatalyst, the following aspects were mainly studied.1. In order to raise the photocatalytic activity, TiO2 was modified by doping Bi ions and Eu ions using combustion method. Doping mechanism was investigated and photodegradation experiments were made to find the best ion concentration of Bi and Eu. The results showed that ions doping can lead to lattice aberrance, thus reducing the recombination of electrion-cavity pairs and increasing quantum yield photocatalytic activities. The optimum doping concentration was different according to different doping ions. The optimum doping concentration of Bi ions is 3% while the optimum doping concentration of Eu ions is 0.5%. 2. Non-metal doping TiO2 have been studied in order to extend its range of photo-response spectrum and increase its photocatalytic activity. N-doped TiO2 and S-doped TiO2 photocatalysts were prepared using sol-gel method, sovolthermal method, respectively. The crystal structure, morphology, BET and absorbency were characterized by XRD, TEM, IR, BET, UV-vis spectrophotometer. Compared with pure TiO2, the grain size of the doping samples was smaller, the BET was larger. The absorbency increased greatly in the visible region because of the narrower of the band gap and the formation of doping level. The photocatalytic activity of photocatalysts was investigated to be high by degrading methylorange and the samples all have a good photocatalytic properity under visible-light irradiation.3. N-La co-doped TiO2 crystals were synthesized using sol-gel method. The effect of ion doping concentration to photocatalytic activity was investigated. Results show that the highest photodegradation was obtained at the optimum concentration of N5% and La 0.5%. Based on the study of N-La co-doped TiO2 nano-sized photocatalysis, N-La co-doped nano-sized photocatalysis films were synthesized. The effects of co-doping and film layers to lattice deformation and photocatalytic activity were studied. The results showed that La3+-doped samples with bigger ion radius could easily result in lattice deformation, and the replacing of Ti4+ with La3+ could form structure defect which was favour for hydroxylation of the surface grains to obviously heighten the photocatalytic activity of films. The films with four layers possessed the highest photodegradation ratio. The degradation ratio to methylorange and nitrobenze under UV irradiation for 3h was up to 73.98%, 96.29%, respectively. At the same time N doping could narrow the bang gap energy, thus result in the red-shift of absorption edge and increase the photocatalytic activity responding to visible light. The degradation ratios to methylorange and nitrobenze were 56.19% and 87.86% after irradiating under visible-light for 3h. It can be seen that N-La co-doping can not only extend the wavelength to visible light but also maintain good property under UV light, which exhibit new application foreground in the use of solar light.In a word, TiO2 photocatalysts were modified by different ions doping and many significative results were obtained including ion doping concentration, preparation methods, degradation efficiency, photocatalysis mechanics and so on. To a certain extent all the results had some innovation, and at the same time laid the foundation for the further study and practical application on nano-photocatalysts.更多还原