超细掺杂TiO₂的制备及其光催化性能的研究

【作者】 杨鹏飞；

【导师】 徐顺；

【作者基本信息】 郑州大学 ， 物理化学， 2002， 硕士

【摘要】 本文以TiCl₃溶液为原料，利用微乳液法制备超细TiO₂及超细掺杂TiO₂光催化剂，并以甲基橙作为光催化实验的目标降解物。 首先结合光催化分析的结果，详细研究了制备方法、不同表面活性剂、烧结温度、烧结时间、催化剂用量、超声波处理以及预搅拌时间等因素对TiO₂光催化活性的影响，从而确定了以CTAB作为表面活性剂的微乳液法制备的前驱体在600℃温度下烧结2个小时获得的TiO₂光催化剂具有更好的活性，以此作为制备方法制得了各种掺杂TiO₂光催化剂，并通过XRD分析了解到这种方法所制备的TiO₂为锐态矿晶型，尺寸在20nm左右。 本文重点研究了TiO₂掺杂Fe³⁺、Ru³⁺、Zn²⁺等十四种过渡金属离子和Mg²⁺、Al³⁺、Sn⁴⁺等五种主族金属元素后，其光催化活性的变化规律。发现Fe³⁺，Ru³⁺等过渡金属元素有正的掺杂效应，其中掺入Fe³⁺将TiO₂的活性提高了将近50％。而大部分稀土金属离子、主族金属元素只有负掺杂效应。并总结出掺杂金属元素从“离子半径”、“离子化合价”、“离子的氧化还原能级”等三个方面作出了对金属离子掺杂效应的贡献：金属离子半径与Ti⁴⁺离子半径相近，将有利于离子均匀掺入TiO₂晶格中，而这是离子产生掺杂效应的前提。第四周期元素离子半径与Ti⁴⁺半径接近，如Co²⁺，Ni²⁺等，因此能产生正的掺杂效应。另一方面，研究发现象Fe³⁺、Co²⁺等中间价态的离子比Cu²⁺、Sn⁴⁺等高价离子有更好的掺杂活性，这可能是因为中间价态的离子可以充当电子捕获中心与空穴捕获中心的双重角色，而高价态离子只能充当一种角色。还有，对于中间价态的离子，如果其氧化还原能级与TiO₂的禁带宽度相匹配，则能显示出很高的活性，而有较大差别时，则活性降低。其中Fe³⁺的氧化电位Fe^3+/4+与TiO₂的价带接近，还原电位Fe^2+/3+与导带接近，因此Fe³⁺有很好的掺杂效应。而对于Ru³⁺，虽然Ru^3+/4+接近TiO₂导带，但Ru^2+/3+与TiO₂价带差别较大，因此活性没有掺Fe³⁺的高。 最后尝试性地以Fe³⁺和La³⁺为杂质离子，研究了TiO₂掺杂两种（或以上）离子后的光催化规律，认为杂质离子的混掺效应是两种离子单掺效应的平均。通过对混掺的研究，提供了一个TiO₂掺杂光催化研究中的研究方向-------多种离子掺杂TiO₂的光催化活性研究。更多还原

【Abstract】 In this paper, the photocatalyst of ultrafine TiO2 and doped ultrafme TiO2 were prepared by means of microemulsion. And methyl orange was applied in the photocatalytic experiment to work as the decomposed compound.At the beginning of this paper, the factors infuluencing the photocatalystic effect of TiO2 were studied in detail, including preparation methods,different sufacial agent, sintering temperature, the dosage of catalyst, ultrasonic treatment,pre-milling time,etc. Consequently,the best conditions for preparation of doped TiO2 were ( 1 ) to use the microemulsion with CTAB as surfacial agent ,(2)TiO2 nH2O was sintered at 600 for two hours. The product prepared in such conditions could show better active properties. And the crystalloid of TiO2 prepared by such method was anatase and the average size was approximately 20nm from XRD analysis.The focus of this paper was to study the law of photocatalystic appearence of TiO2after doping 14 kinds of metal ions , including both transition elements like Fe3+,Ru3+,Zn2+and main family elements like Mg2 Al3+ Sn4+ .It was discovered that Fe3+, Ru3+,etc doped in TiO2 showed positive effects on the photocatalystic oxidation of TiO2, especially Fe3+ could increase the degradation ratio of methyl orange by 50%. However ,most of rare soil elements , main family elements ,etc showed negative effects. The paper also sum-upped that such three factors as ionic radii , combined value and energy level of doped ions contributed to the photocatalystic activities of TiO2. Indetail , metal ions with similar ionic ratii to Ti4+ could easily mix into the crystal lattice of TiO2, which made it possible to activate photocatalyst of TiO2. The elements in fourth period show positive effect just because the sizes of their ratii are similar to Ti4+’s. Secondly, metal ions with medium combined value such as Fe3+ Co2+ showed better effects on TiO2 than those with high value such as Cu2+ Sn4+.It was probably because metal ions with medium combined values could play two roles ........ the center oftrapping h+ and that of trapping e". But those with high values only play one . Lastly, if reducing energy level and oxidizing energy level of ions with medium combined values were both matching with TiO2, the doping effects of doped ions in TiO2 could appear greatly positive . If not, there was negative doping effect on TiO2. For example, the energy level of Fe3+/4+ is near value band of TiO2 and that of Fe2+/3+ is approximate to the conducting band. So Fe3+ showed great doping effect . But the energy level of Ru 2+/3+ is not close to the value band despite that of Ru 3+/4+ is near conducting band of TiO2.Therefore, Fe3+ was better than Ru3+ in spite which had positive doping effect.The last part of this paper tentatively prepared the photocatalyst doping two ions - Fe3+ and La3+ into TiO2 and studied the photocatalystic law ,and concluded that effect of doping two ions was the equilibration of the effect of one ion and that of the other. Eventually, the paper pointed out that such a research direction to study the effects of doping two ions into TiO2 was a promising one.更多还原