【作者】 于江伟；

【导师】 于运花；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2010， 硕士

【摘要】 纳米二氧化钛(TiO2)因其比表面积大、稳定性好、无毒性和光催化效率高等优点在有机污染物处理方面得到了极大的重视。但是,目前在TiO2光催化的应用上存在两个难题：一是纯纳米TiO2粉末的光催化效率有限；二是纳米TiO2粉末在溶液中易团聚流失,不易回收。这两个因素在很大程度上限制了TiO2光催化剂在工业上的应用,而将纳米TiO2进行掺杂改性和负载化则可有效地解决上述两个问题。静电纺丝法作为一种制备有机／无机杂化微纳米纤维的简便快捷方法而得到了迅速发展。本论文采用溶胶-凝胶法和静电纺丝法相结合,制备了钐离子掺杂的二氧化钛前驱体／聚丙烯腈纳米纤维[Sm-TiO(OAc)2/PAN],并通过后续的牵伸预氧化、氨化处理和高温焙烧过程,得到了掺杂钐的二氧化钛／炭纳米纤维(Sm-TiO2/CNFs)光催化剂。采用TEM、FESEM、XRD、FT-IR, EDX和XPS等测试手段对所制备的纳米纤维的形貌结构、晶相结构和化学组成进行了表征,并以甲基橙溶液为目标降解物,考察了Sm-TiO2/CNFs的光催化活性。研究结果表明,电纺Sm-TiO(OAc)2/PAN纳米纤维的表面凹凸不平,直径约700nm。经过250℃牵伸预氧化后,纤维取向度提高,表面变得光滑且由于物理和化学收缩纤维直径缩小至500-600nm。经过氨化处理和600℃焙烧后,预氧化纤维直径进一步收缩至250-350nm,25wt.%左右的锐钛矿型Sm-TiO2纳米颗粒均匀地分布在CNFs表面或内部,Sm-TiO2的平均晶粒尺寸为10nm左右。同样的紫外光照下,Sm-TiO2/CNFs比TiO2/CNFs的光催化活性要高,这是由于Sm3+的掺杂抑制了电子-空穴对的复合,使Sm-TiO2/CNFs表面的吸附氧增多,由此生成了更多的强氧化型自由基将甲基橙分子分解掉。更多还原

【Abstract】 Titanium dioxide (TiO2) has attracted a great deal of attention in organic pollutants treatment because of its large specific surface area, stable chemical properties, nontoxicity and excellent photocatalytic activity. However, there are two problems in the application of TiO2 photocatalyst:First, the photocatalytic efficiency of pure nano-TiO2 powder is quite finite. Second, the nanoparticles are easy reuniting and flowing away in liquid solution, and also difficult to reclaim. These two factors inhibit the industrial application of nano-TiO2 photocatalyst significantly. Many researches have proved that doping modification and immobilization of TiO2 onto the supports with large surface areas are two effective means to solve the problems above.Electrospinning is a simple and effective technique for preparation of organic/inorganic hybrid nanofibres with large surface areas. In this paper, Sm-doped titanium oxoacetate/polyacrylonitrile [Sm-TiO(OAc)2/PAN] nanofibers were fabricated by electrospinning method. The Sm-doped TiO2/carbon nanofibers (Sm-TiO2/CNFs) photocatalyst was obtained through the subsequent heat stretching and preoxidation, ammonia treatment, and calcination of electrospun Sm-TiO(OAc)2/PAN nanofibers. Variations in morphology, crystal structure, and chemical composition of nanofibers were characterized with TEM, FESEM, XRD, FT-IR, EDX and XPS, respectively. The photocatalytic activity of Sm-TiO2/CNFs was characterized by photocatalytic degradation of methyl orange (MO) in aqueous solution under the UV irradiation. The results show that the surface of electrospun Sm-TiO (OAc)2/PAN nanofibers is rough and the nanofiber diameter is about 700nm. After 250℃heat stretching and preoxidation, the nanofibers possess highly orientation and become smoother, the average diameter of nanofibers decreases to 500-600nm due to physical and chemical shrinkage. After ammonia treatment and 600℃calcination, the average diameter of preoxidized nanofibers drop further to 250-350nm, and the surfaces of CNFs are interspersed with about 25wt% of anatase Sm-TiO2 nanoparticles, of which the average grain size is about 10nm. The photocatalytic activity of Sm-TiO2/CNFs is higher than that of TiO2/CNFs under the same UV irradiation conditions because doping Sm3+ may inhibit the recombination of electron-hole pair and increase the content of adsorbed oxygen, resulting in the generatinon of more powerful oxidizing free radical to degrade methyl orange.更多还原