【作者】 李霞；

【导师】 李德亮；

【作者基本信息】 河南大学 ， 环境科学， 2011， 硕士

【摘要】 TiO₂是一种具有开发前景的绿色环保光催化材料,以其成本低廉、氧化性能强、化学性质稳定、无二次污染等优点广泛应用于环境污染的治理。但是,由于其能带与导带之间的带隙较宽,不能充分利用太阳光中的可见光部分。此外,二氧化钛的光生电子和空穴的复合率较高,也限制其在工业上的广泛应用。研究表明,金属或者非金属掺杂是一种提高TiO₂光催化活性的行之有效的方法。适量的金属或者非金属元素掺杂可以改善二氧化钛的光吸收范围、抑制光生电子和空穴的复合,是众多提高TiO₂光催化性能方法的首选。本论文以氮、硼、钴、镧为掺杂元素,以TiO₂/SiO₂作为基体,分别采用原位水解和溶胶-凝胶法制备出一系列掺杂纳米TiO₂/SiO₂光催化材料。采用透射电镜（TEM）、X-射线衍射（XRD）、X-射线光电子能谱（XPS）、紫外可见漫反射（DRS）以及光催化测试等对其晶体形貌和结构、电子结构、光学特性以及光催化特性进行了分析研究,取得了一些有意义的结果,内容如下:（1）采用化学吸附结合原位水解的方法制备了N、Co共掺杂TiO₂/SiO₂/PS结构复合微球,经600℃灼烧以除去PS制成空心复合微球催化剂——CNT。采用TEM、XRD、XPS和DRS等测试手段对样品进行表征。结果表明,所得样品均为锐钛矿相TiO₂;掺杂元素N在TiO₂晶格中主要是以Ti-O-N键的形式存在,Co主要是以CoO_x-MO₂（M=Ti、Si）复合氧化物的形式存在;CNT表面变得更为粗糙,并且尺寸远小于未掺杂样品TiO₂/SiO₂;掺杂N、Co后,催化剂在可见光区的响应范围明显延长,可达到600nm;CNT降解罗丹明B的实验表明,N、Co元素具有协同作用,CNT在可见光下表现出较高的光催化活性。（2）采用溶胶-凝胶的方法制备了B、La共掺杂的TiO₂/SiO₂纳米复合光催化剂——BLT。采用TEM、XRD、DRS、扫描电镜（SEM）、热重分析（TGA）、比表面积分析（BET）等测试手段对样品进行表征。结果表明,所得样品均为锐钛矿相TiO₂,B、La元素的掺杂抑制了样品由锐钛矿相向金红石相的转变;BLT的粒径约为60-100nm,比表面积约为不掺杂样品TiO₂/SiO₂的二倍,相对于纯TiO₂和B、La单掺杂的TiO₂/SiO₂光催化剂,BLT纳米复合光催化剂的光吸收带边发生了明显的红移,对可见光的吸收增强;BLT降解罗丹明B的实验表明,B、La共掺杂具有协同作用,在可见光下表现出较高的光催化活性。（3）采用BLT纳米复合光催化剂在500W氙灯照射下（滤光片滤去400nm以下的紫外光）对甲基紫、结晶紫、甲基绿和碱性红9四种碱性染料进行光催化性能研究,考察了催化剂投加量,溶液初始浓度、溶液初始pH值等条件对光催化性能的影响。结果表明:甲基紫、结晶紫、甲基绿和碱性红9的溶液初始pH值均为4,催化剂投加量均为3.0g/L,溶液初始浓度分别为85mg/L、32mg/L、60mg/L、10mg/L时,光催化效果达到最佳。最佳条件下,甲基紫的脱色率为93.2%,CODcr的去除率为68%;结晶紫的脱色率为85.4%,CODcr的去除率为71%;甲基绿的脱色率为84.4%,CODcr的去除率为76%;碱性红9的脱色率为74.7%,COD_cr的去除率为68%。这四种染料在可见光下光催化降解脱色速率和光催化降解CODcr的去除率均符合准一级反应动力学模式。更多还原

【Abstract】 TiO₂ is one of the most promising green photocatalytic materials, which has been widely used in environmental pollution control because of its prominent behaviors such as low cost, high oxidation, chemical stability and no secondary pollution, etc. However, its wide band gap between valence band and conduction band restricts the utilization of the visible part of solar energy. Moreover, the high recombination rate of photogenerated electrons and holes also restricts its wide application in industry. Many studies show that proper doping with metal or nonmetal as a promising approach can improve its absorbance range and restrain recombination rate of photogenerated electrons and holes, which is the preferred method to improve the photocatalytic activity of TiO₂.In this paper, a series of co-doped nano- TiO₂/SiO₂ photocatalytic materials were synthesized by in-situ hydrolysis and sol-gel method, respectively, with the dopant of N, B, Co and La and using TiO₂/SiO₂ as the precursor. The crystal morphology and structure, electronic structure, optical properties and photocatalytic properties were investigated by TEM, XRD, XPS, DRS and photocatalytic experiments. The significant results are listed as follows:（1）N, Co codoped TiO₂/SiO₂/PS composite microspheres were synthesized by chemical adsorption with in-situ hydrolysis method, then burning at 600℃to prepare the hollow composite microspheres catalyst（CNT） after removing the PS. The samples were characterized by TEM, XRD, XPS, and DRS. The results showed that the samples were of anatase TiO₂; N in the TiO₂ lattice mainly existed in the form of Ti-O-N, and Co mainly CoO_x–MO₂（M=Ti, Si）; the surface of CNT became more rough and the size of it was much smaller than the undoped TiO₂/SiO₂; the visible light response range of the catalyst was extended up to 600nm because of N, Co doping; the degradation experimental showed that N and Co had a synergetic effect that enhanced the photocatalytic activity in visible light.（2）B, La co-doped nano-TiO₂/SiO₂ composite photocatalyst（BLT） was synthesized by sol-gel method. The samples were characterized by TEM, XRD, SEM, DRS, SEM,TGA and BET. The results showed that, the samples were of anatase TiO₂ and doping of B and La inhibited the transformation from the anatase to rutile phase; the diameter of BLT was about 60-100nm and the specific surface area of it was twice as that of undoped sample; compared to pure TiO₂ and B or La doped TiO₂/SiO₂, the visible light response performance of BLT was enhanced because of the obvious red shift occurred at the absorption edge; the degradation experimental showed that B and La had a synergetic effect that enhanced the photocatalytic activity in visible light.（3）The photocatalytic activities of BLT were evaluated by decolorization of methyl violet, crystal violet, methyl green and basic red 9, respectively, at the 500W xenon lamp irradiation （UV under 400nm was filtered out） so as to study the effect of catalyst dosage, initial concentration and initial pH value on photocatalytic activities. The results showed that, the initial pH value was 4, the catalyst dosage was 3.0g/L and the initial concentration was 85mg/L, 32mg/L, 60mg/L, 10mg/L, respectively, when the four basic dyes reached the heightest decolorization rate. On optimum conditions, the decolorization rate of Methyl violet was 93.2% and CODcr removal rate was 68%; crystal violet was 85.4% and 71%; methyl green was 84.4% and 76%; basic red 9 was 74.7% and 68%, respectively. In visible light, photocatalytic decolorization rate and degradation of CODcr of the four dyes were in line with pseudo first order reaction kinetics model.更多还原