【作者】 万磊；

【导师】 龙明策；

【作者基本信息】 上海交通大学 ， 环境工程， 2013， 硕士

【摘要】 半导体光催化技术能够将太阳能转化为化学能，将污染物彻底降解为无污染的H2O、CO₂等无机小分子物质，有望成为解决环境污染和能源问题的有效途径，因而受到了广泛的关注。光催化技术的核心是光催化剂，虽然已有研究表明很多半导体材料本身有一定的光催化活性，然而实现半导体光催化材料的宽谱响应、提高其光催化效率与稳定性是应用于实际污染治理的前提。本文致力于研究可见光响应的高效半导体复合光催化材料，通过改性、复合等手段，制备出有效降解有机污染物的光催化材料，并进行了表征与研究。通过溶胶凝胶相分离方法，在原料中添加表面活性剂P123和氧化石墨烯，制备了一种具有高效光催化活性的结构完整的多孔TiO₂块体。结构表征结果表明，制备的块体呈现大孔和介孔组成的多级孔结构，比表面积可达163m₂/g，主要是由10nm左右的锐钛矿TiO₂纳米晶粒构成。通过光催化降解甲基橙实验评价块体光催化活性。添加0.07wt%的氧化石墨烯所制得的块体在光催化反应前后保持了完整的结构，全谱和可见光下的甲基橙比去除效率与未添加石墨烯的样品相比，分别提高了4.1倍和2.3倍。该方法制备的多孔TiO₂块体在降解水中有机污染物时，可以避免纳米粉体回收和固定化负载，有望直接用于水污染控制之中。采用盐酸水溶液处理BiVO₄的方法，使其可见光催化活性显著增强。BiVO₄粉末浸渍于0.1mol/L的盐酸溶液中反应6小时后，可见光催化降解苯酚的活性比未处理前提高了3.5倍。对盐酸处理后的样品进行表征，研究其晶相组成和表面形貌，采用不同酸和氯化物处理作为对照实验，结果表明由于H⁺和Cl^-的协同作用，使得BiVO₄表面部分溶出并以BiOCl沉积，形成了具有凹陷沟壑表面的BiVO₄颗粒与片状BiOCl的复合异质结构，从而得到了光催化活性增强的催化剂。其中BiOCl含量为2.08%。采用悬浮液光电压法测定BiOCl的平带电位，进行能带分析，并将BiVO₄和BiOCl混合后对混合物进行光催化性能测试，结果表明二者间不存在颗粒间电子转移效应（IPET）。BiVO₄粉末经过盐酸处理后光催化活性的增强主要是由于其表面生成了凹凸不平的沟壑结构，粗糙化的表面结构促进了光生载流子的迁移。这种表面处理的方法为提高半导体材料的光催化活性提供了一条有效的途径。通过将Au/BiVO₄与BiOI以不同比例混合，制备出可见光活性增强的复合催化剂，通过对复合催化剂进行降解苯酚的实验，确定了Au/BiVO₄与BiOI质量比为5:1时，复合体系具有最高的可见光活性。在pH值较低时，复合催化剂的活性受pH值的影响不大，当pH值较高时，其活性随之升高而显著增强。采用降解苯酚的循环实验来评价复合体系的光催化稳定性，结果发现多次循环后，苯酚降解率维持在很高的水平，说明其具有较高的光催化稳定性。对复合体系的机理进行了初步探讨，认为Au/BiVO₄与BiOI复合后高光催化活性的获得很可能是由于复合催化剂形成了Z体系。更多还原

【Abstract】 Photocatalytic technology, which is capable to convert solar energy to chemical energy and to degrade thoroughly pollutants to such inorganic small molecules as H2O and CO2, is a promising avenue to address environmental pollution and energy shortage and, therefore, has drawn much attention. Photocatalyst is the key of the technology and its responsiveness to wide wavelength light, efficiency and persistence determine whether it can be effectively applied in practice although many semiconductor materials have been demonstrated to have photocatalytic activity. This paper is aimed to investigate preparing photo catalysts through modification and recombination which can effectively degrade organic pollutants under visible light irradiation and then to explore their photocatalytic efficiency and discuss the mechanisms.First, a hierarchical porous TiO2monolith (PTM) with well-defined macroporous and homogeneous mesoporous structure is prepared via a sol-gel phase separation method. P123is used as the mesoporous template and graphene oxide has been applied to increase the activity and integrity of the monolithic TiO2. According to SEM and BJH measurements, PTM is mainly composed of10nm anatase crystallines with3.6nm mesopores and2-8um macropores and its specific surface area is up to163m2/g. The PTM with0.07wt%graphene oxide dosage shows a high efficiency for methyl orange (MO) decolorization under both full spectrum and visible light irradiation (λ>400nm) and is4.1times and2.3times more efficient than without grapheme oxide respectively, and it remains intact after the degradation. The prepared porous TiO2monolith can immobilize nanoparticles and avoid separation process, and is promising to be used in water pollution control.Second, BiVO4treated in HC1aqueous solution can achieve enhanced photo catalytic activity. After being treated in0.1mol/L HC1solution for6hours, the photo catalytic activity of BiVO4for phenol degradation under visible light irradiation is3.5times more efficient. Characterizations have been carried out to analyze the crystal component and surface morphology of the treated sample. Compared to the control samples treated in different acids and chlorides, it indicates that, due to the synergistic effect of H+and Cl-ions in the solution, BiVO4partially dissolved and deposited as BiOCl, and finally a composite formed which contains micron-particle BiVO4with pits over the surface and flake BiOCl with its composition of2.08%. The flat band potential of BiOCl was measured by a slurry method. The results of energy band analysis and photo catalytic activity tests of BiVO4and BiOCl mixed particles suggested that there was no interparticle electron transfer effect between them. Therefore, the enhanced photo catalytic performance of the treated BiVO4can be attributed to the uneven surface which can facilitate the separation of photo generated charges. This kind of surface treating method could be effective to develop photo catalysts with enhanced photo catalytic performance.Third, through blending Au/BiVO4and BiOI in different ratios, a complex was obtained with highly improved photo catalytic activity. In tests on the photo catalytic performance of the complex for phenol degradation under visible light irradiation, the complex showed the highest photocatalytic activity when the ratio of Au/BiVO4to BiOI is5:1. Moreover, the photocatalytic activity of the complex is hardly affected by low pH while, with pH increasing, its performance improves drastically. The cycling runs were carried on to evaluate the photocatalytic stability of the complex and the results showed that the degradation rate of phenol maintained a high level, suggesting that the complex has high photocatalytic stability. The last, the complex mechanism was explored and it is argued that the high photocatalytic performance is likely to be attributed to a Z-scheme.更多还原