新型二氧化钛光催化材料的合成及其光催化性能研究

【作者】 曹锋雷；

【导师】 李和兴； 朱建；

【作者基本信息】 上海师范大学 ， 物理化学， 2013， 硕士

【摘要】 纳米TiO₂半导体材料由于其光催化性能高、化学性能稳定、无毒、价格低廉等优点，在光催化处理有机污染物方面被广泛研究。目前以TiO₂光催化材料为基础的光催化技术与传统污染处理技术相比具有诸多优点，例如：利用太阳能、降解有机物无选择性、工艺设备简单易控制、无二次污染等。但还存在诸多技术难题，例如：量子效率不高、可见光利用率低等。如何解决这些不足是当前光催化领域的主要研究方向。改变TiO₂的形貌和结构，从分子、纳米及微米多尺度、多层次的设计新型功能化的光催化剂是改善光催化剂性能和研究构效关系的有效途径之一。近年来以多孔单晶为热点的半导体材料尤其是TiO₂材料获得国内外专家的广泛认同和关注。本论文以TiO₂催化材料为研究对象，从合成方法入手，研究可控合成多孔单晶TiO₂材料以及开发高效氮掺杂TiO₂材料。论文的具体内容主要分为以下三个方面：一、醇热法合成球形多孔单晶TiO₂材料及其光催化性能研究以TiOSO₄为钛源，乙醇和苯甲醇为混合溶剂，在低温条件下，醇热法合成球形多孔单晶TiO₂材料。该材料表面疏松多孔，具有较大的比表面积（SBET=188m2?g-1）。研究结果显示，样品的多孔结构主要与TiO₂纳米晶粒之间的相互堆积有关，同时这些TiO₂纳米晶粒又以相同的晶格取向生长来保持整个样品的单晶特性，其驱动力来源于前驱液中含有的大量SO42-。利用FESEM、TEM和XRD等表征手段，对样品的形貌和结构进行了详细的分析和表征，同时提出形成机理。将球形多孔单晶TiO₂材料应用于苯酚降解实验中，结果显示该材料具有较高的光催化活性。将其应用于光催化降解有机污染物甲基橙，结果显示样品在紫外光照射的情况下，甲基橙的降解活性普遍比商业P-25高35％。二、醇热法合成尺寸可控的球形多孔单晶TiO₂光催化剂及其光催化性能研究以TiOSO₄为钛源，采用双醇混合溶剂，通过调节不同醇溶剂比例，在低温条件下，醇热法合成尺寸可控的球形多孔单晶TiO₂材料。研究结果表明调节苯甲醇和乙醇的比例，可以控制球形多孔单晶TiO₂的粒径从80到2000纳米左右。进一步用异丙醇或正丁醇取代苯甲醇也可以得到类似的结果，证明了该方法的普适性和可控性。三、双氮源制备高活性N-TiO₂可见光催化剂利用氨水和草酸铵为双氮源，用原位沉淀技术制备了高活性N修饰TiO₂可见光催化剂。通过N2吸脱附等温线、XRD、UV-Vis、XPS和IR波谱等技术对催化剂结构和光谱性质进行了系统表征。同时以可见光降解亚甲基蓝水溶液为模型反应，对催化剂的活性进行了评价。结果表明：氨水和草酸铵的协同作用有利于N进入TiO₂晶格，其活性高于单氮源及后修饰的N-TiO₂催化剂。更多还原

【Abstract】 TiO₂semiconductor has been proven to be the most suitable for photocatalytictreatment of organic pollutants in widespread environmental applications amongvarious photocatalysts, owing to its high photocatalytic performance, chemicalstability, non-toxic, and low price. TiO₂-based heterogeneous photocatalysis hasmany advantages compared with the traditional pollution treatment technology, suchas: the use of solar energy, degradation of organic matter without selective, simpleand easy to operation, and no secondary pollution. However, there are still a lot ofproblems in TiO₂-based photocatalysis such as low quantum efficiency and littleutilization of solar energy and so on. As a result, it is the main direction of scientificdevelopment to photocatalysis that how to solve these problems and make thephotocatalytic technique be widely used in practice.The synthesis of new TiO₂materials is an effective way to improve theperformance of the TiO₂photocatalyst, and the synthesis of Mesocrystal TiO₂material and non-metallic ion modified TiO₂photocatalytic materials is the hot spotin such field. Our research work focuses on TiO₂photocatalysts and begins from thesynthesis method. We will study the controlled synthesis of mesocrystal TiO₂material and develop efficient nitrogen-doped TiO₂material.The detailed works are as follows:1. Solvothermal alcoholysis synthesis of spherical mesocrystal TiO₂and itsphotocatalytic propertiesThe mesocrystal TiO₂is synthesized by solvothermal alcoholysis with TiOSO₄inethanol and benzyl alcohol as a mixed solvent under low temperature. The sphericalmesocrystal TiO₂has the porous structure and high surface are （SBET=188m2?g-1）.The results show that the porous structure is formed by the accumulation of TiO₂nanocrystals, while these TiO₂nanocrystals orientation to maintain the same latticeand the SO42-adsorbed on the high energy surface of TiO₂can stabilize the （001）facets by lowering the surface energy, leading to the oriented crystal growth. Thedetailed morphologies and structures of mesocrystal TiO₂are analyzed and characterized using FESEM, TEM and XRD characterizations and the formationmechanism is proposed. Spherical mesocrystal TiO₂is applied to phenol degradationexperiments which show the higher photocatalytic activity and applied to thephotocatalytic degradation of methyl orange which showed the35%higher thancommercial TiO₂（P-25）.2. Solvothermal alcoholysis synthesis of size controlled spherical mesocrystalTiO₂and its photocatalytic propertiesSize controlled spherical mesocrystal TiO₂is synthesized by solvothermalalcoholysis with TiOSO₄in ethanol and benzyl alcohol as a mixed solvent under lowtemperature by adjusting the volume ratio of alcohols. The results showed that thesize of spherical mesocrystal TiO₂is controlled from80to about2000nm. Usingdifferent alcohol solvents, such as isopropanol or n-butanol substituted benzylalcohol can also be obtained similar results.3. Preparation and photocatalytol activity N-doped TiO₂visible lightphotocatalyst from two N-sourcesA highly active N-doped TiO₂visible light photocatalyst was prepared by animproved precipitation method. Ammonium oxalate and ammonium hydroxide wereused as the nitrogen resources and worked as in-situ release and pre-addition of theN elements to modified TiO₂, respectively. The prepared photocatalysts werecharacterized by the BET, XRD, UV-Vis, XPS and IR spectrum. The model reaction ofdegradation methylene blue was used to test the photocatalytic activity ofphotocatalyst under visible light. The results showed that the TiO₂photocatalystmodified by the two N sources displayed higher photocatalytic activity than thesingle N source or post-modifying TiO₂photocatalysts, due to that the two N sourceswere beneficial to make N atoms into the TiO₂lattice.更多还原