高活性氧化物可见光催化剂的设计合成及其机制研究

【作者】 谢明政；

【导师】 井立强；

【作者基本信息】 黑龙江大学 ， 物理化学， 2011， 硕士

【摘要】 光催化技术是近年来兴起的一种新型环境治理技术,得到人们的广泛关注。发展高效的可见光催化剂是实现该技术实用化的关键。针对非金属离子掺杂TiO₂制备工艺条件复杂和普适性差以及BiVO₄粒径尺寸大、活性差的问题,本论文分别开展了发展非金属离子掺杂TiO₂和小粒子BiVO₄光催化剂新方法的研究。在结合水解法和溶剂热法优点的基础上,通过发展相分离的水解‐溶剂热法,可控合成氮、硫、硅等非金属离子掺杂的TiO₂,重点研究合成过程中各合成条件对样品可见光催化活性的影响。研究结果表明:与传统的溶胶‐水热法相比,本方法合成的TiO₂样品表现出了高的光催化活性,这主要是由于其具备了高的晶化度和好的分散性。通过在水相中引入氨水等物质,可控的实现了对TiO₂的氮等非金属离子的掺杂,显著拓宽了样品的光响应范围,样品表现出了高的可见光催化活性,明显要高于高温氮化法制得的样品。此外,通过在有机相中引入正硅酸乙酯也简单的实现了紫外光活性超过P25的高热稳定性硅掺杂TiO₂的合成。针对BiVO₄在生成过程中晶核生长速度快、粒子易生长过大的问题,通过发展EDTA调制的水热法方法可控合成了纳米BiVO₄,重点研究了反应温度等因素对样品粒径尺寸的影响。研究结果表明,降低反应温度、缩短反应时间和增大EDTA的用量,有利于获得小尺寸的BiVO₄,可以得到粒径尺寸为20nm的BiVO₄粒子。基于红外分析的结果,反应过程中EDTA与Bi³⁺反应形成稳定的螯合物,降低了Bi³⁺的浓度,从而抑制了BiVO₄粒子的生长。所获得小粒子BiVO₄表现出了高的可见光催化活性,这主要与其具有小的粒径尺寸和大的比表面积有关。更多还原

【Abstract】 Photocatalytic technology which is developed in recent years is a new environmental control technology, and has caught people’s attention widely. Preparing the visible-light photocatalyst is the key for making this technology practical. To the problems of complicated technology and poor wide suitability in preparing nonmetal doped TiO₂ and large particle size and poor photocatalytic activity of BiVO₄ samples prepared by normal methods, we carried out the study of developing new methods to prepare non-metal doped TiO₂ and nano-sized BiVO₄ photocatalysts.O_n the basis of combining the advantages of hydrolysis process and solvothermal process, we developed the phase-separated hydrolysis-solvothermal process, and through it we prepared the TiO₂ which doped with N, S, Si et al controllable, the effects of reaction temperature et al on the photocatalytic activity of samples were mainly investigated. The results show that, comparing to the TiO₂ prepared by hydrolysis-hydrothermal process, the TiO₂ we prepared has better UV-photocataltic activity due to the higher crystalline degree and dispersibility. By introducing the ammonia et al into the water phase, we obtain the N et al non-metal doped TiO₂ simply. The non-metal doping enhances the visible light absorption of TiO₂ effectively, and the sample exhibits a good Vis-photocatalytic activity, it is worth noting to that the N-doped TiO₂ exhibits better photocatalysis activity than the sample prepared by high-temperature nitriding. In addition, the Si-doped TiO₂ with high thermal stability and photocatalytic activity which is better than the photocatalytic activity of P25 also can be obtained by introducing the C8H20O₄Si into the organic phase.To the problems the BiVO₄ particle is easy to grow too large in synthesis process, we developed a new method to prepare nano-sized BiVO₄ by introducing EDTA. And the effects of reaction temperature et al on the particle size of samples were mainly investigated. The results show that reducing the reaction temperature and time and increasing the addition of EDTA are benign to the controlling the particle size of BiVO₄, the BiVO₄ samples with an average particle size of 20 nm can be obtained. Based on the IR spectra, it is confirmed that the introduction of EDTA can be coordinate with Bi³⁺ to form a stable compound, consequently keeping a low-content free Bi³⁺ in the reaction system and then inhibiting the growth of BiVO₄ crystallites during the hydrothermal processes. The nano-sized BiVO₄ particles show a high Vis-photocatalytic activity, that is mainly due to its small particle size and large surface area.更多还原