【作者】 路莹；

【导师】 全燮；

【作者基本信息】 大连理工大学 ， 环境工程， 2012， 博士

【摘要】 光催化是一种有效的污染控制技术,具有环境友好,污染物降解彻底等优点,近年来广受关注。光催化技术的核心是催化剂,但常用的TiO2催化剂存在着光响应范围窄、量子效率低的缺点,限制了光催化技术的进一步发展。大孔／介孔、光子晶体等结构因为具有特异的物化性质,如大比表面积、高孔容、禁带散射效应和慢光效应等,可促进催化过程中的非均相传质和实现对光的富集；贵金属纳米粒子如Au、Ag等因为具有表面等离子共振效应而在可见光范围内表现出光吸收。将贵金属纳米粒子与宽带隙半导体复合,可有效地扩展TiO2的光响应范围,同时,二者之间的异质结还可以起到促进光生电荷分离的作用。本论文围绕以上内容,主要开展了以下几个方面的工作：(1)采用水热与二次煅烧相结合的联合热处理法制备了具有较高热稳定性及大比表面积的分级肺状大孔/介孔TiO2催化剂。该催化剂具有规则的孔道结构,大孔的孔径范围为2-3μm,壁厚为2-3μm,孔壁上紧密团聚着直径为100-300nm的微球。水热处理方法的引入,使催化剂大孔/介孔结构的稳定性提高,同时,结晶度和比表面积也都大大增加。紫外光下对罗丹明B(RhB)的催化降解实验中,经过联合热处理的分级肺状大孔／介孔TiO2的动力学常数是直接煅烧样品的1.9倍。(2)以联合热处理法制得的大孔/介孔TiO2为载体,在其上沉积Au纳米粒子,制备了具有可见光响应的催化剂HT-400/Au。载体TiO2的分级多孔结构得到了充分地利用,大孔内部、孔壁、甚至微球上都有粒径为30-40nm的Au纳米粒子分布。且通过改变Au前躯体的带电状态,可实现对Au纳米粒子负载量的控制。Au纳米粒子表面等离子共振效应的引入,使催化剂在可见光范围内出现明显的光吸收。可见光(λ＞420nm)下对2,4-二氯苯酚(2,4-DCP)的催化降解试验中,HT-400/Au表现出高的光催化活性,其动力学常数是未负载Au纳米粒子样品的2.2倍,是传统TiO2/Au样品的1.5倍。(3)采用液相沉积和原位水热还原相结合的方法制备了Au纳米粒子与TiO2光子晶体复合的可见光催化剂TiO2PC/Au NPs。TiO2光子晶体具有规则的面心立方体结构,孔径在228nm左右,厚度为2.5-3μm。粒径为15-20nm的Au纳米粒子均匀地分散在三维光子晶体的大孔表面。光子晶体的禁带散射效应和慢光效应强化了Au纳米粒子的表面等离子共振吸收,与传统的TiO2NC/Au NPs相比,TiO2PC/Au NPs表现出更强的光吸收。可见光(λ＞420nm)下对RhB和2,4-DCP的催化降解实验中,TiO2PC/Au NPs的动力学常数分别是TiO2NC/Au NPs的3.5和2.3倍。对这种三维表面等离子催化剂催化机理的分析表明,这是一个羟基自由基主导的降解反应,而羟基自由基主要来源于电子与氧的二次反应。以上结果表明,对半导体催化剂的形貌进行合理的设计,如大孔/介孔、光子晶体等结构的引入,可有效地提高催化过程中的非均相传质和实现对光的富集；对宽带半导体进行适当的修饰,如具有表面等离子共振效应的Au纳米粒子的引入,在拓宽其光学响应范围的同时,还可以利用二者之间的异质结促进光生载流子的分离。本文为高效光催化剂的制备提供了可行的思路与手段,有利于推动光催化技术在污染控制领域的应用。更多还原

【Abstract】 As an efficient pollution control technology, photocatalysis has attracted widespread attention because of its environmental friendly property, excellent photocatalytic activity. The catalyst serves as the core of photocatalytic reaction. However, the common photocatalyst TiO2is troubled by the shortcomings of narrow optical response and low quantum efficiency, limiting the further development of photocatalytic technology. The macro/mesoporous structure and photonic crystal (PC) could enhance the mass transfer and light absorption due to their excellent physicochemical properties, such as large surface area, high pore volume, band gap scattering effect and slow photon effect. Noble-metal nanoparticles like Au, Ag show efficient visible light absorption because of the Localized Surface Plasmon Resonance (LSPR). The incorporation of noble-metal nanoparticles with wide band gap semiconductor can efficiently enlarge the visible light response range, meanwhile, the heterojunction between this two could enhance the separation of photogenerated charge carriers. In this dissertation, several works have been done as follows:(1) Hierarchically lung-like macro/mesoporous TiO2with high thermal stability and specific surface area was successfully fabricated through a facile combination of hydrothermal treatment and calcination process. The catalyst exhibited relatively homogeneous and long-range periodical channels, which were arranged parallel to each other and orthogonal to one side of the monolithic particles, with pore diameter of2-3μm and pore wall thickness of2-3μm. Further observation revealed that the wall of the macroporous structure was composed of many small interconnected TiO2spheres with size of100-300nm. The introduction of hydrothermal treatment enhanced the stability of the macro/mesoporous structure, at the same time, the crystallinity and surface area was also improved. During the photocatalytic degradation of RhB under UV light irradiation, the kinetic constant of porous TiO2experienced the combined thermal treatment was1.9fold higher than that of the one calcined only.(2) The visible-light-responded photocatalyst HT-400/Au was fabricated by depositing Au nanoparticles on macro/mesoporous TiO2prepared from the above combined thermal treatment. The porous structure of TiO2has been fully utilized, both inside and outside of the macropores, even the microspheres were decorated by the Au nanoparticles with the diameter around30-40nm. Additionally, the loading amount of Au nanoparticles could be controlled by changing the charged state of gold precursor. The HT-400/Au exhibited visible light absorption due to the LSPR of Au nanoparticles. During the2,4-DCP degradation under visible light (λ>420nm) irradiation, the HT-400presented high photocatalytic activity, whose kinetic constant was2.2fold larger than that of the sample HT-400without the decoration of Au nanoparticles;1.5fold greater than that of the sample Crushed HT-400without this macro/mesoporous structure.(3) The3D plasmonic photocatalyst TiO2PC/Au NPs was prepared via the liquid-phase deposition and in situ hydrothermal reduction method. The thickness of the TiO2PC structure was about2.5-3μm, and the average diameter of the hollow spheres was around223nm. The Au NPs with the size around15-20nm were uniformly distributed and anchored along the heterogeneous macroporous surface of the3D PC structure. The band gap scattering effect and slow photon effect efficiently intensified the plasmonic absorption of Au nanoparticles. Compared with TiO2NC/Au NPs, the TIO2PC/Au NPs exhibited stronger optical absorption. During the photocatalytic degradation of RhB and2,4-DCP under visible light (λ>420nm) irradiation, the kinetic constant of TiO2PC/Au NPs was3.5and2.3fold higher than that of TiO2NC/Au NPs, respectively. The hydroxyl radicals derived from the electroreduction of dissolved oxygen with electrons via chain reactions was the main reactive oxygen species and finally resulted in the efficient pollutant degradation.The above results illuminated that the well-designed nanostructure like macro/mesoporous, photonic crystal could enhance the mass transfer and light utilization. The proper decoration of wide band gap semiconductor such as the plasmonic Au nanoparticles could expand the light response range, and the separation of photoinduced charge carriers could also be intensified by forming the heterojunction. These studies provide a feasible approach to design photocatalyst with high activity, which would promote the application of photocatalytic technology in the environmental pollution control.更多还原