【作者】 滕伟；

【导师】 李新勇；

【作者基本信息】 大连理工大学 ， 环境工程， 2013， 博士

【摘要】 二十一世纪全球环境污染和能源危机成为人类必须要面对的两大现实问题。光催化作为一种绿色化学技术,用该方法去除环境中难降解的持久性有机污染物的研究已经成为人们研究的热点。TiO2作为最具代表性,同时也是最具应用前景的典型光催化剂,尤其是具有一维有序结构的TiO2纳米管阵列更由于其具有独特的有序阵列结构、高的比表面积以及更好的电荷传递性能而引起了人们的广泛关注。然而由于其禁带宽度是3.2eV,意味着它只能被波长小于387nm的紫外光激发,对占太阳光谱大部分的可见光利用率较低。此外,TiO2在光照下产生的光生电荷与空穴容易在晶体内部发生复合,导致其量子效率偏低。这两个问题限制了TiO2在实际中的应用。针对以上问题,本文以TiO2纳米管阵列为基础,分别采用导电聚合物PANI、贵金属Ag纳米颗粒、Ag/Ag3PO4纳米颗粒对其进行改性,并对复合材料的形貌、结构以及光电化学特性进行系统的表征和讨论。本论文围绕以上内容,主要研究内容与研究结果体现在以下几个方面：(1)采用阳极氧化法结合电化学循环伏安法制备出负载PANI的TiO2纳米管阵列电极。经过PANI负载的TiO2纳米管阵列电极对光的吸收范围发生了明显的红移。经过PANI的负载,复合电极在可见光照下的光生电子与空穴的分离效率有了明显的提高。该负载PANI的TiO2纳米管电极在可见光下对罗丹明B的光电催化降解效率要比原TiO2纳米管阵列电极提高5倍以上。高效的可见光催化活性主要归因于PANI的可见光敏感性,以及与TiO2的能带相匹配。(2)采用阳极氧化法结合超声辅助的紫外光还原法制备了负载Ag纳米颗粒的TiO2纳米管阵列电极。负载Ag纳米颗粒的TiO2纳米管阵列在可见光下具有明显的光电流响应,且电荷的传递速率比未负载的TiO2纳米管阵列有明显的提高。在模拟太阳光照下,负载Ag纳米颗粒的TiO2纳米管阵列电极对2,4,6-三氯苯酚的光电催化降解效率要比纯的TiO2纳米管阵列电极的降解效率有显著提高。采用化学荧光技术结合电子顺磁共振技术检测光催化反应过程中产生的活性氧物种是·OH。通过检测溶液中Cl-浓度的变化分析2,4,6-三氯苯酚的脱氯情况。同时采用液质联用技术结合DFT理论计算的方法分析2,4,6-三氯苯酚降解过程中生成的中间产物,确定2,4,6-三氯苯酚在负载Ag纳米颗粒的TiO2纳米管阵列电极上的降解路径。(3)采用化学沉淀法结合原位溶剂还原法制备了可见光催化剂Ag/Ag3PO4纳米颗粒。该催化剂在可见光下对染料废水具有较高的降解效率。同时对氯酚类的废水同样具有较强的氧化能力。通过对光催化降解过程中的活性氧物种进行检测,发现Ag/Ag3PO4纳米颗粒在可见光照下降解污染物主要是通过空穴的直接氧化。结合DFT理论计算的方法,确定Ag3PO4催化剂作为一种窄带的间接半导体,其禁带宽度在2.57eV左右。可见光照下,电子从O的2p轨道跃迁到Ag的5s轨道。由于O的2p轨道与P的3s轨道发生了杂化作用,这种杂化作用导致电子更容易从价带跃迁到导带上。(4)采用阳极氧化法结合化学浸渍法制备了负载Ag/Ag3PO4纳米颗粒的TiO2纳米管阵列电极。负载Ag/Ag3PO4纳米颗粒的Ti02纳米管阵列电极仍保留其高度有序的阵列结构,且管口并没有发生堵塞的现象。Ag/Ag3PO4纳米颗粒的负载使TiO2纳米管阵列电极对光的吸收波长向可见光区域移动。可见光照下的光电流响应远远高于未负载的TiO2纳米管阵列电极。可见光照下对2-氯苯酚的降解效率能够达到95%以上,而未经负载的TiO2纳米管阵列电极在相同条件下对2-氯苯酚的降解效率仅能达到20%。采用化学荧光技术结合电子顺磁共振技术检测该催化剂光催化反应过程中产生的活性氧物种是-OH。本研究所制备的负载PANI的TiO2纳米管阵列电极、Ag纳米颗粒修饰的TiO2纳米管阵列电极、负载Ag/Ag3PO4纳米颗粒的TiO2纳米管阵列电极均有效地提高了其对可见光的利用效率。对于光催化技术向实际应用的发展具有重要的意义。更多还原

【Abstract】 Human beings have to face the problems of global environmental pollution and energy crisis in twenty-first century. The photocatalytic method as a green chemistry technology has become a research hotspot on the removal of of persistent organic pollutants in the environment. TiO2as a representative and promising photocatalyst, especially TiO2nanotube arrays with a one-dimensional ordered structure caused widespread concern because of its unique and orderly array structure, high specific surface area and better charge transfer performance. However, the bandgap of TiO2is3.2eV, which means it can only be excited by UV light of wavelengths less than387nm. The utilization of visible light accounting for most of the solar spectrum is low. Furthermore, the photo-generated charge and holes of TiO2easily recombine within the crystal composite, leading to the low quantum efficiency. These two problems limit the application of TiO2in practice. In this dissertation, the TiO2nanotube arrays was modified by using a conductive polymer PANI, precious metals Ag nanoparticles and Ag/Ag3PO4nanoparticles, respectively. And the morphology, structure, and photoelectrochemical properties of the composite material were characterized and discussed in detail. The main contents and results are as follows:(1) The PANI-loaded TiO2nanotube arrays were prepared by anodic oxidation method combined with cyclic voltammetry. The obvious red shift absorption was observed after the modification of PANI. Meanwhile, the separation efficiency of photo-generated electrons and holes has been significantly improved after the PANI was loaded. The efficiency of photocatalytic degradation of Rhodamine B (RhB) of the PANI-loaded TiO2nanotubes electrode was more than5times when compared with pure TiO2nanotube array electrode under visible light irradiation. The efficient photocatalytic activity was mainly due to the visible light sensitivity of PANI, and the energy band matched well with TiO2.(2) The Ag-loaded TiO2nanotube arrays were prepared by anodic oxidation method combined with ultrasonic-assisted UV phococatalytic reduction technique. The Ag-loaded TiO2nanotube array has obvious photocurrent response under visible light irradiation. And the charge transfer rate was improved significantly. Compare with pure TiO2nanotube arrays, the2,4,6-trichlorophenol degradation efficiency of Ag-loaded TiO2nanotube array electrode was improved significantly under simulated sunlight irradiation. The reactive oxygen species were·OH during the photocatalytic reaction, which were detected by chemical fluorescence and electron paramagnetic resonance technology. The dechlorination of2,4,6-trichlorophenol was anlysed by the detection of C1-concentration in the solution. The intermediate products of2,4,6-trichlorophenol degradation were identified by DFT calculations and LC-MS technique. And the degradation pathways of2,4,6-trichlorophenol on the surface of Ag-loaded TiO2nanotube arrays electrode were confirmed.(3) A new visible light photocatalyst of Ag/Ag3PO4nanoparticles was fabricated by chemical precipitation combined with in situ solvent reduction method. The photocatalysts showed strong photocatalytic activity for decomposition of dyes under visible light irradiation. And they also had strong oxidation of chlorophenol wastewater. The generation of active species in the photocatalytic system was detected, and the results indicated that the degradation process of the pollutants was mainly due to the direct oxidation by the holes. Combined with DFT theoretical calculation method, Ag3PO4catalyst is a narrowband and indirect semiconductor. And the bandgap is about2.57eV. The electron can be excited from the O2p orbitals to the5s orbital of Ag under visible light. Because of the hybridization of O2p orbital and P3s orbital, the electron can be excited from the valence band to the conduction band more easily.(4) The Ag/Ag3PO4-loaded TiO2nanotube arrays were prepared by anodic oxidation combined with chemical impregnation method. The clusters of Ag/Ag3PO4nanoparticles formed on the surface of the TiO2nanotubes and caused no damage to their ordered structure, and the phenomenon of blocking did not happen. The UV-Vis absorption of Ag/Ag3PCO4-loaded light TiO2nanotube arrays electrode expanded to the visible light region. Photocurrent response of Ag/Ag3PO4-loaded TiO2nanotube arrays in the visible light was much higher than the pure TiO2. The degradation efficiency of2-chlorophenol (CP) can reach more than95%under visible light irradiation with the Ag/Ag3PO4-loaded TiO2nanotube arrays. However, the degradation efficiency of2-CP only reached20%with the pure TiO2nanotube arrays electrode under the same conditions. The reactive oxygen species were OH during the photocatalytic reaction, which were detected by chemical fluorescence and electron paramagnetic resonance technology.The TiO2nanotube arrays electrode loaded with PANI, Ag nanoparticles and Ag/Ag3PO4nanoparticles effectively improve the utilization of visible light. They have great significance for the development of the practical application of photocatalytic technology.更多还原