【作者】 刘海津；

【导师】 刘国光；

【作者基本信息】 河南师范大学 ， 环境科学， 2010， 博士

【摘要】 光催化技术在废水处理、气体净化、杀菌、防污、自洁材料、染料敏化太阳能电池、化妆品、气体传感器等许多领域有着广泛的应用。目前,用于光催化剂的多为N型半导体材料,如TiO2、ZnO、CdS、WO3、SnO2和Fe2O3等,其中TiO2因其活性高、稳定性好、价廉易得、对人体无害等优点而成为最受重视的一种光催化剂。与TiO2纳米颗粒相比,TiO2纳米管具有更大的比表面积、更高的光催化活性和更强的吸附能力,制备和开发TiO2纳米管已成为国内外的一个研究热点。但是,TiO2纳米管作为光催化剂也有自身的缺点。由于TiO2的带隙较宽(锐钛矿3.2 eV),所以只能吸收紫外光。而紫外光只占太阳光能量的4%左右,因此,TiO2对太阳光的利用率很低,如何吸收利用更多的太阳光,提高其在太阳光下的光催化活性,一直是众多科研工作者的研究课题。另外,纳米TiO2回收困难,无形中加大了使用成本,因而限制了它在许多领域中的应用。本研究针对克服TiO2的上述缺点而展开,其目的是制备在紫外和可见光区具有高催化活性的掺杂TiO2纳米管光催化材料,同时将自制的光催化材料用于难降解有机污染物的降解。本研究采用离子交换和电化学掺杂的新方法分别对水热法制备的钛酸纳米管和阳极氧化制备的TiO2纳米管阵列进行金属和非金属掺杂,制备了具有可见光活性的新型光催化剂——钆、氮共掺杂钛酸纳米管和锆、氮共掺杂TiO2纳米管阵列,并利用自制的TiO2纳米管阵列对4, 4’-对二溴联苯进行了光电催化降解的研究工作。主要研究内容包括:(1)用水热法制备钛酸纳米管,然后通过阳离子交换制备了钆掺杂、氮掺杂以及钆、氮共掺杂钛酸纳米管,并以罗丹明B为目标降解物研究了其光催化性能。结果表明,在紫外光照射下,晶型是决定光催化活性的主要因素,600°C煅烧的钆掺杂钛酸纳米管其光催化活性是同样条件下未掺杂纳米管的1.22倍。而在可见光下,晶型、粒径大小、比表面积和纳米管形貌等因素都对光催化活性有一定的作用,400°C煅烧的钆掺杂钛酸纳米管其光催化活性是同样条件下未掺杂纳米管的2.78倍;通过和NH4+的交换制备了氮掺杂钛酸纳米管,在可见区产生了新的吸收带;钆、氮共掺杂钛酸纳米管在紫外区的光催化活性与单独钆掺杂纳米管没有明显的区别,但在可见区,钆、氮共掺杂产生了协同作用。在钆、氮共掺杂钛酸纳米管的作用下,罗丹明B光照2小时的降解率可达78.3%,而在单独掺钆和掺氮的钛酸纳米管作用下,罗丹明B光照2小时的降解率只有61.6%和57.8%,钆、氮共掺杂钛酸纳米管的光催化活性比单独掺钆和单独掺氮的纳米管都有了进一步的提高。(2)用阳极氧化法制备了固定在纯钛片上的TiO2纳米管阵列,通过电化学方法对其进行了锆掺杂和锆、氮共掺杂以提高光催化活性并吸收利用可见光,同样以罗丹明B为目标降解物考察了它们的光催化活性。结果表明,锆掺杂纳米管阵列在紫外区的光催化活性较未掺杂纳米管阵列有了明显的提高,600°C煅烧的纳米管阵列表现出较高的光催化活性。600°C煅烧的锆掺杂纳米管阵列的光催化活性是未掺杂的1.55倍,但其对可见光没有明显的吸收。锆、氮的共掺杂产生了协同效应,不仅提高了紫外区的光催化活性,而且将光响应范围扩展到可见区,其在紫外和可见区的光催化活性分别比未掺杂纳米管阵列提高了42.6%和62.0%。该方法简单、方便、费时少且不需要昂贵的仪器,为中、小实验室进行氮掺杂提供了新的途径,同时为光催化、电极、传感器等新型材料的制备开拓了思路。(3)用自制的纳米管阵列对二溴联苯进行光电催化降解并探讨了其降解机理。结果表明,只有外加电压的条件下,4, 4’-对二溴联苯不会降解;直接光照2小时,4, 4’-对二溴联苯的降解率为42.4%,而在Zr, N/TiO2催化下,其对应的降解率为55.6%,系统再施加1 V的电压时,其降解率为88.7%;光电催化对4, 4’-对二溴联苯的降解效果明显高于单独的光催化和电化学过程。其反应机理是4, 4’-对二溴联苯在光催化剂作用下,首先脱去一个溴生成一溴联苯,然后继续脱溴生成联苯,最后被完全矿化。通过对多溴联苯降解的研究为其它难降解有机污染物的降解提供了新的方法。更多还原

【Abstract】 Photocatalysis has been widely used in wastewater treatment, air cleaning, sterilization, antifouling and self-cleaning materials, dye-sensitized solar cell, cosmetic, air sensor, etc. Most of the photocatalysts are semiconductors, such as TiO2、ZnO、CdS、WO3、SnO2 and Fe2O3. Among them, TiO2 has become the most important one because of its cheap, harmless, good stability and high photocatalytic activity. Comparing with TiO2 nanoparticles, TiO2 nanotubes have higher surface area, higher photocatalytic activity and stronger adsorption ability. Preparing and developing TiO2 nanotubes has become a new focus all over the world. However, TiO2 has some drawbacks. Due to the wide bandgap (3.2 eV for anatase), TiO2 can only absorb UV light. However, the UV light only accounts for 4% of solar energy, thus TiO2 can only utilize a very small part of sunlight. It has been a long-term issue for researchers how to absorb and utilize solar energy more efficiently. Furthermore, it is difficult to recycle nano TiO2, which restricts its application in many fields because of the high cost.This paper is to overcome the drawbacks of TiO2 mentioned above and prepare new efficient photocatalysts of doped TiO2 nanotubes and degrade persistent organic pollutants. New photocatalysts of Gd, N-codoped trititanate nanotubes were prepared by hydrothermal method and ion-exchanging, as well as Zr, N-codoped TiO2 nanotube arrays by two-step electrochemical method. It has mainly the following aspects:(1) Gd-doped, N-doped and Gd, N-codoped trititanate nanotubes were prepared by hydrothermal method and ion-exchanging, and their photocatalytic activities were investigated with Rhodamine B as the model pollutant. The results showed that crystallinity was the key factor for phtotcatalytic activity under UV light irradiation and the efficiency of Gd-doped trititanate nanotubes at 600℃was 1.22 times than that of the non-doped ones prepared under like conditions. However, all the factors such as crystallinity, particle size, surface area and nanotube morphology, etc. played their roles under visible light irradiation. The efficiency of Gd-doped trititanate nanotubes at 400℃was 2.78 times than that of non-doped ones under like conditions; N-doped trititanate nanotubes were prepared by ion-exchanging with NH4+ ion, which evoked a new absorption band in visible light regions; no obvious difference was found between the photocatalytic activities of Gd, N-codoped and Gd-doped nanotubes in UV regions. However, in visible light regions, synergetic action accured between Gd and N codoping, which resulted in a significant enhancement of photocatalytic activity than that with Gd-doping or N-doping nanotubes. In two hours, 78.3% Rhodamine B was degraded with Gd, N-codoped trititanate nanotubes, while 61.6% and 57.8% were degraded with Gd-doped and N-doped nanotubes, respectively.(2) TiO2 nanotube arrays were prepared on pure titanium sheet by anodization and then doped with Zr and N to improve their photocatalytic activities and to absorb solar lights, their photocatalytic activities were investigated with Rhodamine B as model pollutant. The results showed that Zr-doping enhanced the photocatalytic activity of TiO2 nanotube arrays in UV regions. Samples calcined at 600℃exhibited higher photocatalytic activities. The efficiency of Zr-doped TiO2 nanotube arrays at 600℃was 1.55 times than that of non-doped ones. However, Zr-doped TiO2 nanotube arrays couldn’t absorb visible lights. Synergetic reaction occurred between Zr and N codoping, which resulted in an enhancement of photocatalytic activity in UV regions and visible light absorption as well. The codoped nanotube arrays improved the photocatalytic efficiency by 42.6% and 62.0% in UV and visible regions, respectively. This is a simple, convenient, and less time-consuming path for preparing N-doped and N, metal-codoped TiO2 nanotube arrays. Furthermore, it opens a way to preparing new materials for photocatalysis, electrodes and sensors.(3) 4, 4’-dibromobiphenyl was degraded by TiO2、Zr/TiO2 and Zr, N/TiO2 nanotube arrays and its mechanism was investigated. The results showed that 4, 4’-dibromobiphenyl was not degraded in electrochemical process and 42.4% was photodegraded under UV light irradiation in two hours. 55.6% and 88.7% was degraded with Zr, N/TiO2 nanotube arrays in photocatalytic and photoelectrocatalysis process (under bias potential of 1 V), respectively. The degradation mechanism of 4, 4’-dibromobiphenyl was to debrominate step by step and further to mineralize in the end. In conclusion, photoelectrocatalysis process was far more efficient than photocatalysis or electrochemical process alone, which provided a new path for degradation of other persistent organic pollutants.更多还原