【作者】 张双；

【导师】 顾修全；

【作者基本信息】 中国矿业大学 ， 材料学， 2016， 硕士

【摘要】 工业化进程的加速使环境污染成为全球性的严重问题。光催化降解污染物是一种有效地解决环境问题的方法。在众多光催化剂中,TiO₂以良好的化学稳定性、低廉的成本等优点受到了研究者的关注;但存在太阳光利用率低和量子效率低等问题,严重限制了其在实际中的应用。Ag₃PO₄是近几年发现的一种新型光催化剂,其在可见光下的产氧量子效率高达90%,但存在回收困难、光腐蚀严重等缺点。目前对于负载型半导体光催化剂的研究备受人们的关注,它能够利用半导体带边上的差异解决上述问题。本论文基于对Ag₃PO₄优异光催化活性及Ag₃PO₄负载TiO₂的探索开展了如下研究:为了揭示Ag₃PO₄优异光催化活性的内在机制,可将其制备成膜层以评价光电化学性能。烧结对制备牢固的膜层至关重要,但烧结有可能破坏Ag₃PO₄的结构,因此本论文研究了烧结对Ag₃PO₄结构及光催化性能的影响。结果表明当烧结温度低于500°C时,Ag₃PO₄微颗粒具有较好的热稳定性;在100和400°C下烧结30 min得到样品的光催化性能相比未烧结样品有了提高。通过旋涂法制得Ag₃PO₄薄膜,并在400°C下烧结30 min得到薄膜光电极,有光电流响应,但不明显。受阴离子PO₄^3-掺杂BiVO₄的启发,本论文还探索了钒酸根离子掺杂Ag₃PO₄对其光催化性能的影响。一步法钒酸根掺杂Ag₃PO₄得到的样品光催化效果均较差。全面研究了两步法得到样品的形貌、结构及光催化性能,发现NH₄VO₃加入60 m L时得到的样品光催化性能最佳。已有文献报道500°C烧结有助于TiO₂纳米棒阵列（NRAs）光电极的性能的提升,但对其机理研究不够深入,本论文采用电化学手段解释其性能提升的真实原因:除烧结可以提高衬底与TiO₂ NRAs之间的粘附力之外,主要归功于耗尽层区域的宽度增宽,从而提高载流子寿命和传输速度。最后,为了将Ag₃PO₄固定在基底上形成膜层以探讨其光电化学性能,同时可以改善TiO₂的太阳光利用率,本论文尝试通过浸泡法在TiO₂ NRAs上负载Ag₃PO₄。但由于负载的Ag₃PO₄将TiO₂ NRAs的顶端及棒与棒之间的间隙堵住了,不利于载流子传输,所以效果不理想。更多还原

【Abstract】 The acceleration of industrialization has made environmental pollution be a serious problem to the whole world. Photocatalysis might be an effective method to solve such a problem due to the rapid, effective degradation of pollution. Among variety of photoctalysts, TiO₂ has attracted a wide attention because of its good chemical stability and low cost. However, the large scale application of TiO₂ hindered by its limited quantum efficiency and utilization of sunlight. Recently, Ag₃PO₄ was discovered as a novel visible-light-driven photocatalyst with a high quantum yield of approximately 90%. However, there are a few shortcomings in this kind of materials, including difficulty in reuse, poor stability and so on. Since the difference between band offset may be used to solve above problems, supported semiconductor has received extensive concern. In this thesis, a series works related to the exploration on excellent PC activity of Ag₃PO₄ and Ag₃PO₄ loaded TiO₂ will be done.The internal mechanism is expected to be revealed by an evaluation of electrochemical properties of Ag₃PO₄ films. Post-sintering process is a critical step to obtain adhesive Ag₃PO₄ layers onto the conductive substrates, but it may destory the structure of Ag₃PO₄. Thus, it is necessary to investigate the effect of sintering process on Ag₃PO₄. By this study, Ag₃PO₄ had a good thermal stability when the annealing temperature is under 500°C. The sample annealed at 100 and 400 °C for 30 min exhibited the significantly higher PC activity than the pristine one. Furthermore, the photoelectrodes made with Ag₃PO₄ were fabricated using a facile spin coating route, and annealed at 400 °C for 30 min. But the photocurrent is not satisfying.In addition, inspired by PO^4- doped BiVO₄, vanadate doped Ag₃PO₄ and the effects on PC activity were explored in this paper. Vanadate doped Ag₃PO₄ in one step showed poor PC activity. The structure, morphology and visible-light PC performance of Ag₃PO₄ samples doped with vanadate in two steps were studied. The best PC performance appeared when the addition of NH₄VO₃ is 60 m L.It has been demonstrated that the photoelectrochemical（PEC） activity of TiO₂ nanorodarrays（NRAs） was enhanced after annealed at 500 °C, but the mechanism was not studied thoroughly. In this paper, photoelectrochemical approaches were used to explain the real reason: aside from the enhanced adhesion of NRAs on the substrates, the sintering process caused the widening of the depletion regions insides single NRs, leading to enhancement of both the lifetime and transport rate of the photo-generated carriers.For fixing Ag₃PO₄ in substrate to discuss its PEC activity, and improving the utilization of sunlight of TiO₂, Ag₃PO₄ loaded TiO₂ NRAs were fabricated by a sequential chemical bath deposotion and explored preliminarily. But the result was unsatisfactory. It was noteworthy that all gaps among the rods was filled with Ag₃PO₄ particles, which was disadvantageous to the separation of charges.更多还原