摘要
近年，随着水环境中的有机物污染日益加剧，半导体光催化技术作为最有前景的方法之一，受到越来越多的科研工作者的青睐。目前，TiO2是最为常见的半导体光催化剂，但其相对较大的禁带宽度（3.2eV），使得它不能利用太阳光中占很大比例的可见光。因此，开发新型的可见光型催化剂就成为当今光催化领域的热点。
本文采用水热法制备钒酸银（Ag_3VO_4）颗粒，在此基础上，采用浸渍法合成了负载稀土金属（Nd，Ce）的Ag_3VO_4光催化粉体材料。利用手术刀刮涂法在FTO基底上得到Ag_3VO_4负载稀土金属（Nd，Ce）薄膜，以解决Ag_3VO_4粉体在水体系中难分离、回收的问题。同时，为了增加薄膜的粘附性，本文研究了PEG的添加问题。通过SEM，EDS，XRD，XPS及UV-vis吸收光谱等分析方法对Ag_3VO_4薄膜负载Nd、Ce前后进行表征。光催化降解实验以罗丹明B（RhB）作降解底物，并在可见光照射下，分别研究了Nd和Ce负载质量比对光催化降解活性的影响，而且研究了煅烧温度对Ag_3VO_4负载Ce薄膜的影响。结果表明：
水热制备Ag_3VO_4的过程中，水热时间的增加有利于单一的单斜晶Ag_3VO_4相的生成，且水热时间为6h，出现单一的单斜晶Ag_3VO_4相。通过实验证实了PEG虽然增加薄膜的粘性，但会影响Ag_3VO_4薄膜光催化性能，制膜过程不适合添加PEG。Nd的负载量对Ag_3VO_4负载Nd薄膜的光催化性能影响很大，其最佳负载量为2wt%。
Ag_3VO_4负载Ce薄膜中Ce以Ce~(3+)和Ce~(4+)两种氧化物形式存在。Ag_3VO_4负载Ce薄膜对可见光吸收增强, Ce负载量为4wt％的Ag_3VO_4薄膜禁带宽度为2.15eV。Ag_3VO_4负载Ce薄膜的光催化性能都优于纯Ag_3VO_4和P25薄膜，当Ce掺杂量为4wt%时，Ag_3VO_4负载Ce薄膜活性最好。可见光照5h，被降解的RhB达到95%。薄膜最佳煅烧温度为300℃。
In recent years, with the increasing organic pollution of thewater-environment, semiconductor photocatalytic technology as one ofthe most promising methods gets more and more favour of scientificresearchers. Among the various semiconductors, titanium dioxide (TiO2)is most widely used in the research and application for its numerousadvantages. Thanks to the large bandgap (3.2eV) of TiO2, however, thevisible region of the sunlight cannot be completely utilized. Therefore,new type of photocatalysts active under visible light remains hotspot inthe field of photocatalysis.
In this study, Ag_3VO_4was synthesized via a hydrothermal route. Andrare earth (Nd, Ce) loaded Ag_3VO_4was prepared by impregnation method.Considering of the difficulty in separating and recycling Ag_3VO_4powderfrom the water suspension, rare earth (Nd, Ce) loaded Ag_3VO_4thin filmswere fabricated by doctor-blading. The impact of PEG on the quality ofthe thin films was also discussed. The Ag_3VO_4thin films with andwithout rare earth-loaded were characterized by SEM, EDS, XPS andUV-vis absorption spectra. By using rhodanmine B (RhB) as a model pollutant, the photocatalytic activity of Ag_3VO_4thin films with differentloading ratios of Nd and Ce was studied under visible light irradiation. Inaddition, the annealing temperature was optimized for Ce-loaded Ag_3VO_4thin film. The results indicated that long hydrothermal time facilitated theformation of the monoclinic crystal of the Ag_3VO_4, and the single crystalform of monoclinic Ag_3VO_4was obtained with6h for the preparationprocess. Besides, the addition of PEG could reinforce the film, however,with the cost of the photocatalytic ability. The loading amount of Ndgreatly influenced the photocatalytic performance of the Nd-loadedAg_3VO_4film, and the best loading ratio was determined to be2wt%.
Ce was existed in the Ce-loaded Ag_3VO_4with the formats of Ce~(3+)andCe~(4+), leading to better absorption of the visible light. With a bandgap of2.15eV, the4wt%Ce-loaded Ag_3VO_4thin film exhibited the highestefficiency, giving a degradation extent of95%under visible lightirradiation for5hours, which was notably superior to pure Ag_3VO_4andP25. The best calcined temperature was300℃.
引文
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