Research On Preparation And Photocatalytic Activity Of Silver Vanadates Loaded With Rare-Earth Elements

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, Ag₃VO₄was synthesized via a hydrothermal route. Andrare earth (Nd, Ce) loaded Ag₃VO₄was prepared by impregnation method.Considering of the difficulty in separating and recycling Ag₃VO₄powderfrom the water suspension, rare earth (Nd, Ce) loaded Ag₃VO₄thin filmswere fabricated by doctor-blading. The impact of PEG on the quality ofthe thin films was also discussed. The Ag₃VO₄thin 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 Ag₃VO₄thin films with differentloading ratios of Nd and Ce was studied under visible light irradiation. Inaddition, the annealing temperature was optimized for Ce-loaded Ag₃VO₄thin film. The results indicated that long hydrothermal time facilitated theformation of the monoclinic crystal of the Ag₃VO₄, and the single crystalform of monoclinic Ag₃VO₄was 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-loadedAg₃VO₄film, and the best loading ratio was determined to be2wt%.Ce was existed in the Ce-loaded Ag₃VO₄with the formats of Ce³⁺andCe⁴⁺, leading to better absorption of the visible light. With a bandgap of2.15eV, the4wt%Ce-loaded Ag₃VO₄thin film exhibited the highestefficiency, giving a degradation extent of95%under visible lightirradiation for5hours, which was notably superior to pure Ag₃VO₄andP25. The best calcined temperature was300℃.