Date

2019

Author

Kuzyaka, Duygu

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There is an increasing attention on the photocatalysis experimentations providing removal of organic contaminants from water under visible and UV radiation. The role of semiconductor materials as photocatalysts is to degrade highly toxic pollutants. Pore regularity, control of defects, and the presence of stoichiometric amounts of vanadium in the silicate framework allows one to create alternative materials in advanced applications such as photocatalysis. Vanadium, present in specific form within the structure of SiO2 matrix could open up the gateway to investigate and tailor the defects created for specific catalytic applications. For that reason, vanadosilicate AM-6 containing 1-dimensional, semiconducting, and quantum-confined …V-O-V-O-V… chains can be a very interesting material with tailorable defect sites in photocatalysis. Accordingly, vanadosilicate AM-6 thin films with controlled defect sites were produced by tailoring the ratio of V4+/V5+ ratio within the thin film structure. It was shown that the quality of seed crystals (morphology and thickness) affects the quality of thin films grown by secondary growth approach, leading to alterations in the V4+/V5+ ratio. The effect of changing molar composition and vanadium source used for the secondary growth solution was also investigated systematically. Furthermore, it was observed that altering the molar water content of the secondary growth gel also affects the film growth causing differences in the V4+/V5+ ratio. It was found that vanadosilicate AM-6 films with higher amount of V5+ ions arising from seed layer or different synthesis conditions possess better photocatalytic activity under visible light irradiation for the degradation of methylene blue, which can be attributed to the presence of V5+ cation within the framework of AM-6. Photocatalysts production in thin form provides integration of the material to device-oriented applications, hinders the agglomeration originated from the powder form of the photocatalyst and also accelerates the degradation kinetics due to the increase of the contact surface area between the pollutant and the photocatalyst increasing the photocatalytic activity.

Subject Keywords

Photocatalysis., Photocatalysis, Vanadosilicates, AM-6, Thin-Films, Zeo-type Materials

URI

http://etd.lib.metu.edu.tr/upload/12624729/index.pdf
https://hdl.handle.net/11511/45224

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Graduate School of Natural and Applied Sciences, Thesis