Date

2018

Author

Odabaşı, Selda

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The effect of cobalt doping on photocatalytic activity of lead titanate was studied by NO oxidation and TPx analyses. PbTiO3, Pb0.875Co0.125TiO3, Pb0.75Co0.25TiO3 and Pb0.5Co0.5TiO3 were synthesized by sol-gel method. Temperature programmed reduction and UV-desorption experiments were used to demonstrate the reducibility of TiO2, which is a commercial photocatalyst, 0.5 wt% Pt/TiO2 and synthesized perovskites under UV irradiation. By comparing the amount of hydrogen used to reduce fresh and UV treated samples, the reducibility of samples by UV treatment was analyzed. It was found that TiO2 was reduced around 125°C and between 200°C and 700°C. Platinum oxide was reduced around 50°C and 130°C by UV irradiation. The amount of hydrogen to reduce UV treated PbTiO3 was more than to reduce fresh PbTiO3. However, UV treated PbTiO3 was reduced at lower temperatures. The amount of hydrogen to reduce UV treated Pb0.875Co0.125TiO3 was less than to reduce fresh Pb0.875Co0.125TiO3 and UV treated Pb0.875Co0.125TiO3 was reduced at lower temperatures. The amount of hydrogen to reduce UV treated Pb0.75Co0.25TiO3 was less than to reduce fresh Pb0.75Co0.25TiO3 and UV treated Pb0.75Co0.25TiO3 was reduced at lower temperatures. The amount of hydrogen to reduce UV treated Pb0.5Co0.5TiO3 was more than to reduce fresh Pb0.5Co0.5TiO3. However, UV treated Pb0.75Co0.25TiO3 was reduced at lower temperatures. Photocatalytic activity of synthesized perovskite samples was analyzed by photocatalytic NO oxidation under UV and visible light irradiation. The amount of hydrogen consumption increased with increasing cobalt amount in perovskites. The effect of flow rate and relative humidity in air were investigated. For all synthesized perovskites, it was observed that increasing flow rate resulted in a decrease in NO conversion. It means that photocatalytic NO oxidation reaction was kinetic controlled. For lead titanate, as relative humidity increases NO conversion increases under UV irradiation. However, for Co-doped perovskites, as relative humidity increases NO conversion decreases under UV irradiation. It is seen that water poisons the surface of Co-doped perovskites. Dark-light cycling NO oxidation experiments were conducted to see the stability of perovskites. Increasing humidity provided better stability for all perovskites.

Subject Keywords

Lead compounds., Photocatalysis., Titanates., Cobalt.

URI

http://etd.lib.metu.edu.tr/upload/12622405/index.pdf
https://hdl.handle.net/11511/27481

Collections

Graduate School of Natural and Applied Sciences, Thesis