Correlation between Dye Photodegradation and Carrier Dynamics on TiO2 Powders
| Autor: | Pei-Hsuan Hung, 洪培瑄 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 Behavior of photogenerated charge carriers in anatase and rutile TiO2 powders was investigated under continuous light irradiations by time-resolved infrared (IR) absorption spectroscopy. The accumulation process of carriers revealed that most of the carriers survived as free electrons for the anatase TiO2; on the contrary, electrons were soon trapped to the midgap and then slowly being excited to the conduction band for the excited rutile TiO2. This finding strongly suggests a phase-dependent behavior of electrons for the TiO2. In addition, the number of accumulated electrons is dependent on particle size of the TiO2. For anatase TiO2 powders, the amount of both free and trapped electrons raises 10 to 20 times as the particle sizes increases from 9 nm to 400 nm. In the case of rutile, after the excitation, the number of trapped electrons rapidly increases within 20 s and decreases afterwards. Under the UV light irradiations, degradation of methylene blue and methyl orange dyes for anatase TiO2 powders raises 10 times as the particle sizes increases from 9 nm to 400 nm. In addition, the degradation of methylene blue and methyl orange dyes for rutile TiO2 powders raises 2 times as the particle sizes increases from 20 nm to 250 nm. The results are in a good agreement with the number of free electrons being examined by the IR absorption spectroscopy. The number of reactive sites on the particle surface is also a factor to the dye degradation. In other words, specific surface area is not always the main factor to the photodegradation. The number of active electrons is equally important to photocatalysis reactions. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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