| Summary: | 碩士 === 國立中山大學 === 化學系研究所 === 103 === In consideration of recent trend in environmental and economical issues of green-process chemistry, the eco-friendly and recyclable titanium oxide has received much attention with the aim of establishing greener, more sustainable photocatalysts. However, the quality of commercial or bench-made TiO2 is somewhat uncontrollable, and thus frequently affects the reproducibility of TiO2-mediated reactions. In order to understand the reaction mechanisms of TiO2-catalyzed interactions of oxygen, water, and methanol, as well as their cross interactions, a single crystal rutile TiO2(110) was selected in this study in order to exclude the complexity caused by powder samples. Ultrahigh vacuum in combination with temperature programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS), auger electron spectroscopy (AES), LED UV source and density function theory (DFT) calculations were used to study the TiO2 thermal and photo-chemistry.
O2 desorbs molecularly at 270 K and oxygen vacancies (Ov) are responsible for the dissociative adsorption of O2 molecules to form O adatoms (Oa). In the study of water molecules, the multilayer, the second layer and the monolayer molecular desorption peaks were found at 157 K, 180 K and 190 K, respectively. Under 365 nm UV light irradiation, water remained inactive. Methanol was found to turn into formaldehyde which desorbed at 209 K in TPD, once adsorbed on surface and followed by UV irradiation. Coadsorbed O2 and methanol can create methoxy intermediates by OH bond breaking with Oa. Under UV irradiation, formaldehyde and methanol were observed to desorb at 216 K and 260 K. Without UV irradiation, disproportionation of methoxy affords formaldehyde and methanol simultaneously at 500-600 K.
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