Insights into acetone photochemistry on rutile TiO₂(110). 2. new photodesorption channel with CH₃ ejection along the surface normal
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Angle-resolved photon stimulated desorption (PSD) combined with infrared reflection-adsorption spectroscopy and temperature programmed desorption reveal two distinct channels in the photochemistry of acetone on rutile TiO₂(110) surface. During UV irradiation of co-adsorbed oxygen and acetone molecules, methyl radicals (CH₃) are ejected in two different directions: i) normal to the surface and ii) off-normal at ~±66° to the surface normal in the azimuth (i.e. perpendicular to the rows of bridging oxygen and Ti atoms). Both components are relatively narrow and non-cosine, indicating non-thermal evolution of CH₃ radicals. The direction of the “off-normal” PSD component is consistent with orientation of the C–CH₃ bonds in the n²-acetone diolate—a photoactive form of acetone chemisorption on the oxidized TiO₂(110) surface proposed earlier from experimental and theoretical studies. The direction of the “normal” PSD component requires an orientation of a C–CH₃ bond which is not consistent with the n²-acetone diolate structure. The angular distribution of the CH₃ PSD depends on the acetone coverage. The “off-normal” PSD component dominates at lower acetone coverage (< 0.2 ML), but does not increase at higher coverages in accord with the acetone diolate peak intensity in the infrared reflection-absorption spectra. The “normal” PSD component grows with the acetone coverage up to 0.6 ML. The newly discovered “normal” PSD channel is tentatively assigned to a photo-produced n²- acetone enolate as a potential precursor based on the H/D exchange experiments
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1203885
- Report Number(s):
- PNNL-SA-108621; 47565; KC0301020; KC0302010
- Journal Information:
- Journal of Physical Chemistry. C, Vol. 119, Issue 22; ISSN 1932-7447
- Publisher:
- American Chemical Society
- Country of Publication:
- United States
- Language:
- English
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