期刊
SURFACE SCIENCE
卷 605, 期 1-2, 页码 89-94出版社
ELSEVIER
DOI: 10.1016/j.susc.2010.10.004
关键词
Magnesium oxide; Surface chemistry; Geochemistry; Catalysis
资金
- Office of Science, Biological and Environmental Research, Environmental Remediation Sciences Division (ERSD), U.S. Department of Energy [DE-AC02-05CH11231]
- National Science Foundation under (Stanford Environmental Molecular Science Institute) [CHE-0431425]
- Director, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences of the U.S. Department of Energy [DE-AC02-05CH11231]
To understand the interaction of water with MgO(100), a detailed quantitative assessment of the interfacial chemistry is necessary. We have used ambient pressure X-ray photoelectron spectroscopy (XPS) to measure molecular (H2O) and dissociative (OH) water adsorption on a 4 monolayer (ML) thick MgO(100)/Ag(100) film under ambient conditions. Since the entire 4 ML metal oxide (Ox) film is probed by XPS, the reaction of the MgO film with water can be quantitatively studied. Using a multilayer model (Model 1) that measures changes in Ox thickness from O is (film) and Ag 3d (substrate) spectra, it is shown that the oxide portion of the MgO film becomes thinner upon hydroxylation. A reaction mechanism is postulated in which the topmost layer of MgO converts to Mg(OH)(2) upon dissociation of water. Based on this mechanism a second model (Model 2) is developed to calculate Ox and OH thickness changes based on OH/Ox intensity ratios from O is spectra measured in situ, with the known initial Ox thickness prior to hydroxylation. Models 1 and 2 are applied to a 0.15 Torr isobar experiment, yielding similar results for H2O. OH and Ox thickness changes as a function of relative humidity. Published by Elsevier B.V.
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