Formation of Hydroxyl and Water Layers on MgO Films Studied with Ambient Pressure XPS

Journal Article · Sat Jan 01 04:00:00 EST 2011 · Surface Science

DOI:https://doi.org/10.1016/j.susc.2010.10.004· OSTI ID:1020927

Newberg, J T; Starr, D; Yamamoto, S; Kaya, S; Kendelewicz, T; Mysak, E R; Porsgaard, S; Salmeron, M B; Brown, Jr, G E; Nilsson, A; Bluhm, H

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 (H{sub 2}O) 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 1s (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 top-most 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 1s 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 H{sub 2}O, OH and Ox thickness changes as a function of relative humidity.

• Research Organization: Brookhaven National Laboratory (BNL) Center for Functional Nanomaterials
• Sponsoring Organization: DOE - OFFICE OF SCIENCE
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1020927
• Report Number(s): BNL--94962-2011-JA; KC020401H
• Journal Information: Surface Science, Journal Name: Surface Science Journal Issue: 1-2 Vol. 605; ISSN SUSCAS; ISSN 0039-6028
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ADSORPTION
CATALYSIS
CHEMISTRY
DISSOCIATION
GEOCHEMISTRY
HUMIDITY
HYDROXYLATION
MAGNESIUM OXIDES
OXIDES
REACTION KINETICS
SPECTRA
THICKNESS
WATER
X-RAY PHOTOELECTRON SPECTROSCOPY
functional nanomaterials