Water adsorption, desorption, and clustering on FeO(111)
John L Daschbach1, Z Dohnalek, Shu-Rong Liu
1Environmental Molecular Sciences Laboratory, Fundamental Science Division, Pacific Northwest National Laboratory, PO Box 999, Mail Stop K8-88, Richland, Washington 99352, USA.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Water adsorption on iron oxide (FeO(111)) films was studied. Ordered water layers form above 120 K, while lower temperatures lead to disordered water, impacting surface diffusion and clustering.
Area of Science:
- Surface Science
- Materials Science
- Physical Chemistry
Background:
- Understanding water-surface interactions is crucial for catalysis and environmental science.
- Epitaxial growth of iron oxide (FeO(111)) films on platinum (Pt(111)) provides a well-defined model system.
- Molecular adsorption and ordering of water influence surface properties and reactivity.
Purpose of the Study:
- To investigate the adsorption behavior of water on FeO(111) surfaces.
- To determine the influence of temperature on water ordering and clustering.
- To elucidate the role of surface diffusion in water overlayer formation.
Main Methods:
- Temperature Programmed Desorption (TPD) for analyzing desorption kinetics and clustering.
- Infrared Reflection Absorption Spectroscopy (IRAS) for characterizing molecular adsorption and hydrogen bonding.
- Epitaxial growth of 2 ML FeO(111) films on a Pt(111) substrate.
Main Results:
- Water adsorbs molecularly on FeO(111) with significant hydrogen bonding.
- Ordered 2D water islands form when deposited above 120 K, while lower temperatures result in disordered layers with voids.
- Surface diffusion rates differ on bare FeO(111) and water-covered surfaces, influencing overlayer structure.
- TPD reveals monolayer wetting and 2D ordering dynamics.
Conclusions:
- Temperature critically dictates water ordering on FeO(111), transitioning from disordered layers to ordered 2D islands above 120 K.
- Surface diffusion differences are key to understanding temperature-dependent water overlayer structures.
- The study provides insights into water-surface interactions on oxide films, relevant for heterogeneous catalysis and surface chemistry.
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