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The Adsorption of Liquid and Vapor Water on TiO2 (110) Surfaces: The Role of Defects

Published online by Cambridge University Press:  15 February 2011

Li-Qiong Wang ,
Don R. Baer  and
Mark. H. Engelhard
Li-Qiong Wang
Affiliation:
Materials and Chemical Sciences Center, and Environmental Molecular Science Laboratory, Pacific Northwest Laboratory, Richland, WA 99352
Don R. Baer
Affiliation:
Environmental Molecular Science Laboratory, Pacific Northwest Laboratory, Richland, WA 99352
Mark. H. Engelhard
Affiliation:
Environmental Molecular Science Laboratory, Pacific Northwest Laboratory, Richland, WA 99352
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Abstract

The adsorption of liquid and vapor water on defective and nearly defect-free TiO2 (110) surfaces has been examined using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). The study has focused on examining electronic defects as created in vacuum and after exposure to both liquid and vapor water. The defective surfaces were prepared by electron-beam exposure and Ar+ bombardment. With exposure up to 104 L low vapor pressure (<10−5 Torr) water to defective surfaces, little or no changes on Ti 3d defect intensities were observed, in agreement with the previous studies. However, defect intensities were greatly reduced after exposing defective surfaces to ∼ 108 L higher vapor pressure (0.2 - 0.6 Torr) water for 5 min. More significantly, XPS and UPS spectra showed that electron-beam induced defects were completely removed upon liquid water exposure, while defects created by Ar+ bombardment were only partially removed. It was found that surface defects created by Ar+ bombardment were removed more readily than sub-surface defects. For a nearly defect-free surface, water coverages were ∼ 0.02 ML at 104 L exposure to low vapor pressure water, ∼ 0.07 ML at 108 L exposure to higher vapor pressure water, and ∼ 0.125 ML with liquid water exposure, respectively.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 357: Symposium C – Structure and Properties of Interfaces in Ceramics , 1994 , 97
Copyright
Copyright © Materials Research Society 1995

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