Interactions of small molecules with TiO{sub 2}(110) surfaces: The role of defects

Journal Article · Wed May 01 04:00:00 EDT 1996 · Journal of Vacuum Science and Technology, A

DOI:https://doi.org/10.1116/1.580291· OSTI ID:288270

Wang, L ^[1]; Shultz, A N ^[2]; Baer, D R; Engelhard, M H ^[3]

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1. Materials and Chemical Sciences Center, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)
2. Physics Department, Oregon State University, Corvallis, Oregon 97331 (United States)
3. Environmental Molecular Sciences Laboratory, Pacific Northwest Laboratory, Richland, Washington 99352 (United States)

In this article, the adsorption behavior and the surface redox reactivity among small molecules including N{sub 2}O, O{sub 2}, H{sub 2}O and HCOOH on TiO{sub 2}(110) surfaces are compared. New measurements of the interaction of HCOOH with defect-free and defective TiO{sub 2}(110) surfaces and initial results from N{sub 2}O adsorption on defects are combined with earlier work involving O{sub 2} and H{sub 2}O. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) were used to monitor the amount of species adsorbed on the surface and the presence of electronic defects. The defective surfaces were prepared by Ar{sup +} bombardment and electron-beam exposure. Both O{sub 2} and N{sub 2}O {open_quote}{open_quote}heal{close_quote}{close_quote} defects (defect healing means an observation of the reducing of defect state intensity in both XPS and UPS spectra) even if they do not readily stick on the TiO{sub 2}(110) surfaces at 300 K. H{sub 2}O also heals defects, but at a much slower rate than either O{sub 2} or N{sub 2}O. In contrast, HCOOH exposure produces little healing even though the rate of adsorption for HCOOH (with saturation exposure of 10{sup 3} L) is much faster than for H{sub 2}O. The interactions of small molecules with defective TiO{sub 2}(110) surfaces involve not only the adsorption and dissociation of molecules on the surface but also the surface redox reaction in which the reduced Ti states (such as Ti{sup 3+}) are oxidized by the surface adsorbates to Ti{sup 4+}, resulting in the reduced Ti 3{ital d} defect intensity. {copyright} {ital 1996 American Vacuum Society}

• Research Organization: Pacific Northwest National Laboratory
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 288270
• Report Number(s): CONF-9510385--
• Journal Information: Journal of Vacuum Science and Technology, A, Journal Name: Journal of Vacuum Science and Technology, A Journal Issue: 3 Vol. 14; ISSN 0734-2101; ISSN JVTAD6
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ADSORPTION
CRYSTAL DEFECTS
DISSOCIATION
ELECTRONIC STRUCTURE
FORMIC ACID
NITROGEN OXIDES
OXYGEN
REDOX REACTIONS
SORPTIVE PROPERTIES
TITANIUM OXIDES
WATER VAPOR