Chemisorption of high coverages of atomic oxygen on the Pt(111), Pd(111), and Au(111) surfaces

Journal Article · Tue May 01 00:00:00 EDT 1990 · Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA)

DOI:https://doi.org/10.1116/1.576675· OSTI ID:6787515

Parker, D H; Koel, B E ^[1]

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1. Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO (USA) Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO (USA)

Studies of the interaction of oxygen with some transition metal surfaces are limited by activation barriers to adsorption and reaction of O{sub 2}. These barriers can be surmounted by using oxidants more powerful than O{sub 2} to chemisorb oxygen on these surfaces under ultrahigh vacuum (UHV) conditions, but at high effective'' pressures of O{sub 2}. We report here on the use of very reactive molecules, such as nitrogen dioxide (NO{sub 2}) and ozone (O{sub 3}) to study the interaction of high concentrations of oxygen atoms on the Pt(111), Pd(111), and Au(111) single crystal surfaces. Chemisorbed oxygen adatom coverages of {Theta}{sub 0}{le}0.75 monolayer (ML) on Pt(111), {Theta}{sub 0}{le}1.4 ML on Pd(111), and {Theta}{sub 0}{le}0.80 ML on Au(111) surfaces have been characterized. On the Pd(111) surface, higher concentrations ({Theta}{sub 0}{le}3.1 ML) can be formed and the initial stages of oxidation, including migration of oxygen into the subsurface region and formation of Pd oxide can be studied. This method of cleanly forming high coverages of oxygen on metal surfaces allows for new insight into the nature of oxygen--metal interactions. For example, in the case of Pt(111) and Au(111), temperature programmed desorption (TPD) can be used to determine kinetic parameters of O{sub 2} adsorption and desorption as a function of oxygen coverage and upper limits for the metal--oxygen bond strengths over a large range of oxygen coverages can be determined from the activation energy of O{sub 2} desorption. Also, the kinetics of oxidation reactions can be studied over a much larger range of oxygen coverage than previously carried out under UHV conditions on surfaces that are relatively unreactive to O{sub 2} chemisorption, such as Pt(111) and Au(111). We report preliminary results concerning transient kinetic studies of CO oxidation over Pt(111) and Au(111) surfaces.

• OSTI ID: 6787515
• Journal Information: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA), Journal Name: Journal of Vacuum Science and Technology, A (Vacuum, Surfaces and Films); (USA) Vol. 8:3; ISSN JVTAD; ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ADSORPTION
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
ELEMENTS
GOLD
METALS
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
OZONE
PALLADIUM
PLATINUM
PLATINUM METALS
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
TRANSITION ELEMENTS