A comparison of Pt overlayers on. alpha. -Al sub 2 O sub 3 (0001), ZnO(0001)Zn, and ZnO(000 1 )O

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.459653· OSTI ID:6243221

Roberts, S; Gorte, R J ^[1]

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1. Department of Chemical Engineering, University of Pennsylvania, Philadelphia, PA (USA)

The growth of Pt films on ZnO(0001)Zn and ZnO(000{bar 1})O and their adsorption properties for CO have been studied and compared to results obtained for Pt on {alpha}-Al{sub 2}O{sub 3}(0001). Samples were prepared by vapor deposition of Pt onto flat substrates in ultra high vacuum, and metal coverages were measured using a quartz-crystal, film thickness monitor. On both ZnO surfaces, Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) indicate that Pt grows in as a 2D film at 300 K, in contrast to results for Pt on {alpha}-Al{sub 2}O{sub 3}(0001) where 3D particles are formed under these conditions. Furthermore, transmission electron diffraction (TED) showed that the Pt grew as an ordered overlayer on the ZnO crystals. Heating the Pt/ZnO surfaces resulted in the formation of Pt particles starting at {similar to}650 K, but the Pt particles were still oriented with the ZnO. On both ZnO surfaces, temperature programmed desorption (TPD) curves for CO from high Pt coverages ({gt}one monolayer) and from Pt particles formed by heating thinner films were identical to TPD curves for CO from Pt on {alpha}-Al{sub 2}O{sub 3}(0001). The main desorption features were observed at 400 and 510 K and are interpreted as being due to different site geometries on the Pt by comparison to results from Pt single crystals. However, for Pt at submonolayer coverages prior to particle formation, the TPD curves for CO from Pt on ZnO(0001)Zn were shifted down in temperature by {similar to}60 K compared to results for Pt on ZnO(000{bar 1})O. These results are interpreted as indicating a chemical interaction between Pt and the Zn{sup +2} ions which are in direct contact.

• DOE Contract Number: FG02-85ER13350
• OSTI ID: 6243221
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 93:7; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
COATINGS
DEPOSITION
ELEMENTS
FILMS
HIGH TEMPERATURE
INTERACTIONS
METALS
MORPHOLOGY
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE
PHYSICAL VAPOR DEPOSITION
PLATINUM
PLATINUM METALS
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SURFACE COATING
SURFACE PROPERTIES
THIN FILMS
TRANSITION ELEMENTS
VAPOR DEPOSITED COATINGS
ZINC COMPOUNDS
ZINC OXIDES