Chemical and electronic properties of Pt in bimetallic surfaces: Photoemission and CO-chemisorption studies for Zn/Pt(111)
- Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973 (United States)
On platinum zinc surfaces at 150--300 K, CO adsorbs only on Pt sites. CO molecules bonded to these sites exhibit a significantly lower adsorption energy (4--8 kcal/mol) and a larger O 1[ital s] binding energy (0.2--0.4 eV) than molecules bonded to clean Pt(111). To explain these changes in the Pt[leftrightarrow]CO interaction, we have examined the electronic properties of Zn/Pt(111) surfaces using core and valence level photoemission, and [ital ab] [ital initio] self-consistent-field calculations. At 80 K, Zn atoms deposited on Pt(111) remain on top of the surface. Above 400 K, alloy formation occurs. In general, the formation of Pt--Zn bonds produces a large depletion in the density of Pt 5[ital d] states around the Fermi level, with a shift in the centroid of the Pt 5[ital d] band and 4[ital f] core levels toward higher binding energy. This is accompanied by an important redistribution of charge, in which Pt loses 5[ital d] electrons and gains (6[ital s],6[ital p]) electrons. The electronic perturbations induced by Zn on Pt reduce its CO-chemisorption ability by weakening the strength of the Pt(5[ital d])--CO(2[pi]*) bonding interactions. The changes in the Pt properties observed after bonding this metal to Zn are as large as those found for Pt bonded to early transition metals, and much larger than those found when Pt is bonded to late-transition metals. In the bimetallic surfaces, the perturbations in the Pt properties increase when the fraction of empty states in the valence band of the metal bonded to Pt rises.
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6605571
- Journal Information:
- Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 102:10; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104 -- Metals & Alloys-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALLOYS
BINDING ENERGY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
CLEANING
COUPLING
ELECTRONIC STRUCTURE
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
EMISSION
ENERGY
ENERGY LEVELS
FERMI LEVEL
FERMIONS
INDUSTRY
INTERFACES
LEPTONS
METALS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PETROLEUM INDUSTRY
PHOTOEMISSION
PLATINUM
PLATINUM METALS
REDUCTION
SECONDARY EMISSION
SEPARATION PROCESSES
SORPTION
SURFACE CLEANING
SURFACE FINISHING
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TRANSITION ELEMENTS
VALENCE
ZINC