CO adsorption on (111) and (100) surfaces of the Pt/sub 3/Ti alloy: evidence for parallel binding and strong activation of CO

Journal Article · Tue Jul 01 04:00:00 UTC 1986 · J. Catal.; (United States)

OSTI ID:5586374

Mehandru, S P; Anderson, A B; Ross, P N

An atom superposition and electron delocalization molecular orbital (ASED-MO) study has been made of CO adsorption on a 40-atom cluster model of the (111) surface and a 36-atom cluster model of the (100) surface of the Pt/sub 3/Ti alloy. Parallel binding to high-coordinate sites associated with Ti and low CO bond scission barriers are predicted for both surfaces. The preference for parallel adsorption is a consequence of the nature of the CO ..pi..=to-surface donation interactions. On Ti sites the ..pi.. orbitals donate to the early empty Ti 3d band and the antibonding counterpart orbitals are empty. Thus the ..pi.. donation makes substantial contributions to the adsorption bond order that are in addition to the contributions from 5 sigma donation and metal backbonding to the ..pi../sup */ orbitals. Altogether these bonding interactions favor the lying down orientation. On Pt sites, on the other hand, the ..pi.. donation antibonding counterpart orbitals are occupied so that the net interaction with Pt is a closed-shell repulsion. CO bonds upright in order to minimize the ..pi.. interaction, and concomitantly, the closed-shell repulsion, while maintaining 5sigma donation and ..pi../sup */ backbonding stabilizations. Comparisons are made with the results for a 40-atom cluster model of the unalloyed Pt(111) surface. It is shown that the extended Hueckel parameterization is inappropriate for studying CO and adsorption to Pt with ASED-MO theory because it incorrectly favors adsorption bonding through the oxygen end.

• Research Organization: Case Western Reserve Univ., Cleveland, OH
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5586374
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 100:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ADSORPTION
ALLOYS
BINDING ENERGY
BOND LENGTHS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL BONDS
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LENGTH
MATHEMATICAL MODELS
MOLECULAR ORBITAL METHOD
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
THEORETICAL DATA
TITANIUM ALLOYS
VALENCE