title: Geometric requirements for hydrocarbon catalytic sites on platinum surfaces.
abstract: Vibrational spectroscopic measurements and density functional calculations were used to identify a preferential catalytic mechanism for the transformation of acetylene, HC-CH, to vinylidene, C-CH2, on surfaces of Pt-Sn ordered alloys. In this mechanism, two adjacent Pt atoms adsorb an acetylene molecule and a third neighboring Pt atom is required for stabilizing the reacting H atom during the transformation. Therefore, unlike a direct H shift along the C-C bond in organometallic compounds with a single transition-metal atom, this mechanism has a geometric site requirement of three adjacent Pt atoms in the form of a three-fold site. The same geometric site requirement is identified for preferential C-H bond cleavage of acetylene with the formation of adsorbed C-CH and H species. In the absence of three-fold Pt sites, the reaction mechanism changes, and reactions of H transfer and C-H bond cleavage are suppressed.
authors.affiliation: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (USA).
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.forename: Haibo
authors.initials: H
authors.lastname: Zhao
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Yang
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Koel
authors.forename: Simon G
authors.initials: SG
authors.lastname: Podkolzin
keywords: acetylene; alloys; heterogeneous catalysis; platinum; reaction mechanisms