title: Structure effects of benzene hydrogenation studied with sum frequency generation vibrational spectroscopy and kinetics on Pt(111) and Pt(100) single-crystal surfaces.
abstract: Sum frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have identified at least two reaction pathways for benzene hydrogenation on the Pt(100) and Pt(111) single-crystal surfaces at Torr pressures. Kinetic studies at low temperatures (310-370 K) show that benzene hydrogenation does not proceed through cyclohexene. A Langmuir-Hinshelwood-type rate law for the low-temperature reaction pathway is identified. The rate-determining step for this pathway is the addition of the first hydrogen atom to adsorbed benzene for both single-crystal surfaces, which is verified by the spectroscopic observation of adsorbed benzene at low temperatures on both the Pt(100) and Pt(111) crystal faces. Low-temperature SFG studies reveal chemisorbed and physisorbed benzene on both surfaces. At higher temperatures (370-440 K), hydrogenation of benzene to pi-allyl c-C(6)H(9) is observed only on the Pt(100) surface. Previous single-crystal studies have identified pi-allyl c-C(6)H(9) as the rate-determining step for cyclohexene hydrogenation to cyclohexane.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Kaitlin M
authors.initials: KM
authors.lastname: Bratlie
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Kliewer
authors.forename: Gabor A
authors.initials: GA
authors.lastname: Somorjai