title: Energetics of cyclohexene adsorption and reaction on Pt(111) by low-temperature microcalorimetry.
abstract: The heat of adsorption and sticking probability of cyclohexene on Pt(111) were measured as a function of coverage using single-crystal adsorption calorimetry in the temperature range from 100 to 300 K. At 100 K, cyclohexene adsorbs as intact di-sigma bonded cyclohexene on Pt(111), and the heat of adsorption is well described by a second-order polynomial (130 - 47 theta - 1250 theta(2)) kJ/mol, yielding a standard enthalpy of formation of di-sigma bonded cyclohexene on Pt(111) at low coverages of -135 kJ/mol and a C-Pt sigma bond strength of 205 kJ/mol. At 281 K, cyclohexene dehydrogenates upon adsorption, forming adsorbed 2-cyclohexenyl (c-C6H(9,a)) and adsorbed hydrogen, and the heat of adsorption is well described by another second-order polynomial (174 - 700 theta + 761 theta(2)) kJ/mol. This yields a standard enthalpy of formation of adsorbed 2-cyclohexenyl on Pt(111) at a low coverage of -143 kJ/mol. At coverages below 0.10 ML, the sticking probability of cyclohexene on Pt(111) is close to unity (>0.95), independent of temperature.
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
authors.forename: Ole
authors.initials: O
authors.lastname: Lytken
authors.forename: Wanda
authors.initials: W
authors.lastname: Lew
authors.forename: Jonathan J W
authors.initials: JJ
authors.lastname: Harris
authors.forename: Ebbe K
authors.initials: EK
authors.lastname: Vestergaard
authors.forename: J Michael
authors.initials: JM
authors.lastname: Gottfried
authors.forename: Charles T
authors.initials: CT
authors.lastname: Campbell