Energetics of adsorbed CH3 on Pt(111) by calorimetry.

The enthalpy and sticking probability for the dissociative adsorption of methyl iodide were measured on Pt(111) at 320 K and at low coverages (up to 0.04 ML, where 1 ML is equal to one adsorbate molecule for every surface Pt atom) using single crystal adsorption calorimetry (SCAC). At this temperature and in this coverage range, methyl iodide produces adsorbed methyl (CH(3,ad)) plus an iodine adatom (I(ad)). Combining the heat of this reaction with reported energetics for Iad gives the standard heat of formation of adsorbed methyl, ΔH(f)(0)(CH3,ad), to be −53 kJ/mol and a Pt(111)–CH3 bond energy of 197 kJ/mol. (The error bar of ±20 kJ/mol for both values is limited by the reported heat of formation of I(ad).) This is the first direct measurement of these values for any alkyl fragment on any surface.

[1]  E. Karp,et al.  Energetics of Adsorbed CH3 and CH on Pt(111) by Calorimetry: Dissociative Adsorption of CH3I , 2013 .

[2]  E. Karp,et al.  Energetics of adsorbed methanol and methoxy on Pt(111) by microcalorimetry. , 2012, Journal of the American Chemical Society.

[3]  I. Harrison,et al.  Dynamically biased RRKM model of activated gas-surface reactivity: vibrational efficacy and rotation as a spectator in the dissociative chemisorption of CH4 on Pt(111). , 2012, Physical chemistry chemical physics : PCCP.

[4]  E. Karp,et al.  The Energy of Adsorbed Hydroxyl on Pt(111) by Microcalorimetry , 2011 .

[5]  E. Karp,et al.  Energy of Molecularly Adsorbed Water on Clean Pt(111) and Pt(111) with Coadsorbed Oxygen by Calorimetry , 2011 .

[6]  Xinggui Zhou,et al.  Density functional study of the chemisorption of C1, C2 and C3 intermediates in propane dissociation on Pt(111) , 2010 .

[7]  C. Campbell,et al.  Improved pyroelectric detectors for single crystal adsorption calorimetry from 100 to 350 K. , 2010, The Review of scientific instruments.

[8]  C. Campbell,et al.  Energetics of cyclohexene adsorption and reaction on Pt(111) by low-temperature microcalorimetry. , 2008, Journal of the American Chemical Society.

[9]  M. Ternan,et al.  Methane oxidation mechanism on Pt(111): a cluster model DFT study. , 2006, The journal of physical chemistry. B.

[10]  W. Goddard,et al.  Chemisorption of (CHx and C2Hy) hydrocarbons on Pt(111) clusters and surfaces from DFT studies. , 2005, The journal of physical chemistry. B.

[11]  C. Campbell,et al.  Calorimeter for adsorption energies of larger molecules on single crystal surfaces , 2004 .

[12]  H. Celio,et al.  Sensitivity improvement in surface infrared spectroscopy: Design, characteristics, and application of a high-temperature graphite source , 2004 .

[13]  N. Saliba,et al.  Probing the chemistry of CH3I on Pt–Sn alloys , 2004 .

[14]  D. Harrington,et al.  A thermal desorption study of iodine on Pt( 1 1 1 ) , 2003 .

[15]  William A. Goddard,et al.  Oxidation of Methanol on 2nd and 3rd Row Group VIII Transition Metals (Pt, Ir, Os, Pd, Rh, and Ru): Application to Direct Methanol Fuel Cells , 1999 .

[16]  I. Harrison,et al.  Orientation and decomposition kinetics of methyl iodide on Pt(111) , 1995 .

[17]  P. Stair,et al.  Carbon-carbon coupling of methyl groups on Pt(111) , 1993 .

[18]  C. Campbell,et al.  The effects of postdosed bismuth on the chemistry of CH3 and CH3I on Pt(111) , 1992 .

[19]  F. Zaera.  Preparation and Reactivity of Alkyl Groups Adsorbed on Metal Surfaces , 1992 .

[20]  F. Zaera.  Study of the surface chemistry of methyl iodide coadsorbed with hydrogen on Pt(111) , 1992 .

[21]  H. Hoffmann,et al.  Detection of chemisorbed methyl and methylene groups : surface chemistry of methyl iodide on Pt(111) , 1991 .

[22]  G. Mitchell,et al.  CH3 and CH3I chemistry on Pt(111): the influence of CO , 1991 .

[23]  F. Zaera.  Mechanism for the catalytic exchange of methane with deuterium on Pt(111) surfaces , 1991 .

[24]  Christopher R. Arumainayagam,et al.  Dissociative chemisorption of methane on Pt(111) , 1989 .

[25]  Michael A. Henderson,et al.  The chemisorption of methyl halides (Cl, Br and I) on Pt(111) , 1987 .

[26]  D. King,et al.  Molecular Beam Investigation of Adsorption Kinetics on Bulk Metal Targets: Nitrogen on Tungsten , 1972 .

[27]  J. D. Cox,et al.  Thermochemistry of organic and organometallic compounds , 1970 .