Adsorption Energy of tert-Butyl on Pt(111) by Dissociation of tert-Butyl Iodide: Calorimetry and DFT

作者：Silbaugh Trent L; Giorgi Javier B; Xu Ye; Tillekaratne Aashani; Zaera Francisco; Campbell Charles T^*

来源：Journal of Physical Chemistry C, 2014, 118(1): 427-438.

DOI：10.1021/jp4097716

Dissociative and molecular adsorption of tert-butyl iodide on Pt(111) has been studied by single-crystal adsorption calorimetry (SCAC), photoelectron spectroscopy (XPS), reflection/adsorption infrared spectroscopy (RAIRS), and density functional theory (DFT) calculations. Up to a t-BuI total coverage of 0.07 ML, t-BuI adsorbs dissociatively at 100 K to form t-Bu-ad plus I-ad, with an integral heat of reaction of 223 kJ/mol. At higher coverage, up to a total coverage of 0.15 ML, t-BuI adsorbs molecularly directly to the Pt surface atoms with an average heat of adsorption of 91 kJ/mol. At 0.15 ML, the first layer is saturated. Between 0.15 and 0.38 ML, t-BuI adsorbs molecularly on top of the first layer with a constant heat of adsorption of 44.5 +/- 1.9 kJ/mol. The standard enthalpy of formation of adsorbed tert-butyl on Pt(111) at 1/25 ML coverage is estimated from the heat measurements to be -168 +/- 20 kJ/mol, giving a (CH3)(3)C-Pt(111) bond enthalpy of 216 +/- 20 kJ/mol. DFT calculations were performed using the GGA-PBE and optB86b vdW density functionals to determine the heats of reaction and binding energies of relevant adsorbates. Comparison to the measured energies shows that optB86b vdW-DF is more accurate than GGA-PBE for describing the adsorption and bonding of t-buI and t-Bu on Pt(111) because these energies contain large contributions from dispersion forces.

• 出版日期2014-1-9