Abstract
The adsorption of CH3O and H on the (100) facet of gold was studied using self-consistent periodic density functional theory (DFT-GGA) calculations. The best binding site, energy, and structural parameter, as well as the local density of states, of each species were determined. CH3O is predicted to strongly adsorb on the bridge and hollow sites, with the bridge site as preferred one, with one of the hydrogen atoms pointing toward a fourfold vacancy (bridge-H hollow). The top site was found to be unstable, the CH3O radical moving to the bridge –H top site during geometry optimization. Adsorption of H is unstable on the hollow site, the atom moving to the bridge site during geometry optimization. The 4-layer slab is predicted to be endothermic with respect to gaseous H2 and a clean Au surface.
Highlights
The methoxy group CH3O and hydrogen H species have been identified as two intermediates in the decomposition of methanol through an initial O-H bond scission on several transition metal surfaces
We note that the X-ray photoelectron diffraction (XPD) [5], surface extended X-ray absorption fine structure (SEXAFS) [6] and near-edge X-ray absorption fine structure (NEXAFS) [6] studies for CH3O/Cu(111) and reflection absorption infrared spectroscopy (RAIRS) [14] for CH3O/ Ag(111), showed that the CH3O radical resides in threefold hollow site and the C–O bond is normal to the surface
The NEXAFS study of Outka et al [9] shows that methoxy C–O axis will be found with an angle of 20 ̊ - 40 ̊ relative to the Cu(100) surface normal
Summary
The methoxy group CH3O and hydrogen H species have been identified as two intermediates in the decomposition of methanol through an initial O-H bond scission on several transition metal surfaces. We note that the XPD [5], SEXAFS [6] and NEXAFS [6] studies for CH3O/Cu(111) and RAIRS [14] for CH3O/ Ag(111), showed that the CH3O radical resides in threefold hollow site and the C–O bond is normal to the surface. In the PED study [7], it was found that the CH3O radical adopted a geometry in which the C–O bond was close to perpendicular to the surface and the O atom occupied a threefold hollow site, fcc. A later study of Lindner et al [13] with a combined NEXAFS and photoelectron research concluded that the C–O axis is perpendicular to the surface and that a low symmetry adsorption site between the bridge and the 4-fold hollow site is occupied
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