ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Density functional calculations in combination with cluster and slab models (periodic super-cell approach) were used to investigate the bonding and chemistry SO2 on Cu(100). For small coverages of SO2, the stability of the different bonding modes increases according to the η1-S〈η2-S,O〈η2-O,O〈η3-S,O,O sequence. Large coverages make impossible η3-S,O,O bonding, and under such conditions the most stable conformations involve η2-O,O or η2-S,O bonding. These adsorption geometries can be expected when SO2 is coadsorbed with substantial amounts of O. The bonding mechanism of SO2 on copper involves a Cu(3d,4s)→SO2(LUMO) electron transfer that leads to a weakening and elongation of the S–O bonds. The η3-S,O,O conformations exhibit the biggest adsorption energies, the largest charge transfers, and the weakest S–O bonds. These conformations are ideal precursors for the dissociation of the SO2 molecule. From a thermochemical viewpoint, it is much easier to generate SO3(3SO2→2SO3+S,ΔE=∼+1 kcal/mol) than to form SO(SO2→SO+O,ΔE=∼+20 kcal/mol) as an intermediate during the decomposition of sulfur dioxide on Cu(100). SO and SO3 behave as net electron acceptors when bonded to copper, with the electron density on their S atoms increasing in the following order: SO3〈SO2〈SO〈S. At small coverages, SO3 prefers an adsorption geometry in which its C3v axis is perpendicular to the surface and the molecule is bonded to copper through the oxygen atoms (η3-O,O,O bonding). In a crowded surface, the SO3 can be forced into a η2-S,O bonding conformation to minimize lateral adsorbate↔adsorbate repulsions. The multidentate nature of SO2 and SO3 opens the possibility for a complex DeSOx chemistry on metal surfaces. © 2001 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1377884
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