The reaction pathways for HSCH3 adsorption on Au(111) : a Density Functional Theory study.

LUSTEMBERG, P.; MARTIARENA, M.L.; MATÍNEZ, A.E.; BUSNENGO, H.F.

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2008 vol. 24 p. 3274 - 3279

0743-7463

   Density functional theory was used to investigate the reaction pathways for HSCH3 adsorption on Au(111) at low coverage. A molecular adsorbed state was found with the S atom bond on Top sites (E ∼ -0.38 eV) and molecular adsorption is nonactivated. The H-SCH3 dissociation process is energetically less favorable and becomes slightly exothermic only when surface relaxation is considered (∆E ∼ -0.2 eV). All the reaction pathways present a sizable activation energy barrier, with the lowest being ∼0.52 eV (0.41 eV taking into account slab relaxation). In the corresponding saddle point of the potential energy surface, the S atom of the methylthiolate molecule is placed on Top sites and the H near a Bridge site. The high barrier obtained explains the complete absence of reactive methanethiol dissociation found in recent experiments.