A DFT Study of Thiophene Adsorption on the Rh(111) Surfaces

Thiophene adsorption on the Rh(111) surfaces has been investigated by density functional theory. The results show that the adsorption at the hollow and bridge sites is the most stable. The molecular plane of the thiophene ring is distorted, the C=C bond is stretched to 1.448 angstrom and the C-C bond is shortened to 1.390 angstrom. The C-H bonds tilt 22 similar to 42 degrees away from the surface. The calculated adsorption geometries are in reasonable agreement with population analysis and density of states. The thiophene molecule obtains 0.74 electrons, reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal. The reaction paths and transition states for desulfurization of the molecule have been investigated. The bridge adsorption structure of thiophene leads to a thiol via an activated reaction with an energetic barrier of 0.30 eV. This second step is slightly difficult, and dissociation into a C4H4 fragment and a sulfur atom is possible, with an energetic barrier of 0.40 eV.