Dissociative adsorption of H2 on W and W/Cu: Prominent features of surface alloying

MARTÍNEZ, A.E.

San Sebastian/Donostia (España)

Workshop; Elementary reactive processes at surfaces; 2007

Donostia International Physics Center

The dissociative adsorption of H2 on the W(100)-c(2x2)Cu surface alloy is analyzed and compared with results corresponding to the W(100) surface. The former system has been exhaustively studied from the experimental point of view, showing a higher barrier to dissociation than the clean surface. Also, a pure indirect channel to dissociation at low energies has been reported. Even though close to Cu atoms dissociative adsorption is highly activated, the W(100)-c(2x2)Cu surface is found to preserve non activated pathways for H2 dissociation, which explains the large dissociative adsorption probability observed at low energies in experiments. Despite the presence of Cu atoms in the alloy surface, the attraction towards top-W sites experienced by H2 incoming molecules in the entrance channel is not strongly altered. However, the differences observed between both surfaces in the exit channel are noticeable and can be related to the changes in the stability of the atomic adsorption sites. In this work we will present results of dynamical calculations for both systems, focussing our analysis in those features that can be ascribed to the surface alloying.