DFT Study of Dissociative Adsorption of Hydrogen Sulfide on Cu(111) and Au(111)

ABUFAGER, P.N.; LUSTEMBERG, P.; CRESPOS, C.; BUSNENGO, H.F.

LANGMUIR

AMER CHEMICAL SOC

Año: 2008 vol. 24 p. 14022 - 14026

0743-7463

Density functional theory (DFT) is used to investigate the reaction pathways for H2S adsorption on Au(111) andCu(111) at low coverage as well as the full decomposition of H2S on Cu(111). On both surfaces, a weakly bondedmolecular state is found with the S atom bond on top sites being molecular adsorption, a nonactivated process. TheH-SH dissociation process is endothermic on Au(111), and all reaction pathways present high activation energybarriers which explains the extremely low dissociation probability of H2S on defect-free Au(111) estimated fromexperiments. This scenario slightly changes for H2S/Cu(111): (i) dissociated configurations are energetically morefavorable than the molecular state and (ii) the H-SH bond cleavage process presents a relatively small activationenergy barrier. This is not inconsistent with low but nonzero reactive sticking probability of thermal H2S moleculesreported in experiments. The complete energy profile for the H2S adsorption and full decomposition is compatiblewith the accumulation of S-adatoms observed experimentally.