A mechanistic study of H2S adsorption and dissociation on Cu2O(111) surfaces: Thermochemistry, reaction barrier

The interaction mechanism of H2S with different Cu2O(1 1 1) surfaces, including perfect, oxygen-vacancy and sulfur-containing surfaces, have been systematically studied using periodic density functional calculations. Different kinds of possible modes of H2S, as well as the resultant SH and S species adsorbed on these surfaces are identified. Two types of pathways via molecular and dissociative adsorption processes are mapped out. Our results show that sulfur species (H2S, SH and S) interact with surface Cu centers; H2S exists in the form of molecular adsorption on perfect and sulfur-containing surfaces; the dissociative adsorption of H2S occurs predominantly on oxygen-vacancy surface, suggesting that oxygen-vacancy exhibits a strong catalytic activity toward the dissociation of H2S. On the other hand, the dissociation processes of the molecular and dissociative adsorption H2S, leading to final product S species on these Cu2O(1 1 1) surfaces, show that the overall dissociation process is exothermic. Meanwhile, with respect to molecular adsorption H2S, the activation barrier and reaction energy of the overall dissociation process on perfect and oxygen-vacancy surfaces indicate that H2S can easily dissociate into S species. Importantly, in the case of dissociative adsorption of H2S, the dissociation of H2S into S species is a spontaneous process with respect to molecular adsorption H2S. However, on sulfur-containing surface, the presence of surface S atom goes against the H-S bond-breaking process both thermodynamically and kinetically. Finally, the vibrational frequencies for the adsorbed H2S, SH and S species on these surfaces have been obtained, which can be applied to guide surface vibrational spectroscopy in experiment. (c) 2012 Elsevier B.V. All rights reserved.