Insight into the properties of stoichiometric, reduced and sulfurized CuO surfaces: Structure sensitivity for H2S adsorption and dissociation

Abstract

A mechanistic and kinetic study about the adsorption and dissociation of H2S on different types of CuO(111) surfaces, including the stoichiometric, reduced and sulfurized surfaces, has been carried out to probe into the structure sensitivity for H2S adsorption and dissociation. Here, density functional theory calculations have been employed. Our results show that sulfur-containing species (H2S, SH and S) dominantly interact with the surface Cu via S atom, and H is mainly adsorbed at the outermost surface oxygen site. H2S dominantly exists in the form of dissociative adsorption leading to SH and H species, meanwhile, a small quantity of molecular adsorption H2S also exist on these surfaces. The complete dissociation of molecular adsorption H2S on three CuO(111) surfaces clearly show that the overall dissociation process is exothermic, the stoichiometric surface is the most favorable; the sulfurized surface suppresses the HS bond activation and dissociation. Consequently, the catalytic activity toward molecular adsorption H2S dissociation follows the order: Stoichiometric>Reduced>Sulfurized surface, which have been also confirmed by projected density of states (pDOS), d-band analysis, and the inter-atomic distances. Therefore, H2S dissociation over CuO(111) surface is a structure-sensitive reaction, the effect of surface structure on H2S adsorption and dissociation may play an important role in improving high-performance H2S gas sensors, in which molecular adsorption H2S can be detected on the sulfurized surfaces. In addition, the vibrational frequencies of the adsorbed H2S and SH species on these surfaces can provide a theoretical guidance for the experimental vibrational spectroscopy.