Oxidation of the hexagonal Mo2C(101) surface by H2O dissociative adsorption

Abstract

Oxidation of the hexagonal Mo₂C(101) surface by H₂O dissociative adsorption was investigated using periodic density functional theory. At coverage (θ_H2O) up to 0.5 ML, all H₂O molecules adsorb on the top of surface Mo_A atoms, while further H₂O adsorption relies only on hydrogen bonding at θ_H2O > 0.5 ML. Up to 0.5 ML coverage, H₂O dissociation into surface OH is very facile and exothermic, and the dissociation of OH into O + H can establish equilibrium. Surface O can easily react with H₂O to generate surface OH. The most abundant oxygenate species on Mo₂C(101) should be surface OH instead of surface O atoms. The highest coverage of surface OH is 0.5 ML. These results provide new insight into the understanding of surface compositions on Mo₂C under an H₂O environment, and surface OH rather than surface O atoms should play an essential role in mechanisms of many related reactions.