Molybdenum Oxides vs. Molybdenum Sulfides: Geometric and Electronic Structures

In light of the recent attention MoS2 has received regarding its possibilities for use in the photocatalytic evolution of H2, we have conducted a comparative computational investigation of some key properties that determine water reactivity such as the molecular structure and water adsorption properties of molybdenum oxide and sulfide clusters. Using density functional theory methods, we have found that while Mo3O − 6 and Mo3S − 6 assume very similar ring-type isomers, Mo3O − 9 and Mo3S − 9 clusters are very different with Mo3O − 9 having a ring-type structure and Mo3S − 9 having a more open, linear-type geometry. The more rigid ∠(Mo–S–Mo) bond angle is the primary geometric property responsible for producing such different lowest energy isomers. Additionally, due to a stronger oxide-water hydrogen bond, water is found to adsorb more strongly to Mo3O − 6 than to Mo3S − 6 although dispersion effects reduces this difference when Molybdenum centers contribute to the binding.