Structure and adsorption properties of MoO₃: Insights from periodic density functional calculations

Structure and electronic properties of MoO₃ bulk and the (010) surface, as well as molecular adsorption of water on the (010) surface are investigated using periodic boundary density functional calculations. The bulk structure is calculated to be in good agreement with experiment. The structure and electronic properties of the (010) surface are confirmed to be very similar to those of the bulk. The terminal oxygen in both the bulk and the (010) surface is the least ionic among the three types of lattice oxygens. This study shows that the molecular adsorption of H₂O hardly takes place at the asymmetric and symmetric oxygens, but occurs at the terminal oxygen of the (010) surface. The results of the H₂O adsorption on the (010) at 1 and 0.5 monolayer coverages are interpreted based on charge-transfer interactions between the surface and H₂O species, and provide key information about the structural and energetic properties, in which each stable adsorption structure is suggested to orient on the surface via hydrogen bonding. These results also provide novel model systems for understanding the structure and adsorption states of MoO₃.