Periodic density functional theory study of the dissociative adsorption of molecular oxygen over La₂O₃

Results of spin-polarized, gradient-corrected, periodic density functional theory calculations are reported for the dissociative adsorption of molecular oxygen over the oxide surface of La₂O₃(001). The diatomic surface oxygen species formed from O₂ dissociation are characterized structurally by a bent orientation with respect to the surface and an O_surface-O bond length of 1.47 Å; both attributes are consistent with structural features characteristic of classical peroxides. The overall reaction energy for O₂ dissociation into surface peroxide species was calculated to be endothermic by only 12.1 kcal/mol. Several reaction pathways leading to the product were examined; the lowest energy path identified involves a three-center transition state and has an apparent activation barrier of 33.0 kcal/mol. We comment on the role that peroxide species may play in the C-H bond activation step of catalytic oxidative coupling of methane.