Generation of molybdenum hydride species on monolayer oxide/metal composite via addition of molecular hydrogen across metal-oxygen bond is investigated for the first time utilizing periodic Van der Waals density-functional calculations. Lewis acid-base pair constructed by the interfacially defected oxide film and the metal support provides novel active sites for activating H-2. The produced heterolytic dissociative state exhibits negative dissociative adsorption energy of -0.315 eV which thermodynamically facilitate the dissociation process of H-2 on insulating oxide films. The penitential energy pathways are calculated to reveal the dynamics and reaction processes for H-2 splitting at the oxide-metal interface. The differential charge density contour, electronic density plots, particular occupied orbitals, work function and electron localization function of H-2 dissociation are interpreted to better understand the electronic properties of the unique dissociation behavior of H-2 at interfacially defected magnesia. It is anticipated that the results here could help understand the mechanism of hydrogenation reactions on nanostructured oxide film and provide useful clue for enhancing the reactivity of insulating oxide toward activating H-2. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.