  The formation of highly reactive oxygen species (ROS) on metal oxide surfaces
have attracted considerable interest due to their diverse applications. In this
work, we have performed densi-ty-functional theory calculations to investigate
the co-adsorption of oxygen and water on ul-trathin MgO(100) films deposited on
Mo(100) substrate. We reveal that the molecular oxygen can be stepwise
decomposed completely with the assistance of water. Consequently, a series of
highly ROS including superoxide, hydroperoxide, hydroxyl and single oxygen
adatom are formed on Mo(100) supported MgO(100) thinfilms. The reaction
barriers accompanied by the generation of ROS are reported, and the influence
of the thickness of MgO(100) films is also discussed. The most promising routes
to produce these fascinating species provide valuable information to understand
the importance of synergistic effect, namely the substrate, the co-adorbed
species, and the film thickness, in multiphase catalyst design.
