Remarkably Strong Chemisorption of Nitric Oxide on Insulating Oxide Films Promoted by Hybrid Structure

We report herein the remarkably strong chemical adsorption behaviors of nitric oxide on magnesia (001) film deposited on metal substrate by employing periodic density functional calculations with van der Waals corrections. As far as we know, the strong chemical adsorption of a single molecular nitric oxide over perfect inert oxide insulators such as magnesia has not yet been reported, without introduction of defects or morphological irregularities. Unlike the very weak physical interaction between nitric oxide and perfect magnesia, the molybdenum-supported magnesia (001) enhances adsorption capacities significantly, and the nitric oxide is chemisorbed strongly and preferably trapped in a flat adsorption configuration on metal-supported oxide film, due to the substantially large adsorption energies (1.65 eV) and transformation barrier heights. Bader charge populations, projected density of states, differential charge densities, electron localization function, and typical occupied orbitals are analyzed to uncover the electronic properties and nature of bonding between nitric oxide and surface as well as the bonding within the magnesia molybdenum hybrid structure. Nitric oxide in flat configurations gains more electrons than that in bridge and top configurations, which is responsible for the largest adsorption strength in flat configuration. On the whole, the thinner oxide films are more severely oxidized, leading to the remarkably enhanced activity of monolayer magnesia (001). The strong chemical binding interaction between nitric oxide and magnesia deposited on a molybdenum slab offers new opportunities for toxic gas detection and treatment. We anticipate that the hybrid structure-promoted remarkable chemical adsorption of nitric oxide on magnesia in this study will provide an inspiring clue for enhancing chemical activity and properties of insulating oxide.