Theoretical Study of Hydrogen Permeation through Mixed NiO-MgO Films Supported on Mo(100): Role of the Oxide-Metal Interface

This work presents a periodic density functional study of the adsorption and permeation of atomic H on Ni-doped MgO oxide thin films supported on a Mo(100) surface. We find that the binding of atomic H is affected by the presence of a metallic support. The chemisorption energies increase considerably when the oxide film is supported. The H permeation through the NiO-MgO oxide was also studied. H migration through the unsupported NiO-MgO oxide is thermodynamically inhibited, while the presence of the metallic Mo makes permeation thermodynamically favored. We attribute the promoting effect to the different character of adsorbed H at the unsupported Ni-doped MgO oxide and at the oxide-Mo interface. In the former case, H forms hydroxyl groups, whereas in the latter case it appears as hydride due to the formation of strong metal-hydrogen bonds. These results illustrate the important role that the oxide metal interface could play in the mechanism for pure and mixed oxides reduction.