Reduction Properties of (001) Maghemite Surfaces

Using Density Functional Theory (DFT) calculations we have studied the reduction properties of the (001) maghemite (y - Fe 2 O 3 ) surface, which is a promising material for catalysis applications. We have calculated the formation energies of oxygen vacancies on the surface correlating them with the oxygen atom positions. We have found that the oxygen vacancy formation energy is lower for the oxygen atoms not bonded to the tetrahedral irons in the layer below the surface. Also, the presence of an iron vacancy in the third layer below the surface lowers the oxygen vacancy formation energy. An high oxygen vacancy formation energy correlates with a change in the oxidation state of some iron atoms.