A first-principles study of the structure, electronic properties, and oxygen binding of FeO/Pt(111) and FeO2/Pt(111)

The ultrathin oxide films of bilayer FeO and trilayer FeO2 superstructures on Pt(111) with periodicity of (root 84x root 84)R10.9 degrees are studied in detail by density functional theory, and the corresponding structural properties, electronic properties, and oxygen activities in different domains (FCC, HCP, and TOP) are calculated. It is found that for both superstructures, the in-plane lattice constants slightly increase in the order FCC HCP > TOP for FeO/Pt(111), and FCC > TOP > HCP for FeO2/Pt(111). The surface electrostatic potentials and the binding energies of the surface oxygen atoms are found to follow the same order as the surface corrugation. There is net charge transfer from the supported FeO film to the Pt substrate for FeO/Pt(111), and the calculated oxidation state of iron is +2.36. In contrast, for FeO2/Pt(111), there is charge transfer from the Pt substrate to the supported FeO2 film, and the calculated oxidation state of iron is +2.95 (ferric state). Compared with Pt(111), the change of the surface work function of FeO/Pt(111) is negligible, while it is 1.24 eV for FeO2/Pt(111). The role of the surface dipole of the supported oxide film and the charge transfer of the ultrathin oxide film are discussed. (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved