AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA2
Comparison of Physisorption on MgO(100) and TiO@sub 2@(110) Surfaces

Wednesday, November 17, 2004, 2:20 pm, Room 210B

Session: Metal Oxides and Clusters II: TiO@sub 2@ and Photocatalysis
Presenter: Z. Dohnálek, Pacific Northwest National Laboratory
Authors: Z. Dohnálek, Pacific Northwest National Laboratory
J. Kim, Pacific Northwest National Laboratory
B.D. Kay, Pacific Northwest National Laboratory
Correspondent: Click to Email
Characterization of oxide surfaces represents one of the current challenges in surface science. In this study we employ physisorption of weakly bound species such as N@sub 2@, O@sub 2@, CH@sub 4@, and Ar to determine the distribution of binding sites on the surfaces of MgO(100) and TiO@sub 2@(110). Cooling of the oxide surfaces to cryogenic temperatures (T < 30K) is critical for conduction such measurements. Both surfaces were extensively studied in the past and represent an ideal platform to correlate surface sites with binding energies of various adsorbates. On MgO(100) only a single temperature programmed desorption (TPD) monolayer feature is observed for all the adsorbates. This is a result of simplicity of unreconstructed MgO(100) surface with checkerboard like arrangement of Mg@super 2+@ and O@super 2-@ ions. TPD spectra observed on TiO@sub 2@(110) are in sharp contrast with those from MgO(100). In this case the surface structure composed of rows of Ti@super 4+@ ions and bridge-bonded oxygens leads to two distinct adsorption geometries. The coverage of the adsorbates in these two geometries is approximately the same and it in agreement with 1:1 ratio of Ti@super 4+@ and bridge-bonded O sites. Typical defects are also probed on both surfaces. On MgO(100) their coverages are determined to be on the order of 15%. Lower coordination of the defect sites results in increased adsorbate binding energies. The effect of oxygen vacancies on the physisorption on TiO@sub 2@(110) is currently being investigated. @FootnoteText@ Pacific Northwest National Laboratory is operated for the Department of Energy by Battelle under Contract DE-AC06-76RLO 1830.