IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoP

Paper SS2-MoP20
Surface Structure Influence on Reactivity of Small Molecules on SrTiO@sub 3@(100) Surfaces

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Surfaces and Interfaces Poster Session
Presenter: L. Wang, Pacific Northwest National Laboratory
Authors: L. Wang, Pacific Northwest National Laboratory
K.F. Ferris, Pacific Northwest National Laboratory
M.H. Engelhard, Pacific Northwest National Laboratory
Correspondent: Click to Email
Interactions of water, methanol and HCOOH with stoichiometric, stepped, and reduced SrTiO3(100) surfaces have been studied using temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and electronic structural calculations. Comparison of TPD spectra and equilibrium adsorption geometries for H2O on SrTiO3(100) with unreconstructed TiO2 (110) and (100) surfaces reveals the structural influence on the water adsorption and desorption behavior. A unique geometric arrangement of surface atoms on stoichiometric (TiO2-terminated) SrTiO3(100) surfaces due to the lack of surface bridging oxygen atoms results in very different adsorption and desorption properties of H2O on SrTiO3(100) compared to TiO2 (110) and (100) surfaces. Electronic structure calculations show that stepped SrTiO3(100) surfaces enhance the localized interaction between the adsorbed molecule and the oxide surface. No reaction products were observed at above 400 K for methanol on annealed stepped SrTiO3(100). However, reactivity of methanol on SrTiO3(100) surfaces are enhanced for the reducing SrTiO3(100) surfaces prepared by Ar+ sputtering. Reaction products of H2, CH4 and CO were observed at above 400 K on the reduced SrTiO3(100) surface. Formic acid was dissociated to form formate and a surface proton below 250 K on SrTiO3(100) surfaces. Formate was decomposed primarily through dehydration to produce CO and H2O, instead of through dehydrogenation to produce CO2 and H2. Different reaction pathways were observed for formaldehyde formation from formic acid on SrTiO3(100) surfaces. On stoichiometric and stepped surfaces, formaldehyde was produced through bimolecular coupling of two formates. However, on reduced surfaces, formaldehyde formation involves the reduction of surface formate by the oxidation of reduced Ti cations.