Dresden 2017 – scientific programme
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O: Fachverband Oberflächenphysik
O 89: Oxide and Insulator Surfaces: Adsorption III
O 89.1: Talk
Thursday, March 23, 2017, 10:30–10:45, TRE Phy
Adsorption of Water on (Ca,Sr)3Ru2O7 surfaces — •Wernfried Mayr-Schmölzer, Daniel Halwidl, Florian Mittendorfer, Ulrike Diebold, Josef Redinger, and Michael Schmid — Institute of Applied Physics, TU Vienna
Perovskite oxides are promising materials for a wide range of applications as diverse as sensors, fuel cells and catalysts. Surprisingly an atomic scale knowledge of their surface chemistry is still rather poor. Here we present a combined DFT, STM and XPS study of the first monolayer H2O formation on the (001) surfaces of three Ruddelsden-Popper type compounds, Sr3Ru2O7, Ca doped Sr3Ru2O7 and Ca3Ru2O7. All cleave nicely, yielding flat rocksalt-like SrO-, (Sr,Ca)O- and CaO-type terminated surfaces. Adsorbed H2O monomers dissociate on all surfaces by transferring an H to an apical O while the remaining OH resides at a nearby Sr-Sr, Ca-Sr, or Ca-Ca bridge, respectively. On the SrO-type surface dimers of dissociated H2O are formed, which at higher coverage combine to chains and cages[1]. The CaO-type surface is much more reactive (Δ EAdsH2O≈ 0.4eV) and also shows chains of dissociated H2O, but due to the different rotation and tilting of the RuO octahedra they only occur along the [010] direction. On the Ca doped SrO-type surface the dissociated H2O molecule is preferably located at the dopant site and reactivity is increased by 0.1eV compared to the pure SrO-type surface. Additionally the dopant impedes dimer formation.
[1]D. Halwidl et. al., Nature Materials, 15(4), 450-455.