Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 77: Gerhard Ertl Young Investigator Award
O 77.5: Hauptvortrag
Donnerstag, 10. März 2016, 12:30–13:00, S051
Surface Chemistry of Oxygen and Water on Anatase TiO2 (101) — •Martin Setvin1, Ulrich Aschauer2, Jan Hulva1, Michael Schmid1, Annabella Selloni3, and Ulrike Diebold1 — 1TU Wien — 2ETH Zurich — 3Princeton University
TiO2 is a prototypical material used in photocatalysis, e.g. in water remediation or photocatalytic water splitting. Two polymorphs of TiO2, rutile and anatase, are used industrially with anatase typically preferred in applications. The surface chemistry of water and oxygen is the basis for majority of (photo)catalytic processes on TiO2; most prominently in the photocatalytic water splitting and the oxygen reduction reaction. We report adsorption of water and oxygen studied by a combination of experimental and theoretical techniques (STM, nc-AFM, TPD, XPS, DFT). Special attention is paid to the activation of adsorbed O2 molecules, i.e. electron transfer from the reduced anatase sample to the adsorbate. We show that this can occur in regions with a surplus of excess electrons, e.g., in the vicinity of subsurface donors and at step edges. In other regions the adsorbed O2 molecules remain neutral. With nc-AFM we show they can be charged by an electron injected from the tip. We find a small energy barrier of 0.3 eV for this process. Interaction between co-adsorbed H2O and O2 is used to illustrate the reactivity of thus activated O2. When the two species react they both dissociate, with terminal (OH)− groups as the final product of the reaction, stable at room temperature. This species as well as the reaction intermediates, OOH and HOOH, are identified with atomically-resolved SPM measurements.