Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 89: Oxide and Insulator Surfaces: Adsorption III
O 89.3: Vortrag
Donnerstag, 23. März 2017, 11:00–11:15, TRE Phy
Electron Transfer between Anatase TiO2 (101) and an Adsorbed O2 Molecule: Direct Observation by nc-AFM — •Martin Setvin, Jan Hulva, Gareth Parkinson, Michael Schmid, and Ulrike Diebold — TU Wien
The electron transfer between the substrate and an adsorbed molecule is a key process in catalysis, photocatalysis, electrochemistry or redox chemistry. We use a low temperature q-Plus STM/AFM to study the electron transfer between the anatase TiO2 (101) surface and a single adsorbed O2 molecule. We can directly distinguish neutral physisorbed O2 molecules in the triplet state from negatively charged (O2)− radicals, based on their different chemical reactivity towards the tip apex. Neutral O2 molecules are inert, while the (O2)− radicals readily form a chemical bond with the tip. By biasing the tip, we can charge and discharge the molecules at will and we show that the identical processes occur during UV illumination of the sample. Using the Kelvin-probe force spectroscopy, we investigate in detail the process of charge transfer between the substrate and the adsorbed molecule. The experiments point towards a key importance of the physisorbed O2 state and its electron affinity. The AFM data are supported by area-averaged spectroscopic techniques such as temperature programmed desorption or photoelectron spectroscopy.