Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 89: Oxide and Insulator Surfaces: Adsorption III

O 89.4: Vortrag

Donnerstag, 23. März 2017, 11:15–11:30, TRE Phy

Methanol adsorption and reaction on a CuWO4 monolayer on Cu(110) — •Matthias A. Blatnik, Carl Drechsel, Nassar Doudin, Falko P. Netzer, and Svetlozar Surnev — Surface and Interface Physics, Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria

Here we investigate the chemical reactivity of CuWO4 nanolayers on Cu(110), with a coverage between 0 and 1 ML, towards adsorption and reaction of methanol (CH3OH) using a combination of high-resolution XPS and STM. Methanol has been dosed at 110 K, at which temperature it adsorbs molecularly as a multilayer. On heating to 160 K the methanol multilayer transforms into a methanol monolayer, methoxy (CH3O) and some formaldehyde (CH2O) intermediates. After heating to 260 K the methanol monolayer has fully converted into methoxy and some hydrocarbon (CHx) adsorbates, which remain stable up to 310 K. After heating to 450 K methoxy has been desorbed from most of the CuWO4 surface, except on those with coverages between 0.65 ML and 0.8 ML. The latter CuWO4 surfaces show the largest methoxy yield and degree of reduction. This is a strong indication that the oxidation reaction is promoted at the periphery of the oxide islands, which expose a large number of active under-coordinated reaction sites. This is indeed confirmed by the STM measurements, which show that the methanol oxidation reaction is initiated at the boundaries between the Cu-O and CuWO4 islands. Finally, flashing above 500 K results in the complete methoxy removal from the CuWO4 surfaces