Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 100: Metal Substrates: Adsorption and Reactivity
O 100.5: Vortrag
Freitag, 20. März 2015, 11:30–11:45, MA 043
Following PtAg/Pt(111) surface alloy formation by CO adsorption — •Thomas Diemant, Konstantin M. Schüttler, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm
The influence of the structure of a bimetallic surface on the chemical and catalytic properties is of high interest to further the understanding of the working principles of bimetallic catalysts. In this context, the growth of Ag films on a Pt(111) substrate at room temperature, the formation of PtAg/Pt(111) surface alloys by annealing to higher temperature (up to 900 K) and the consequences of surface alloy formation on the CO adsorption properties were studied by a combination of XPS, TPD and IR spectroscopy (IRRAS) measurements using CO as probe molecule in the two latter methods. Previous STM studies by Röder et al.[1] and in our institute had revealed a change of the atom distribution from extended Ag overlayer islands on the Pt(111) substrate directly after deposition at RT to disperse PtAg surface alloys.
The modification of the electronic properties of the components in the bimetallic surface layer upon alloy formation, which starts at 600 K, is resolved in XPS by a shift of the Ag(3d) peak to lower binding energy. The CO adsorption also starts to change drastically after heating to this temperature. New features in the CO TPD spectra (extra peak at higher desorption temperature) and in the IRRAS (2025 cm−1) occur, which we attribute to the formation of isolated Pt sites surrounded by Ag atoms.
[1] Röder et al., Phys. Rev. Lett. 71 (1993) 2086.