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O: Fachverband Oberflächenphysik

O 62: Metal Substrates: Adsorption of Inorganic Molecules

O 62.4: Vortrag

Donnerstag, 28. Februar 2008, 10:15–10:30, MA 042

Adsorption and thermal decomposition of NO₂ on two stepped platinum surfaces — •Michael Peter Andreas Lorenz¹, Regine Streber¹, Christian Papp¹, Andreas Bayer¹, Reinhard Denecke², and Hans-Peter Steinrück¹ — ¹Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen — ²Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstr. 2, 04103 Leipzig

The adsorption of NO₂ on stepped Pt surfaces, namely Pt(322) and Pt(355), and its behaviour during heating to elevated temperatures was studied by in-situ high resolution XPS using synchrotron radiation at BESSY II. The motivation for our study was to obtain high oxygen precoverages, in order to study CO oxidation on stepped surfaces in this coverage regime. For the flat Pt(111) surface, Dahlberg et al. [1] showed that by dosing NO₂ oxygen coverages can be obtained, which are three times higher than those obtained by conventional exposure to O₂; for the more reactive stepped surfaces one could expect even higher coverages. Our study shows that at low temperatures, up to 250 K, NO₂ molecularly adsorbs on both surfaces as could be observed in the O 1s and N 1s regions. During heating, NO₂ starts to decompose to NO and O above 270 K. Thereby, NO desorbs completely up to 400 K. Significantly higher oxygen coverages than those formed by dissociation of O₂ can only be reached by adsorption of NO₂ at 400 K, resulting in the formation of clean oxygen layers without any nitrogen impurities. Supported by BMBF (05 ES3XBAI5).

[1] D. Dahlgren, J. C. Hemminger, Surf. Sci. 123 (1982) L739