Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 21: Adsorption an Oberfl
ächen II

O 21.4: Vortrag

Dienstag, 25. März 2003, 15:45–16:00, HSZ/03

Coadsorption of NO with atomic oxygen on Pt(111) studied by high-resolution XPS — •Junfa Zhu, Martin Kinne, Thomas Fuhrmann, Reinhard Denecke, and Hans-Peter Steinrück — Physikalische Chemie II, Universität Erlangen-Nürnberg,Egerlandstr. 3, D-91058 Erlangen, Germany

Adsorption of NO on a Pt(111) surface pre-covered with an ordered p(2x2)-O layer has been studied by high-resolution X-ray photoelectron spectroscopy (HRXPS) and temperature-programmed XPS (TPXPS) using third-generation synchrotron radiation at BESSY II, Berlin. From O 1s binding energies, changes in the bonding configuration of NO induced by the p(2x2)-O layer as compared to the clean Pt(111) surface [1] have been unequivocally derived. Preadsorbed atomic oxygen occupies three-fold fcc hollow sites [2] and blocks the NO adsorption on these sites, which are the energetically preferred sites on clean Pt(111). As a consequence, NO initially populates on-top sites, which is the only species at 250 K. For higher coverages at 110 K, NO can sequentially adsorb at hcp hollow sites, thereby inducing a shift of the O 1s binding energy of atomic oxygen towards lower energies by about 0.3 eV. Furthermore, the bond strength of the hcp hollow NO species to the substrate is weakened by the presence of atomic oxygen, as evidenced by its lower desorption temperature as compared to the pure NO layer. While the total saturation coverage of NO on p(2x2)-O/Pt(111) is smaller compared to the clean Pt surface, the initial sticking coefficient of NO remains the same.

[1] J.F. Zhu et al., Surf. Sci. (submitted)

[2] N. Materer et al., Surf. Sci. 325, (1995), 207