Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 28: Surface reactions II
O 28.5: Vortrag
Dienstag, 28. März 2006, 16:45–17:00, WIL C207
Ammonia oxidation on Pt single crystal surfaces in an intermediary pressure range up to 1 mbar — •Yingfeng Zeng1, Sebastian Günther2, Ling Zhou3, and Ronald Imbihl1 — 1Institute for Physical Chemistry, Hannover University, Callinstr. 3-3a, D-30167 Hannover, Germany — 2LMU München, Department Chemie, Butenandstr. 11 E, D-81377 München, Germany — 3Division of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford St., Cambridge, MA 02138, USA
The kinetics of ammonia oxidation on Pt(443), Pt(533) and Pt(100), have been investigated under stationary reaction condition in the 10−4 to 10−2 mbar range with low-energy electron diffraction (LEED), ellipsomicroscopy and rate measurement. Rate hysteresis in T-cycling occurs associated with structural modification of the Pt substrate is verified by LEED measurements with Pt(533) and Pt(443). Surprisingly, the occurrence of a hysteresis depends on the total pressure. For Pt(533) and Pt(443) we found a hysteresis at 10−3 mbar, but no hysteresis at P≥ 10−2 mbar, on Pt(443) hysteresis vanishes at P ≤ 10−4 mbar. On Pt(100) we found under all conditions a very broad hysteresis due to the phase transition of substrate from (1×1) to hex. The origin of the P-dependent hysteresis on Pt(443) and Pt(533) is discussed in terms of reversible and irreversible structural changes of the Pt surfaces.