par Chau, Thoi-Dai 
;Visart de Bocarmé, Thierry ;Kruse, Norbert
Référence Surface and interface analysis, 36, 5-6, page (528-532)
Publication Publié, 2004
;Visart de Bocarmé, Thierry ;Kruse, Norbert Référence Surface and interface analysis, 36, 5-6, page (528-532)
Publication Publié, 2004
Article révisé par les pairs
| Résumé : | We have studied the catalytic reduction of nitric oxide (NO) with hydrogen (H2) on platinum using both field ion microscopy (FIM) and pulsed field desorption mass spectrometry (PFDMS). Under certain conditions of temperature and gas pressure this reaction exhibits non-linear behaviour, i.e. hysteresis effects and rate oscillations occur. Ensembles of kink sites of the <100> zones are found to act as pacemakers, which is in line with earlier studies demonstrating {012} planes to ignite in a quasi-concerted manner. Experiments with tips of varying radius of curvature always lead to the same sequence of image patterns. Large variations in the H2 partial pressure has little influence on the frequency of the rate oscillations. Using PFDMS under the reaction conditions we show that NO+ rather than H2O+/H3O+ (the neutrals are formed during the reaction process) is the imaging species in FIM. Interestingly, PtOx (x<=3) ions are seen in the mass spectra, indicating that the reaction is controlled by a vacant site mechanism with the inclusion of partial oxidation of the Pt surface. |
