par Bryl, Robert ;Olewicz, Tomasz;Visart de Bocarmé, Thierry ;Kruse, Norbert
Référence European Conference on Surface Science (28: 2011-08-28 ->2011-09-02: Wroclaw, Pologne)
Publication Non publié, 2011-08-31
Communication à un colloque
Résumé : Adsorption of oxygen on metal surfaces can lead to considerable morphological changes of the metal crystal. In the case of fcc metals oxygen-caused faceting was observed on {210} planes (Ir, Pt, Cu, Ni). Faceting of platinum group metals has been studied recently due to their rich catalytic properties and widespread in numerous catalytic applications. In that context Field Ion Microscopy seems to be a great tool for studies of adsorbate-induced thermal faceting of platinum group metals. The specimen – a metal tip with an apex of some 5-30 nm diameter - can be regarded as a good model of a morphologically diversified particle of a real catalyst. Faceting experiments carried on curved surfaces can show morphological and structural changes of many different planes simultaneously, giving an insight into the adsorbate caused evolution of the microcrystals of the catalyst.In this contribution the influence of adsorbed oxygen on the near-equilibrium shape of the nano-crystal will be presented on examples iridium and palladium initially conditioned with a close-to-hemispherical tip morphology.. The clean Ir tip annealed at 850-1000 K exposes only low index {001} and {111} planes. When the Ir tip is pre-exposed to even as little as 0.3 L of O2 the development of {113}, {111}, {100} and reconstructed {110} planes upon annealing is observed. In case of Pd tip exposures of 1-6 L of oxygen are sufficient to provoke development of {110}, {111}, {001}, {012} and {112} planes.