par Owczarek, Sylwia;Lambeets, Sten ;Barroo, Cédric ;Bryl, Robert ;Markowski, Leszek;Visart de Bocarmé, Thierry
Référence Topics in Catalysis, 61, page (1313-1322), 10.1007/s11244-018-0984-4
Publication Publié, 2018-05-03
Article révisé par les pairs
Résumé : Thermal faceting of clean and oxygen-covered Pt nanocrystals was investigated at the nanoscale by means of field ion microscopy (FIM) and field emission microscopy (FEM) in the 500–700 K temperature range. FIM and FEM are used to study the morphology of the crystal prepared in the form of a sharp tip. The tip extremity is observed with nanoscale lateral resolution and corresponds to a suitable model of a single nanoparticle of a real catalyst. By contrast to similar studies on iridium, palladium and rhodium, small oxygen exposures (~ 10 L) and annealing treatments at 700 K did not lead to strong surface modifications. The field ion micrograph was similar to the pattern obtained for the nanocrystals annealed under vacuum conditions, revealing only low index {001} and {111} facets. For higher oxygen doses, i.e. ≥ 100 L, and in field-free conditions, the flat {100}, {111} and {113} facets were developed after annealing the tip at 700 K, which was attributed to the formation of oxide layers. For comparison, the surface modification was studied under oxygen-rich conditions but in the presence of an electric field at 700 K. The results showed that only former reconstruction was observed regardless of oxygen doses. These results are also promising in the frame of engineering catalysts since different gas exposure may lead to the extension or shrinking of specific facets, which may impact the efficiency of the catalyst.