Surface science and catalysis : behavior of bimetallic surfaces during CO oxidation
Résumé
A catalyst is a very divided material generally composed of active phase nanoparticles supported on a powder support. In such configuration the synthesis methods generally lead to collections of supported nanoparticles in which a large number of parameters vary (size distribution, exposed faces, chemical composition,
). In order to determine the influence of a given parameter on the catalytic behavior of the catalyst it is thus essential to minimize the influence of other parameters. To a great extent this can be done by using extended catalytic surfaces (singlecrystal, vicinal, polycrystal) where only a few (ideally one) parameters vary (orientation/surface coordination, chemical composition,
). The study of these catalytic surfaces requires the use of surface science techniques often developed for UHV operation. In recent years an effort has been made so that such techniques can now be operated in (quasi) realistic reaction cond itions and are able to yield information on the evolution of catalytic surfaces (structure/morphology, chemical composition/segregation,
) in real-time during the catalytic reaction. In this work we present the study of the evolution of Pd70Au30 (110) and Pt3Sn(111) surfaces during CO oxidation by several surface science techniques developed either at laboratory level (environmental STM and PM-IRRAS) or within synchrotron facilities (in situ SXRD at ESRF and Near Ambient Pressure XPS at ALS-Berkeley and SOLEIL).