A DETAILED STUDY OF THE METALLIC FUNCTION OF BIMETALLIC PLATINUM-RHODIUM POST COMBUSTION CATALYSTS BY XAS, MET - CORRELATIONS WITH THEIR CATALYTIC ACTIVITY

In automobile catalytic converters, the reaction between carbon oxide (CO) and nitrogen oxides (SOX) over Pt-containing catalyst particle is done in order to obtain CO2 and NO2 In this paper, we report a struct ural characterization of the metallic part of a bimetallic Pt-Rh catal yst conducted through the combined use of three characterization techn iques i.e. X-ray absorption spectroscopy (Exafs) and high resolution m icroscopy by transmission (STEM). Eased on all these results, a cohere nt model seems to distinguish two families of metallic cluster. One is made of nanometric size Pt clusters for which the diameter is less th an the nanometer. The second one, made of Pt and Ph atoms has a diamet er more important. For this second one, the repartition of the metals is not statistic. It seems that platinum is at the core of the cluster , the surface being composed by a mixture of Pt and Ph atoms.