A Detailed Study of the Metallic Function of Bimetallic Platinum-Rhodium Post Combustion Catalysts by X.A.S., M.E.T. : Correlations with their Catalytic Activity

In automobile catalytic converters, the reaction between carbon oxide (CO) and nitrogen oxides (NOx) over Pt-containing catalyst particle is done in order to obtain CO2 and NO2. In this paper, we report a stuctural characterization of the metallic part of a bimetallic Pt-Rh catalyst conducted thrugh the combined use of three characterization techniques i.e. X-ray absorption spectroscopy (Exafs) and high resolution micmscopy by transmission (STEM). Based on all these results, a coherent model seems to distinguish two families of metallic cluster. One is made of nanometric size Pt clusters for which the diameter is less than the nanometer. The second one, made of Pt and Rh atoms has a diameter 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 Rh atoms