X-ray absorption spectroscopic characterization of Pt-Rh/Al2O3-type catalysts for abatement of pollutant automotive gas emissions

The XAS technique is well adapted for the study of T.W.C's with low noble metal contents (Pt, Ph). The existence of contracted interatomic distances d(PtO), d(RhO) is shown by comparison with bulk references of PtO2 and Rh2O3 due to particle size effects at temperatures less than 800 degrees C whereas at 1600 degrees C these interatomic distances are abnormalous high due to it very strong metal-support interaction confirming our previous results. The evidence of true alloy phases at T >800 degrees C reveals a characteristic form of the Fourier Transform (F.T.) well simulated by modelisation of the F.T. moduli for PtxRh1-x (0 <x <1).