Complementary aspects of X-ray absorption spectroscopy and anomalous diffraction in the case of nanometric entities on light oxide support: Metallic aggregates and spinel-type oxide

A combined approach based on X-ray Absorption Spectroscopy, classical X-Ray Diffraction and Anomalous Wide Angle X-ray Scattering has been used in the case of nanometer scale metallic particle supported on zeolite and for the supported system 'Zn"/Al2O3. For the first material, we report a set of data obtained on a bimetallic PtCo catalyst. Exafs yields information on the local order around platinum before and after the reduction step. Also, diffraction experiments at two energies before the Pt L-III edge are reported and the results obtained from the two techniques are discussed. For the spinel, major information regarding the cation distribution, the electronic state of the metal atoms as well as the size of the zinc based metal oxide clusters are obtained. Through numerical simulations of the modulations of the X-rays absorption coefficient taking into account multiple scattering processes and ab initio calculations of the differential diffraction intensities based on the Debye equation, we have pointed out the fact that the tetrahedral site of the spinel occupied by the zinc atoms are partially occupied.