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 da ta obtained on a bimetallic PtCo catalyst. Exafs yields information on the local order around platinum before and after the reduction step. Also, diff raction experiments at two energies before the Pt L-III edge are reported a nd the results obtained from the two techniques are discussed. For the spin el, major information regarding the cation distribution, the electronic sta te of the metal atoms as well as the size of the zinc based metal oxide clu sters are obtained. Through numerical simulations of the modulations of the X-rays absorption coefficient taking into account multiple scattering proc esses and ab initio calculations of the differential diffraction intensitie s based on the Debye equation, we have pointed out the fact that the tetrah edral site of the spinel occupied by the zinc atoms are partially occupied.