Preparation of Rhodium/Ce_xPr_(1-x)O2 Catalysts:A Nanostructural and Nanoanalytical Investigation of Surface Modifications by Transmission and Scanning-Transmission Electron Microscopy

摘要

By using a combination of transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques,we have followed in detail the structural and chemical changes occurring on the very surface layers of powder Ce_xPr_(1-x)O2 mixed oxides,used as supports,during the preparation of rhodium-supported catalyst by wet impregnation techniques.Results demonstrate the occurrence of Pr~(3+) leaching out of the Ce-Pr solid solution during the impregnation step,which promotes a severe spatial redistribution of lanthanide cations at the surface of the mixed oxide.A highly heterogeneous surface composition is reached after the metal deposition.Mobilization of the support also affects the features of the final surface structure of the metal-supported nanoparticles,which become decorated by patches of support material.All these facts seem crucial to properly understand the redox and catalytic behavior of this kind of materials.