Tuning the Integration Rate of Ce(Ln)O 2 Nanoclusters into Nanoparticulated ZrO 2 Supports: When the Cation Size Matters.

Three nanostructured catalysts with low total rare earth elements (REEs) content (i.e., 15 mol.%) were prepared by depositing CeO(2)or Ln(3+)-doped CeO2(Ln(3+)= Y(3+)or La3+; Ln/Ce = 0.15) on the surface of ZrO(2)nanoparticles, as nanometre-thick, fluorite-type clusters. These samples were subjected to successive reduction treatments at increasing temperatures, from 500 to 900 degrees C. A characterisation study by XPS was performed to clarify the diffusion process of cerium into the bulk of ZrO(2)crystallites upon reduction to yield Ce(x)Zr(1-x)O(2-delta)surface phases, and the influence of the incorporation of non-reducible trivalent REE cations, with sizes smaller (Y3+) and larger (La3+) than Ce(4+)and Ce3+. For all nanocatalysts, a reduction treatment at a minimum temperature of 900 degrees C was required to accomplish a significant cerium diffusion. Notwithstanding, the size of the dopant noticeably affected the extent of this diffusion process. As compared to the undoped ZrO2-CeO(2)sample, Y(3+)incorporation slightly hindered the cerium diffusion, while the opposite effect was found for the La3+-doped nanocatalyst. Furthermore, such differences in cerium diffusion led to changes in the surface and nanostructural features of the oxides, which were tentatively correlated with the redox response of the thermally aged samples.