Characterization of high surface area Zr-Ce(1 : 1) mixed oxide prepared bya microemulsion method

A Zr-Ce mixed oxide with ca. a 1:1 atomic ratio is prepared by a microemuls ion method and studied by X-ray diffraction, transmission electron microsco py, and Raman, X-ray photoelectron (XPS) and electron paramagnetic resonanc e (EPR) spectroscopies. The results show-the formation of a high surface ar ea material (S-BET = 96 m(2) g(-1)) constituted by homodispersed particles of a major pseudocubic phase t" (as shown by Raman); the stabilization of t he latter phase, instead of the normally more stable tetragonal phase t', i s probably due to the small crystallite size (ca.. 5 nm). XPS indicates a m oderate degree of surface enrichment in cerium. An EPR study is carried out on the superoxide species formed on the material by O-2 adsorption after o utgassing at temperatures up to T-v = 773 K; this shows that the reduced su rface centers thermally formed on this mixed oxide are similar to those fou nd on pure ceria but are generated more easily than on the latter, thus evi dencing a surface redox reactivity higher than that of the CeO2 single oxid e.