Chlorine-free, finely textured three-dimensionally ordered macroporous mixed oxides of nominal composition Zr0.6Ce0.4O2 were prepared by the opal template technique. Electron microscopy showed a well-defined porosity that can be controlled with the infiltration process. By using thermal analysis and X-ray photoelectron spectroscopy (XPS), the oxygen storage and the redox response to different environments have been investigated. Multiple high temperature oxidation-reduction cycles decrease the initial high sensitivity of the surface oxidation state of Ce to the environment (aging processes). This has been ascribed to the development of Ce(III)-rich phases. Analysis of X-ray diffraction, energy-dispersive X-ray spectroscopy, and photoemission data indicated the coexistence of a Zr-rich and a Ce-rich phase. In XPS, we observe binding energy shifts in consequence of the redox treatments and explain them as shifts of the Fermi level linked to variations in the Ce oxidation state. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3474223] All rights reserved.