Preparation and characterization of nanocrystalline, high-surface area Cu-Ce-Zr mixed oxide catalysts from homogeneous co-precipitation

Cu0.23Ce0.54Zr0.23-mixed oxides were prepared by homogeneous co-precipitation with urea. The resulting materials exhibit high-surface area and nanocrystalline primary particles. The material consists of a single fluorite-type phase according to XRD and TEM. STEM–EDS analysis shows that Cu and Zr are inhomogeneously distributed throughout the ceria matrix. EXAFS analysis indicates the existence of CuO-like clusters inside the ceria–zirconia matrix. The pore structure and surface area of the mixed oxides are affected by preparation parameters during both precipitation (stirring) and the following heat treatment (drying and calcination). TPR measurements show that most of the copper is reducible and not inaccessibly incorporated into the bulk structure. Reduction–oxidation cycling shows that the reducibility improves from the first to the second reduction cycle, probably due to a local phase segregation in the metastable mixed oxide with gradual local copper enrichment during heat treatment.