Flame-made nanocrystalline ceria/zirconia: structural properties and dynamic oxygen exchange capacity

Ceria/zirconia nanocrystals were prepared by flame-spray synthesis. Application of carboxylic acid-derived solvents allowed the continuous production of homogeneous mixed oxides with narrow particle-size distribution. The high preparation temperature favored the formation of a highly crystalline solid solution of the constituents. Structural and textural properties of the ceria-zirconia nanoparticles were characterized by high-resolution electron microscopy, nitrogen adsorption, and X-ray diffraction. The redox properties of the nanoparticles were investigated by temperature-programmed reduction and by dynamic oxygen exchange capacity (OEC) measurements using H2, CO, and propene as reductants. For CO and H2 a similar reduction was found, whereas propene afforded a considerably higher degree of reduction. While the flame-made powders had very stable specific surface area (up to 80 m2/g) even after severe calcination (2 h at 900 °C in air) their OEC was lower than in corresponding ceria-zirconia prepared by coprecipitation. This difference is traced to the high crystallinity and low defect concentration of the flame-made material.