Effect of surface area and bulk structure on oxygen storage capacity of Ce0.67Zr0.33O2

The oxygen storage capacity (OSC) of Ce0.67Zr0.33O2 catalysts were investigated with CO-He pulses at 500 degrees C and CO-O-2 dynamic pulses at 300-700 degrees C after redox and hydrothermal treatments. BET, XRD, and EPR were used to study the effects of the pretreatment on the surface and bulk structures of the catalyst. The results show that during the CO-He pulses, migration of oxygen from the bulk to the surface becomes important. The rate of oxygen migration depends on the structure of the solid and the number of the oxygen vacancies in the lattice. The experiments with dynamic Pulses Of CO-O-2 reveal that DOSC is closely related to the surface area of the samples of the same composition. However, at high temperatures, oxygen in the bulk also contributes to DOSC due to bulk-to-surface migration. A mechanism describing the reaction between the surface oxygen and CO and the oxygen migration process from the bulk to the surface is proposed. (c) 2007 Elsevier Inc. All rights reserved.