Effect of Thermal Aging on the Transient Kinetics of Oxygen Storage and Release of Commercial CexZr1-xO2-based Solids

The use of powerful analytical methodologies for the evaluation of the performance of commercial oxygen storage materials based on oxygen transient isothermal isotopic exchange experiments is illustrated in this study. CexZr1-xO2-based oxygen storage materials were investigated. The materials were characterized for their dynamic oxygen storage and release properties through the pulse injection technique allowing the measurement of the oxygen storage capacity (OSC), and for their surface and bulk oxygen mobility through transient isothermal O-18 isotopic exchange experiments. Very high OSC values were obtained after calcination in air at T-calc. = 700 or 850 degrees C. However, after thermal aging at 1000 or 1100 degrees C of the as prepared samples, a significant deterioration of their OSC was observed. This fact was found to correlate with the significant increase in the activation energy of surface oxygen mobility. On the contrary, smaller increase in the activation energy of bulk oxygen diffusion with increasing T-calc. was observed.