Influence of high temperature treatments under net oxidizing and reducing conditions on the oxygen storage and buffering properties of a Ce0.68Zr0.32O2 mixed oxide

TPR, TPO, O-2 pulses and magnetic balance experiments have been performed t o study the effect of two different aging treatments, in oxidizing atmosphe re and in reducing conditions, on the redox behavior of a Ce0.68Zr0.32O2 mi xed oxide. It has been observed that, although the samples resulting from both treatme nts have similar textural properties, their redox behavior is significantly different. In particular, aging in H-2 improves the oxygen storage capacit y (OSC) at low temperatures by decreasing the temperature at which reductio n takes place. Also, the oxygen buffering capacity (OBC) is enhanced after aging under reducing conditions. Ln addition, the study of the re-oxidation of the samples reveals that the rate of the O-2 uptake increases if compar ed with the fresh sample or that aged in air. High resolution electron micr oscopy and Raman spectroscopy data have also been used to obtain informatio n on the possible origin of such effects. (C) 1999 Elsevier Science B.V. Al l rights reserved.