Redox behavior of high-surface-area Rh, Pt-, and Pd-loaded Ce0.5Zr0.5O2 mixed oxide

The temperature programmed reduction, oxygen uptake, and surface area stabi lity of high-surface-area Rh-, Pt-, and Pd-loaded Ce0.5Zr0.5O2 solid soluti on have been investigated. It is observed that the presence of the noble me tal strongly favors the reduction of the support compared with the metal-fr ee Ce0.5Zr0.5O2. A further improvement is observed on sintering induced by repetitive reduction/oxidation processes. Indeed, the temperature of suppor t reduction decreases from 650-950 to about 450 K for the Rh- and Pt-loaded samples and to 520 K in the presence of Pd. In contrast, the low-temperatu re reduction of Rh/CeO2 (surface area 194 m(2) g(-1)) is strongly encumbere d after such treatments. The roles of noble metal and added ZrO2 in promoti ng low-temperature reduction are discussed. (C) 1999 Academic Press.