XANES STUDIES OF THE REDUCTION BEHAVIOR OF (CE1-YZRY)O-2 AND RH (CE1-YZRY)O-2/

Using X-ray absorption near-edge spectroscopy (XANES) at the Ce L-III edge, we have measured the extent of reduction of Rh-loaded and Rh-fre e, mixed Ce-Zr oxides under hydrogen as a function of temperature. The high surface area, mixed oxides were synthesized by sol-gel technique s and hypercritical drying. Using a simple spectrum subtraction method , the degree of reduction has been measured and compared with previous results for CeO2 and (Ce0.5Zr0.5)O-2 Addition of Zr lowers the temper ature of reduction and increases the extent of Ce reduction. Rh cataly zes the reduction process at low temperatures but does not substantial ly affect the extent of reduction achieved at high temperature. A syne rgism between Rh and Zr is found which leads to very high reducibility in the range of 400-600 K.