XANES studies of the reduction behavior of (Ce1-yZry)O2 and Rh/(Ce1-yZry)O2

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-free, mixed Ce-Zr oxides under hydrogen as a function of temperature. The high surface area, mixed oxides were synthesized by sol-gel techniques 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 temperature of reduction and increases the extent of Ce reduction. Rh catalyzes the reduction process at low temperatures but does not substantially affect the extent of reduction achieved at high temperature. A synergism between Rh and Zr is found which leads to very high reducibility in the range of 400-600 K.