Thermal stability of oxygen storage properties in a mixed CeO2-ZrO2 system

TLDR: In this paper, a low temperature (500°C) route for calcination of hydroxide precipitates and firing mixtures of acetates was investigated and the results showed that the addition of zirconia increased the oxygen storage capacities over ceria alone for both preparation methods.

Abstract: CeO 2 and CeO 2 /ZrO 2 supports were prepared by two low temperature (500°C) routes: calcination of hydroxide precipitates and firing mixtures of acetates. The supports were loaded with 0.5% Pt and characterized both fresh and aged (at 800 and 1000°C). X-ray diffraction analyses show that a CeO 2 /ZrO 2 solid solution is formed in the samples prepared by precipitation of the hydroxides and calcination at 500°C. To our knowledge this is the lowest temperature chemical route (not including high energy ball milling) to CeO 2 /ZrO 2 solid solutions yet reported. Samples prepared by firing the acetate mixtures had almost exclusively CeO 2 and ZrO 2 in separated phases. Oxygen storage measurements showed that the addition of zirconia increased the oxygen storage capacities (on a per gram of catalyst basis) over ceria alone for both preparation methods. In the phase separated materials the amount of reversibly stored oxygen was 1.7–2.5 times more per gram catalyst than that of ceria only. The beneficial effects of zirconia are most pronounced in the solid solutions which had oxygen storage 3–5 times higher than ceria. When the Zr concentration is optimized, the solid solution materials aged at 1000°C showed higher oxygen storage than fresh CeO 2 . For both preparation methods, the optimal (per gram catalyst) Zr concentration was found to be 25 mol% Zr for samples aged at 1000°C, however, the performance of the solid solution materials was somewhat insensitive to Zr loading between 15 and 50 mol% Zr.