Single-Phase PrOy−ZrO2 Materials and Their Oxygen Storage Capacity: A Comparison with Single-Phase CeO2−ZrO2, PrOy−CeO2, and PrOy−CeO2−ZrO2 Materials

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High-surface-area PrO y −ZrO 2 mixed oxide, crystallized in the cubic fluorite structure, is synthesized for the first time as a single-phase material over a wide range of composition by sol−gel processing. X-ray powder diffraction shows that the material remains single phase even after thermal treatment in air to 900 °C. The oxygen storage capacity of PrO y −ZrO 2, where praseodymium undergoes Pr 3+ ↔ Pr 4+ interconversion, is assessed by temperature-programmed reduction with H 2 . The results show that there is little oxygen storage capacity unless the PrO y concentration exceeds 25 mol %. A comparison of oxygen storage capacity from similarly prepared single-phase CeO 2 −ZrO 2, PrO y −CeO 2, and PrO y −CeO 2 −ZrO 2 materials is presented. Measurements of lattice parameter and reducibility suggest that there are preferred associations that lead to PrO y −ZrO 2 and CeO 2 −ZrO 2 rather than PrO y −CeO 2 in the ternary mixed oxide. An evaluation of model Pd catalysts, using PrO y −ZrO 2 and CeO 2 −ZrO 2 as support materials, in functional tests approximating warmed-up, steady-state operation of an automotive catalyst, is also reported.