Herein we demonstrate the extra-low-temperature oxygen storage capacity (OSC) of cerium oxide nanocrystals with cubic (100) facets. A considerable OSC occurs at 150 °C without active species loading. This temperature is 250 °C lower than that of irregularly shaped cerium oxide. This result indicates that cubic (100) facets of cerium oxide have the characteristics to be a superior low-temperature catalyst.

Monodisperse polyhedral nanoparticles (NPs) and nanorods (NRs) of cerium dioxide, CeO 2 , were synthesized by thermal decomposition of ammonium cerium(IV) nitrate, (NH 4 ) 2 Ce(NO 3 ) 6 , at 180 °C in an organic solution of oleylamine (OAm) and/or oleic acid (OA). The 4 nm CeO 2 NPs were synthesized in diphenyl ether solution of OAm and OA with the molar ratio of Ce/OAm/OA = 1:3:3, while the 6 nm CeO 2 NPs were made in 1-octadecene solution of OAm with Ce/OAm = 1:6. The NRs were formed in 1-octadecene with Ce/OAm/OA = 1:3:1.5. The CeO 2 NPs were assembled on γ-Al 2 O 3 via polyvinylpyrrolidone and were annealed at 500 °C under air to remove organic coating. They were well-dispersed on Al 2 O 3 and showed the increased oxygen storage capacity compared to the physical mixture of aggregated CeO 2 and γ-Al 2 O 3 powder. The reported CeO 2 NPs are promising for oxygen storage and release applications.

ZAWRjAÅnÌÌ_f \ÉyÚ·ZECIyÑWRjECIÌK¥zñÌe¿ {c¾FEEÇYERºÀbE]zìpvE²XØ µE·äNMEcÓ«MEY³(The CeO 2 ZrO 2 solid solution is the most important oxygen storage/release material for use in automobile catalysts. In particular, the ceriazirconia solid solution with a pyrochlore structure exhibits the highest oxygen storage capacity (OSC). In this study, CeO 2 ZrO 2 solid solutions containing Y 2 O 3 were synthesized and their OSCs were measured to clarify the influence of an ordered arrangement of Ce and Zr ions on the OSC. As a result of this study, it is concluded that an ordered arrangement of Ce and Zr ions markedly improves the OSC of CeO 2 ZrO 2 solid solutions.

The oxygen storage capacity (OSC) of a ceriazirconia(CeO 2 ZrO 2 ) solid solution containing 50 mol÷ ZrO 2 is approximately 400 mmolO 2 /g, which corresponds to approximately 50÷ of the theoretical OSC limit calculated from the valence change of the Ce ion. There are two possible explanations for the OSC suppression of approxi mately 50÷ of the theoretical OSC limit. The first mechanism is based on the thermodynamic reaction equilibri um; the second one is based on chemical kinetics. To clarify the reason for the suppression, the effect of the specific surface area of CeO 2 ZrO 2 solid solutions was estimated by measuring the OSC of CeO 2 ZrO 2 solid so lutions with 3 levels of specific surface area. OSC was independent of the specific surface area of the CeO 2 ZrO 2 solid solutions in the composition range 60 mol÷ ZrO 2 . The amount of bulk oxygen, which is released from inside the crystal lattice, could be estimated to be constant even though the specific surface area of the material changed in the composition range 50 mol÷ ZrO 2 . Therefore, the mechanism of the OSC suppression was the thermodynamic equilibrium of the redox reaction of CeO 2 ZrO 2 solid solutions.

à/ZAWRjAÅnÌÌ_f \ÉyÚ·àSÊÌe¿ {c¾FERºÀbE]zìpvEEÇYEcÓ«ME·äNME òEY³( )Lc¤G}¤ºC4801192 ¤m §·vè¬As an important oxygen storage material, ceriazirconia solid solution is widely used in automotive threeway catalysts. For the CeZr solid solution being usually used with a noble metal, the evaluation of oxygen storage capacity (OSC) should be conducted with the CeZr solid solution loaded with a noble metal. The measured OSC of noblemetalloaded CeZr solid solution consists of two parts: the stored oxygen within the solid solu tion itself and the adsorbed oxygen on the loaded noble metal particles. Therefore, it is very necessary to clarify the influence of metal loading on the measured OSC in order to ascertain the exact OSC of the solid solution it self. In this research, the authors attempted to clarify the above issues by characterizing the OSC performance of CeZr solid solutions with platinum (Pt) loading from 0.000110 mass÷. We found that increasing the amount of Pt loading increases the oxygen storage and release rates and that increasing the temperature also increases the oxygen storage rate, although the oxygen release rate is not affected by increasing the temperature. The apparent OSC reached saturation over a certain amount of Pt loading and temperature. The saturated OSC increased with increasing temperature.