Effect of Ordered Arrangement of Ce and Zr Ions on Oxygen Storage Capacity of Ceria-Zirconia Solid Solution

Abstract

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.

Some recent results on the correlation of nano-structural and redox properties in ceria-zirconia mixed oxides

“…Accordingly, a considerable research effort has been devoted to gain a deeper understanding of the structural changes induced on the oxides by the ageing cycles mentioned above. A number of techniques, including X-ray diffraction (XRD) [13,14,18,20,23,24,31], EXAFS [29,30,31], Raman spectroscopy [14,17,18,24], High Resolution Electron Microscopy (HREM) [21,22,25,26] and High Angle Annular Dark Field Scanning-Transmission Electron Microscopy (HAADF-STEM) [25] have been applied in these structural investigations. Among them, XRD, Raman spectroscopy, and more recently HREM and HAADF-STEM have been the most extensively applied ones.…”

“…Despite the difficulty inherently associated to the eventual occurrence of such a large variety of phases, there are some structural facts which may be considered as well established. As outlined by a number of authors [13,18,20,23,26] order ↔ disorder phenomena induced on the Ce-Zr cationic sublattice by the SR-MO and SR-SO ageing treatments would play an essential role in determining their redox response. In effect, it is generally acknowledged that associated to SR-type reduction treatments an oxygen deficient, cation-ordered, pyrochlore-type phase, is formed.…”

“…If this reduced phase is further re-oxidised under mild conditions (MO), the cationic sub-lattice remains unmodified and a highly active oxidized pyrochlore (-like phase) is formed. The occurrence of Ce-Zr ordering in the -like phase is experimentally evidenced by the appearance of characteristic super-structure features in the XRD diagrams [18,20,23], as well as in the HREM [25,26] and HAADF-STEM [25] images of this phase. Fig.…”

“…Particularly noticeable are the reversible changes of reducibility induced on the ceria-zirconia samples by appropriate modification of the thermal ageing conditions [13][14][15]. Because of the very challenging nature of this phenomenon, numerous studies have dealt with this topic in recent years [16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Effect of preparation procedure on the formation of nanostructured ceria–zirconia mixed oxide catalysts for ethyl acetate oxidation: Homogeneous precipitation with urea vs template-assisted hydrothermal synthesis

“…The facilitated effect of Ce 4+ precursor instead of Ce 3+ one on the preparation of homogeneous bi-component material is reported in [20]. Suda et al [43] established that wet milling process provided formation of solid solution with complex morphological content. Sellick et al [11] reported minor increase of catalytic activity in naphthalene oxidation with Zr addition when precipitation by urea instead of carbonate was used.…”