| abstract |
The purpose of the present invention is to provide: an oxygen absorbing and releasing material comprising a ceria/zirconia-based composite oxide having improved HC and NOx purification performance; and a three-way catalyst capable of reducing a NOx discharge amount. To solve said problem, the present invention provides an oxygen absorbing and releasing material, which is a ceria/zirconia-based composite oxide, containing 0.1-20 mol% (exclusive of 20 mol%) of Gd 2 O 3 and has an ionic conductivity of 2×10 -5 S/cm or more at 400°C. In addition to the above, an oxygen absorbing and releasing material is provided which is characterized in that a molar ratio of cerium to zirconium is 0.2-0.6 in terms of cerium/(cerium+zirconium), and an oxygen absorbing and releasing speed (OSC speed) Δt 50 is 20.0 seconds or more or an oxygen absorbing and releasing amount (OSC amount) is 300 μmol-O 2 /g or more. Furthermore, by applying the oxygen absorbing and releasing material to a catalyst, it is possible to obtain a catalyst which assists in the purification of exhaust gas that constantly changes according to the driving state and has a higher hazardous ingredient purification performance of precious metals than before. In particular, it is possible to obtain an automobile exhaust gas purification system having excellent CO, NOx and HC purification capacity. |