OXYGEN ABSORBING AND RELEASING MATERIAL, CATALYST, EXHAUST GAS PURIFYING SYSTEM, AND EXHAUST GAS TREATMENT METHOD

The problem to be solved by the present invention is to provide an oxygen storage and release material comprising a ceria-zirconia-based complex oxide improved in ability to remove HC and NOx and a three-way catalyst able to reduce an amount of NOx emission. Further, to solve this problem, an oxygen storage and release material comprising a ceria-zirconia-based complex oxide containing Gd2O3in 0.1 mol% or more and less than 20 mol% and having an ion conductivity of 2×10-5S/cm or more at 400°C is provided. Further, in addition to the above, an oxygen storage and release material having a molar ratio of cerium and zirconium of 0.2 or more and 0.6 or less by cerium/(cerium+zirconium) and an speed of oxygen storage and release "Δt50" of 20.0 seconds or more or amount of oxygen storage and release of 300 µmol-O2/g or more etc. was obtained. Further, by applying the oxygen storage and release material to the catalyst, it is possible to assist the purification of exhaust gas as it changes every instant in accordance with the driving conditions and possible to obtain a catalyst with a higher ability to remove harmful components of catalytic precious metals than before. In particular, it is possible to obtain an automotive exhaust gas purification system excellent in ability to remove CO, NOx, and HC.