How the exhaust gas purifying catalyst device and an exhaust gas purification

PROBLEM TO BE SOLVED: To improve NOx purification performance within a prescribed time after switching from an HCCI combustion mode in which Nox is hardly generated to an SI combustion mode, in an exhaust gas purification catalyst device including a three-way catalyst and an oxidation catalyst.SOLUTION: An exhaust gas purification catalyst device has a constitution in which a CeZr-based complex oxide 51 having high oxygen release speed and a non-Ce-based complex oxide 71 having lower oxygen release speed than the CeZr-based complex oxide 51 are used jointly as an OSC material carrying Rh.SELECTED DRAWING: Figure 1