The development of a more efficient oxygen storage material is a very important approach for the optimization of automotive catalysts. To investigate the influence of the physical parameters, the Pt particle size and specific surface area (SSA) on the OSC (oxygen storage capacity) performance of the Pt/CeO2-ZrO2-Y2O3 (CZY) catalysts, a series of Pt/CZY catalysts were prepared and characterized. The OSC performance was evaluated by CO oxidation from 200 to 400 degrees C, while alternately feeding CO(2.0 vol%)/N-2 and O-2 (1.0 vol%)/N-2 for 60 s at a flow rate of 7.01/min. The CO2 generation was analyzed continuously and used to indicate the OSC performance and oxygen storage/release behavior. The oxygen surface diffusion and bulk diffusion rates on the catalysts were further characterized by the O-18/O-16 isotopic exchange reaction and correlated with the OSC performances. The characterization results of the Pt particle size and SSA of the Pt/CZY catalysts indicated that the Pt particle size and SSA of Pt/CZY appeared to be a hyperbolic distribution, being interdependent and difficult to control independently. OSC performance results by CO oxidation at 200 and 300 degrees C showed that smaller Pt particle size favored OSC performance and appeared to be the optimum around 70 m(2)/g for the SSA. This corresponds with the oxygen mobility results obtained from the O-18/O-16 isotopic exchange reaction at 400 degrees C, that is, the oxygen surface and bulk diffusion showed a peak at the Pt particle size of 6 nm and an SSA of 40 m(2)/g. (C) 2008 Elsevier Ltd. All rights reserved.