Supported bimetallic catalysts have been shown to improve properties and catalytic performance of monometallic catalysts in various fuel conversion reactions. To investigate the effect of support on bimetallic Pt-Cu system, Pt-Cu supported on gamma-Fe2O3 and CeO2 were synthesized using electron beam irradiation method and preferential CO oxidation (PROX) performance was investigated in relation to structural and chemical properties of the catalysts. The difference in performance among the catalysts existed in both oxygen transport ability and selectivity. While oxygen transport ability was influenced by support property such as crystallite size (within the comparison among catalysts supported on CeO2 and gamma-Fe2O3), selectivity was rather influenced by support material which led to clear differences in reducibility, reduction degree of catalyst, and alloying extent of Pt-Cu. CeO2-supported catalysts are unique in the view point that they were able to convert CO selectively in high CO conversion region compared to Fe2O3-supported catalyst. Pt-Cu with small CeO2 crystallite maintained high O-2 conversion (high capacity for oxygen transport) in O-2-rich atmosphere in addition to high selectivity. Compared to monometallic Cu which lost its activity in the O-2-rich wet condition, or compared to monometallic Pt which exhibited poor selectivity, Pt-Cu realized both high activity and selectivity on CeO2 of small crystallite size, leading to more than 99% of CO conversion at 100 degrees C. By modifying the structure, it was demonstrated that Pt-Cu/CeO2 system can be improved to have low-temperature activity comparable to monometallic Pt while keeping high selectivity of the original Pt Cu catalyst in the practical PROX condition. (C) 2012 Elsevier B.V. All rights reserved.