The influence of surface properties of CeO2 support on the structure of Pt-Cu bimetallic system in an aqueous-phase synthesis process using electron beam irradiation and the resulting impact on PROX performance were investigated. The exposed hydroxyls on CeO2 surface with low hydrogen-bonding water led to cluster-like Pt-Cu phase with low crystallinity and high oxidation state. It was attributed to a strong interaction of CeO2 and Pt-Cu phase. In CO atmosphere, such oxidic or fine Pt-Cu phase was reduced to platinum and partially reduced CuOx, and CeO2 was concomitantly reduced to retain carbonate species on its surface. This in turn affected catalytic performance, i.e., a significant increase in O-2 conversion was observed in an oxygen-rich PROX condition compared to a stoichiometric condition while selectivity was retained in higher level than monometallic Pt. The higher oxidation state of Pt in the excess O-2 was suggested to be responsible for the drastic change in activity. The surface chemical property of CeO2 was shown to affect PROX activity through the structure and oxidation state of Pt-Cu species which originates from metal-ceria interaction in the synthesis stage. (C) 2013 Elsevier B.V. All rights reserved.