Ce1-xMnxO2 mixed oxides were used as supports for preparing 7%CuO/Ce1-xMnxO2 catalysts by impregnation for the preferential oxidation (PROX) of CO in excess hydrogen. Incorporating an appropriate amount of manganese into CeO2 to form Ce1-xMnxO2 solution increased the mobility of lattice oxygen and improved performance of CuO/Ce1-xMnxO2 catalysts in the PROX of CO. CO oxidation proceeded at the interfacial perimeter through an interaction between CuO clusters and Ce1-xMnxO2, involving not only the redox behavior of CeO2 but also that of MnOx. The PROX reaction was not weakened as the fraction of manganese incorporated in the 7%CuO/Ce1-xMnxO2 catalysts increased up to 0.3. A small amount of doped Me and an appropriate amount of incorporated Al2O3 could obtain a good candidate such as 7%CuO/Ce0.9Mn0.1O2-20%Al2O3 for a PROX unit in a polymer electrolyte membrane fuel cell system for removing CO. Its activity was comparable with, and its selectivity was much larger than, that of the noble catalyst 5%Pt/Al2O3. (C) 2011 Elsevier B.V. All rights reserved.