A series of copper cerium oxide catalysts was prepared by melt infiltration routes using silica hollow spheres (SHS) as the support material. Their catalytic activity in CO oxidation and preferential oxidation of CO in H-2 stream (BROX) strongly depend on the Cu/Ce ratio. Lower ratios resulted in higher activity, indicating that finely dispersed CuO clusters that strongly interact with ceria are the active sites. The highest activity is found for an atomic Cu/Ce ratio of 1/8. The catalysts prepared by melt infiltration are more active than their counterparts prepared by conventional solution impregnation methods. The difference is attributed to the higher proportion of finely dispersed CuO clusters strongly interacting with ceria in the melt infiltrated catalysts. (C) 2012 Elsevier B.V. All rights reserved.