A homogeneous ceria-based mixed-
metal oxide, useful as a
catalyst support, a co-catalyst and / or a
getter has a relatively large surface area per weight, typically exceeding 150 m<2> / g, a structure of nanocrystallites having diameters of less than 4 nm, and including pores larger than the nanocrystallites and having diameters in the range of 4 to about 9 nm. The ratio of pore volumes, VP, to skeletal structure volumes, VS, is typically less than about 2.5, and the surface area per
unit volume of the
oxide material is greater than 320 m<2> / cm<3>, for low internal
mass transfer resistance and large
effective surface area for reaction activity. The
mixed metal oxide is ceria-based, includes Zr and or Hf, and is made by a novel co-
precipitation process. A highly dispersed catalyst
metal, typically a
noble metal such as Pt, may be loaded on to the
mixed metal oxide support from a catalyst
metal-containing solution following a selected acid surface treatment of the oxide support. Appropriate ratioing of the Ce and other metal constituents of the oxide support contribute to it retaining in a cubic phase and enhancing catalytic performance.
Rhenium is preferably further loaded on to the mixed-metal oxide support and passivated, to increase the activity of the catalyst. The metal-loaded mixed-metal oxide catalyst is applied particularly in
water gas shift reactions as associated with fuel
processing systems, as for
fuel cells.