NOVELTY - A homogeneous, nanocrystalline, mixed metal oxide of cerium and other metal constituent(s) has a surface area of at least 150 m2/g, average crystallite size less than 4 nm and agglomerated to form a skeletal structure with pores, average pore diameters of greater than 4 nm and normally greater than average crystallite size. The surface area of the skeletal structure per volume of the material of the structure is greater than 320 m2/cm3.    USE - Used as catalyst support, co-catalyst or getter for water gas shift and/or preferential oxidation reactions (claimed) in fuel processing systems for fuel cells.    ADVANTAGE - The ceria-based mixed metal oxides are stable, have high surface areas, small crystallites and meso-pores and pore volumes sized to optimally balance the reduction of mass transfer resistance. They have enhanced redox capability.    DETAILED DESCRIPTION - A homogeneous, nanocrystalline, mixed metal oxide of cerium and other metal constituent(s) consisting of zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum (Ta), lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), molybdenum (Mo), tungsten (W), rhenium (Re), rhodium (Rh), antimony (Sb), bismuth (Bi), titanium (Ti), vanadium (V), manganese (Mn), cobalt (Co), copper (Cu), gallium (Ga), calcium (Ca), strontium (Sr), or barium (Ba), has a surface area of at least 150 m2/g, average crystallite size less than 4 nm and agglomerated to form a skeletal structure with pores, average pore diameters of greater than 4 nm and normally greater than average crystallite size. The surface area of the skeletal structure per volume of the material of the structure is greater than 320 m2/cm3. INDEPENDENT CLAIMS are also included for:    (1) a process for the preparation of the mixed metal oxide including dissolving urea and salts in the Ce and the other metal constituent(s) in water to form a dilute metal salt solution; heating the solution to near boiling and coprecipitating homogeneously an oxide of the Ce and the other constituent as a nanocrystalline coprecipitate; replacing water existing in the coprecipitate with a water miscible, low surface-tension solvent that displaces water; drying the coprecipitate to remove all of any remaining water and the solvent; and calcining the dried coprecipitate at a moderate temperature for an interval sufficient to remove adsorbed impurities; and    (2) a process (P2) for the preparation of the catalyst, comprising contacting the mixed metal oxide with a solution containing an acid consisting of amino acids, hydroxy dicarboxylic acids, hydroxy polycarboxylic acid, or keto polycarboxylic acids to treat the surface of the mixed metal oxide; and loading the surface-treated, mixed metal oxide with the noble metal by contacting the surface-treated mixed metal oxide with a solution containing the noble metal.