Surface area control during the synthesis and reduction of high area ceria catalyst supports

Precipitation of ceria from (NH4)(2)[Ce(NO3)(6)] with a 'ammonium carbonate' solution produces powders, with surface areas determined by the initial [Ce] concentrations. Samples, free of carbonate impurities and with reproducible surface areas of up to 200 m(2) g(-1), have been obtained after controlled dehydration and calcination to 600 degrees C. Temperature-programmed reduction (in 3% H-2/N-2) of samples with a range of surface areas, has confirmed that the net hydrogen uptake by ceria between 120 and 700 degrees C comprises two components. The first is a constant amount which represents sorption of interstitial hydrogen into the ceria lattice. The second is proportional to the surface area of the sample and originates from partial reduction of surface Ce-IV and hydroxylation of the surface oxide.