THE EFFECTS OF NONSTOICHIOMETRY AND DOPANTS IN NANOCRYSTALLINE CERIUMOXIDE-BASED CATALYSTS ON REDOX REACTIONS

Nanocrystalline pure and doped non-stoichiometric CeO2-x were synthesi zed by inert gas condensation. These materials were investigated as ca talyst for redox reactions such as SO2 reduction by CO, and CO oxidati on by O-2. By controlling the stoichiometry of the oxide catalyst the effect of bulk oxygen-deficiency on surface catalytic activity was rev ealed. Nanocrystalline CeO, catalysts exhibited high catalytic activit y, reversibility, and excellent resistance against deactivation by CO2 . Cu-doping of CeO2-x was found to further promote catalytic activity. Nanocrystalline homogeneous Cu-Ce mixed-metal oxide was synthesized b y magnetron sputtering from a mixed metal target. Annealing at 650 deg rees C resulted in Cu segregation and formation of CuO clusters. Catal ytic activity in CO oxidation by O-2 was not affected by this annealin g treatment. STEM Cu elemental mapping illustrated that although some large CuO clusters were formed in thermal treatments, substantial Cu s till remained highly dispersed.