High Temperature Growth of CeOx on Au 111 and Behavior under Reducing and Oxidizing Condition

Inverse oxide metal model catalysts can show superior activity and selectivity compared with the traditional supported metal oxide architecture, commonly attributed to the synergistic overlayer support interaction. We have investigated the growth and redox properties of ceria nanoislands grown on Au 111 between 700 and 890 C, which yields the CeO2 Au 111 model catalyst system. We have observed a distinct correlation between deposition temperature, structural order, and oxide composition through low energy electron microscopy, low energy electron diffraction, intensity voltage curves, and X ray absorption spectroscopy. Improved structural order and thermal stability of the oxide have been achieved by increasing the oxygen chemical potential at the substrate surface using reactive oxygen O O2 instead of molecular O2 during growth. In situ characterization under reducing H2 and oxidizing atmospheres O2, CO2 indicates an irreversible loss of structural order and redox activity at high reduction temperatures, while moderate temperatures result in partial decomposition of the ceria nanoislands Ce3 Ce4 to metallic cerium Ce0 . The weak interaction between Au 111 and CeOx would facilitate its reduction to the Ce0 metallic state, especially considering the comparatively strong interaction between Ce0 and Au0. Besides, the higher reactivity of atomic oxygen promotes a stronger interaction between the gold and oxide islands during the nucleation process, explaining the improved stability. Thus, we propose that by driving the nucleation and growth of the ceria Au system in a highly oxidizing regime, novel chemical properties can be obtained