Exposed surfaces on shape-controlled ceria nanoparticles revealed through AC-TEM and water-gas shift reactivity

Aberration-corrected transmission electron microscopy and high-angle annular dark field imaging was used to investigate the surface structures and internal defects of CeO2 nanoparticles (octahedra, rods, and cubes). Further, their catalytic reactivity in the water–gas shift (WGS) reaction and the exposed surface sites by using FTIR spectroscopy were tested. Rods and octahedra expose stable (111) surfaces whereas cubes have primarily (100) facets. Rods also had internal voids and surface steps. The exposed planes are consistent with observed reactivity patterns, and the normalized WGS reactivity of octahedra and rods were similar, but the cubes were more reactive. In situ FTIR spectroscopy showed that rods and octahedra exhibit similar spectra for [BOND]OH groups and that carbonates and formates formed upon exposure to CO whereas for cubes clear differences were observed. These results provide definitive information on the nature of the exposed surfaces in these CeO2 nanostructures and their influence on the WGS reactivity

CO-PROX reactions on copper cerium oxide catalysts prepared by melt infiltration

A series of copperceriumoxidecatalysts was prepared by meltinfiltration routes using silica hollow spheres (SHS) as the support material. Their catalytic activity in CO oxidation and preferential oxidation of CO in H2 stream (PROX) strongly depends on the Cu/Ce ratio. Lower ratios resulted in higher activity, indicating that finely dispersed CuO clusters that strongly interact with ceria are the active sites. The highest activity is found for an atomic Cu/Ce ratio of 1/8. The catalystsprepared by meltinfiltration are more active than their counterparts prepared by conventional solution impregnation methods. The difference is attributed to the higher proportion of finely dispersed CuO clusters strongly interacting with ceria in the melt infiltrated catalysts