2 research outputs found
Imaging the Atomic Surface Structures of CeO<sub>2</sub> Nanoparticles
Atomic
surface structures of CeO<sub>2</sub> nanoparticles are
under debate owing to the lack of clear experimental determination
of the oxygen atom positions. In this study, with oxygen atoms clearly
observed using aberration-corrected high-resolution electron microscopy,
we determined the atomic structures of the (100), (110), and (111)
surfaces of CeO<sub>2</sub> nanocubes. The predominantly exposed (100)
surface has a mixture of Ce, O, and reduced CeO terminations, underscoring
the complex structures of this polar surface that previously was often
oversimplified. The (110) surface shows “sawtooth-like”
(111) nanofacets and flat CeO<sub>2–<i>x</i></sub> terminations with oxygen vacancies. The (111) surface has an O termination.
These findings can be extended to the surfaces of differently shaped
CeO<sub>2</sub> nanoparticles and provide insight about face-selective
catalysis
Adhesion and Atomic Structures of Gold on Ceria Nanostructures: The Role of Surface Structure and Oxidation State of Ceria Supports
We
report an aberration-corrected electron microscopy analysis of the
adhesion and atomic structures of gold nanoparticle catalysts supported
on ceria nanocubes and nanorods. Under oxidative conditions, the as-prepared
gold nanoparticles on the ceria nanocubes have extended atom layers
at the metal–support interface. In contrast, regular gold nanoparticles
and rafts are present on the ceria nanorod supports. Under the reducing
conditions of water–gas shift reaction, the extended gold atom
layers and rafts vanish. In addition, the gold particles on the nanocubes
change in morphology and increase in size while those on the nanorods
are almost unchanged. The size, morphology, and atomic interface structures
of gold strongly depend on the surface structures of ceria supports
((100) surface versus (111) surface) and the reaction environment
(reductive versus oxidative). These findings provide insights into
the deactivation mechanisms and the shape-dependent catalysis of oxide
supported metal catalysts