Imaging the Atomic Surface Structures of CeO₂ Nanoparticles

Atomic surface structures of CeO₂ 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 CeO₂ 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_2–<i>x</i> terminations with oxygen vacancies. The (111) surface has an O termination. These findings can be extended to the surfaces of differently shaped CeO₂ 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