Three-Dimensional Tomographic Analyses of CeO₂ Nanoparticles

Abstract

A detailed morphological and structural analysis of CeO 2 nanoparticles has been performed using electron tomography in scanning transmission mode in high angle annular dark field. The nanoparticles have been prepared through a solvothermal synthesis assisted by microwave heating. An adequate choice of the synthesis parameters leads to particles with various well-defined morphologies: cubes, octahedrons, and nanorods. In the case of cubic CeO 2 nanoparticles, the three-dimensional analysis allowed us to precisely calculate the type and the proportion of the minor facets exposed at the nanoparticle surface. For the CeO 2 nanoparticles with an octahedron shape, it has been demonstrated that the ambiguous interpretation of the objects giving triangular views in classical transmission electron microscopy can be prevented; furthermore, precise assignments of their external shape, surface crystallography, and type of minor facets were realized. In the case of nanorods, it was shown that the external shape and the transversal symmetry are strongly dependent on the nanorod sizes. The presence of a well-defined porosity inside the rods was also evidenced thanks to the ability of the electron tomography to solve the internal structure of a nano-object.

Adsorption and Reaction of Acetaldehyde on Shape-Controlled CeO2 Nanocrystals: Elucidation of Structure–Function Relationships

“…Because the cracking fragments for acetaldehyde and the products have considerable overlap in the mass spectrum, the analysis required that QMS mass intensities be corrected. This correction was performed as described previously, 7 by creating a matrix containing the mass fragment intensities for each product (acetaldehyde, H 2 , methane, H 2 O, CO, ethanol, O 2 , CO 2 , 1,3-butadiene, 2-butene, crotyl alcohol, acetone, furan, crotonaldehyde, benzene, and toluene) contributing to the masses of 2, 15,18,28,29,31,32,44,54,56,57,58,68,70,78, and 90 and solving the resulting equation to convert mass intensity to product yield (partial pressure). The mass fragment intensities were corrected for QMS sensitivity parameters, including ionization efficiency, quadrupole transmissions, and multiplier gain, as described previously.…”

“…21,27,28 However, recent results suggest that, depending on the annealing treatment, CeO 2 wires and rods could actually expose a variety of facets, including {111} facets, and possess large numbers of nanoscopic structural defects. 29 Here, the structure of the CeO 2 wires will be referred to as a defect structure. CeO 2 is known to possess strong basic sites and weaker acidic sites.…”

Growth, Structure, and Stability of the High-Index TbOx(112) Surface on Cu(111)

“…Determining such relationships is particularly important for understanding the surface chemical properties of REO nanoparticles, which expose multiple types of facets. 28,29 Recent work has focused on the chemical properties of CeO 2 (100) in the form of well-defined thin films 30 as well as nanocrystal shapes. 31 Researchers have also shown that both CeO x (100) and (111) orientated nanoparticles can coexist on Cu(111), 32,33 and it has been reported recently that CeO x (100) islands can be produced on Ru(0001) by annealing in an oxygen-depleted environment.…”

The Characterization and Structure-Dependent Catalysis of Ceria with Well-Defined Facets

“…Florea et al performed tomographic analysis of CeO 2 cubes, octahedra, and wires to give an insight into the nature of the surface terminations and faceting ( Figure 2) [97]. For example, ideal cubes would expose six {100} facets, while octahedra would expose only {111} facets.…”

“…For example, ideal cubes would expose six {100} facets, while octahedra would expose only {111} facets. However, tomographic studies found that the rods are porous and the surface is rough, resulting in a highly defective surface that can have pentagonal or hexagonal geometries depending on the synthesis conditions and diameter of the rods [97]. Therefore, it is important to be able to determine the extent of faceting on their surfaces, edges, and corners.…”