Atomic Scale Structure and Reduction of Cerium Oxide at the Interface with Platinum

Abstract

A detailed atomic scale description of the interfaces between cerium oxide and metals is necessary for a clear understanding of interfacial interactions, and it may open the way to the optimization of the properties of the combined material in view of its applications. In this study the interface between cerium oxide epitaxial fi lms and the (111) surface of platinum is studied\ud by aberration-corrected scanning transmission electron microscopy and by ab initio density functional theory calculations. Local modifi cations of the registry between the cerium oxide and platinum lattices and the occurrence of nanometric platinum islands at the interface are detected by high-angle annular dark fi eld imaging. Moreover, the preferential adsorption sites of Ce and O atoms at the interface are determined by a comparison of the images acquired in annular bright-fi eld mode and the results of density functional theory calculations. The presence of a non-negligible concentration of Ce 3+ ions at the interface is detected by electron energy loss spectroscopy and it is rationalized in terms of interfacial charge transfer as evidenced by the calculations. This work provides an insight into the atomic and electronic structure of the technologically relevant CeO 2 /Pt interface and it helps to clarify the\ud properties of the combined material

Electronic properties of epitaxial cerium oxide films during controlled reduction and oxidation studied by resonant inelastic X-ray scattering

“…In cerium oxide ultrathin films the interaction with the metallic substrate has been hypothesized to be responsible for the formation of ordered arrays of oxygen vacancies either on the surface 11 of a thin film or at the interface 37 . In the specific case of Pt we have shown that an in-plane lattice contraction is induced by epitaxy in ultrathin films 38 , and we detected a non-negligible Ce 3+ concentration at the interface 35 . The latter effect may certainly modify the surface oxygen vacancy formation energy in thinner films, while it is expected to have a negligible effect on the surface of thicker films, possibly explaining the higher reducibility observed on the 2 ML film.…”

Structure, Morphology and Reducibility of Epitaxial Cerium Oxide Ultrathin Films and Nanostructures

“…The interface electronic configuration was shown to be dominated by charge rearrangements due to electrostatic interactions, but some charge transfer from the substrate to the oxide was also detected [33]. On 3 ML thick films, a different absorption geometry was found to be the most stable, as confirmed by STEM measurements [32]. …”

“…A measurable, though incomplete, reduction has been measured by spatially resolved electron energy loss also for the cerium ions at the interface with the Pt(111) surface [32]. The charge transfer, probably influenced by the metal work function, which is lower for the copper substrate, certainly also modifies other properties in the film, such as its reducibility and reactivity.…”

Understanding CeO2‐Based Nanostructures through Advanced Electron Microscopy in 2D and 3D

“…The interface between CeO 2 epitaxial films and the (111) Pt surface is also studied by a combination of AC‐STEM and ab initio density functional theory . A statistical analysis of the size of the coincidence cells indicates that the registering locally changes from 3:4 to 2:3 and 5:7 without a preferential coincidence cell size ( Figure a).…”