Ceria Nanocrystals Exposing Wide (100) Facets: Structure and Polarity Compensation

Abstract

Compact CeO₂(111) films grown on Ru(0001) can be transformed into well-shaped nanoparticles by annealing them in an oxygen-poor environment. With increasing temperature, the particles undergo a distinct shape evolution that finally leads to crystallites exposing wide (100) facets. The atomic structure of the (100) termination is determined with a combination of high-resolution scanning tunneling microscopy and density functional theory. Two surface reconstructions are identified that are compatible with the need to compensate for the intrinsic dipole of the (100) plane and with a substantial reduction of the oxide material. Our study provides insights into the rarely explored (100) surface of ceria, which can be considered as model system for studying chemical processes on the polar termination of reducible oxides

Water‐Gas‐Shift over Metal‐Free Nanocrystalline Ceria: An Experimental and Theoretical Study

“…DFT calculations were performed to clarify the energetics of H 2 O and CO interaction with ceria substrates, to investigate the possible role of reduced ceria, and to suggest plausible reaction pathways for the WGS. The adsorption on the most stable reconstruction of the (1 0 0) surface leads to strongly bound CO and H 2 O Figure S4). Furthermore, the lattice expansion observed in XRD and the presence of Ce 3+ species revealed by XAS could be indicative of the presence of O vacancies.…”

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

“…Nilius et al have assigned the rectangular features to (100)-oriented nanostructures and they identified, by a comparison with DFT calculations, the mechanism for the stabilization of the polar surface in the formation of two different surface reconstructions, namely (2 × 2) and c (2 × 2) [24]. As previously mentioned, rectangular (100)-oriented cerium oxide islands were also stabilized on the Cu(111) surface [25,34].…”

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

“…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. 34 Work by Mullins and coworkers shows that the CeO 2 (100) surface is more active but less selective than CeO 2 (111) for dehydrogenation of alcohols, 35 and more recent work reveals very different activities of CeO 2 (111) and CeO 2 (100) with respect to hydrogenation and oxidation reactions, 31 clearly demonstrating that the surface chemical properties of ceria can depend sensitively on the surface structure. These findings highlight the need to advance the basic understanding of REO surface structure-reactivity relationships, and they motivate further efforts to develop model REO thin films with orientation other than (111).…”