Epitaxial Cubic Ce₂O₃ Films via Ce–CeO₂ Interfacial Reaction

Abstract

Thin films of reduced ceria supported on metals are often applied as substrates in model studies of the chemical reactivity of ceria based catalysts. Of special interest are the properties of oxygen vacancies in ceria. However, thin films of ceria prepared by established methods become increasingly disordered as the concentration of vacancies increases. Here, we propose an alternative method for preparing ordered reduced ceria films based on the physical vapor deposition and interfacial reaction of Ce with CeO2 films. The method yields bulk-truncated layers of cubic c-Ce2O3. Compared to CeO2 these layers contain 25% of perfectly ordered vacancies in the surface and subsurface allowing well-defined measurements of the properties of ceria in the limit of extreme reduction. Experimentally, c-Ce2O3(111) layers are easily identified by a characteristic 4 × 4 surface reconstruction with respect to CeO2(111). In addition, c-Ce2O3 layers represent an experimental realization of a normally unstable polymorph of Ce2O3. During interfacial reaction, c-Ce2O3 nucleates on the interface between CeO2 buffer and Ce overlayer and is further stabilized most likely by the tetragonal distortion of the ceria layers on Cu. The characteristic kinetics of the metal-oxide interfacial reactions may represent a vehicle for making other metastable oxide structures experimentally available.

High performance sol–gel synthesized Ce0.9Sr0.1(Zr0.53Ti0.47)O4sensing membrane for a solid-state pH sensor

“…For the three spectra, the rst peak at 531.4 eV represents Ce(OH) x , the second peak at 530 eV indicates the Ce 3+ state, and the third peak at 529.1 eV indicates the Ce 4+ state. 23,24 The intensity of the O 1s peak corresponding to the Ce 2 O 3 component is lower than that of CeO 2 , but is higher relative to our previous reports (the CZT lm).…”

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

“…This probably indicates that the reduction proceeds by the formation of oxygen vacancies at random sites on the film surface or subsurface, without a detectable ordering or a significant structural rearrangement. Only at higher degrees of reduction has clear evidence for C-type Ce 2 O 3 structure stabilization been obtained using the Cu(111) [49] and the Si(111) substrates [9,14]. In the first case, the authors used a complex preparation procedure involving the deposition of metallic Ce on a CeO 2 buffer layer, followed by 900 K annealing [49].…”

A novel thermophotocatalyst of mixed-phase cerium oxide (CeO2/Ce2O3) homocomposite nanostructure: Role of interface and oxygen vacancies

“…In spite of having unfavorable band edge location with respect to the redox potential for dissociation of water molecules, many of its complementary attributes make ceria an interesting photo/catalyst material. An important property of ceria-based catalysts is its high oxygen storage capacity and its ability to release or uptake oxygen depending on switching between Ce 4 þ /Ce 3 þ redox cycles [1]. As a result it finds diverse applications in photocatalysis, fuel reforming (in solid oxide fuel cell), thermal catalysis, UV blocking/shielding, solar cell, material polishing, and as luminescent material [2][3][4][5][6].…”