Design of thin-film nanocatalysts for on-chip fuel cell technology

Article CUP, CNR & FAU - JPC Letters

Epitaxial Cubic Ce2O3 Films via Ce–CeO2 Interfacial Reaction


ACS Journal of Physical Chemistry Letters 4 (6), 866 (2013) - read more on ACS pages

Vitalii Stetsovych, Federico Pagliuca, Filip Dvořák, Tomáš Duchoň, Mykhailo Vorokhta, Marie Aulická, Jan Lachnitt, Stefan Schernich§, Iva Matolínová, Kateřina Veltruská, Tomáš Skála, Daniel Mazur, Josef Mysliveček*,†, Jörg Libuda§, and Vladimír Matolín

Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Universitàdi Modena e Reggio Emilia and S3, Istituto Nanoscienze - CNR, Via G. Campi 213/a, 41125 Modena, Italy
§ Lehrstuhl für Physikalische Chemie II and Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany

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.