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Tuning the Pr valence state to design high oxygen mobility, redox and transport properties in the CeO2-ZrO2-PrOx phase diagram

hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
hal.structure.identifierInstitut de recherches sur la catalyse et l'environnement de Lyon [IRCELYON]
dc.contributor.authorFRIZON, Vincent
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorBASSAT, Jean-Marc.
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorPOLLET, Michaël
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorDURAND, Etienne
hal.structure.identifierSolvay (France)
dc.contributor.authorHERNANDEZ, Julien
hal.structure.identifierPSA Peugeot - Citroën [PSA]
dc.contributor.authorPAJOT, Karine
hal.structure.identifierInstitut de recherches sur la catalyse et l'environnement de Lyon [IRCELYON]
dc.contributor.authorVERNOUX, Philippe
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorDEMOURGUES, Alain
dc.date.issued2019-02-19
dc.identifier.issn1932-7447
dc.description.abstractEnThe preparation and characterization of pure fluorite-type phases allowed exploring the CeO2–ZrO2–PrOx (CZP) phase diagram. On the basis of magnetic susceptibility measurements, the Pr4+/Pr3+ molar ratio of several oxides annealed at T = 700 °C under air was determined; the higher the Zr content, the lower the Pr4+ concentration. Thermogravimetric analysis and temperature-programmed reduction measurements showed various Pr and Ce reduction steps. The Pr4+ reduction starts at T = 250 °C and is maximum around T = 400 °C. For the most reducible compositions, which exhibit the lowest Zr content and the highest Pr rate, the reduction phenomena strongly depend on the Pr/Ce molar ratio. As a remarkable result, Pr and Ce reductions can simultaneously take place at lower temperature (T > 430 °C) than for oxides of the CeO2–ZrO2 solid solution evidencing that the increase of Pr content also allows enhancing the reducibility of Ce4+ at low temperature. On the basis of a discussion taking into account the probability of oxygen surroundings in disordered fluorite networks and the rate of oxygen released in materials after the first reduction step performed at T < 500 °C, a mapping of the most probable labile oxygen sites in the CZP phase diagram is proposed. In particular, it is shown that for the oxides containing 10 atom % Zr, the most labile oxygen site should be systematically coordinated with one Zr atom, one Ce, and two Pr atoms. In the same series (10 atom % Zr), the electronic transport properties allowed showing semiconducting behavior with a strong increase of the total conductivity as the Pr content increases. On the basis of the thermal variation of the Seebeck coefficient, these phenomena are associated with hopping of electrons and holes, involving intra-atomic charge transfers, which depend on the reduction temperature of Pr4+ ions under air. Finally, the oxygen mobility strongly increases with the Pr content in this series. The oxygen tracer self-diffusion coefficient D* has been estimated by two independent measurements, and the best value is around 10–8 cm2/s at T = 400 °C for the Ce0.45Zr0.1Pr0.45O2–x composition, which is quite high in this temperature range. These fundamental properties of CZP phases design very promising new materials like automotive exhaust catalysts, gas sensors, electrolytes, or oxygen electrodes for solid oxide fuel cells.
dc.language.isoen
dc.publisherAmerican Chemical Society
dc.title.enTuning the Pr valence state to design high oxygen mobility, redox and transport properties in the CeO2-ZrO2-PrOx phase diagram
dc.typeArticle de revue
dc.identifier.doi10.1021/acs.jpcc.8b11469
dc.subject.halChimie/Matériaux
bordeaux.journalJournal of Physical Chemistry C
bordeaux.page6351-6362
bordeaux.volume123
bordeaux.issue11
bordeaux.peerReviewedoui
hal.identifierhal-02089434
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-02089434v1
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