Structural changes of Ce–Pr–O oxides in hydrogen: a study by in situ X-ray diffraction and Raman spectroscopy

Rossignol, Sylvie; Gérard, François; Mesnard, D.; Kappenstein, Charles; Duprez, Daniel

doi:10.1039/b306726b

Cited by 86 publications

(88 citation statements)

References 22 publications

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“…2(a) Table I. The average equilibrium lattice parameter of the reduced ceria is slightly larger than the equilibrium lattice parameter of perfect ceria (about 5.495Å;) calculated within the PBE+U method with U = 5 eV [9], which is consistent with experimental observations [20]. However, at a moderate compression (20 kbar) [ Fig.…”

Section: A Equation Of State and Enthalpysupporting

confidence: 80%

Volume-dependent electron localization in ceria

2015

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We have performed a numerical study of the process of electron localization in reduced ceria. Our results show that different localized charge distributions can be attained in a bulk system by varying the lattice parameter. We demonstrate that the effect of electron localization is mainly determined by lattice relaxation and an accurate account for the effects of electronic correlation is necessary to achieve localized charge distribution.

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Section: A Equation Of State and Enthalpysupporting

confidence: 80%

Volume-dependent electron localization in ceria

2015

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“…Change of the slope, at approximately 873 K, gives evidence of structural modifications associated with a modification of cell volume of the doped ceria, such as the formation of oxygen vacancies. Similar behavior has been observed for other related doped-cerium oxides [13]. The formation of oxygen vacancies at high temperature and reducing atmosphere is highly advantageous for the electrical conductivity of anode material based on the increased oxygen ion mobility that results in improved cell performance.…”

Section: Resultssupporting

confidence: 63%

Role of Dopants on Ceria-based Anodes for IT-SOFCs Powered by Hydrocarbon Fuels

Fuerte¹,

Valenzuela²,

Escudero³

2017

ujeee

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The direct use of hydrocarbon or hydrocarbon-derived fuels to generate electrical power has the potential to accelerate substantially the use of fuel cells in transportation and distributed-power applications. Most fuel-cell research has involved the use of hydrogen as the fuel, although the practical generation and storage of hydrogen remains an important technological hurdle. Although hydrocarbon fuels have been successfully oxidised or reformed electrochemically, the susceptibility to carbon formation or poor power densities has prevented the application of these fuels in practical applications. In this manuscript, the effect of different dopants on the properties of Cu-ceria based anodes for IT-SOFCs powered by hydrocarbon fuels has been explored. Four dopants atoms (Co, Ca, Ag and Rh) with different properties and concomitant varied effects on properties of the final material are studied. They have been selected in order to improve the electrical and textural properties of anode material as well as the catalytic activity for hydrocarbon oxidation. Results revealed a strong dependence of the final properties of the anode formulation and mechanism involved in the electro-oxidation of the different fuels. Different doping successfully improves the behaviour of anode material for IT-SOFCs powered by hydrocarbon fuels and reasonable power densities can be achieved.

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“…This is the room temperature value. [30][31][32][33] The thermal expansion coefficient is around 1.12-1.23ϫ 10 −5 K −1 measured over 298-1273 K, 31,32,34 giving about 5.391 Å at 0 K. This can also be seen by extrapolating the 300-1300 K data of Rossignol et al 32 or from simulations using classical interatomic potentials. 33 Hence the best fit is actually around U =4 eV ͑see Fig.…”

Section: A Applying Lda+ U To Ceriasupporting

confidence: 56%

Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria

Castleton

Kullgren

Hermansson

2007

The Journal of Chemical Physics

344

339

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We examine the real space structure and the electronic structure ͑particularly Ce4f electron localization͒ of oxygen vacancies in CeO 2 ͑ceria͒ as a function of U in density functional theory studies with the rotationally invariant forms of the LDA+ U and GGA+ U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U Ϸ 3 eV and that the degree of localization reaches a maximum at ϳ6 eV for LDA+ U or at ϳ5.5 eV for GGA+ U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into atomic corelike states; at maximum localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total atomic charge we find that the two ions only make a net gain of ͑0.2-0.4͒e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA+ U the crystal structure is actually best described with U =3-4 eV, while the experimental band structure is obtained with U =7-8 eV. ͑For GGA+ U the lattice parameters worsen for U Ͼ 0 eV, but the band structure is similar to LDA + U.͒ The best overall choice is U Ϸ 6 eV with LDA+ U and Ϸ5.5 eV for GGA+ U, since the localization is most important, but a consistent choice for both CeO 2 and Ce 2 O 3 , with and without vacancies, is hard to find.

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Structural changes of Ce–Pr–O oxides in hydrogen: a study by in situ X-ray diffraction and Raman spectroscopy

Cited by 86 publications

References 22 publications

Volume-dependent electron localization in ceria

Volume-dependent electron localization in ceria

Role of Dopants on Ceria-based Anodes for IT-SOFCs Powered by Hydrocarbon Fuels

Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria

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