Thermodynamic modelling of the cerium–oxygen system☆

Zinkevich, M.; Djurović, D.; Aldinger, Fritz

doi:10.1016/j.ssi.2006.02.044

Cited by 230 publications

(205 citation statements)

References 50 publications

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“…(2), which, in turn, corresponds to the oxygen-rich limit and therefore describes the highest formation energy for an oxygen vacancy. However, for a direct comparison with the experimental data, the minimum energy required to form an oxygen vacancy would be more appropriate, or equivalently, the maximum oxygen-vacancy [64].…”

Section: Oxygen Vacanciesmentioning

confidence: 99%

Disentangling the role of small polarons and oxygen vacancies in CeO2

et al. 2017

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The outstanding performance of cerium oxide (CeO 2 ) as ion conductor or catalyst strongly depends on the ease of Ce 4+ ↔Ce 3+ conversion and oxygen vacancyformation. An accurate description of Ce 3+ and oxygen vacancy is therefore essential to further progress in this area. Using the HSE06 hybrid functional, we investigate the formation and migration of small polarons (Ce 3+ ) and their interaction with oxygen vacancies in CeO 2 , considering the small polaron and vacancy as independent entities.Oxygen vacancies are double donors and can bind up to two small polarons, forming a positively charged or neutral complex. We compute the electron self-trapping energy (i.e., energy gain when forming a small polaron), the small-polaron migration barrier, vacancy formation and migration energies, and vacancy-polaron binding energies. We find that small polarons weakly bind to oxygen vacancies, yet this interaction significantly contributes to the activation energy for hopping electronic conductivity.The results are compared with previous calculations and discussed in the light of available experimental data.

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Section: Oxygen Vacanciesmentioning

confidence: 99%

Disentangling the role of small polarons and oxygen vacancies in CeO2

et al. 2017

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“…These points were computed using the comprehensive thermodynamic model developed by Zinkevich et al, [ 23 ] which is based on a critical evaluation of the data in the literature. The compositions used (Table 1 ) proceed from the lowest extent of reduction on the right-hand side of the curve (CeO 1.999 ) to the highest extent on the left-hand end (CeO 1.76 ) of the curve in the fi gure.…”

Section: Ceriamentioning

confidence: 99%

Considerations in the Design of Materials for Solar‐Driven Fuel Production Using Metal‐Oxide Thermochemical Cycles

Miller

McDaniel

Allendorf

2013

Advanced Energy Materials

166

146

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With demand for energy increasing worldwide and an ever‐stronger case building for anthropogenic climate change, the need for carbon‐neutral fuels is becoming an imperative. Extensive transportation infrastructure based on liquid hydrocarbon fuels motivates development of processes using solar energy to convert CO2 and H2O to fuel precursors such as synthesis gas. Here, perspectives concerning the use of solar‐driven thermochemical cycles using metal oxides to produce fuel precursors are given and, in particular, the important relationship between reactor design and material selection is discussed. Considering both a detailed thermodynamic analysis and factors such as reaction kinetics, volatility, and phase stability, an integrated analytical approach that facilitates material design is presented. These concepts are illustrated using three oxide materials currently receiving considerable attention: metal‐substituted ferrites, ceria, and doped cerias. Although none of these materials is “ideal,” the tradeoffs made in selecting any one of them are clearly indicated, providing a starting point for assessing the feasibility of alternative materials developed in the future.

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“…The catalytic activity of ceria stems from two important aspects: (1) the redox reactions between the two oxidation states of cerium (Ce 3+ vs. Ce 4+ ) accompanied by the formation of oxygen vacancies and (2) the uncommon ability of ceria to retain the cubic crystal structure even when ~ 15% of the lattice oxygen anions are missing [7] [8]. It was shown that the concentration of the reduced cerium cations and oxygen vacancies could be even higher on ceria surfaces [9] than in the bulk.…”

Section: Introductionmentioning

confidence: 99%

Surface structure of coherently strained ceria ultrathin films

et al. 2016

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Cerium oxide, or ceria, is an important material for solid oxide fuel cell and water splitting devices. Although the ceria surface is active in catalytic and electrochemical reactions, how its catalytic properties are affected by the surface structure under operating conditions is far from understood. We investigate the structure of the coherently strained CeO 2 ultrathin films on yttriastabilized zirconia (001) single crystals by specular synchrotron X-ray diffraction (XRD) under oxidizing conditions as a first step to study the surface structure in situ. An excellent agreement between the experiment data and the model is achieved by using a "stacks and islands" model that has a two-component roughness. One component is due to the tiny clusters of nm scale in lateral dimensions on each terrace, while the other component is due to slightly different CeO 2 thickness that span over hundreds of nm on neighboring terraces. We attribute the non-uniform thickness to step de-pairing during the thin film deposition which is supported by the surface morphology results on the microscopic level. Importantly, our model also shows that the polarity of the ceria surface is removed by a half monolayer surface coverage of oxygen. The successful resolution of the ceria surface structure using in situ specular synchrotron XRD paves the way to study the structural evolution of ceria as a fuel cell electrode under catalytically relevant temperatures and gas pressures.

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Thermodynamic modelling of the cerium–oxygen system☆

Cited by 230 publications

References 50 publications

Disentangling the role of small polarons and oxygen vacancies in CeO2

Disentangling the role of small polarons and oxygen vacancies in CeO2

Considerations in the Design of Materials for Solar‐Driven Fuel Production Using Metal‐Oxide Thermochemical Cycles

Surface structure of coherently strained ceria ultrathin films

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