Oxygen vacancy formation and migration in ceria

Nolan, Michael; Fearon, Joanne; Watson, Graeme W.

doi:10.1016/j.ssi.2006.07.045

Cited by 324 publications

(262 citation statements)

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“…Reported activation energies for ionic conductivity are higher due to the contribution of the vacancy formation energy or vacancy-impurity binding energies. For comparison, results based on density functional theory (DFT) calculations for the oxygen-vacancy migration energy barrier vary from 0.46 eV to 1.08 eV [28][29][30], depending on the approximation for the exchange-correlation functional and on the supercell size (vacancy concentration).…”

Section: Introductionmentioning

confidence: 99%

“…There have appeared numerous studies of bulk CeO 2 based on DFT calculations, many focusing on the oxygen vacancy [10][11][12][13][14][15][16][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. DFT calculations using the local density approximation (LDA) or the generalized gradient approximation (GGA) for the exchange-correlation term underestimate the separation between the top of the valence band (O 2p band) and the empty Ce 4f bands in CeO 2 by ~35 % [16,[31][32][33].…”

Section: Introductionmentioning

confidence: 99%

“…The DFT+U method has also been employed to study the electronic properties of CeO 2 and the impact of oxygen vacancies [29,30,[33][34][35][36][37][38][39][40][41][42]. In this approach, an extra on-site Coulomb interaction is added to the Ce 4f states, leading to a split between occupied and unoccupied states.…”

Section: Introductionmentioning

confidence: 99%

“…For the oxygen vacancy, the excess electrons are localized on individual Ce atoms, turning two Ce 4+ into two Ce 3+ species, which, by Coulomb attraction, sit near to the vacancy [29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The results of DFT+U studies are largely dependent on the U value, bringing some uncertainty to the results and raising questions on what value of U should be used to describe the properties of perfect and reduced CeO 2 .…”

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Disentangling the role of small polarons and oxygen vacancies in CeO2

et al. 2017

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“…考虑到 Ce 和 Sm 含有高角量子数 4f 电子而 DFT 方法对这些电子间相互作用描述不足的原因, 本文采用引入 Hubbard 参数 U 的方法, 其中 Ce 的 U 值选取 6.0 eV, 其他理论研究表明, Ce 的 U 值应大于 5 eV [20] [20,27] . [12,31,32] . …”

Section: 计算模型与方法unclassified

Electronic Structures and Oxygen Ion Migration Energies of Metal Doped CeO₂Systems：A DFT+U Study

贾桂霄¹,

郝文兴²,

潘飞³

et al. 2013

Acta Chim. Sinica

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Doping energies of Ca, Ba, Sm and Zr in CeO 2 systems and influences of dopings on oxygen ion migration energies and vacancy formation energies were studied using DFT and DFT＋U methods. The calculated results showed that the doping energies increased with doping cation radius for doped CeO 2 systems without oxygen vacancies, and for doped CeO 2 systems with oxygen vacancies, the doping energies were related to the valence of the doping cations besides their radius. Calculations on electronic structures of various doped CeO 2 systems showed that Fermi level shifted to the high energy in reduced CeO 2 , Zr-and Sm-doped CeO 2 systems, however, in Ca-and Ba-doped CeO 2 systems, negative charges due to the substitution of Ca 2＋ and Ba 2＋ with lower chemical valence for Ce 4＋ and positive charges due to the formation of oxygen ion vacancy were neutralized, so Fermi level scarcely shifted. Ce 3＋ existed in the reduced CeO 2 system and the Zr-doped CeO 2 system, which would lead to mixed conductivity with ion and electron one, and electron state of Ce 3＋ layed between Ce4f and O2p. However, the reduction of Ce 4＋ was restrained in Ca-, Ba-and Sm-doped CeO 2 systems. The migration of an oxygen vacancy was investigated using the nudged elastic band method. The calculated results indicated that a straightforward migration path between two adjacent oxygen sites for oxygen vacancy hopping was obtained. For Ca-, Ba-, Sm-and Zr-doped CeO 2 systems, the migration energies of oxygen ions were smaller than that of CeO 2 system. In these doped CeO 2 systems, the migration energy of oxygen ions for Ba was the smallest and its doping energy are the largest, so Ba was maybe introduced through adding the third class dopant in experiment.

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Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO₂₋_x‐Based Heterojunctions

Zheng

Mofarah

Cazorla

et al. 2021

Adv Funct Materials

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Critical catalysis studies often lack elucidation of the mechanistic role of defect equilibria in solid solubility and charge compensation. This approach is applied to interpret the physicochemical properties and catalytic performance of a free-standing 2D-3D CeO 2−x scaffold, which is comprised of holey 2D nanosheets, and its heterojunctions with MoO 3−x and RuO 2 . The band gap alignment and structural defects are engineered using density functional theory (DFT) simulations and atomic characterization. Further, the heterojunctions are used in hydrogen evolution reaction (HER) and catalytic ozonation applications, and the impacts of the metal oxide heteroatoms are analyzed. A key outcome is that the principal regulator of the ozonation performance is not oxygen vacancies but the concentration of Ce 3+ and Ce vacancies. Cation vacancy defects are measured to be as high as 8.1 at% for Ru-CeO 2−x . The homogeneous distribution of chemisorbed, Mo-oxide, heterojunction nanoparticles on the CeO 2−x holey nanosheets facilitates intervalence charge transfer, resulting in the dominant effect and resultant ≈50% decrease in overpotential for HER. The heterojunctions are tested for aqueous-catalytic ozonation of salicylic acid, revealing excellent catalytic performance from Mo doping despite the adverse impact of Ce vacancies. The present study highlights the use of defect engineering to leverage experimental and DFT results for band alignment.

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Oxygen vacancy formation and migration in ceria

Cited by 324 publications

References 20 publications

Disentangling the role of small polarons and oxygen vacancies in CeO2

Disentangling the role of small polarons and oxygen vacancies in CeO2

Electronic Structures and Oxygen Ion Migration Energies of Metal Doped CeO₂Systems：A DFT+U Study

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO₂₋_x‐Based Heterojunctions

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Oxygen vacancy formation and migration in ceria

Cited by 324 publications

References 20 publications

Disentangling the role of small polarons and oxygen vacancies in CeO2

Disentangling the role of small polarons and oxygen vacancies in CeO2

Electronic Structures and Oxygen Ion Migration Energies of Metal Doped CeO2Systems：A DFT+U Study

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO2−x‐Based Heterojunctions

Contact Info

Product

Resources

About

Electronic Structures and Oxygen Ion Migration Energies of Metal Doped CeO₂Systems：A DFT+U Study

Decoupling the Impacts of Engineering Defects and Band Gap Alignment Mechanism on the Catalytic Performance of Holey 2D CeO₂₋_x‐Based Heterojunctions