Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides

Zhou, Gege; Geng, Wentong; Sun, Lu; Wang, Xue; Xiao, Wei; Wang, Jianwei; Wang, Ligen

doi:10.3390/ma12244041

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Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides

by

Gege Zhou

^1,2,

Wentong Geng

²,

Lu Sun

¹,

Xue Wang

¹,

Wei Xiao

¹,

Jianwei Wang

¹

and

Ligen Wang

^1,*

¹

General Research Institute for Nonferrous Metals, Materials Computation Center, GRIMAT Engineering Institute Co. Ltd., Beijing 100088, China

²

School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

^*

Author to whom correspondence should be addressed.

Materials 2019, 12(24), 4041; https://doi.org/10.3390/ma12244041

Submission received: 6 November 2019 / Revised: 23 November 2019 / Accepted: 25 November 2019 / Published: 5 December 2019

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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Abstract

Ceria is one of the most important functional rare-earth oxides with wide industrial applications. Its amazing oxygen storage/release capacity is attributed to cerium’s flexible valence conversion between 4+ and 3+. However, there still exists some debate on whether the valence conversion is due to the Ce-4f electron localization-delocalization transition or the character of Ce–O covalent bonds. In this work, a mixed valence model was established and the formation energies of oxygen vacancies and electronic charges were obtained by density functional theory calculations. Our results show that the formation energy of oxygen vacancy is affected by the valence state of its neighboring Ce atom and two oxygen vacancies around a Ce⁴⁺ in CeO₂ have a similar effect to a Ce³⁺. The electronic charge difference between Ce³⁺ and Ce⁴⁺ is only about 0.4e. Therefore, we argue that the valence conversion should be understood according to the adjustment of the ratio of covalent bond to ionic bond. We propose that the formation energy of oxygen vacancy be used as a descriptor to determine the valence state of Ce in cerium oxides.

Keywords: cerium oxide; electron valence state; first-principles calculation; oxygen vacancy

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MDPI and ACS Style

Zhou, G.; Geng, W.; Sun, L.; Wang, X.; Xiao, W.; Wang, J.; Wang, L. Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides. Materials 2019, 12, 4041. https://doi.org/10.3390/ma12244041

AMA Style

Zhou G, Geng W, Sun L, Wang X, Xiao W, Wang J, Wang L. Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides. Materials. 2019; 12(24):4041. https://doi.org/10.3390/ma12244041

Chicago/Turabian Style

Zhou, Gege, Wentong Geng, Lu Sun, Xue Wang, Wei Xiao, Jianwei Wang, and Ligen Wang. 2019. "Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides" Materials 12, no. 24: 4041. https://doi.org/10.3390/ma12244041

APA Style

Zhou, G., Geng, W., Sun, L., Wang, X., Xiao, W., Wang, J., & Wang, L. (2019). Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides. Materials, 12(24), 4041. https://doi.org/10.3390/ma12244041

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Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides

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