Atomistic origin of high-concentration Ce³⁺ in {100}-faceted Cr- substituted CeO₂ nanocrystals

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Atomistic origin of high-concentration Ce³⁺ in {100}-faceted Cr- substituted CeO₂ nanocrystals

Hao, X; Yoko, A; Inoue, K; Xu, Y; Saito, M; Chen, C; Seong, G; ... Ikuhara, Y; + view all (2021) Atomistic origin of high-concentration Ce³⁺ in {100}-faceted Cr- substituted CeO₂ nanocrystals. Acta Materialia , 203 , Article 116473. 10.1016/j.actamat.2020.11.015. Green open access

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Abstract

Improving the potential of promising CeO2-based nanocatalysts in practical applications requires an atomic-scale analysis of the effects of active dopants on the distribution of Ce valence states and the formation of oxygen vacancies (VOs). In this study, a Cr dopant is introduced into the cubic {100}-faceted CeO2 nanocrystals (NCs) with an average size of 7.8 nm via supercritical water. The Cr dopants substitute Ce sites in the amount of approximately 3 mol%. Based on the aberration-corrected STEM-EELS, the effects of Cr dopant on the distribution of cation valence states in the Cr-doped CeO2 NCs are investigated layer by layer across the ultrafine Cr-substituted CeO2 NC perpendicular to the {100} exposed facet. It is found that an increased amount of Ce3+ cations is present in Cr-substituted CeO2 NCs, particularly in the internal atomic layers, compared to the pristine CeO2 NCs. The atomic-scale analysis of the local structure combined with theoretical calculations demonstrates that Cr dopant reduces the formation energy of VOs and increases mobility of oxygen atoms for the nano-sized CeO2. These effects, in principle, result in an improved oxygen storage capacity and provide a fundamental understanding of role of the dopant in the formation and distribution of VOs in the doped CeO2 NCs.

Type:	Article
Title:	Atomistic origin of high-concentration Ce³⁺ in {100}-faceted Cr- substituted CeO₂ nanocrystals
Open access status:	An open access version is available from UCL Discovery
DOI:	10.1016/j.actamat.2020.11.015
Publisher version:	http://dx.doi.org/10.1016/j.actamat.2020.11.015
Language:	English
Additional information:	This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords:	Cr-substituted CeO2 nanocrystals, STEM-EELS, The distribution of Ce3+ cations, {100} exposing facets, Oxygen storage capacity
UCL classification:	UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI:	https://discovery.ucl.ac.uk/id/eprint/10115177