Hao, X; Yoko, A; Inoue, K; Xu, Y; Saito, M; Chen, C; Seong, G; ... Ikuhara, Y; + view all Hao, X; Yoko, A; Inoue, K; Xu, Y; Saito, M; Chen, C; Seong, G; Tomai, T; Takami, S; Shluger, AL; Xu, B; Adschiri, T; Ikuhara, Y; - view fewer (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.

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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.

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