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

• Published in: Acta materialia 2021-01, Vol.203, p.116473, Article 116473
• Main Authors: Hao, Xiaodong, Yoko, Akira, Inoue, Kazutoshi, Xu, Yang, Saito, Mitsuhiro, Chen, Chunlin, Seong, Gimyeong, Tomai, Takaaki, Takami, Seiichi, Shluger, Alexander L., Xu, Bingshe, Adschiri, Tadafumi, Ikuhara, Yuichi
• Format: Article
• Language: English
• Subjects: Cr-substituted CeO2 nanocrystals; Oxygen storage capacity; STEM-EELS; The distribution of Ce3+ cations; {100} exposing facets
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2020.11.015

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 cerium valence states 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 the 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. [Display omitted]