Surface-driven electron localization and defect heterogeneity in ceria

Zhang, Xingfan, Yoko, Akira, Zhou, Yi, Jee, Woongkyu, Mayoral, Alvaro, Liu, Taifeng, Guan, Jingcheng, Lu, You, Keal, Thomas W., Buckeridge, John, Ninomiya, Kakeru, Nishibori, Maiko, Yamamoto, Susumu, Matsuda, Iwao, Adschiri, Tadafumi, Terasaki, Osamu, Woodley, Scott M., Catlow, C. Richard A. ORCID: https://orcid.org/0000-0002-1341-1541 and Sokol, Alexey A. 2025. Surface-driven electron localization and defect heterogeneity in ceria. Journal of the American Chemical Society 147 (37) , 33888–33902. 10.1021/jacs.5c10679

PDF - Published Version Available under License Creative Commons Attribution. Download (6MB)

Abstract

The exceptional performance of ceria (CeO2) in catalysis and energy conversion is fundamentally governed by its defect chemistry, particularly oxygen vacancies. The formation of each oxygen vacancy (VO••) is assumed to be compensated by two localized electrons on cations (Ce3+). Here, we show by combining theory with experiment that while this 1 VO••: 2Ce3+ ratio accounts for the global charge compensation, it does not apply at the local scale, particularly in nanoparticles. Hybrid quantum mechanical/molecular mechanical (QM/MM) defect calculations, together with synchrotron X-ray photoelectron spectroscopy (XPS) measurements, show that electrons have a strong preference to localize and segregate on surfaces, which can overcome the trapping force from the VO•• sites in the bulk. At a given Fermi level, the surface VO•• tends to trap more electrons than those in bulk, resulting in a higher Ce3+ to VO•• ratio on surfaces than that in the bulk, driven by the preferential localization of electrons and enhanced VO••–Ce3+coupling. Large-scale unbiased Monte Carlo simulations on ceria nanoparticles confirmed this trend and further show that the surface segregation of electrons is more pronounced at low reduction levels and in smaller nanoparticles. In highly reduced ceria nanoparticles, however, the enhanced repulsive interactions lead to a less significant extent of defect heterogeneity or even reverse the location preference of defects in some nanoparticles. Our findings underscore the need to consider both the overall nonstoichiometry and local defect behavior in easily reducible oxides, with direct relevance to their performance in catalytic and energy applications.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Chemistry
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2025-09-09
Publisher:	American Chemical Society
ISSN:	0002-7863
Date of First Compliant Deposit:	22 September 2025
Date of Acceptance:	26 August 2025
Last Modified:	22 Sep 2025 14:03
URI:	https://orca.cardiff.ac.uk/id/eprint/181251

Actions (repository staff only)

Edit Item