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Interaction of Hydrogen with Ceria: Hydroxylation, Reduction, and Hydride Formation on the Surface and in the Bulk
Author(s) -
Li Zhaorui,
Werner Kristin,
Chen Lu,
Jia Aiping,
Qian Kun,
Zhong JianQiang,
You Rui,
Wu Lihui,
Zhang Liyuan,
Pan Haibin,
Wu XinPing,
Gong XueQing,
Shaikhutdinov Shamil,
Huang Weixin,
Freund HansJoachim
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202005374
Subject(s) - hydride , hydrogen , stoichiometry , chemistry , catalysis , inorganic chemistry , oxygen , reactivity (psychology) , redox , photochemistry , organic chemistry , medicine , alternative medicine , pathology
The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO 2 ) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO 2 (111) thin films and CeO 2 powders, and theoretical calculations of CeO 2 (111) surfaces with oxygen vacancies (O v ) at the surface and in the bulk. We show that, on a stoichiometric CeO 2 (111) surface, H 2 dissociates and forms surface hydroxyls (OH). On the pre‐reduced CeO 2− x samples, both films and powders, hydroxyls and hydrides (Ce−H) are formed on the surface as well as in the bulk, accompanied by the Ce 3+ ↔ Ce 4+ redox reaction. As the O v concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H 2 /CeO 2 interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria‐based catalysts in a hydrogen‐rich atmosphere.