One Oxygen Vacancy, Two Charge States: Characterization of Reduced α‑MoO3(010) through Theoretical Methods
Molybdenum oxides are finding increasing applications that rely on their redox character. For the most common polymorph, α-MoO3, oxygen vacancy formation leaves two electrons on the surface that can be stored as small polarons. Detailed density functional theory calculations that properly account fo...
| Autores: | , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2018 |
| País: | España |
| Institución: | Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| Repositorio: | Recercat. Dipósit de la Recerca de Catalunya |
| OAI Identifier: | oai:recercat.cat:2072/359772 |
| Acceso en línea: | http://hdl.handle.net/2072/359772 https://doi.org/10.1021/acs.jpclett.8b00536 |
| Access Level: | acceso abierto |
| Palabra clave: | 54 |
| Sumario: | Molybdenum oxides are finding increasing applications that rely on their redox character. For the most common polymorph, α-MoO3, oxygen vacancy formation leaves two electrons on the surface that can be stored as small polarons. Detailed density functional theory calculations that properly account for the self-interaction term, Ueff = 3.5 eV, show that the vacancy generates two different configurations: either two Mo5+ centers (Mo5+□ and Mo5+O) or a single double-reduced Mo4+. These states are separated by 0.22 eV with a barrier for interconversion of 0.33 eV, and thus both are populated at catalytic temperatures, as shown by first-principles molecular dynamics. At higher reduction levels, vacancies can only be accumulated along a preferential direction and the energy difference between the 2×Mo5+ and Mo4+ configurations is reduced. These results point out the need for a revision of the experimental assignments based on our characterization that includes charges, vibrational frequencies, and XPS signatures |
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