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Desvelando las relaciones estructura-propiedad en Sr2Fe ((1.5) Mo ((0.5) O ((6-δ), un material de electrodo para
Ana B Muñoz-García1, Daniel E Bugaris, Michele Pavone
1Department of Mechanical and Aerospace Engineering, Program in Applied and Computational Mathematics, and Gerhard R. Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, USA.
Journal of the American Chemical Society
|March 28, 2012
Resumen
Este estudio detalla el Sr2Fe1.5Mo0.5O6-δ (SFMO), un nuevo material de célula de combustible de óxido sólido. SFMO exhibe vacíos de oxígeno y una excelente conductividad de iones-electrones mixtos, crucial para el rendimiento de la pila de combustible.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- La electroquímica es electroquímica.
- Química del estado sólido.
Sus antecedentes:
- Las pilas de combustible de óxido sólido (SOFC) requieren materiales de electrodo avanzados para un funcionamiento eficiente a temperatura intermedia.
- Las perovskitas de molibdato de hierro y estroncio son candidatos prometedores debido a su potencial de conductividad iónica y electrónica mixta.
Objetivo del estudio:
- Caracterizar experimental y teóricamente la estructura cristalina, la estequiometría del oxígeno y las propiedades electrónicas de Sr(2)Fe(1.5)Mo(0.5)O(6-δ) (SFMO).
- Para aclarar la relación entre la estructura del material, las vacantes de oxígeno y su desempeño como electrodo SOFC.
Principales métodos:
- Difracción de neutrones en polvo con refinamiento Rietveld para determinar la estructura cristalina y el contenido de oxígeno.
- La Teoría Funcional de Densidad más los cálculos de Hubbard U (DFT+U) para predecir la estructura electrónica y la formación de vacantes de oxígeno.
- Análisis de la estructura electrónica para comprender los mecanismos de conductividad.
Principales resultados:
- La SFMO se cristaliza en un grupo espacial Pnma ortorrómbico, no en una simple perovskita cúbica.
- El material exhibe vacíos de oxígeno, con una composición determinada de Sr(2)Fe(1.5)Mo(0.5)O(5.90(2)).
- Los cálculos de DFT+U confirman la presencia y concentración de vacíos de oxígeno y revelan una fuerte hibridación Fe d-O p responsable de una alta conductividad electrónica y difusividad iónica.
Conclusiones:
- SFMO es un material viable para electrodos SOFC debido a su estructura ortorrómbica, vacantes de oxígeno inherentes y excelente conductividad de iones-electrones mixtos.
- La fácil formación de vacantes de oxígeno y la alta difusividad de iones de óxido están vinculadas a la estructura electrónica, específicamente la hibridación Fe d-O p.
- Esta comprensión facilita el desarrollo de eficientes celdas de combustible de óxido sólido de temperatura intermedia.
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