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Observación directa a escala atómica de la dinámica catiónica inducida por redox en un catalizador monocapa soportado

Zhenxing Feng¹, Chang-Yong Kim, Jeffrey W Elam

¹Department of Materials Science and Engineering, Institute for Catalysis in Energy Processes, and DND-CAT, Synchrotron Research Center, Northwestern University, Evanston, Illinois 60208, USA.

Journal of the American Chemical Society

|December 24, 2009

Resumen

Los átomos de tungsteno (W) en la hematita cambian posiciones y estados de oxidación de manera reversible con el ciclo redox. Esto revela el comportamiento dinámico de los cationes en los catalizadores soportados por óxido.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Ciencias de la superficie Ciencias de la superficie.
La catálisis de la catálisis.

Sus antecedentes:

La deposición de la capa atómica (ALD) permite un crecimiento preciso de la película delgada.
La hematita (alfa-Fe2O3) es un material óxido clave en la catálisis.
La comprensión de las interfaces metal-óxido es crucial para el diseño del catalizador.

Objetivo del estudio:

Para investigar la evolución estructural y química a escala atómica del tungsteno en la hematita.
Para observar los cambios inducidos por redox reversibles en la interfaz W/Fe{2) O{3).
Para dilucidar la dinámica catiónica en catalizadores soportados por óxido.

Principales métodos:

Imágenes atómicas de ondas estacionarias de rayos X in situ.
Espectroscopia de fotoelectrones de rayos X (XPS).
Las mediciones de la estructura fina de absorción de rayos X (XAFS).

Principales resultados:

Las imágenes directas a escala atómica revelaron el movimiento reversible del catión W en relación con los sitios de Fe.
XPS mostró cambios en el estado de oxidación W de 6+ a 5+ durante el ciclo redox.
Los cambios estructurales y químicos observados son consistentes con la incorporación de W en sitios de Fe.

Conclusiones:

El ciclo redox induce una dinámica catiónica significativa y reversible en la interfaz W/hematita.
La incorporación de W en sitios de Fe con coordinación variable explica el comportamiento observado.
Estos hallazgos ofrecen información sobre el mecanismo de los catalizadores soportados por óxido.

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