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Estructura atómica de los electrocatalizadores de nanocuadro Pt3Ni mediante espectroscopia de absorción de rayos X in
Nigel Becknell1, Yijin Kang2, Chen Chen1
1Department of Chemistry, University of California , Berkeley, California 94720, United States.
Journal of the American Chemical Society
|December 15, 2015
Resumen
El estudio de la estructura del catalizador in situ es clave para el rendimiento. Para los nanocuadros Pt3Ni, la alta actividad de la reacción de reducción de oxígeno (ORR) se basa en la formación de una superficie protectora de piel de platino.
Área de la Ciencia:
- Ciencias de los materiales
- La electroquímica
- Catálisis
Sus antecedentes:
- El rendimiento del catalizador está intrínsecamente vinculado a su estructura atómica.
- Los catalizadores a menudo cambian en condiciones de reacción, lo que requiere estudios in situ.
- Los catalizadores Pt-Ni son prometedores para la reacción de reducción de oxígeno (ORR), pero su comportamiento en la superficie requiere una investigación detallada.
Objetivo del estudio:
- Para investigar la estructura atómica in situ de los electrocatalizadores de nanocuadro Pt3Ni.
- Para correlacionar la estructura de la superficie con el rendimiento de la reacción de reducción de oxígeno (ORR).
- Comprender el mecanismo de formación de Pt-skin y su impacto en la actividad ORR.
Principales métodos:
- Espectroscopia de absorción de rayos X in situ (XAS) para sondear la estructura del catalizador en condiciones de reacción.
- Deposición electroquímica de hidrógeno bajo potencial y electrooxidación de monóxido de carbono para evaluar las propiedades de unión superficial.
- Análisis XAS ex situ e in situ para comparar los estados del catalizador.
Principales resultados:
- Las superficies de nanocuadro exhiben diferentes fuerzas de unión a los adsorbados, en correlación con las diferencias estructurales.
- La unión de adsorbato más fuerte está relacionada con superficies de Pt más ásperas debido a la segregación incompleta de Pt y la disolución de Ni.
- Una alta actividad de ORR se correlaciona con una segregación significativa de Pt, formando una capa de piel Pt beneficiosa.
Conclusiones:
- La alta actividad ORR de los nanocuadros huecos de Pt3Ni es críticamente dependiente de la formación de una estructura superficial Pt-skin.
- La caracterización in situ es esencial para comprender el comportamiento dinámico del catalizador.
- El control de la segregación de Pt y la disolución de Ni es clave para optimizar los electrocatalizadores ORR.
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