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La electro-oxidación del monóxido de carbono en aleaciones superficiales Pt{11}/Sn bien ordenadas
Brian E Hayden1, Michael E Rendall, Oliver South
1Department of Chemistry, The University of Southampton, Southampton SO17 1BJ, U.K. beh@soton.ac.uk
Journal of the American Chemical Society
|June 19, 2003
Resumen
Los catalizadores de aleación de platino y estaño mejoran la electro-oxidación de CO a través de un mecanismo bifuncional. El estaño activa el agua, promoviendo la oxidación de CO en potenciales específicos, cruciales para los catalizadores de células de combustible tolerantes al CO.
Área de la Ciencia:
- La electroquímica es electroquímica.
- Ciencia de los materiales Ciencia de los materiales.
- Ciencias de la superficie Ciencias de la superficie.
Sus antecedentes:
- La electro-oxidación de monóxido de carbono (CO) es fundamental para las células de combustible de hidrógeno.
- Los catalizadores a base de platino son esenciales, pero también son susceptibles al envenenamiento por CO.
- La aleación de platino con estaño (Pt-Sn) ofrece una potencial tolerancia al CO.
Objetivo del estudio:
- Para investigar la electro-oxidación de CO en superficies modelo de aleación de platino y estaño.
- Para aclarar el papel del estaño en la promoción de la oxidación del CO.
- Comprender el mecanismo de la tolerancia al CO en los catalizadores Pt-Sn.
Principales métodos:
- Preparación de las superficies modelo Pt(111)/Sn con estructuras definidas.
- Medidas electroquímicas ex situ (voltametría cíclica, voltametría de desmontaje).
- Espectroscopia de fotoemisión ex situ para sondear los estados de la superficie.
Principales resultados:
- Se identificó una pareja redox superficial relacionada con la adsorción/desorción de hidróxido en sitios de Sn.
- Los átomos de estaño cambian entre los estados metálico y oxidado que se correlacionan con la pareja redox.
- La electro-oxidación de CO ocurre en potenciales que coinciden con la adsorción de hidróxido en sitios de Sn, lo que indica un mecanismo bifuncional.
Conclusiones:
- El estaño promueve significativamente la electro-oxidación de CO a través de la activación del agua.
- La estructura de aleación Pt-Sn es estable y efectiva para la oxidación de CO por debajo de 0,5 V (RHE).
- Estos hallazgos son vitales para el desarrollo de catalizadores de ánodo basados en platino tolerantes al CO para pilas de combustible.
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