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Oxidación electrocatalítica de los alcoholes sobre el oro en medios alcalinos: catálisis de base o de oro?
Youngkook Kwon1, Stanley C S Lai, Paramaconi Rodriguez
1Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
Journal of the American Chemical Society
|April 21, 2011
Resumen
La catálisis básica, no la interacción del catalizador, impulsa la oxidación del alcohol en los ánodos de la pila de combustible. Este proceso, influenciado por la acidez del alcohol, es clave para las células de combustible de medios alcalinos eficientes.
Área de la Ciencia:
- La electroquímica es electroquímica.
- Ciencia de los materiales Ciencia de los materiales.
- La catálisis de la catálisis.
Sus antecedentes:
- La comprensión de la electro-oxidación de los combustibles orgánicos es crucial para el desarrollo de eficientes pilas de combustible alcalinas.
- El papel de las interacciones catalizador-superficie frente a la catálisis en la fase de solución en la electrooxidación alcalina sigue siendo objeto de debate.
Objetivo del estudio:
- Para dilucidar los mecanismos catalíticos que rigen la electro-oxidación de los alcoholes en electrodos de oro en medios alcalinos.
- Para comparar la actividad del oro con el platino para la electro-oxidación del alcohol e identificar los factores que contribuyen a un rendimiento superior.
Principales métodos:
- Estudios comparativos de la actividad de oxidación electroquímica de varios alcoholes con diferentes valores de pK (a) en electrodos de oro.
- Análisis de la cinética de la reacción y correlación con la acidez del alcohol (pK(a)) utilizando relaciones de tipo Hammett.
- Investigación de las propiedades de la superficie de los electrodos, específicamente la resistencia a la formación de óxidos envenenantes, comparando el oro y el platino.
Principales resultados:
- El primer paso de desprotonación en la oxidación del alcohol es catalizado por bases y sigue una correlación de tipo Hammett con pK (a).
- El segundo paso de desprotonación es rápido y catalizado por el oro.
- El oro exhibe una mayor actividad de oxidación que el platino debido a su resistencia al envenenamiento superficial, que es fundamental para el funcionamiento sostenido de la pila de combustible.
Conclusiones:
- La catálisis basal, impulsada por la acidez del alcohol, es el factor principal responsable de la alta actividad de electrooxidación de los combustibles orgánicos en medios alcalinos.
- La interacción del catalizador con los iones de hidróxido juega un papel secundario en comparación con la catálisis básica.
- La estabilidad del oro contra la formación de óxidos superficiales lo convierte en un material de ánodo superior para pilas de combustible alcalinas en comparación con el platino.
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