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Diferenciar entre catálisis de oxidación de agua homogénea y heterogénea: confirmación de que [Co4 ((H2O) 2
James W Vickers1, Hongjin Lv, Jordan M Sumliner
1Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
Journal of the American Chemical Society
|August 28, 2013
Resumen
El anión polioxometalato Co4POM actúa como catalizador de la oxidación molecular del agua, no el óxido de cobalto. Los experimentos confirman el Co4POM.
Área de la Ciencia:
- La catálisis es la catálisis.
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- La electroquímica es electroquímica.
Sus antecedentes:
- Distinguir la catálisis homogénea de la heterogénea es un desafío.
- El catalizador de la oxidación del agua [Co4 ((H2O) 2 ((PW9O34) 2)) ((10-) (Co4POM) se informó inicialmente como un catalizador molecular eficiente.
- Estudios posteriores cuestionaron si los subproductos de óxido de cobalto (CoOx) eran responsables de la actividad de Co4POM.
Objetivo del estudio:
- Examinar a fondo las especies activas responsables de la catálisis de la oxidación del agua por Co4POM.
- Para determinar si Co4POM funciona como un catalizador molecular o un precursor de CoOx. heterogéneo.
Principales métodos:
- Cuantificación del Co2+aq liberado utilizando la voltametría de extracción adsortiva catódica y la espectrometría de masas de plasma acoplada inductivamente.
- Análisis de la dependencia de la evolución del O2 catalítico en las concentraciones de amortiguadores, pH y catalizador para Co4POM, Co2+) y CoOx.
- Experimentos de extracción con disolventes para diferenciar el Co4POM del Co2+ y el CoOx.
Principales resultados:
- La cantidad de cobalto liberado no pudo explicar la actividad de oxidación del agua observada.
- Co4POM, Co2+) y CoOx exhibieron distintas dependencias de las condiciones de reacción.
- Co4POM fue extraído selectivamente en tolueno, a diferencia de Co2+) y CoOx.
Conclusiones:
- Co4POM funciona como un catalizador de oxidación de agua molecular bajo las condiciones reportadas.
- La actividad catalítica se atribuye a las especies intactas de Co4POM, no a los subproductos de CoOx.
- Estudios previos que sugieren CoOx como la especie activa se concilian con las vías de descomposición conocidas de Co4POM en diferentes condiciones.
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