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¿Cuál es el paso limitante de la reacción de reducción de oxígeno en los catalizadores Fe-N-C?
Saerom Yu1, Zachary Levell1, Zhou Jiang1
1Texas Materials Institute and Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States.
Journal of the American Chemical Society
|November 13, 2023
Resumen
El paso limitador de velocidad para la reducción de oxígeno en los catalizadores de hierro-carbono es el oxígeno que reemplaza el agua, no la hidrogenación. Este paso crucial
Área de la Ciencia:
- La electroquímica
- Ciencias de los materiales
- Catálisis
Sus antecedentes:
- La reacción de reducción de oxígeno (ORR) es vital para las tecnologías de energía renovable.
- Los átomos de hierro individuales en el grafeno dopado con nitrógeno (Fe-N-C) son catalizadores ORR prometedores.
- El paso limitador de velocidad en la ORR en Fe-N-C sigue sin identificarse, lo que dificulta la mejora del catalizador.
Objetivo del estudio:
- Para determinar el paso limitador de velocidad del ORR en catalizadores Fe-N-C.
- Para aclarar los mecanismos subyacentes y las energías de activación de cada paso.
- Proporcionar información para optimizar el rendimiento del catalizador Fe-N-C.
Principales métodos:
- Se utilizaron simulaciones de dinámica molecular desde el principio.
- Las simulaciones se llevaron a cabo con un potencial de electrodo constante.
- Se calcularon las energías de activación para todos los pasos de reacción.
Principales resultados:
- El paso limitador de la velocidad se identificó como O2 reemplazando el H2O adsorbido en los sitios de Fe.
- Esto ocurre a través de un mecanismo concertado de desorción-adsorción.
- La barrera de activación disminuye con la disminución del potencial del electrodo, contrariamente a las expectativas.
Conclusiones:
- El estudio desafía la creencia prevaleciente de que la hidrogenación limita la tasa de ORR en Fe-N-C.
- Se observaron cinéticas dependientes del potencial, explicadas por energías de unión alteradas de Fe-O2 y Fe-H2O.
- Los estudios cinéticos son cruciales para el avance de la investigación de la electrocatálisis heterogénea.
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