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Calor de adherencia directa y calor de adsorción diferencial como sondas de las transiciones estructurales: O2 en la
Andrew D Karmazyn1, Vittorio Fiorin, David A King
1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
Journal of the American Chemical Society
|October 28, 2004
Resumen
La adsorción de oxígeno en las transiciones de Ni[211] de la adsorción química a la formación de óxidos. El alto calor de adsorción inicial se debe a los sitios de paso, con repulsiones que impulsan el cambio.
Área de la Ciencia:
- Ciencias de la superficie Ciencias de la superficie.
- Química de los materiales Química de los materiales
- Química Física es la química física.
Sus antecedentes:
- Comprender la interacción del oxígeno con las superficies de níquel es crucial para los procesos de catálisis y oxidación.
- La superficie de Ni[211], con sus sitios de paso únicos, ofrece una plataforma distinta para estudiar los fenómenos de adsorción en comparación con las superficies de bajo índice.
Objetivo del estudio:
- Para investigar el comportamiento de adsorción del oxígeno en la superficie de Ni[211].
- Para determinar las temperaturas de adsorción dependientes de la cobertura y las probabilidades de adherencia.
- Para dilucidar la transición de la quimiosorbción a la formación de óxidos en esta superficie escalonada.
Principales métodos:
- Se empleó calorimetría de adsorción de cristal único para medir las temperaturas de adsorción y las probabilidades de adherencia.
- Los experimentos se llevaron a cabo a una temperatura constante de 300 K.
- La adsorción se estudió en función de la cobertura de oxígeno en la superficie de Ni[211].
Principales resultados:
- Se observó un alto calor inicial de adsorción (620 kJ / mol), atribuido a los átomos de paso de baja coordinación.
- Una rápida disminución en el calor de adsorción con el aumento de la cobertura indica fuertes repulsiones laterales de adatom.
- Los datos sugieren una transición de la quimiosorción disociativa a la formación de óxidos por encima de 2 ML de cobertura adatómica.
Conclusiones:
- La superficie de Ni[211] exhibe propiedades únicas de adsorción de oxígeno impulsadas por la disponibilidad del sitio de paso y las repulsiones adatómicas.
- La transición a la formación de óxidos es compleja e influenciada por los sitios de paso.
- Estos hallazgos proporcionan información sobre las reacciones superficiales y los mecanismos de oxidación en superficies metálicas escalonadas.
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