Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195, Berlin, Germany.
Dalton Trans. 2010 Sep 28;39(36):8484-91. doi: 10.1039/c003133j. Epub 2010 May 29.
The role of surface, and subsurface hydrogen species in olefin cis-trans isomerization and hydrogenation over a model Pd/Fe(3)O(4)/Pt(111) catalyst was investigated by pulsed molecular beam experiments and infrared reflection-absorption spectroscopy. We show that non-equivalent hydrogen species are involved in the two reaction pathways: whereas cis-trans isomerization proceeds with the surface hydrogen species, the presence of hydrogen absorbed in the subsurface region of Pd particles is required for the hydrogenation pathway. The activity and selectivity toward both reaction channels was found to significantly change on Pd particles when they are modified with strongly dehydrogenated carbonaceous deposits. Sustained hydrogenation activity was observed only on C-precovered particles, whereas sustained cis-trans isomerization proceeds on both C-free and C-containing catalyst. We discuss the possible microscopic origins of this effect.
通过脉冲分子束实验和红外反射吸收光谱研究了表面和亚表面氢物种在模型 Pd/Fe(3)O(4)/Pt(111)催化剂上的烯烃顺反异构化和加氢反应中的作用。我们表明，两种反应途径涉及不等效的氢物种：顺反异构化是通过表面氢物种进行的，而 Pd 颗粒亚表面区域中吸附的氢对于加氢途径是必需的。当 Pd 颗粒被强烈脱氢的碳质沉积物修饰时，发现它们对两种反应通道的活性和选择性都有显著的变化。只有在 C 覆盖的颗粒上才能观察到持续的加氢活性，而 C 自由和 C 包含的催化剂上都能持续进行顺反异构化。我们讨论了这种效应的可能微观起源。
