Yamaguchi Masato, Zhang Yufei, Kudoh Satoshi, Koyama Kohei, Lushchikova Olga V, Bakker Joost M, Mafuné Fumitaka
Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
Radboud University, Institute for Molecules and Materials, FELIX Laboratory, 6525 ED Nijmegen, Netherlands.
J Phys Chem Lett. 2020 Jun 4;11(11):4408-4412. doi: 10.1021/acs.jpclett.0c01133. Epub 2020 May 21.
Iridium and rhodium are group IX elements that can both catalytically reduce NO. To understand the difference in their reactivity toward NO, the adsorption forms of NO onto clusters of Ir and Rh are compared using vibrational spectra, recorded via infrared multiple-photon dissociation spectroscopy. The spectra give evidence for the existence of at least two specific adsorption forms. The main IrNO isomer is one in which NO is dissociated, whereas one other is a local minimum structure in the reaction pathway leading to dissociative adsorption. In contrast to adsorption onto Rh, where less than 10% of the isomeric population was found in the global minimum associated with dissociative adsorption, a substantial fraction (about 50%) of NO dissociates on Ir. This higher efficiency is attributed to a considerably reduced activation barrier for dissociation on Ir. The key chemical property identified for dissociation efficiency is the cluster's affinity to atomic oxygen.
铱和铑是第IX族元素，二者均可催化还原一氧化氮（NO）。为了解它们对NO反应活性的差异，利用通过红外多光子解离光谱记录的振动光谱，比较了NO在铱和铑团簇上的吸附形式。光谱证明至少存在两种特定的吸附形式。主要的IrNO异构体是NO发生解离的一种异构体，而另一种是导致解离吸附的反应途径中的局部最小结构。与吸附在铑上不同，在铑上与解离吸附相关的全局最小值中发现的异构体数量不到10%，而相当一部分（约50%）的NO在铱上发生解离。这种更高的效率归因于铱上解离的活化能垒大幅降低。确定的解离效率的关键化学性质是团簇对原子氧的亲和力。
