Collisional Activation of N sub(2)O Decomposition and CO Oxidation Reactions on Isolated Rhodium Clusters

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 117; no. 36; pp. 8855 - 8863-8855-8863
• Main Authors: Parry, Imogen S, Kartouzian, Aras, Hamilton, Suzanne M, Balaj, OPetru, Beyer, Martin K, Mackenzie, Stuart R
• Format: Journal Article
• Language: English
• Published: 02-09-2013
• Subjects: Chemisorption; Clusters; Cobalt; Nitrous oxides; Oxidation; Parents; Rhodium; Surface chemistry
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp405267p

The reactions of nitrous oxide decorated rhodium clusters, Rh sub(n)N sub(2)O super(+) (n = 5, 6), have been studied by Fourier transform ion cyclotron resonance mass spectrometry. Collision induced dissociation with Ar is shown to lead to one of two processes; desorption of the intact N sub(2)O moiety (indicating molecular adsorption in the parent cluster) or N sub(2)O decomposition liberating molecular nitrogen with the latter becoming increasingly dominant at higher collision energies. Consistent with the results of earlier studies, which employed infrared excitation [Hermes, A. C.; et al. J. Phys. Chem. Lett. 2011, 2, 3053], Rh sub(5)ON sub(2)O super(+ ) is observed to behave qualitatively differently to Rh sub(5)N sub(2)O super(+) with decomposition of the nitrous oxide dominating the chemistry of the former. In other experiments, the reactivity of Rh sub(n)N sub(2)O super(+) clusters with CO has been studied. Chemisorption of super(13)CO is calculated to deposit ca. 2 eV into the parent cluster, initiating a range of chemical processes on the cluster surface, which are fit to a simple reaction mechanism. Clear differences are again observed in the reaction branching ratios for Rh sub(5)N sub(2)O super(+) and Rh sub(6)N sub(2)O super(+) parent cluster ions. For the n = 5 cluster, the combined N sub(2)O reduction/CO oxidation is the most significant reaction channel, while the n = 6 cluster preferentially is oxidized to Rh sub(6)O super(+) with loss of N sub(2) and CO. Even larger differences are observed in the reactions of the N sub(2)O decorated cluster oxides, Rh sub(n)ON sub(2)O super(+ ), for which more reaction possibilities arise. The results of all studies are discussed in relation to infrared driven processes on the same parent cluster species [Hamilton, S. M.; et al. J. Am. Chem. Soc. 2010, 132, 1448; J. Phys. Chem. A, 2011, 115, 2489].