Morse, M. D. and Gausic, M. E. and Heath, J. R. and Smalley, R. E. (1985) Surface reactions of metal clusters. II. Reactivity surveys with D2, N2, and CO. Journal of Chemical Physics, 83 (5). pp. 2293-2304. ISSN 0021-9606 http://resolver.caltech.edu/CaltechAUTHORS:MORjcp85
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Reactions on the surface of a variety of transition metal clusters have been studied in the gas phase at near room temperature using a newly developed fast-flow reaction device. Initial examples of the use of this device are provided by survey studies of the reactivity of iron, cobalt, nickel, copper, and niobium clusters in contact with low concentrations of D2, N2 and CO. Dissociative chemisorption of D2 is found to occur with dramatic sensitivity to cluster size in the cases of iron, cobalt, and niobium clusters, the detailed pattern of reactivity differing markedly for each metal. The corresponding reaction is also observed with nickel clusters, but here the reactivity shows only a slow, steady increase with cluster size. Copper clusters are found to be completely unreactive to H2 chemisorption under these conditions. Molecular nitrogen is found to chemisorb readily to clusters of cobalt and niobium, with a reactivity pattern very similar to that observed with D2. Iron clusters are found to show slight reactivity with N2; only a small amount of chemisorption is observed on the most reactive clusters at high N2 concentration, but the pattern of this reactivity with cluster size is consistent with that observed in D2 chemisorption. In contrast to these highly structured reactivity patterns of D2 and N2, carbon monoxide is found to show only a slow, monotonic increase in reactivity with cluster size. It is suggested that these dramatic reactivity patterns for chemisorption on metal clusters provide stringent tests for future theories as to the nature of chemisorption on metal surfaces at a detailed, molecular level.
|Additional Information:||Copyright © 2008 American Institute of Physics. Received 31 January 1985; accepted 17 May 1985. We wish to acknowledge extremely valuable discussions with R.H. Hauge and Z. Kafifi of Rice University. It was in these discussions that H2 dissociative chemisorption was first suggested as a pivotal experiment for the new metal cluster reaction apparatus. Our thanks also go to D.M. Cox, A. Kaldor, D.J. Trevor, and R.L. Whetten of Exxon Research and Engineering for their continued interest and support in this work, and communication of their early metal cluster reaction results prior to publication. Research on bare metal clusters in this laboratory is supported by the Department of Energy, Division of Chemical Sciences, together with the Robert A. Welch Foundation, and the Exxon Education Foundation. The beam apparatus used in this work was developed and constructed largely under funding from the National Science Foundation in support of our research on nonmetal adducts of metal clusters. Acknowledgment is also made to the Donors of the Petroleum Research Fund for partial support of this research. [M.E.G. was a] Robert A. Welch Foundation Predoctoral Fellow.|
|Subject Keywords:||ATOMIC CLUSTERS, DEUTERIUM, NITROGEN, CARBON MONOXIDE, IRON, COBALT, NICKEL, COPPER, NIOBIUM, CHEMISORPTION, CHEMICAL REACTIONS, SURFACES, CATALYSIS|
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|Deposited On:||22 Jun 2008|
|Last Modified:||26 Dec 2012 10:07|
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