Ammonia Dehydrogenation on Cobalt Cluster Cations Doped with Niobium
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Reactivity of bimetallic cobalt-niobium cluster cations, Co n Nb m + (n = 1–4, 6; m = 1–3), toward ammonia was investigated at near thermal energy using a guided ion beam tandem mass spectrometer. The dehydrogenation of NH3 is dominantly observed in the single-collision reactions of all the bimetallic clusters studied here. Most of the clusters containing one niobium atom, Co n Nb+, exhibit large cross sections for the NH3 dehydrogenation compared to the corresponding single-element clusters, Co n+1 + and Nb n+1 +. Density functional theory calculations reveal that both the transition states involved in the first and the second cleavages of N–H bonds of NH3 are significantly stabilized for Co4Nb+, which gives rise to the higher reactivity toward the NH3 dehydrogenation. The multiple-collision reactions of Co n Nb+ (n = 3, 4, and 6) result in the formation of Co n NbN2 +, which can be generated via complete dehydrogenation of two NH3 molecules, in addition to the formation of Co n NbN x H x +.
KeywordsAmmonia Cobalt Niobium Bimetallic clusters Dehydrogenation
Calculations were performed using the Fujitsu PRIMERGY RX300 S7 of the Research Center for Computational Science, Okazaki Research Facilities, National Institutes of Natural Sciences. This work was supported by the Special Cluster Research Project of Genesis Research Institute, Inc.
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