LAUSR

Reactivity of bimetallic cobalt-niobium cluster cations, ConNbm+ (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, ConNb+, exhibit large cross sections for the NH3 dehydrogenation compared to the corresponding single-element clusters, Con+1+ and Nbn+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 ConNb+ (n = 3, 4, and 6) result in the formation of ConNbN2+, which can be generated via complete dehydrogenation of two NH3 molecules, in addition to the formation of ConNbNxHx+.