Dehydrogenation of ammonia by early transition metals: formation of metal nitride clusters

The dehydrogenation of NH3 by Ti, Zr, and Nb cations, produced in a laser-i nduced plasma reactor, is found to form both neutral and cationic clusters. Depending on the conditions, either the production of neutral metal nitrid e clusters is favored or, the formation of cationic 'precursor' metal nitri de clusters containing additional intact NH3 is observed. The neutral clust ers are formed when full dehydrogenation of the NH3 is achieved, while the cationic precursor species are formed under conditions where a large fracti on of the NH3 remains intact. Metastable dissociation studies show that int act NH3 molecules are bound to the developing transition metal nitride clus ters. (C) 1999 Elsevier Science B.V. All rights reserved.