The role of preparation route upon the ambient pressure ammonia synthesis activity of Ni2Mo3N

The preparation route has been shown to have a significant influence upon the catalytic behaviour of Ni2Mo3N samples for ambient pressure ammonia synthesis. Materials prepared from a NiMoO4 precursor necessarily contain a significant fraction of Ni impurity phase. Materials prepared from this precursor are relatively inactive for ammonia synthesis, whereas Ni2Mo3N of much greater phase purity and catalytic activity can be prepared from precursors employing a modified Pechini method with the use of citrate gels. Ni2Mo3N can be prepared by N-2/H-2 pre-treatment which represents a significant advantage over routes employing ammonolysis. Bulk lattice nitrogen appears to be relatively unreactive in Ni2Mo3N, although heterolytic nitrogen isotopic exchange studies indicate that a significant degree is exchangeable subject to pre-treatment conditions. The modified Pechini method based route has also been shown to be applicable to the preparation of CoNiMo3N of relatively high phase purity, thereby allowing access to the preparation of quaternary nitrides for catalytic screening. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).