PNNL

Abstract

A substantial effort worldwide has been given to materials development for onboard hydrogen storage over the past decade.1-6 One interesting family of potential hydrogen storage materials are ammonia borane (AB-NH3BH3) and the related amineboranes. Ammonia borane having a H content of 19.6 mass% encounters relatively high kinetic barrier in dehydrogenation. Recently some work has been reported on approaches to lower the ammonia borane dehydrogenation temperature by introducing nanoscaffold, using Ir-based catalysts or ionic liquids.4-6 Some work has focused on modifying the thermodynamics of ‘stable’ hydrides with additives that stabilize the dehydrogenated products.7 We have been thinking about this from the opposite point of view, i. e., altering the chemical composition of ammonia borane through the addition of amides and hydrides in order to destabilize it.8 The rationale behind this is that the inherent polarity and intermolecular interactions (dihydrogen bonding) of ammonia borane can be altered, and result in different dehydrogenation mechanism. In this paper we report that the interaction between LiH and ammonia borane leads to the replacement of a hydrogen by lithium to yield LiNH2BH3 with substantial resultant changes in dehydrogenation behavior. Battelle operates the Pacific Northwest National Laboratory for the US Department of Energy.