The Onset of Dehydrogenation in Solid Ammonia Borane: An Ab Initio Metadynamics Study

Abstract

The discovery of effective hydrogen storage materials is fundamental for the progress of a clean energy economy. Ammonia borane (H3BNH3, AB) has attracted great interest as a promising candidate but the reaction path that leads from its solid phase to hydrogen release is not yet fully understood. To address the need for insights in the atomistic details of such a complex solid state process, in this work we use ab‐initio molecular dynamics and metadynamics to study the early stages of AB dehydrogenation. We show that the formation of ammonia diborane (H3NBH2(μ‐H)BH3) leads to the release of NH4+, which in turn triggers an autocatalytic H2 production cycle. Our calculations provide a model for how complex solid state reactions can be theoretically investigated and rely upon the presence of multiple ammonia borane molecules, as substantiated by standard quantum‐mechanical simulations on a cluster.

Exploring the Chemistry of Low‐Temperature Ignition by Pressure‐Accelerated Dynamics

“…[29] They have been shown to be applicable to a great variety of problems. [37][38][39][40][41][42][43][44][45] Still, there are limitations to these methods. It has been found, for example, that the construction of bias potentials is not trivial.…”

“…With the existing methods, it is possible to extend feasible timescales by multiple orders of magnitude . They have been shown to be applicable to a great variety of problems . Still, there are limitations to these methods.…”

Willstaetter Lecture: D. Gelman / Roelen Award: F. Glorius / European Chemistry Gold Medal: M. Parrinello

“…The Car–Parrinello molecular dynamics method is used in the context of chemistry, materials sciences, and biological systems. Parrinello, who was already present in this section, recently published a Communication in Angewandte Chemie on an ab initio metadynamics study on the onset of dehydrogenation in ammonia borane …”

Breviarium de Motu Simulato Ad Atomos Pertinenti

“…[56,57] This approach is working well and has helped solving complex problems. [58,41] These variables capture the sigmoidal character of the CV but they do not use any information on the transition state, nonetheless they work remarkably well. However, one can put in place a strategy to improve the CVs when adding information on the the transition states.…”