Enhanced Effect of an External Electric Field on NH₃BH₃ Dehydrogenation: an AIMD Study for Thermolysis

Abstract

How to improve the dehydrogenation properties of ammonia borane (AB, NH 3 BH 3 ) is always a challenge for its practical application in hydrogen storage. In this study, we reveal the enhanced effect of an external electric field ( E ext ) on AB dehydrogenation by means of the ab initio molecular dynamics method. The molecular rotation induced by an electrostatic force can facilitate the formation of the H–N···B–H framework, which would aggregate into poly-BN species and further suppress the generation of the volatile byproducts. Meanwhile, the dihydrogen bond (N–H δ+ ··· δ− H–B) is favorably formed under E ext , and the interaction between relevant H atoms is enhanced, leading to a faster H 2 liberation. Correspondingly, the apparent activation energy for AB dissociation is greatly reduced from 18.42 to around 15 kcal·mol –1 with the application of an electric field, while that for H 2 formation decreases from 20.4 to about 16 kcal·mol –1 . In the whole process, the cleavage of the B–H bond is more favorable than that of the N–H bond, no matter whether the application of E ext . Our results give a deep insight into a positive effect of an electric field on AB dehydrogenation, which would provide an important inspiration for hydrogen storage in industry applications.