Promotion of hydrogen release from ammonia borane with magnesium nitride

Abstract

Hydrogen release from ammonia borane (NH₃BH₃, AB) can be greatly promoted by mechanical milling with magnesium nitride (Mg₃N₂). For example, a post-milled 6AB/Mg₃N₂ sample started to release hydrogen from ∼65 °C and gave a material-based hydrogen capacity of ∼11 wt% upon heating to 300 °C. In addition to the improved dehydrogenation kinetics, the 6AB/Mg₃N₂ sample also showed satisfactory performance in suppressing the volatile byproducts. X-ray diffraction, Fourier transform infrared spectroscopy and solid-state ¹¹B MAS NMR, as well as a series of designed experiments, were carried out to gain mechanistic understanding of the property improvements that arise from addition of Mg₃N₂. Our study found that the formation of 3Mg(NH₂BH₃)₂·2NH₃, which is in single or mixed amidoborane ammoniate phases in nature, is an important mechanistic step in the dehydrogenation process of the 6AB/Mg₃N₂ sample.