Lithium amidoborane hydrazinates: synthesis, structure and hydrogen storage properties

Abstract

The first metal amidoborane hydrazinate with a composition of LiNH₂BH₃·NH₂NH₂ was successfully synthesized and characterized in the present study. LiNH₂BH₃·NH₂NH₂ exhibits a monoclinic P2₁/n space group with lattice parameters of a = 10.0650 Å, b = 6.3105 Å, c = 7.4850 Å, and β = 107.497°. Meanwhile, lithium amidoborane hydrazinates with different molar ratios of LiNH₂BH₃ (LiAB) and NH₂NH₂ were synthesized and characterized. It was found that 4LiAB–NH₂NH₂ can release 1.6 equiv. and 2.5 equiv. of H₂/LiAB at 75 °C and 170 °C, respectively. Therefore, around 7.1 wt% and 11.1 wt% of hydrogen can be released from 4LiAB–NH₂NH₂ at 75 °C and 170 °C, respectively, which are higher values than those for pristine LiAB. A dehydrogenation mechanism, which may be initiated by the “homogeneous dissociation” of N–N in hydrazine, is also proposed and discussed in this study.