Lithium amidoborane hydrazinates: synthesis, structure and hydrogen storage properties

The first metal amidoborane hydrazinate with a composition of LiNH2BH3 center dot NH2NH2 was successfully synthesized and characterized in the present study. LiNH2BH3 center dot NH2NH2 exhibits a monoclinic P2(1)/n space group with lattice parameters of a = 10.0650 angstrom, b = 6.3105 angstrom, c = 7.4850 angstrom, and beta = 107.497 degrees. 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 H-2/LiAB at 75 degrees C and 170 degrees C, respectively. Therefore, around 7.1 wt% and 11.1 wt% of hydrogen can be released from 4LiAB-NH2NH2 at 75 degrees C and 170 degrees 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.