Dehydrogenation properties of two phases of LiNH2BH3.

Lithium amidoborane (LiNH 2 BH 3) is known as one of the most prospective hydrogen storage materials. In this paper, the differences between two allotropes (α-LiNH 2 BH 3 and β-LiNH 2 BH 3) of LiNH 2 BH 3 in the dehydrogenation properties was reported for the first time. A series of mixtures of α-LiNH 2 BH 3 /β-LiNH 2 BH 3 with different mass ratios were prepared by ball milling for different time and the contents of two phases in samples were determined with Rietveld's method. The thermal decomposition behaviors of samples were investigated by DSC. It shows that the initial dehydrogenation temperature of samples decreases with the content of α-LiNH 2 BH 3 phase increasing. The initial dehydrogenation temperature of α-LiNH 2 BH 3 is about 61 °C, which is approximately 15 °C lower than that of β-LiNH 2 BH 3. Dehydrogenation kinetic analysis shows that α-LiNH 2 BH 3 has the lower activation energy (157 kJ mol−1) and higher rate (k = 1.422 × 101 min−1) than that of β-LiNH 2 BH 3 (272 kJ mol−1 and 1.023 × 10−1 min−1, respectively). It is suggested that α-LiNH 2 BH 3 is more supportive for hydrogen desorption. It gives a critical clue on exploring the dehydrogenation mechanism of lithium amidoborane. Moreover, the significant decrease of desorption temperature will shine a light on on-board hydrogen storage systems. • The two allotropes of LiNH 2 BH 3 have different dehydrogenation properties. • The onset dehydrogenation temperature of α-LiNH 2 BH 3 is lower than that of β-LiNH 2 BH 3. • α-LiNH 2 BH 3 has the lower activation energy and higher rate than that of β-LiNH 2 BH 3. [ABSTRACT FROM AUTHOR]