Dehydrogenation properties of two phases of LiNH2BH3

Abstract Lithium amidoborane (LiNH2BH3) is known as one of the most prospective hydrogen storage materials. In this paper, the differences between two allotropes (α-LiNH2BH3 and β-LiNH2BH3) of LiNH2BH3 in the dehydrogenation properties was reported for the first time. A series of mixtures of α-LiNH2BH3/β-LiNH2BH3 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-LiNH2BH3 phase increasing. The initial dehydrogenation temperature of α-LiNH2BH3 is about 61 °C, which is approximately 15 °C lower than that of β-LiNH2BH3. Dehydrogenation kinetic analysis shows that α-LiNH2BH3 has the lower activation energy (157 kJ mol−1) and higher rate (k = 1.422 × 101 min−1) than that of β-LiNH2BH3 (272 kJ mol−1 and 1.023 × 10−1 min−1, respectively). It is suggested that α-LiNH2BH3 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.