Reversible hydrogen storage in AlH <sub>3</sub> −LiNH <sub>2</sub> system
Liang Zhang, Zhiling He, Hua Ning, Hui Luo, Qinqin Wei, Peilin Qing, Xiantun Huang, Xinhua Wang, Guangxu Li, Cunke Huang, Zhiqiang Lan, Wenzheng Zhou, Jin Guo, M. Ismail, Haizhen Liu
Abstract
Abstract As a hydrogen storage material, both AlH 3 and LiNH 2 possess a high hydrogen capacity. However, the dehydrogenated AlH 3 can hardly absorb hydrogen under normal conditions, while LiNH 2 will generate NH 3 rather than H 2 upon decomposition. In this work, we report that the combination of AlH 3 and LiNH 2 through simple ball milling leads to partial reversibility of the AlH 3 −LiNH 2 system and the suppression of NH 3 liberation. The negatively charged H δ − in AlH 3 will react with the positively charged H δ + in LiNH 2 through a redox reaction to form Li 2 NH, AlN, and H 2 at 120−170 °C. After dehydrogenation at above 270 °C, Li 3 AlN 2 is generated, which is crucial for the reversibility of this system. The more the Li 3 AlN 2 generated, the better the reversibility of this system. The dehydrogenation capacity of AlH 3 + 2LiNH 2 at the third cycle (3.0 wt%) is higher than that of AlH 3 + LiNH 2 (1.2 wt%) due to the generation of more Li 3 AlN 2 . The role of AlH 3 /Al in the AlH 3 −LiNH 2 system is to fix the nitrogen into the form of AlN and Li 3 AlN 2 and thus suppress the liberation of NH 3 . Therefore, the synergy of AlH 3 and LiNH 2 leads to the reversibility of the Li–Al–N–H system and the suppression of NH 3 .