Solid state synthesis of nano-sized AlH 3 and its dehydriding behaviour

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2015, Vol.17 (6), p.3466-3474
• Main Authors: Duan, C. W., Hu, L. X., Xue, D.
• Format: Article
• Language: English
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/C5GC00426H

Aluminum hydride (AlH 3 ) has a high gravimetric hydrogen capacity (10.1 wt%) and has attracted considerable attention due to its potential application for hydrogen storage. Up to now, almost all the routes developed for the synthesis of AlH 3 are energy-consuming and economically impractical for mass production. In this study, a cost effective route of solid state reactive milling was proposed to synthesize AlH 3 using aluminum chloride and cheap metal hydrides as starting reagents, with the LiH/AlCl 3 , MgH 2 /AlCl 3 , and CaH 2 /AlCl 3 reaction systems being experimentally investigated. The reaction progress and products during reactive milling were characterized by XRD and 27 Al NMR, and the morphology as well as the microstructure of the as-milled samples by SEM and TEM, respectively. It was found that nano-sized γ-AlH 3 could be synthesized by reactive milling with commercial AlCl 3 and nanocrystalline MgH 2 as reagents. Based on the XRD and NMR analyses as well as the TEM observation, the average size of the γ-AlH 3 phase in the as-synthesized γ-AlH 3 /MgCl 2 nanocomposite was estimated to be about 8.5 nm. By an isothermal dehydrogenation test, the as-synthesized γ-AlH 3 was found to have a quite high hydrogen desorption capacity and fast kinetics, with a hydrogen desorption amount of about 9.71 wt% within 9080 s at 220 °C.