Optimized desolvation-crystallization of α-AlH3 from a cost-effective NaAlH4/LiAlH4 hybrid system

The widespread implementation of hydrogen energy is critically constrained by the challenge of storage. Aluminum hydride (α-AlH 3 ), a binary hydride stable under ambient conditions with high volumetric hydrogen density, represents a promising candidate. However, when it is traditionally prepared from lithium aluminum hydride (LiAlH 4 ) and aluminum chloride (AlCl 3 ), the process is cost-prohibitive for scale-up. This study presents a cost-effective synthesis strategy by systematically investigating the effects of different molar ratios of LiAlH 4 /NaAlH 4 /AlCl 3 (4:0:1, 1:3:1, 0.5:3.5:1, 0:4:1). Results indicate that the introduction of LiAlH 4 significantly enhances reaction efficiency and kinetics. The optimal ratio of 1:3:1 effectively compensated for the slower kinetics of NaAlH 4 , achieving over 94% conversion of AlCl 3 to AlH 3 ·nEt 2 O etherate. Desolvation studies revealed that AlH 3 ·nEt 2 O derived from NaAlH 4 required higher temperatures for complete phase transformation, whereas systems with LiAlH 4 content below 25% were insufficient to effective desolvation. The α-AlH 3 crystals produced from the 1:3:1 ratio exhibited a well-defined cubic morphology and high thermal stability, with a decomposition temperature of 165 °C. By replacing 75% of the costly LiAlH 4 with NaAlH 4 , this hybrid approach achieved an approximately 50% reduction in the material cost. These findings provide critical process parameters and a viable pathway for the cost-effective, large-scale production of high-performance α-AlH 3 for hydrogen storage applications.