Wet Chemical Synthesis of Non-solvated Rod-Like α'-AlH as a Hydrogen Storage Material.

Aluminum hydride (AlH) is a promising candidate for hydrogen storage due to its high hydrogen density of 10 wt%. Several polymorphs of AlH (e.g., α, β, and γ) have been successfully synthesized by wet chemical reaction of LiAlH and AlCl in ether solution followed by desolvation. However, the synthesis process of α'-AlH from wet chemicals still remains unclear. In the present work, α'-AlH was synthesized first by the formation of the etherate AlH through a reaction of LiAlH and AlCl in ether solution. Then, the etherate AlH was heated at 60°C under an ether gas atmosphere and in the presence of excess LiAlH to remove the ether ligand. Finally, α'-AlH was obtained by ether washing to remove the excess LiAlH. It is suggested that the desolvation of the etherate AlH under an ether gas atmosphere is essential for the formation of α'-AlH from the etherate AlH. The as-synthesized α'-AlH takes the form of rod-like particles and can release 7.7 wt% hydrogen in the temperature range 120-200°C.