Wet Chemical Synthesis of Non-solvated Rod-Like α'-AlH3 as a Hydrogen Storage Material.

Haizhen Liu,Xiantun Huang,Li Xu,Hongyu Ma,Hua Ning,Shuangyu Liu,Longfei Zhang,Hui Luo,Jin Guo,Zhiqiang Lan,Shichao Gao,Xinhua Wang,Chenglin Lu

doi:10.3389/fchem.2019.00892

Abstract

Aluminum hydride (AlH3) is a promising candidate for hydrogen storage due to its high hydrogen density of 10 wt%. Several polymorphs of AlH3 (e.g., α, β, and γ) have been successfully synthesized by wet chemical reaction of LiAlH4 and AlCl3 in ether solution followed by desolvation. However, the synthesis process of α'-AlH3 from wet chemicals still remains unclear. In the present work, α'-AlH3 was synthesized first by the formation of the etherate AlH3 through a reaction of LiAlH4 and AlCl3 in ether solution. Then, the etherate AlH3 was heated at 60°C under an ether gas atmosphere and in the presence of excess LiAlH4 to remove the ether ligand. Finally, α'-AlH3 was obtained by ether washing to remove the excess LiAlH4. It is suggested that the desolvation of the etherate AlH3 under an ether gas atmosphere is essential for the formation of α'-AlH3 from the etherate AlH3. The as-synthesized α'-AlH3 takes the form of rod-like particles and can release 7.7 wt% hydrogen in the temperature range 120–200°C.

Highlights

Aluminum hydride (AlH3) is a kinetically stable metal hydride under ambient conditions
Brower et al (1976) found that the etherate AlH3 will decompose to Al if heated under a vacuum, but, in the presence of excess LiAlH4, the ether can be removed without decomposition
On the synthesis of AlH3 by the wet chemical reaction in the ether solution, the conditions used in the desolvation stage [reaction (4)] significantly affect the desolvation product of AlH3·nEt2O (Brower et al, 1976). α-AlH3 can be obtained by heating the AlH3·nEt2O at 60–80◦C under a vacuum in the presence of excess LiAlH4 and LiBH4, while γ-AlH3 is formed when the AlH3·nEt2O is heated at 60–70◦C under a vacuum in the presence of only excess LiAlH4 (Brower et al, 1976)

Summary

Introduction

Aluminum hydride (AlH3) is a kinetically stable metal hydride under ambient conditions. Synthesis of Non-solvated α’-AlH3 the wet chemical method. LiAlH4 was reacted with AlCl3 in the ether solution to form AlH3·nEt2O and LiCl [reaction (1)].

Results

Conclusion