Fabrication of AlLi and Al ₂Li ₃/Al ₄Li ₉ intermetallic compounds by molten salt electrolysis and their application for hydrogen generation from water

The concept of "hydrogen on demand" has been widely publicized. More importantly, the materials used to produce hydrogen on demand should be in themselves safe to handle. In present work, Al-Li intermetallic compounds (IMC) were fabricated in air by electrolysis from LiCl-KCl molten salt at 480 ± 25 °C. Bulk AlLi IMC and the bulk compound with mixture of Al ₂Li ₃ and Al ₄Li ₉ (Al ₂Li ₃/Al ₄Li ₉ IMC) were not pyrophoric and can be safely handled in air. When both compounds in contact with water, vigorous reaction occurred and H ₂ was directly produced. The by-products after H ₂ generation from AlLi IMC were a mixture of Li-containing α-Al and Li-Al hydrotalcite (hereafter referred to as Li-Al LDH). The by-product after H ₂ generation from Al ₂Li ₃/Al ₄Li ₉ compound was a mixture of LiOH·H ₂O and Li-Al LDH. Those by-products can be easily separated from water and may be reused as a resource. Approximately 500-860 ml of H ₂ per weight (g) of the IMC compounds was generated in deionized water at room temperature. Experimentally, AlLi IMC powder and Al ₂Li ₃/Al ₄Li ₉ compound exhibit gravimetric hydrogen capacity of 7.0 wt.% and 5.4 wt.%, respectively. Although the energy consumed for fabricating Al-Li IMC compounds is a little larger than the energy provided by the generated H ₂, the Al-Li IMC compounds are promising materials for producing hydrogen on demand without the necessity of hydrogen storage. Highlights: AlLi and Al ₂Li ₃/Al ₄Li ₉ compounds vigorously reacted with water to generate hydrogen. Al-Li IMC could exhibit gravimetric hydrogen capacity of 5.4-7.0 wt.%. No catalyst was used in the hydrogen generation reaction. The Al-Li intermetallic compounds could be prepared in air.