| Summary: | In this study, the Al–20at%Ca alloy was synthesized by mechanical alloy from the elemental powder mixture. Subsequently, the alloy particles were reacted at room temperature to determine the amount of hydrogen released. For these purposes, the powders reacted with different types of water, such as distilled water, tap water, and seawater, and also in the presence of NaCl and CaO additives. Both milled samples and reaction powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-IR, and Raman spectroscopy (RS). The XRD patterns of the powders prepared show a nanocrystalline alloy consisting of a solid-cubic solution of Al and the tetragonal intermetallic phase CaAl<sub>4</sub>. Studies of XRD and SEM, as well as direct measurements of H<sub>2</sub>, indicated that the best results of H<sub>2</sub> generation were obtained when the alloy reacts with distilled water. Both NaCl and CaO additives improve hydrogen generation, reaching 100% efficiency in distilled water and seawater, and without induction time. Samples with a combination of NaCl and distilled water showed the best reaction times to generate the entire theoretical amount of hydrogen. The XRD and DSC–TGA standards also confirmed the presence of bayerite Al(OH)<sub>3</sub> as a secondary reaction product.
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