Hydrogen generation through hydrolysis of gas-atomized Ca–Mg eutectic alloys

The hydrolysis of gas-atomized Ca–25 at.% Mg eutectic alloy powder was studied to assess its viability for hydrogen generation. This powder, which consists of Ca and Mg 2 Ca phases, underwent nearly complete hydrolysis at room temperature to form Ca(OH) 2 and Mg(OH) 2 . In contrast, MgH 2 failed to react completely because of the development of a dense Mg(OH) 2 passivation layer with low water solubility, whereas Ca flakes showed high but uncontrollable reactivity. The gas-atomized powder particles had a spherical shape and a globular nanoscale eutectic structure, which improved water accessibility and reaction efficiency. The reaction kinetics were accurately described using a logistic growth model. Its activation energy of 36.6 kJ/mol indicates a surface-controlled and thermally activated mechanism. These findings highlight the potential of Ca–Mg eutectic powder for efficient hydrogen generation under mild conditions, especially for on-site or portable applications.