Rapid hydrogen generation behavior of Mg-In-Ga alloy systems with a local galvanic cell structure

In Mg-In-Ga alloys, the eutectic microstructure formed by the Mg phase and the secondary Mg5Ga2 phase can act as a local galvanic cell. This study aimed to develop Mg-In-Ga alloys and investigate their microstructure, surface potential distribution, and hydrolysis performance. As exemplified by the Mg85In5Ga10 alloy, which achieved 604.4 mL g-1 of hydrogen within 9.2 min and a rate of 79.3 mL (g·min)-1, the Mg-In-Ga alloy system was found to exhibit high hydrolysis performance. We elucidated that this rapid hydrolysis is driven by three essential factors: (i) galvanic action originating from the α-Mg/Mg5(Ga,In)2 structure, (ii) self-acceleration by reaction heat, and (iii) outward release of the hydroxide layer. In and Ga remain as liquid residues after hydrolysis, potentially enabling recyclability of these elements. Additionally, heat-treatment control of Mg5(Ga,In)2 dissolution and precipitation allows reversible switching between high reactivity and long-term storage stability. These findings provide design guidelines for Mg-based hydrogen-generating materials that integrate high reactivity, storage stability, and resource circularity. The concept extends beyond the Mg-In-Ga system, providing a basis for on-demand hydrogen supply and lightweight distributed energy systems.