Liquid phase-enabled reaction of Al–Ga and Al–Ga–In–Sn alloys with water

The water-reactivity of Al–Ga and Al–Ga–In–Sn alloys is investigated as a means to utilize the chemical potential energy of Al to split water for the production of H2. Al in bulk quantities of these alloys participates in a heterogeneous reaction with water to produce H2 and α-Al(OH)3 (bayerite). Low melting point phases in these alloys are believed to enable the observed reaction upon liquefaction by providing a means of transport for Al in the alloys to reach a reaction site. In the Al–Ga binary system, this reaction-enabling phase is shown to form at a temperature corresponding to the system’s eutectic melting point. In the Al–Ga–In–Sn quaternary system this reaction-enabling phase liquefies at 9.38 °C, as shown using differential scanning calorimetry (DSC). Alloys with the composition 50 wt% Al-34 wt% Ga-11 wt% In-5 wt% Sn are reacted with distilled water in a series of controlled experiments, and H2 yield from these reactions is measured as a function of time and temperature. Applying kinetic analysis to the yield data shows the apparent activation energy for the reaction process to be 43.8 kJ/mol. A physicochemical model for the alloy–water reaction is presented in the context of the observed experimental results and relevant scientific literature.