Use of the aluminum gallium indium tin system for energy storage and conversion

Abstract

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 generate H2 and heat. Bulk quantities of these alloys participate in a heterogeneous reaction with water to produce H₂ and α-Al(OH)₃ (bayerite) as confirmed by gas chromatography and X-ray diffractometry, respectively. Experiments suggest the reaction is enabled by a mechanism involving multiple alloy phases, where Al solvated in a liquid phase is transported to an interface between the alloy and water resulting in the Al being consumed by reaction. Differential scanning calorimetry indicates that for the Al-Ga-In-Sn quaternary system, the temperature at which this reaction-enabling phase liquefies is 9.38°C. H₂ yield data is collected from the reaction of 50 wt% Al-34 wt% Ga-11 wt% In-5 wt% Sn alloys with water and analyzed with respect to time and temperature. Samples of this composition produced an average H ₂ yield of 83.8%. A fit to the data using fractional order kinetic analysis establishes the activation energy for the rate-limiting step to be 43.8 kJ/mol.