Studies of the Hydrolysis of Aluminum Activated by Additions of Ga–In–Sn Eutectic Alloy, Bismuth, or Antimony

We study the Ga–In–Sn eutectic-catalyzed interaction of aluminum alloys with water resulting in the process of hydrolysis and generation of hydrogen. The aluminum alloys were prepared by melting aluminum with additions of Ga–In–Sn eutectic (5 wt.%), bismuth (3 wt.%), or antimony (3 wt.%). The temperature-dependent kinetics of their hydrolysis in a temperature range 25–70°C is studied by using a volumetric technique. The most efficient activation of the hydrolysis process is achieved for the Al–Ga–In–Sn alloy. The addition of bismuth to the Al–Ga–In–Sn alloy significantly decreases the hydrolysis rate, whereas the addition of antimony has only a weak effect on the process, despite the fact that the standard electrode potentials of bismuth and antimony have close values. The interactions of the studied alloys with water can be well fitted as a topochemical process. The modified Prout–Tompkins equation is used to get the effective hydrolysis-rate constants and it is shown that they increase following the temperature rise within the temperature range from 25 to 70°C. The activation energies of the process of hydrolysis for the studied alloys are calculated from the temperature dependence of the values of effective rate constants, which indicates that, within the main range of hydrogen generation (after the completion of the induction period and prior to the onset of deceleration of hydrogen release), the process of hydrolysis can be described as a diffusion-limited process.