Hydrogen generation by aluminum-water reaction in acidic and alkaline media and its reaction dynamics

Abstract

The additives AlCl3, CoCl2, Al(OH)3, Ca(OH)2, and NaAlO2 are added to water to regulate its pH value (pH = 2-13) in this study. The effects of media on the aluminum-water reaction are investigated. Up to an increase in temperature, the hydrogen generation rate in different media increases. H+, OH−, Cl−, or Co produced from the additive favors the initial removal of the oxide film and aluminum corrosion. Therefore, the initial hydrogen generation rate increases in acidic and alkaline media. The synergistic effect of the formed fresh Co and Cl− catalyzes aluminum-water reactions. However, the amount of hydrogen decreases with increasing mass of CoCl2 because of agglomeration of the catalyst Co. The higher concentration of OH− ions aids hydrogen generation. However, the reaction rate became slow after the rapid consumption of OH−, when the concentration of OH− was relatively small. Hydrogen is quickly generated and Al is completely reacted upon following additions of Al due to the cooperation between H+, Cl−, OH− ions, and the formed Al(OH)3.