Disposable hydrogen generators: Magnesium hydride oxidation in aqueous salts solutions

The impact of mechanochemical activation and methods of addition of non-hydrolyzing salts of NaCl, NH 4 Cl, NH 4 Br и MgCl 2 ∙(either dry powder or solution) on the reaction rate and yield of hydrogen production upon magnesium hydride oxidation by water was investigated. It was established that addition of halides increases the hydrogen yield from 22% to 99% (of theoretical value) while the rate of hydrogen production has increased from ∼220 to 1700 mL/min g (MgH 2 ). The addition of dry salts during the mechanochemical treatment of the hydride always results in much higher reaction rate compared to the use of the same salt solutions. It was observed that activation by NH 4 Cl and MgCl 2 results in bell-shaped change in the hydrogen release rate. Of all evaluated halide salt activators, the greatest overall yield (∼99%) was achieved in the presence of 0.17 M NaCl solution. The reaction rate at these conditions was rather slow; it took up to 4 h to complete the oxidation. The highest rate of oxidation, when 94% of theoretical yield was achieved in 3 min, was observed in the presence of 0.85 M NH 4 Br. • Non-hydrolysable halides enhance H 2 generation by MgH 2 oxidation with water. • Performance of salts depends on adding techniques. • Paired combination of salts gives no additional effect. • The highest reaction rate and H 2 yield was observed for NH 4 Br.