Hydrogen Generation by Hydrolysis of MgH₂-LiH Composite

As a most promising material for hydrogen generation by hydrolysis, magnesium hydride (MgH₂) is also trapped by its yielded byproduct Mg(OH)₂ whose dense passivated layers prevent the further contact of intimal MgH₂ with water. In this work, LiH, as a destroyer, has been added to promote the hydrogen properties of MgH₂. The results demonstrate that even 3 wt % LiH was added into MgH₂-G, the hydrogen generation yield can increase about 72% compared to the hydrogen generation yield of MgH₂-G. The possible mechanism is that Mg²⁺ from the hydrolysis of MgH₂ preferentially bound with OH^- ions from the hydrolysis of LiH to form Mg(OH)₂ precipitation, which is dispersed in water rather than coated on the surface of MgH₂. Moreover, adding MgCl₂ into hydrolysis solution, using ball milling technology, and increasing the hydrolysis temperature can make the hydrolysis rate higher and reaction process more complete. It is noted that a too high weight ratio of LiH with too high of a hydrolysis temperature will make the reaction too violent to be safe in the experiment. We determinate the best experimental condition is that the LiH ratio added into MgH₂ is 3 wt %, the hydrolysis temperature is 60 °C, and the concentration of MgCl₂ hydrating solution is 1 M. MgH₂-LiH composite hydrogen generation technology can meet the needs of various types of hydrogen supply and has broad application prospects.