Effect of Various Additives on the Hydrolysis Performance of Nanostructured MgH 2 Synthesized by High-Energy Ball Milling in Hydrogen

Magnesium hydride is a promising material for hydrogen generation via hydrolysis owing to high hydrogen storage capacity, mild reaction conditions, and low cost of magnesium metal. Unfortunately, the hydrolysis reaction of MgH 2 is rapidly hindered due to the formation of a passive Mg(OH) 2 layer. Various additives can be used to improve the efficiency of the reaction. The present study examines the influence of 5 wt.% EDTA and TiC–2TiB 2 additives on the hydrolysis of the nanostructured MgH 2 and compares it with the hydrolysis performance of pure MgH 2 and MgH 2 + 5 wt.% AlCl 3 for the first time. MgH 2 was synthesized by high-energy ball milling of Mg powder in hydrogen gas, while MgH 2 -based nanocomposites were prepared either by mixing the obtained MgH 2 with 5 wt.% of additives or by milling Mg with 5 wt.% of additive in hydrogen. The synthesized MgH 2 is nanosized, containing a mixture of β-MgH 2 and high-pressure γ-modification of MgH 2 . The hydrogen generation performance in terms of MgH 2 conversion rate and hydrogen yield was determined volumetrically. It was found that the MgH 2 + 5 wt.% EDTA composite displays the lowest reactivity among the tested materials, probably due to the interaction of MgH 2 with EDTA during the ball milling. Pure MgH 2 and MgH 2 + 5 wt.% (TiC–2TiB 2 ) composite demonstrate almost twice as better hydrolysis performance, which is, however, still quite far from application requirements. The maximum hydrogen yield of 557 mL/g MgH 2 and conversion rate of 30.3% was observed for MgH 2 + 5 wt.% AlCl 3 composition after 10 min of hydrolysis, which can be attributed to the destabilization of the Mg(OH) 2 layer by chlorine ions.