An efficient hydrolysis of MgH2-based materials

The reaction of magnesium hydride with water is a very promising means to generate hydrogen for fuel cell applications as MgH2 is cheap, non-toxic, has a very long shelf life as well as an extremely high hydrogen storage capacity of up to 15.3 wt.% in hydrolysis reactions. However, pure MgH2 reacts only very slowly and incompletely with water and previous attempts to increase the hydrogen release kinetics and yields often involved the addition of large amounts of Bronsted acids, high-energy ball milling or expensive noble metal catalysts. Here, we present a systematic study on how MgH2 is easily activated by the addition of small amounts of certain metal halides to make it react with water in a highly dynamic fashion. Possible mechanisms of this activation are discussed, which were illuminated by in situ measurements of pH and hydrogen normal volume flux during hydrolysis reactions under pseudo-isothermal conditions as well as ex situ X-ray powder diffraction. Furthermore, application-related issues like the influence of water hardness and quality on the hydrolysis reaction are addressed.