An efficient hydrolysis of MgH2-based materials

Abstract The reaction of magnesium hydride with water is a very promising means to generate hydrogen for fuel cell applications as MgH 2 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 MgH 2 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 MgH 2 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.