Improving hydrogen storage properties of MgH2 by addition of alkali hydroxides

In this study, alkali hydroxides (NaOH, LiOH, KOH) were attempted as new-type catalytic additives to improve the hydrogen storage properties of MgH 2 by ball milling . It is shown that the additives readily react with the MgH 2 to form perovskite-structured NaMgH 3 and KMgH 3 , but not the LiMgH 3 . Although the in-situ formed perovskite hydrides remain stable during hydriding/dehydriding cycles, both NaMgH 3 and KMgH 3 show predominant catalytic role on the hydriding and dehydriding of MgH 2 . In contrast, the LiOH modified MgH 2 presents much inferior sorption kinetics because of the absence of LiMgH 3 . The catalytic mechanism of perovskite hydrides can be explained by the high hydrogen mobility in the perovskite structure . This study shows that such cheap hydroxides could be used as efficient catalysts to improve the hydrogen storage properties of high-capacity metal hydrides and complex hydrides .