Towards easily tunable hydrogen storage via a hydrogen-induced glass-to-glass transition in Mg-based metallic glasses

The exploration of favourable hydrogen storage materials is of great importance for the realization of a sustainable hydrogen energy society. Here, we report a hydrogen-induced glass-to-glass transition in Mg-based metallic glasses (MGs) with a storage capacity as high as 5 wt%-H. The hydrogen storage capacity of metallic glassy hydrides (MGHs) is obviously higher than that of their crystalline counterparts owing to the free volume and disordered atomic structure associated with glasses. The glass-to-glass transition is demonstrated by direct experimental observation using aberration-corrected scanning transmission electron microscopy combined with ab initio molecular dynamics simulations. Remarkably, the dehydrogenation temperature of the MGHs can be efficiently tuned as it shows a close relationship with the enthalpy of mixing between the alloying element and hydrogen, and can be decreased from ∼350 °C to ∼150 °C when alloying with 5 at.%-Cu. MGs therefore have great potential as solid-state hydrogen storage materials.