Synthesis, crystal structure, electronic state, and reversible hydriding/dehydriding reactions of light metal-based YMgAl and its hydride

Hydriding and dehydriding reactions of intermetallic YMgAl were investigated to explore hydrogen storage materials composed of light metals. X-ray diffraction and thermogravimetric analyses revealed that YMgAl undergoes lattice expansion at room temperature under 1.0 MPa H 2 , forming YMgAlH 2.3 . The hydride released 1.60 wt.% H 2 below 523 K, reverting to YMgAl. Using neutron diffraction, deuterium atomic positions were investigated using a deuterated YMgAl. D atoms occupy three crystallographically different positions. Although D atoms were basically in interstitial sites in YMgAl, some were located near Al atoms with interatomic distances of about 1.80-1.90 Å. The density functional theory (DFT) calculations revealed that H atoms near Al exhibited electronic characteristics similar to those of the hydride ion. The calculated heat of hydrogenation for YMgAlH 2.3 at T = 0 K was −40 kJ mol −1 H 2 . These findings indicate that YMgAl is a promising reversible hydrogen storage material operating under moderate temperature and pressure conditions.