Hydrogen storage properties of Mg98.5Gd1Zn0.5 and Mg98.5Gd0.5Y0.5Zn0.5 alloys containing LPSO phases.

In this work, the as-cast Mg-rich Mg 98.5 Gd 1 Zn 0.5 and Mg 98.5 Gd 0.5 Y 0.5 Zn 0.5 alloys are prepared by the semi-continuous casting method, and their hydrogen storage performance and catalytic mechanisms are investigated by experimental and first-principles calculations approaches. The results show that the LPSO phases decompose and in-situ form the RE(Gd/Y)H x (x = 2,3) nano-hydrides upon hydrogenation. These nano-hydrides not only serve as the in-situ catalysts to promote the hydrogen ab/desorption of Mg matrix, but also present the pinning effect to inhibit the growth of Mg / MgH 2 grains during hydrogenation and dehydrogenation. Comparatively, the two alloys exhibit the similar hydrogen absorption kinetics, while the hydrogen desorption kinetics of Mg 98.5 Gd 1 Zn 0.5 is superior to that of Mg 98.5 Gd 0.5 Y 0.5 Zn 0.5. The first-principles calculations reveal that the GdH 2 and YH 2 hydrides exhibit different catalytic effects on weakening the bond strength of H–H within H 2 and Mg–H within MgH 2 , which interprets well the differences in the hydrogen ab/desorption kinetics between Mg 98.5 Gd 1 Zn 0.5 and Mg 98.5 Gd 0.5 Y 0.5 Zn 0.5 alloys. • The Mg-rich Mg-Gd-Zn and Mg-Gd-Y-Zn alloys are prepared by semi-continuous casting. • The LPSO phases decompose and in-situ form RE(Gd / Y)H x (x = 2,3) upon hydrogenation. • The RE(Gd/Y)H x (x = 2,3) show in-situ catalytic and pinning effects on Mg alloys. • The desorption rate of Mg 98.5 Gd 1 Zn 0.5 is faster than that of Mg 98.5 Gd 0.5 Y 0.5 Zn 0.5. • The GdH 2 and YH 2 both weaken the bond strength of H–H within H 2 and Mg–H with MgH 2. [ABSTRACT FROM AUTHOR]