Design of LPSO-introduced Mg 96 Y 2 Zn 2 alloy and its improved hydrogen storage properties catalyzed by in-situ formed YH 2

The long period stacking ordered (LPSO) structure in Mg-based alloy presents a high content of Mg and evenly-dispersed transition metal (TM) and rare earth (RE) elements, which shows great potential in hydrogen storage. In this work, Mg 96 Y 2 Zn 2 alloy with high proportion of LPSO structure was prepared, forming fine α-Mg dendrite and the interdendrite region with homogeneous Zn and Y distributions. Results indicate that Mg 96 Y 2 Zn 2 alloy decomposes into YH 2 + Mg(Zn) composite after hydrogen ab/desorption, of which nanosized YH 2 is in-situ formed from the irreversible decomposition of LPSO and eutectic phase and Mg(Zn) is generated from the dissolution of Zn atoms in Mg lattice. This composite can absorb 5.36–5.79 wt% hydrogen and desorb hydrogen at a lower temperature than pure MgH 2, which ascribes to the “hydrogen pump” effect of YH 3 and the catalyst of MgZn 2. The hydrogenation process of Mg 96 Y 2 Zn 2 alloy is dominated by one-dimension diffusion rate of hydrogen atoms, while the dehydrogenation process is dominated by two-dimension interface movement of the metal/hydride phases. The in-situ formed YH 2 nanophase and Mg(Zn) originated from LPSO structure are stable and evenly dispersed, thus the Mg 96 Y 2 Zn 2 alloy shows enhanced hydrogenation capacity and kinetics.