Design of LPSO-introduced Mg96Y2Zn2 alloy and its improved hydrogen storage properties catalyzed by in-situ formed YH2

Abstract

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, Mg96Y2Zn2 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 Mg96Y2Zn2 alloy decomposes into YH2 + Mg(Zn) composite after hydrogen ab/desorption, of which nanosized YH2 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 MgH2, which ascribes to the “hydrogen pump” effect of YH3 and the catalyst of MgZn2. The hydrogenation process of Mg96Y2Zn2 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 YH2 nanophase and Mg(Zn) originated from LPSO structure are stable and evenly dispersed, thus the Mg96Y2Zn2 alloy shows enhanced hydrogenation capacity and kinetics.