Hydrogen-Induced Reversible Phase Transformations and Hydrogen Storage Properties of Mg–Ag–Al Ternary Alloys

Abstract

Overly stable thermodynamics and sluggish kinetics hinder the practical applications of Mg-based hydrogen storage alloys. Compositional and structural modifications are important strategies in tuning these hydrogen storage properties. In this study, Mg-based Mg–Ag–Al ternary alloys were investigated to explore their performance as hydrogen storage alloys. Mg80Ag15Al5 exhibits a reaction pathway that differs from that in pure Mg, in which the intermediate phase, consisting of a new ternary solid solution MgAg(Al), reacts with MgH2 during dehydriding and contributes to an increase in the dehydriding equilibrium pressure (0.22 MPa at 300 °C) and to a reversible hydrogen storage capacity of 1.7 wt %. Adjusting the composition to Mg85Ag5Al10 results in a reversible hydrogen storage capacity of approximately 3.8 wt % and an elevated equilibrium pressure (0.26 MPa at 300 °C). These Mg–Ag–Al ternary alloys also show enhanced hydrogen sorption kinetics relative to that of Mg, and the apparent activation energies f...