Structural and kinetic adjustments of Zr-based high-entropy alloys with Laves phases by substitution of Mg element

Abstract

Exploration of high-entropy alloys for hydrogen storage has recently attracted attention owing to their serious defects, high-entropy induced reduction of thermodynamic stability and abundant raw metal elements. In this study, new Zr-based high-entropy alloys with Laves phases were designed where their structure and hydrogen storage properties were adjusted by introducing Mg element. The results show that the addition of Mg element makes the crystal structure of Zr₂MgV_2−xFe_xCrNi (x = 0 and 1) alloys change from AB₂ type to A₃B₄ type structure, which further leads to the improvement of their hydrogen storage capacity and hydrogen sorption kinetics. The Zr₂MgV₂CrNi and Zr₂MgVFeCrNi high-entropy alloys can rapidly absorb 0.8 wt% (0.43 H/M) and 0.9 wt% (0.48 H/M) hydrogen at room temperature, respectively, three times higher than those of the Zr-based alloys without Mg-substitution. And more importantly, the absorbed hydrogen of Zr₂MgV₂CrNi and Zr₂MgVFeCrNi high-entropy alloys can be partially released at room temperature with distinct desorption processes. These capacity and kinetic enhancements should be related to the higher lattice parameters, lower electron concentration, severe lattice distortion and smaller average valence electron concentration (VEC) of those alloys. The development of Mg-containing Zr-based high-entropy alloys with Laves phases provides a new idea for the design of new hydrogen storage materials.