Improving the hydrogen cycling properties by Mg addition in Ti-V-Zr-Nb refractory high entropy alloy

A novel high entropy alloy containing Mg and refractory elements has been prepared by mechanochemical synthetic method under inert atmosphere. The Mg0.10Ti0.30V0.25Zr0.10Nb0.25 alloy adopts a single-phase bcc lattice and can absorb hydrogen within 1 minute at room temperature forming a hydride phase with 1.7 H/M (2.7 wt.%) capacity. During the reaction with hydrogen the alloy undergoes a single-step and reversible phase transformation from bcc (alloy) to fcc lattice (hydride). The absorption/desorption cycling properties prove a small fading of the capacity for the first cycle followed by stabilization to 1.5 H/M (2.4 wt.%) for the next cycles. A simple comparison between this quinary HEA and the quaternary alloy containing only refractory elements Ti0.325V0.275Zr0.125Nb0.275 proves an important enhancement of the cycling properties by Mg addition. These insights seem to suggest that insertion of light-weighted metals such as, Mg, can guide future design of novel HEA with improved performances for hydrogen storage. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

A novel high entropy alloy containing Mg and refractory elements was prepared through mechanochemical synthesis, showing fast hydrogen absorption and stable cycling properties at room temperature. The addition of Mg significantly enhanced the cycling stability and hydrogen absorption capacity of the alloy, providing important insights for the design of novel high entropy alloys with improved hydrogen storage performance in the future.