Zirconium-Modified Medium-Entropy Alloy (TiVNb) 85 Cr 15 for Hydrogen Storage.

In this study, we investigate the effect of small amounts of zirconium alloying the medium-entropy alloy (TiVNb) 85 Cr 15 , a promising material for hydrogen storage. Alloys with 1, 4, and 7 at.% of Zr were prepared by arc melting and found to be multiphase, comprising at least three phases, indicating that Zr addition does not stabilize a single-phase solid solution. The dominant BCC phase ( HEA 1 ) is the primary hydrogen absorber, while the minor phases HEA 2 and HEA 3 play a crucial role in hydrogen absorption/desorption. Among the studied alloys, Zr4 (TiVNb) 81 Cr 15 Zr 4 shows the highest hydrogen storage capacity, ease of activation, and reversibly retrievable hydrogen. This alloy can absorb hydrogen at room temperature without additional processing, with a reversible capacity of up to 0.74 wt.%, corresponding to hydrogen-to-metal ratio H/M = 0.46. The study emphasizes the significant role of minor elemental additions in alloy properties, stressing the importance of tailored compositions for hydrogen storage applications. It suggests a direction for further research in metal hydride alloys for effective and safe hydrogen storage.