Atomic occupation of Nb in AB ₂ ‐type alloy and its effect on hydrogen storage property

Abstract AB 2 ‐type hydrogen storage alloys are promising due to their low cost, rapid hydrogen ab/desorption, and good cycling stability, but their narrow operating temperature range and poor plateau performance limit practical applications. In this work, Ti 0.75 Zr 0.3‐ x Cr 0.75 Mn 1.25 Nb x alloys were synthesized, with partial Zr substitution by Nb, to develop a wide‐temperature‐range hydrogen storage alloy. The optimized alloy Ti 0.75 Zr 0.22 Cr 0.75 Mn 1.25 Nb 0.08 exhibited an increase in effective hydrogen desorption capacity from 1.64 wt% to 1.77 wt% at 25 °C. Similarly, the alloy Ti 0.75 Zr 0.20 Cr 0.75 Mn 1.25 Nb 0.10 maintained an effective hydrogen desorption capacity of 1.71 wt% at − 20 °C, demonstrating its performance across different operating conditions. Nb substitution enhanced hydrogen desorption by reducing hysteresis, increasing plateau pressure, and optimizing cycling stability (95.49% capacity retention after 200 cycles). DFT calculations revealed that hydrogen atoms preferentially occupy A2B2 interstitial sites, whereas Nb atoms substitute at A‐site positions, forming weaker Nb‐H bonds that reduce hydride stability and improve desorption performance. This work demonstrates that Nb substitution effectively optimizes AB 2 ‐type alloys and supports the development of wide‐temperature‐range hydrogen storage materials.