Tailoring AB ₂ Alloys for Enhanced Solid‐State Hydrogen Storage: Unraveling Compositional Effects on Kinetics, Diffusion, and Thermodynamics

Abstract AB ₂ ‐type alloys are highly promising for commercial solid‐state hydrogen storage, and however, they face challenges such as poor activation, difficulty in balancing plateau pressure and capacity, and large hysteresis. Herein, these issues are addressed by systematically investigating the impact of elemental composition on the hydrogen storage kinetics, hydrogen diffusion, and thermodynamic stability of AB ₂ ‐type alloys. A series AB ₂ ‐type alloys with varying A‐side and B‐side compositions is synthesized via vacuum arc melting. The hydrogen absorption plateau pressures are precisely controlled from 0.003 to 0.342 MPa. The AB ₂ ‐type alloys achieved a maximum hydrogen absorption capacity of 1.903–2.061 wt.% at room temperature. Theoretical calculations revealed that the Zr at the A‐side and Cr at the B‐site enhance hydrogen affinity by lowering adsorption energies. The synergistic contribution of B‐side elements is equally important for the enhancement of hydrogen storage capacity compared to the effect of A‐side elements on hydrogen storage performance. Electron transfer analysis further indicates that increased Zr and Cr content strengthen metal‐hydrogen bonds, which improves storage capacity but may hinder hydrogen release. These findings provide crucial guidance for designing high‐performance AB ₂ hydrogen storage materials.