Notable hydrogen storage properties in nanocrystalline Al–Cr–Cu–Fe–Ni high entropy alloy

• Nanocrystalline Al–Cr–Cu–Fe–Ni HEA synthesized via high-energy attritor ball milling exhibits a single-phase BCC structure with a lattice parameter of 0.289 nm. • The alloy achieves rapid hydrogen absorption of 2.1 wt% within 3 minutes and desorption of 1.6 wt% in 6 minutes at 300°C and 50 atm, demonstrating excellent kinetics. • Exceptional cyclic stability is observed, with only 0.2 wt% capacity loss over 25 cycles, indicating high reversibility. • The combination of rapid kinetics and stable cycling makes this HEA a promising candidate for practical solid-state hydrogen storage applications.