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

The hydrogen storage mechanism of a single-phase nanocrystalline mechanically alloyed Al–Cr–Cu–Fe–Ni high-entropy alloy (HEA) was investigated in this study. The alloys were synthesized from the elemental powders using high-energy attritor ball mill with hexane as the process control agent. The material obtained after 40 h of milling was nanocrystalline and exhibited body-centered cubic (BCC) phase with a lattice parameter of 0.289 nm. The nanocrystalline Al–Cr–Cu–Fe–Ni HEA demonstrated remarkable hydrogen storage capacity at 300°C and 50 atm hydrogen pressure, absorbing 2.1wt% of hydrogen within 3 min and desorbing approximately 1.6wt% of hydrogen in 6 min. These rapid absorption and desorption processes highlighted the efficiency of the alloy for hydrogen uptake and release. Additionally, the alloy exhibited good cyclic stability, with a loss of only 0.2wt% of its hydrogen capacity across 25 cycles. The exceptional cycle stability and rapid kinetics of hydrogen storage and release make the nanocrystalline Al–Cr–Cu–Fe–Ni HEA a viable choice for hydrogen storage applications.