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

The hydrogen storage mechanisms of a single-phase nanocrystalline Al-Cr-Cu-Fe-Ni high-entropy alloy (HEA) that has been mechanically alloyed have been investigated in detail in this work. The alloys have been synthesized from elemental powders using a high-energy attritor ball mill with hexane as a process control agent. After 40 hours of milling, the resultant material was nanocrystalline in nature and exhibited a 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 2.1 wt.% of hydrogen within 3 minutes. At the same temperature, it desorbs about 1.6 wt.% of hydrogen in 6 minutes. These rapid absorption and desorption highlight the alloy efficiency in hydrogen uptake and release. Additionally, the alloy exhibits good cyclic stability, retaining nearly all its hydrogen capacity across 25 cycles, with only a slight loss of 0.2 wt.%. The exceptional cycle stability and quick kinetics of hydrogen storage and release make the nanocrystalline Al-Cr-Cu-Fe-Ni HEA a viable choice for hydrogen storage applications.