Nanoscale Nickel-Chromium Powder as a Catalyst in Reducing the Temperature of Hydrogen Desorption from Magnesium Hydride

The composite material MgH₂-EEWNi-Cr (20 wt. %) with a hydrogen content of 5.2 ± 0.1 wt. % is characterized by improved hydrogen interaction properties compared to the original MgH₂. The dissociation of the material occurs in three temperature ranges (86-117, 152-162, 281-351 °C), associated with a complex of effects consisting of changes in the specific surface area of the material, alterations in the crystal lattice during ball milling, and changes in the electronic structure in the presence of a Ni-Cr catalyst, based on first-principles calculations. The decrease in desorption activation energy (Ed = 65-96 ± 1 kJ/mol, ΔEd = 59-90 kJ/mol) is due to the catalytic effect of Ni-Cr, leading to a faster decomposition of the hydride phase. Based on the results of ABINIT calculations, Ni-Cr on the MgH₂ surface leads to a significant decrease in hydrogen binding energy (ΔEb = 60%) compared to pure magnesium hydride due to the formation of Ni–H and Cr–H covalent bonds, which reduces the degree of H–Mg ionic bonding. The results obtained allow us to expand our understanding of the mechanisms of hydrogen interaction with storage materials and the possibility of using these as mobile hydrogen storage and transportation materials.