Improving hydrogen storage characteristics of Mg–Ni-based alloys by adding Y and melt spinning

Slow hydrogen absorption/desorption kinetics and high thermal stability are regarded as major setbacks for the real application of Mg-based hydrogen storage alloys. Overcoming these shortcomings, the Mg_25-xY_xNi₁₀ (x = 0, 1, 3, 5, 7) alloys with nanocrystalline and amorphous structures were synthesized by melt spinning technology to improve their hydrogen absorption/desorption properties. The dehydrogenation activation energy of the alloy was estimated using the Arrhenius and Kissinger methods. The starting dehydrogenation temperature and thermodynamic parameters (ΔH, ΔS) of Y partially substituted Mg alloys prepared by melt spinning technique were significantly decreased. The partial substitution of Y for Mg is the main reason for the decrease in the hydrogen storage capacity of Mg–Y–Ni alloys, and the hydrogen absorption capacity increases in the beginning and then declines with the spinning rate rising. Partial substitution of Mg by Y and melt spinning resulted in a significant improvement in the dehydrogenation kinetics of the alloy along with a slight decrease in the hydrogen absorption kinetics. The dehydrogenation activation energy of the alloys decreased significantly with increasing Y content and spinning rate, when the spinning rate was increased from 0 m/s to 30 m/s, the $E_k^{\text{de}}$-value of Y₅ alloy decreased from 68.61 kJ/mol to 53.84 kJ/mol, and when the Y content was increased from 0 to 7, the $E_k^{\text{de}}$-value of the alloy decreased from 65.96 kJ/mol to 48.86 kJ/mol. The decrease in dehydrogenation activation energy was also considered to be the main reason for the enhanced dehydrogenation kinetics of the alloys.