Recoverable Ni₂Al₃ nanoparticles and their catalytic effects on Mg-based nanocomposite during hydrogen absorption and desorption cycling

The Mg-3.9 wt% Ni₂Al₃ nanocomposite is produced by hydrogen plasma-metal reaction method. The particle size of Mg is in range of 40–160 nm with an average size of 90 nm. The Ni₂Al₃ nanoparticles (NPs) of about 9 nm uniformly disperse on the surface of Mg NPs and in situ transform to Mg₂NiH_0.3 and Al after hydrogen absorption process. Surprisingly, the Mg₂NiH_0.3 and Al can recover to the initial state of Ni₂Al₃ after hydrogenation/dehydrogenation cycle. The Mg-Ni₂Al₃ nanocomposite shows enhanced hydrogen sorption rate and storage capacity. It can quickly uptake 6.4 wt% H₂ within only 10 min at 573 K, and release 6.1 wt% H₂ within 10 min at 623 K. The apparent activation energies for hydrogenation and dehydrogenation are calculated to be 55.4 and 115.7 kJ mol⁻¹ H₂. The enhanced hydrogen storage performances of the Mg-Ni₂Al₃ nanocomposite are attributed to both the nanostructure of Mg and the catalytic effects of Ni₂Al₃ NPs.