Synergistic catalytic effects of the Ni and V nanoparticles on the hydrogen storage properties of Mg-Ni-V nanocomposite

The Mg-5.0 wt%Ni-2.3 wt%V nanocomposite has been produced through reducing NiCl₂ with the Mg-V nanoparticles (NPs) prepared by hydrogen plasma metal reaction (HPMR) approach. The in situ formed Ni and V particles of about 15 nm uniformly decorate on the surface of Mg NPs. The Ni NPs transform into Mg₂Ni while the V NPs remain unchanged after first hydrogen absorption and desorption cycle at 673 K. They show synergistic catalytic effects on the hydrogen storage properties of Mg-Ni-V nanocomposite. The nanocomposite can absorb 4.6 wt% H₂ within 30 min at 473 K and desorb 5.2 wt% H₂ within 10 min at 623 K. The activation energies of hydrogenation/dehydrogenation processes are decreased to 52.8 and 85.1 kJ per mol H₂, lower than those of the Mg-5.4 wt%Ni nanocomposite of 63.2 and 89.3 kJ per mol H₂. The enhanced hydrogen storage performances of the Mg-Ni-V nanocomposite are mainly attributed to the synergistic catalytic effects of the Mg₂Ni and V catalysts, and the nanosize effect of Mg NPs on the decrease of the hydrogen diffusion distance.