Synthesis and hydrogen storage properties of Mg-La-Al nanoparticles

Mg-2 at.% La-2.6 at.% Al composite nanoparticles are prepared by hydrogen plasma-metal reaction (HPMR) method. The electron microscopy and X-ray diffraction studies reveal that these nanoparticles are made of single crystalline Mg of about 160 nm, and a little amount of polycrystalline Al ₂La of 15 nm dispersing on the surface of Mg. The addition of Al effectively reduces the oxidation of Mg nanoparticles. After hydrogenation, Al ₂La disproportionates into single crystalline LaH ₃ of 15 nm. The composite nanoparticles can absorb 5.0 wt.% H ₂ in 30 min even at 473 K, and the storage capacity is as high as 6.8 wt.% at 673 K. They can also release 6.0 wt.% H ₂ in less than 10 min at 673 K. The catalytic effect of LaH ₃ nanoparticles, nanocrystalline structure and low oxide content of Mg accelerate the hydrogen sorption process of Mg-La-Al composite nanoparticles with a low hydrogen absorption activation energy of 23.1 kJ mol ^-1.