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

Abstract

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 Al2La of 15 nm dispersing on the surface of Mg. The addition of Al effectively reduces the oxidation of Mg nanoparticles. After hydrogenation, Al2La disproportionates into single crystalline LaH3 of 15 nm. The composite nanoparticles can absorb 5.0 wt.% H2 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.% H2 in less than 10 min at 673 K. The catalytic effect of LaH3 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.