Improvement of Hydrogen Absorption and Desorption Kinetics of Metallic Magnesium by Mechanical Activation

One of the problems hindering the commercial application of metallic Mg is its poor kinetics performance of hydrogen absorption and desorption. At present, the mechanical activation process has exhibited excellent potential for improving the hydrogen storage kinetic performance of magnesium hydride. Herein, the high-energy ball-milling method was used to improve the kinetics by generating nanocrystalline structures inside Mg metals and changing the surface state of the Mg particles. Significantly, mechanical activation treatment greatly improves the first hydrogenation/dehydrogenation kinetic properties. Experimental results showed that after 120 min of milling, only 330 min are needed to absorb 7.3 wt% of hydrogen, which is 9 times faster than the 3176 min needed for untreated material. The time needed to release all of the hydrogens is therefore 12 times faster. A unique activation mechanism formed layered structure and nanocrystalline during the mechanical milling process, which promoted hydrogen dissociation on the particle surface and diffusion along the layer interfaces and grain boundaries.