Abstract: Mg-Li alloy is a lightweight hydrogen storage material with high hydrogen capacity, but its poor kinetics limited its practical applications. In this work, MCM-22 molecular sieve was added to Mg-Li alloy by friction stir processing (FSP) as the catalyst to enhance the kinetic properties of Mg-Li alloy (denoted as Mg-Li-MCM-22). The resulting Mg-Li-MCM-22 possesses the reversible hydrogen storage capacity of ca. 6 wt.% and can release 5.62 wt.% hydrogen within 50 min at 623 K, showing improved kinetics. The Chou model and Johnson-Mehl-Avrami-Kolmogorov (JMAK) model calculations reveal that the lattice defects generated by FSP improve the kinetics of hydrogen adsorption/desorption. The pinning effect of MCM-22 particles produces more grain boundaries and dislocations, thus, increasing the diffusion rate of hydrogen atoms and providing more nucleation sites, therefore, reducing the dehydrogenation activation energy. This work provides a new strategy for the preparation of hydrogen storage materials.

Key words: Mg-Li alloy, Hydrogen storage, Hydriding/dehydriding reaction kinetics, Friction stir processing, Molecular sieve