Enhancing Mg-Li alloy hydrogen storage kinetics by adding molecular sieve via friction stir processing

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.