Comparative study for microstructure and hydrogen storage capabilities of Mg₉₅Zn₂R₃ (R]Y, La) alloys

For the sake of enhancing the hydrogen storage kinetics of Mg-based alloys, the functions of Y and La on microstructure evolution and de/hydrogenation behavior of Mg-Zn alloy are examined and discussed. The thermodynamic calculations reveal that the kind of rare-earth element affect solidification paths of the alloys. La introduction enables the eutectoid transformation. The hydrogenation kinetics of Mg95Zn2Y3 and Mg95Zn2La3 is dominated by hydrogen diffusion. The fine alpha-Mg grains and alternating structured eutectoid phase in Mg95Zn2La3 provide abundant phase boundary for hydrogen diffusion. Besides, the residual Mg content in hydrogenated Mg95Zn2La3 is far lower than that in Mg95Zn2Y3, which is ascribed to the weakened effect of nucleation-growth-impingement caused by growing MgH2. The hydrogen desorption kinetics of Mg95Zn2Y3 and Mg95Zn2La3 is determined by the nucleation and growth of Mg/MgH2. The fine La8H18.4 nanophases and Mg grains provide plenty of nucleation sites for Mg on MgH2. Additionally, La8H18.4 nanophase exhibits more positive role than YH2/YH3 phase in promoting hydrogen desorption. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.