Channel role of nano-Mg2Ni in enhancing hydrogen absorption and desorption performances in Mg/Mg2Ni system

Mg2Ni is considered as a promising material for both storage hydrogen and catalyze MgH2 decomposition. Using Mg2Ni-Mg as a matrix material may achieve the combination of both advantages. Herein, hypoeutectic and hypereutectic Mg100-xNix (x = 11, 15, 22) alloys are prepared in this work to investigate the relationship between Mg2Ni in different microstructures and hydrogen storage performances. The results indicate that Mg2Ni connected Mg-Mg2Ni eutectics are formed besides the lamellar eutectic in Mg85Ni15 and Mg78Ni22 alloys because Mg2Ni precipitates firstly in eutectics, which are different from the a-Mg connected Mg-Mg2Ni eutectics in Mg89Ni11 alloy. Mg100-xNix alloys show rapid hydrogen absorption rates at ranges of both 125-175 & DEG;C and 275-325 & DEG;C because the presents of abundant interfaces generated by nano-Mg2Ni particles. Mg89Ni11 alloy with hydrogenation capacities of 3.6 wt% at 125 & DEG;C due to the large hydrogenation driving force of a-Mg. The Mg78Ni22 hydride with the highest proportion nano-Mg2Ni phase presents the fastest dehydrogenation rates. Two independent decomposition peaks are observed in the DSC curves of Mg100-xNix hydrides and the desorption temperature of Mg2NiH4 becomes lower with increasing Mg2Ni content due to Mg2Ni nanoparticles providing channels for the rapid diffusion of H atoms, and the reduced H concentration is conducive to the decomposition of MgH2.& COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).