Hydrogen storage properties of nanocrystalline Mg2Ni prepared from compressed 2MgH2[sbnd]Ni powder.

Abstract In the present work, nanocrystalline Mg 2 Ni with an average size of 20–50 nm was prepared via ball milling of a 2MgH 2 Ni powder followed by compression under a pressure of 280 MPa. The phase component, microstructure, and hydrogen sorption properties were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), pressure-composition-temperature (PCT) and synchronous thermal analyses (DSC/TG). Compared to the non-compressed 2MgH 2 Ni powder, the compressed 2MgH 2 Ni pellet shows lower dehydrogenation temperature (290 °C) and a single-phase Mg 2 Ni is obtained after hydrogen desorption. PCT measurements show that the nanocrystalline Mg 2 Ni obtained from dehydrogenated 2MgH 2 Ni pellet has a single step hydrogen absorption and desorption with fairly low absorption (−57.47 kJ/mol H 2) and desorption (61.26 kJ/mol H 2) enthalpies. It has very fast hydrogen absorption kinetics at 375 °C with about 3.44 wt% hydrogen absorbed in less than 5 min. The results gathered in this study show that ball milling followed by compression is an efficient method to produce Mg-based ternary hydrides. Highlights • Single phase Mg 2 Ni was prepared from ball milled 2MgH 2 Ni compressed pellet. • Enthalpies of hydrogenation/dehydrogenation of Mg 2 Ni/Mg 2 NiH 4 were −57.47 kJ/mol H 2 and 61.26 kJ/mol H 2 respectively. • Nanocrystalline Mg 2 Ni hydrogen absorption was very fast and absorbed 3.44 wt% hydrogen in less than 5 min. [ABSTRACT FROM AUTHOR]