Enhanced hydrogen sorption in a Li-Mg-N-H system by the synergistic role of Li(NH)BH and ZrFe.

The present investigation describes the synergistic role of Li(BH)(NH) and ZrFe in the hydrogen storage behaviour of a Li-Mg-N-H hydride system. The onset desorption temperature of ZrFe-catalysed Mg(NH)-LiH-Li(BH)(NH) is ∼122 °C, which is 83 °C, 63 °C, and 28 °C lower than that of thermally treated 2LiNH-1MgH, 2LiNH-1MgH-4 wt%ZrFe, and 2LiNH-1MgH-0.1LiBH composites, respectively. Native Mg(NH)-LiH-Li(BH)(NH) absorbed only 2.78 wt% of H within 30 min. On the other hand, the ZrFe-catalysed Mg(NH)-LiH-Li(BH)(NH) sample absorbed 3.70 wt% of hydrogen within 30 min and 5 wt% of H in 6 h at 180 °C and 7 MPa H pressure. Mg(NH)-LiH-Li(BH)(NH) catalyzed with ZrFe shows negligible degradation of the storage capacity even after repeated cycles of de/rehydrogenation. The effect of ZrFe and Li(BH)(NH) on a Mg(NH)/LiH composite has been described and discussed with the help of structural (X-ray diffraction), microstructural (electron microscopy), and vibrational modes of molecules through FTIR studies. The present results suggest that an optimum catalysis may originate from the synergistic action of an in situ formed quaternary hydride (Li(BH)(NH)) and an intermetallic-like ZrFe, which acts as a pulverizer cum catalyst.