Enhanced hydrogen sorption in a Li-Mg-N-H system by the synergistic role of Li 4 (NH 2 ) 3 BH 4 and ZrFe 2 .

The present investigation describes the synergistic role of Li-4(BH4)(NH2)(3) and ZrFe2 in the hydrogen storage behaviour of a Li-Mg-N-H hydride system. The onset desorption temperature of ZrFe2-catalysed Mg(NH2)(2)-LiH-Li-4(BH4)(NH2)(3) is similar to 122 degrees C, which is 83 degrees C, 63 degrees C, and 28 degrees C lower than that of thermally treated 2LiNH(2)-1MgH(2), 2LiNH(2)-1MgH(2)-4 wt% ZrFe2, and 2LiNH(2)-1MgH(2)-0.1LiBH(4) composites, respectively. Native Mg(NH2)(2)-LiH-Li-4(BH4)(NH2)(3) absorbed only 2.78 wt% of H-2 within 30 min. On the other hand, the ZrFe2-catalysed Mg(NH2)(2)-LiH-Li-4(BH4)(NH2)(3) sample absorbed 3.70 wt% of hydrogen within 30 min and 5 wt% of H-2 in 6 h at 180 degrees C and 7 MPa H-2 pressure. Mg(NH2)(2)-LiH-Li-4(BH4)(NH2)(3) catalyzed with ZrFe2 shows negligible degradation of the storage capacity even after repeated cycles of de/rehydrogenation. The effect of ZrFe2 and Li-4(BH4)(NH2)(3) on a Mg(NH2)(2)/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-4(BH4)(NH2)(3)) and an intermetallic-like ZrFe2, which acts as a pulverizer cum catalyst.