Enhanced hydrogen desorption properties of LiBH4-Ca(BH4)2 by a synergetic effect of nanoconfinement and catalysis

NbF5 and eutectic 0.68LiBH4-0.32Ca(BH4)2 were successively infiltrated into highly ordered mesoporous carbon (CMK-3) to obtain a LiBH4-Ca(BH4)2-NbF5@CMK-3 composite. A synergetic effect of nanoconfinement and catalysis on hydrogen desorption properties of the composite was achieved. The onset desorption temperature of LiBH4-Ca(BH4)2-NbF5@CMK-3 is dramatically lower than 120 °C compared with that of as-milled LiBH4-Ca(BH4)2 or LiBH4-Ca(BH4)2@CMK-3. A hydrogen amount as high as 13.3 wt% can be released within 250 min for LiBH4-Ca(BH4)2-NbF5@CMK-3, compared with only 10.4 wt% for pure LiBH4-Ca(BH4)2, in which nanoconfinement and catalysis both make some contribution. The cycling hydrogen desorption performance of the composite becomes better likewise due to the addition of NbF5. Further microstructure analysis reveals that F− tended to bind with Ca2+ to form CaF2, whereas Nb compound is believed to catalyze the whole system in the form of Nb-based boride (NbB2).