In Situ Introduction of Li 3 BO 3 and NbH Leads to Superior Cyclic Stability and Kinetics of a LiBH 4 -Based Hydrogen Storage System.

LiBH is a high-capacity hydrogen storage material; however, it suffers from high dehydrogenation temperature and poor reversibility. To tackle those issues, we introduce a new LiBH-based system with in situ formed superfine and well-dispersed LiBO and NbH as co-reactants. Those are synthesized by the addition of niobium ethoxide [Nb(OEt)] to LiBH, heat treatment of the mixture, and then hydrogenation, where LiBO and NbH are generated from the reaction of Nb(OEt) and LiBH. After optimization, the system with a normalized composition of LiBH-0.04(LiBO + NbH) in molar fraction shows superior hydrogen storage reversibility and kinetics. The initial and main dehydrogenation temperatures of the system are 200 and 90 °C lower than those of the pristine LiBH, respectively, and 8.2 wt % H is released upon heating to 400 °C. A capacity of 7.2 wt % H, corresponding to a capacity retention of 91%, is sustained after 30 cycles in an isothermal cyclic regime of dwelling at 400 °C for 60 min for dehydrogenation and dwelling at 500 °C and 50 bar H pressure for 20 min for hydrogenation. Such a high cyclic stability for a LiBH-based system has never been reported to date. The in situ introduced LiBO and NbH have a synergistic catalysis effect on the improvement of the hydrogen storage performance of LiBH, showing highly effective bidirectional action on both dehydrogenation and hydrogenation.