The milled LiBH4/h-BN composites exhibiting unexpected hydrogen storage kinetics and reversibility

The effect of nanoscale h-BN addition by milling on the de-/re-hydrogenation of LiBH4 was investigated. With the increasing h-BN ratio, the milled LiBH4/h-BN composites showed lower dehydrogenation temperature. For the LiBH4-3BN composite (mole ratio 1:3), the on-set dehydrogenation temperature was reduced from 290 °C for the milled pure LiBH4 down to 175 °C, and the initial dehydrogenation capacity could reach 3.1 wt.% (equivalent to 13.7 wt.% of the component LiBH4) within ∼2 h at 400 °C. Under moderate rehydrogenation conditions of 400 °C and 10 MPa H2 pressure, the 2nd and 3th cyclic dehydrogenation capacity of LiBH4-3BN composite almost remained unchanged, indicating remarkably improved rehydrogenation reversibility in comparison to milled pure LiBH4. FTIR analysis reveals specific interaction between h-BN and LiBH4 probably originating from the polar mechanism between polarizable B-H bond and B-N bond, which should be responsible for the enhanced dehydrogenation kinetics and reversibility. This work demonstrates the specific catalytic role of nanoscale h-BN and its potential for reversible hydrogen storage by compositing with high-capacity borohydrides.