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

Abstract

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.