A fleeting glimpse of the dual roles of SiB₄ in promoting the hydrogen storage performance of LiBH₄

Abstract

In this study, the positive effects and dual roles of SiB4 on the dehydrogenation and rehydrogenation performance of the LiBH4–SiB4 system are reported. Characterizations were performed through temperature programmed desorption mass spectrometry (TPD-MS), isothermal kinetics measurements, and XRD and FTIR analyses. For the hydrogen desorption from LiBH4, SiB4 played the role of a catalyst to kinetically facilitate the structural destabilization of LiBH4 and its intermediate phase Li2B12H12. Accordingly, a dehydrogenation capacity of 2.24 at. H/f.u. LiBH4 (close to 10.3 wt% H) was attained at a relative temperature of 350 °C. For hydrogen absorption to generate LiBH4, SiB4 was unexpectedly found to act as a reactant to thermodynamically improve the rehydrogenation process by reacting with LiH under moderate conditions of 10 MPa H2 and 400 °C, and a superior reversible capacity of 2.16 at. H/f.u. LiBH4 was achieved. These experimental results remind us to take into account the explicit role(s) of the employed components during the dehydrogenation and rehydrogenation reactions when designing a desirable LiBH4-based system.