A high-performance hydrogen generation system: Hydrolysis of LiBH4-based materials catalyzed by transition metal chlorides

Abstract

Lithium borohydride (LiBH4) has received much attention due to its high hydrogen density of 18.5 wt%. However, in the hydrolytic process for hydrogen supply, the sluggish kinetics of LiBH4 and the agglomeration of by-product greatly limit its wide utilization. In this work, transition-metal chlorides (CoCl2, NiCl2, FeCl3) are firstly adopted to explore the hydrogen liberation behaviors of LiBH4. The hydrolysis kinetics can be well-controlled by tuning the concentration of chlorides. Among the above chlorides, CoCl2 displays much faster reaction kinetics, delivering a hydrogen generation rate ranging from 421 to 41701 mL min−1 g−1 with a maximum conversion of 95.3%, much higher than the value of 225 mL min−1 g−1 H2 with Pt–LiCoO2. The maximum gravimetric hydrogen density may reach 8.7 wt% at H2O/LiBH4 = 2–6 mol/mol. Furthermore, NH3 is introduced to solve the issue of uncontrollable kinetics of LiBH4 by forming its ammoniates, where LiBH4·NH3 catalyzed by CoCl2 could stably release over 4350 mL g−1 H2 per unit weight of LiBH4 within 30 min at 40 °C, with a hydrogen density of ∼7.1 wt% and a hydrogen yield of 97.0%. Our approaches adopting non-noble metal chlorides are efficient and affordable for hydrogen supply to PEMFCs via hydrolysis of LiBH4-based materials.