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

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) H-2 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 center dot NH3 catalyzed by CoCl2 could stably release over 4350 mL g(-1) H-2 per unit weight of LiBH4 within 30 min at 40 degrees C, with a hydrogen density of similar to 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. (C) 2020 Elsevier Ltd. All rights reserved.