Achieving a novel solvent-free regeneration of LiBH 4 combining hydrogen storage and production in a closed material cycle

LiBH 4 has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity, which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversion via anodic oxidation reaction of direct borohydride fuel cells (DBFCs). However, the realization of practical hydrogen applications heavily depends on the effective synthesis of high-purity LiBH 4 and recycling of the spent fuels (LiBO 2 ·xH 2 O). The present work demonstrates a convenient and high-efficiency solvent-free strategy for regenerating LiBH 4 with a maximum yield close to 80%, by retrieving its by-products with MgH 2 as a reducing agent under ambient conditions. Besides, the hydrogen released from the regeneration course can completely compensate the demand for consumed MgH 2. The isotopic tracer method reveals that the hydrogen stored in LiBH 4 comes from both MgH 2 and coordinated water bound to LiBO 2. Here, the expensive MgH 2 can be substituted with the readily available and cost-effective MgH 2 −Mg mixtures to simplify the regeneration route. Notably, LiBH 4 catalyzed by CoCl 2 can stably supply hydrogen to proton exchange membrane fuel cell (PEMFC), thus powering a portable prototype vehicle. By combining hydrogen storage, production and utilization in a closed cycle, this work offers new insights into deploying boron-based hydrides for energy applications.