Progress in sodium borohydride as a hydrogen storage material: Development of hydrolysis catalysts and reaction systems

Over the past decade, sodium borohydride (NaBH4) has been extensively investigated as a potential hydrogen storage material. The development of catalyst materials for on demand NaBH4 hydrolysis, and the design of practical reaction systems for hydrogen storage based on NaBH4 are key research areas. Progress in the former area has been promising, with many non-noble catalysts being reported with activities comparable to those of higher-cost noble metal catalysts. However, the design of practical hydrogen storage systems remains a critical issue, as identified by the U.S. Department of Energy (DOE) in their “No-Go” recommendation in 2007. The problems of by-product precipitation and catalyst blockage at high NaBH4 concentrations must be addressed in order to produce a hydrogen storage system capable of meeting the DOE target of 5.5 wt% H2 (2015). It is likely that a new, novel reaction system design will be required to achieve these targets, given the limitations identified in conventional systems. Moreover, a new process for regenerating spent NaBH4 will need to be developed, in order to lower its cost to a viable level for use as a transportation fuel.