Kinetics of hydrolysis of sodium borohydride for hydrogen production in fuel cell applications: A review

Hydrogen generation from the hydrolysis of sodium borohydride (NaBH4) solution has drawn much attention since early 2000s, due to its high theoretical hydrogen storage capacity (10.8 wt%) and potentially safe operation. However, hydrolysis of NaBH4 for hydrogen generation is a complex process, which is influenced by factors such as catalyst performance, NaBH4 concentration, stabilizer concentration, reaction temperature, complex kinetics and excess water requirement. All of these limit the hydrogen storage capacities of NaBH4, whose practical application, however, has not yet reached a scientific and technical maturity. Despite extensive efforts, the kinetics of NaBH4 hydrolysis reaction is not fully understood. Therefore, better understanding of the kinetics of hydrolysis reaction and development of a reliable kinetic model is a field of great importance in the study of NaBH4 based hydrogen generation system. This review summarizes in detail the extensive literature on kinetics of hydrolysis of aqueous NaBH4 solution.

► State of the art on the kinetics of NaBH4 hydrolysis. ► Analysis of mechanistic and empirical approaches to modeling of self-, pH-catalyzed and metal- catalyzed NaBH4 hydrolysis. ► Identification of major factors that influence NaBH4 hydrolysis kinetics under various ranges of operation. ► Performance comparison and shortcomings of established kinetic models.