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

Hydrogen generation from the hydrolysis of sodium borohydride (NaBH 4) 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 NaBH 4 for hydrogen generation is a complex process, which is influenced by factors such as catalyst performance, NaBH 4 concentration, stabilizer concentration, reaction temperature, complex kinetics and excess water requirement. All of these limit the hydrogen storage capacities of NaBH 4, whose practical application, however, has not yet reached a scientific and technical maturity. Despite extensive efforts, the kinetics of NaBH 4 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 NaBH 4 based hydrogen generation system. This review summarizes in detail the extensive literature on kinetics of hydrolysis of aqueous NaBH 4 solution. ► State of the art on the kinetics of NaBH 4 hydrolysis. ► Analysis of mechanistic and empirical approaches to modeling of self-, pH-catalyzed and metal- catalyzed NaBH 4 hydrolysis. ► Identification of major factors that influence NaBH 4 hydrolysis kinetics under various ranges of operation. ► Performance comparison and shortcomings of established kinetic models.