Hydrolysis of sodium borohydride in concentrated aqueous solution

Sodium borohydride is being commercialized to provide hydrogen storage for portable fuel cells. Prior kinetic studies have focused on catalytic hydrolysis of dilute aqueous solutions at room temperature. This work reports on a new NMR method for studying the kinetics of non-catalyzed sodium borohydride hydrolysis in highly concentrated solutions. The effects of initial NaBH4 concentration, temperature and pH on conversion are studied. It is found that higher initial NaBH4 concentration and higher temperature both improve the reaction rate. The reaction rate is slowed down with increasing pH of basic solutions and is accelerated with decreasing pH of acidic solutions. In addition, temperature effect seems to be more important than that of the acidic pH on the reaction rate.