Hydrogen release from a mixture of NaBH4 and Mg(OH)2

Hydrogen generating reaction between sodium borohydride, NaBH4, and magnesium hydroxide, Mg(OH)2 (brucite), was studied. Reaction rate was found to depend on the degree of reactants homogenization and/or their particle size. Kinetic of the reaction was studied in isothermal approach in the temperature range of 240–360 °C. It is shown that the reaction obeys 2D diffusion mechanism and its activation energy is 155.9 kJ/mol. Powder XRD analysis and Raman spectroscopy reveal that mechanically activated mixture of NaBH4 and Mg(OH)2 reacts yielding MgO as the only crystalline phase in the temperature range of 240–318 °C. At higher temperatures a new crystalline tetragonal phase of as yet undetermined composition is developed.