Kinetic characteristics of sodium borohydride formation when sodium meta-borate reacts with magnesium and hydrogen

Sodium borohydride is attracting considerable interests as a hydrogen storage medium. In this paper, we investigated the effects of hydrogen pressure, reaction temperature and transition metal addition on sodium borohydride synthesis by the reaction of sodium meta-borate with Mg and H2H2. It was found that higher H2H2 pressure was beneficial to NaBH4NaBH4 formation. The increase in reaction temperature first improved NaBH4NaBH4 formation kinetics but then impeded it when the temperature was raised to near the melting point of Mg. It was also found that some additions of transition metals such as Ni, Fe and Co in the NaBO2+Mg+H2NaBO2+Mg+H2 system promoted the NaBH4NaBH4 formation, but Cu addition showed little effect. The activation energy of the NaBH4NaBH4 formation from Mg, NaBO2NaBO2 and H2H2 was estimated to be 156.3 kJ/mol NaBH4NaBH4 according to Ozawa analysis method.