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 H-2. It was found that higher H-2 pressure was beneficial to NaBH4 formation. The increase in reaction temperature first improved NaBH4 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 + H-2 system promoted the NaBH4 formation, but Cu addition showed little effect. The activation energy of the NaBH4 formation from Mg, NaBO2 and H2 was estimated to be 156.3 kJ/mol NaBH4 according to Ozawa analysis method. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.