Simultaneous preparation of sodium borohydride and ammonia gas by ball milling.

Hydrogen and ammonia are both potential energy carriers being considered for large scale energy transport. Sodium borohydride (NaBH 4) has been widely applied as a potential solid-state hydrogen storage material. It can produce hydrogen gas and sodium metaborate (NaBO 2) after hydrolysis with water at room temperature. The regeneration of NaBH 4 from NaBO 2 could significantly reduce the cost of NaBH 4 and enable its wide-spread industrial use. In this work, we demonstrate a simple method for regenerating NaBH 4 from NaBO 2 ·4H 2 O using Mg 2 N 3 , which combines NaBH 4 production with NH 3 gas production in a single step at room temperature. NaBH 4 is successfully synthesized from NaBO 2 ·4H 2 O using the Mg 3 N 2 reducing agent via ball milling under a hydrogen atmosphere. NaBH 4 is formed at a 76.6% yield by planetary ball milling at 600 rpm under 40 bar hydrogen for 12 h. NH 3 gas is also formed, which can be easily separated from the solid products. Therefore, this one-step process could produce two different types of carbon-free hydrogen carriers suitable for energy export from renewable sources. • One step process to store hydrogen in NaBH 4 and NH 3. • Lower cost for NaBH 4 regeneration. • Mg 3 N 2 can be considered as a promising reductant for simultaneous synthesis of NaBH 4 and NH 3. • The hydrogen pressure have a effect on the ball milling. [ABSTRACT FROM AUTHOR]