Enhancing NaBH4 regeneration using an Al-rich alloy.

Onsite hydrogen generation by sodium borohydride hydrolysis resolves hydrogen energy supply system challenges. However, the spent-NaBH 4 regeneration is still a problem in the closed loop of this irreversible reaction. As the by-product is the key to the problem, NaB(OH) 4 is regarded as not the boron source but the hydrogen source of NaBH 4 regeneration. Therefore, in this study, inexpensive Al metal and NaB(OH) 4 are ball milled under argon to regenerate NaBH 4 without additional hydrogen input. However, the ball-milling reaction is hindered by the flexible Al and impact oxide layer, and the NaBH 4 yield is only approximately 22 %. Therefore, a brittle intermetallic compound Mg 2 Al 3 is reacted with NaB(OH) 4 by ball milling, achieving a NaBH 4 yield of over 42 %. The mechanism study shows that the brittleness of the raw material plays an important role in promoting the ball-milling reaction. This study achieves NaBH 4 regeneration using only Al as the reducing agent and provides a promising method to promote the mechanochemical regeneration of NaBH 4. • NaBH 4 regeneration was achieved using only Al as the reducing agent. • Ball milled Mg 2 Al 3 and NaB(OH) 4 achieved the highest NaBH 4 yield of 42 %. • Brittle reducing agent enhances the ball-milled regeneration of NaBH 4. [ABSTRACT FROM AUTHOR]