A recycling hydrogen supply system of NaBH₄ based on a facile regeneration process: A review

NaBH₄ hydrolysis can generate pure hydrogen on demand at room temperature, but suffers from the difficult regeneration for practical application. In this work, we overview the state-of-the-art progress on the regeneration of NaBH₄ from anhydrous or hydrated NaBO₂ that is a byproduct of NaBH₄ hydrolysis. The anhydrous NaBO₂ can be regenerated effectively by MgH₂, whereas the production of MgH₂ from Mg requires high temperature to overcome the sluggish hydrogenation kinetics. Compared to that of anhydrous NaBO₂, using the direct hydrolysis byproduct of hydrated NaBO₂ as the starting material for regeneration exhibits significant advantages, i.e., omission of the high-temperature drying process to produce anhydrous NaBO₂ and the water included can react with chemicals like Mg or Mg₂Si to provide hydrogen. It is worth emphasizing that NaBH₄ could be regenerated by an energy efficient method and a large-scale regeneration system may become possible in the near future.