Enhancing the Regeneration Process of Consumed NaBH4 for Hydrogen Storage

Sodium borohydride (NaBH 4 ) is regarded as an excellent hydrogen-generated material, but its irreversibility of hydrolysis and high cost of regeneration restrict its large-scale application. In this study a convenient and economical method for NaBH 4 regeneration is developed for the first time without hydrides used as starting materials for the reduction process. The real hydrolysis by-products (NaBO 2 · 2H 2 O and NaBO 2 · 4H 2 O), instead of dehydrated sodium metaborate (NaBO 2 ), are applied for the regeneration of NaBH 4 with Mg at room temperature and atmospheric pressure. Therefore, the troublesome heat-wasting process to obtain NaBO 2 using a drying procedure at over 350 °C from NaBO 2 · x H 2 O is omitted. Moreover, the highest regeneration yields of NaBH 4 are achieved to date with 68.55% and 64.06% from reaction with NaBO 2 · 2H 2 O and NaBO 2 · 4H 2 O, respectively. The cost of NaBH 4 regeneration shows a 34-fold reduction compared to the previous study that uses MgH 2 as the reduction agent, where H 2 is obtained from a separate process. Furthermore, the regeneration mechanism of NaBH 4 is clarified and the intermediate compound, NaBH 3 (OH), is successfully observed for the first time during the regeneration process.