Hydrolysis and regeneration of sodium borohydride (NaBH4) – A combination of hydrogen production and storage

Sodium borohydride (NaBH 4 ) hydrolysis is a promising approach for hydrogen generation , but it is limited by high costs, low efficiency of recycling the by-product, and a lack of effective gravimetric storage methods. Here we demonstrate the regeneration of NaBH 4 by ball milling the by-product, NaBO 2 ·2H 2 O or NaBO 2 ·4H 2 O, with MgH 2 at room temperature and atmospheric pressure without any further post-treatment. Record yields of NaBH 4 at 90.0% for NaBO 2 ·2H 2 O and 88.3% for NaBO 2 ·4H 2 O are achieved. This process also produces hydrogen from the splitting of coordinate water in hydrated sodium metaborate. This compensates the need for extra hydrogen for generating MgH 2 . Accordingly, we conclude that our unique approach realizes an efficient and cost-effective closed loop system for hydrogen production and storage.