Enhancing the Regeneration Process of Consumed NaBH4 for Hydrogen Storage

4 years ago

Enhancing the Regeneration Process of Consumed NaBH4 for Hydrogen Storage

Hui Wang, Jiangwen Liu, Liuzhang Ouyang, Min Zhu, Michael Felderhoff, Wei Chen

Sodium borohydride (NaBH4) 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 NaBH4 regeneration is developed for the first time without hydrides used as starting materials for the reduction process. The real hydrolysis by-products (NaBO2·2H2O and NaBO2·4H2O), instead of dehydrated sodium metaborate (NaBO2), are applied for the regeneration of NaBH4 with Mg at room temperature and atmospheric pressure. Therefore, the troublesome heat-wasting process to obtain NaBO2 using a drying procedure at over 350 °C from NaBO2·xH2O is omitted. Moreover, the highest regeneration yields of NaBH4 are achieved to date with 68.55% and 64.06% from reaction with NaBO2·2H2O and NaBO2·4H2O, respectively. The cost of NaBH4 regeneration shows a 34-fold reduction compared to the previous study that uses MgH2 as the reduction agent, where H2 is obtained from a separate process. Furthermore, the regeneration mechanism of NaBH4 is clarified and the intermediate compound, NaBH3(OH), is successfully observed for the first time during the regeneration process. The high-energy ball milling method has significantly contributed toward the regeneration of NaBH4 without extra hydrogen, using NaBO2·2H2O and cheap Mg powder as raw materials. The optimal regeneration yield can reach 68.55%. Through controlling the amount of water, NaBH4 hydrolysis reaction can release 6.33 wt% H2 with CoCl2 as catalyst and reproduce NaBO2·2H2O.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700299