Phosphorus oxide promoted solid state hydrolysis of sodium borohydride for efficient onsite hydrogen production

The hydrolysis of solid sodium borohydride (NaBH4) as a hydrogen source for portable fuel cells offers the advantages of excellent safety and convenient storage, making it the optimal alternative to NaBH4 solutions. However, the hydrolysis process is relatively slow and requires the addition of a catalyst to enhance its efficiency. Recent studies have demonstrated that introducing H+ can effectively promote the hydrolysis of NaBH4. In this study, therefore, selects solid acid anhydride, phosphorus pentoxide (P2O5), as a promoter for the hydrolysis of NaBH4. By controlling the ratio of H+ to H_ in the NaBH4-P2O5 system, the conditions for hydrogen production via NaBH4 hydrolysis are optimized. Subsequently, to cater to the requirements of portable fuel cell applications, the optimal NaBH4-P2O5 hydrogen production system is selected, with hydrogen generation rate being controlled by regulating water flow speed. In order to enhance the practical applicability of NaBH4-P2O5, the scale-up of hydrogen production from this system is also undertaken. Finally, to validate the practicality of this reaction system, integration with a proton exchange membrane fuel cell (PEMFC) toy car using the NaBH4-P2O5 hydrogen generation system is performed. The results indicate that a NaBH4 conversation exceeding 90 % can be achieved when the ratio of H+ to H_ is approximately 0.14, and within the range of H+/H_ ratios from 0.05 to 0.14, the maximum hydrogen density reached 6 %. Furthermore, it was found that adjusting the water flow rate only impacts the rate of hydrogen production without significantly affecting the NaBH4 conversion, which consistently surpassed 90 %. Similar high NaBH4 conversion, above 90 %, were also attained in the scaled-up experiments of the NaBH4-P2O5 system. When implemented in a 5W PEMFC, this hydrogen production system delivered an output power of approximately 1.76 W, thereby affirming its operational feasibility and effectiveness.