Hydrogen generation from solid NaBH4 with catalytic solution for planar air-breathing proton exchange membrane fuel cells

In the pursuit of the development of alternative mobile power sources with high energy densities, this study elucidated a new hydrogen generation approach from solid NaBH₄ using a new catalyst, sodium hydrogen carbonate (NaHCO₃), which was placed in a small and compact cartridge. A planar air-breathing PEMFC system fitted with the cartridge has been investigated for testing hydrogen generation from NaBH₄ and NaHCO₃. NaHCO₃ allowed the hydrogen cartridge to control hydrogen generation and to improve the power density, fuel efficiency, energy efficiency, and cell response. The cell performance of solid NaBH₄ air-breathing PEMFC system strongly depended on the operating conditions: the feeding rates and concentrations of catalytic solutions for NaBH₄ hydrolysis. In various concentrations (5 - 12 wt %) of NaHCO₃ aqueous solutions, 10 wt % NaHCO₃ aqueous solution exhibited the highest maximum power density of 128 mW cm⁻² at 0.7 V, which was estimated to be a Faradic efficiency of 78.4% and an energy efficiency of 46.3%. The data illustrated that NaHCO₃ was an effective catalyst for hydrogen generation with the solid NaBH₄, which is considered as a hydrogen carrier for air-breathing micro PEMFCs operated without auxiliary hydrogen controller or devices.