100-200°C Polymer Fuel Cells for use with NaAlH4

The complex hydride NaAlH4 is attracting much attention right now because of high hydrogen storage capacity and a practical desorption temperature that can be brought down below 150 ° C. However, this is still far from the working temperature of conventional perfluorosulfonic acid based polymer fuel cells (e.g.

Nafion cells). A hydrogen desorption temperature below 80 ° C is mandatory if the excess heat of such a fuel cell shall be used for hydrogen desorption from a NaAlH4 storage system. Our approach is to increase the working temperature of the polymer fuel cell. The present paper reports our recent work on polymer fuel cells operating at temperatures up to 200 ° C.

The key component to make this possible is an electrolyte membrane of polybenzimidazole (PBI) doped with phosphoric acid. Cells are operated at temperatures up to 200 ° C without any humidification. Continuous service for more than 6 months at 150 ° C is demonstrated. The temperature and amount of the excess heat is more than enough to run a metal hydride tank based on NaAlH4.