Preparation of Polybenzimidazole/Lithium Hydrazinium Sulfate Composite Membranes for High-Temperature Fuel Cell Applications

PBI-LiHzS composite membranes were prepared by casting N,N'-DMAc solutions containing PBI and LiHzS, where the LiHz5 contents in the membranes were between 2.5 and 10 wt.-%. LiHzS was obtained by reacting hydrazine sulfate and lithium carbonate in water. PBI-LiHzS composite membranes were thermally stable up to approximately 300 degrees C and their acid-absorbing capabilities were comparable to those of the pure PBI membranes. The proton conductivity of PBI-LiHzS composite membranes (2.12 x 10(-2) S . cm(-1) at 180 degrees C and 0% RH) was higher than that of pure PBI membranes when used at the same acid doping levels. The mechanical stability of the composite membranes having less than 5 wt.-% of LiHzS was found to be close to that of pure PBI membranes.