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 LiHzS 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 °C and their acid-absorbing capabilities were comparable to those of the pure PBI membranes. The proton conductivity of PBILiHzS composite membranes (2.12×10^-2 S·cm^-1 at 180 °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.