A novel titanium PBI-based composite membrane for high temperature PEMFCs

A novel PBI-based composite membrane with titanium oxide has been prepared. In order to compare the results obtained with this titanium PBI-based composite membrane, a standard PBI membrane, a PBI membrane prepared by a direct doping and casting method with TFA and a sulphonated PBI membrane were prepared. The membranes were physico-chemically and electrochemically characterised for use as electrolytes in high-temperature PEMFCs. All of the membranes were cast from the same polymer with the same molecular weight. The sulphonated and the composite membranes with TiO2 reached the highest doping levels under the same conditions. The sulphonated PBI membrane showed the highest conductivity at 125 °C (0.18 S cm−1). Only the composite membrane with TiO2 retained high conductivity values at the higher temperatures and this is a result of its high doping level and high water retention capacity. The TiO2–PBI composite membrane showed the best performance and achieved a power density of 800 mW cm−1 at 150 °C. The results suggest that TiO2/PBI-based composite membranes are promising electrolytes for high temperature PEMFCs.