Polybenzimidazole and ionic liquid composite membranes for high temperature polymer electrolyte fuel cells

Elevating the operating temperature of polymer electrolyte fuel cells (PEFCs) can facilitate the reaction kinetics and improve the CO tolerance of catalysts, and simplify the complex water-heat management system of fuel cells. In this study, we fabricated the ionic liquid-based polymer electrolyte that can operate up to 250 °C without external humidification. The membrane utilized polybenzimidazole (PBI) as the polymer matrix, and ionic liquids as the proton conductive fillers. Among all the investigated ionic liquids, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]) shows favorable performance and stability. The PBI-[dema][TfO] composite membrane exhibits high proton conductivity of 108.9 mS cm at 250 °C. The single cell with PBI-[dema][TfO] composite membrane and Pt/C as the electrode shows output performance of 144 and 62 mW/cm at 125 °C and 250 °C, respectively. This work demonstrates that it is very promising to fabricate high temperature PEFCs using the ionic liquid-based polymer electrolyte.