Novel composite membranes based on dicationic ionic liquid and polybenzimidazole mixtures as strategy for enhancing thermal and electrochemical properties of proton exchange membrane fuel cells applications at high temperature

• Novel proton exchange membranes were obtained by PBI and dicationic ionic liquid.
• The nanocomposites show high proton conductivity of 78 mS cm−1 at 180 °C.
• A high power density of 0.40 W cm−2 at a cell voltage of 0.5 V was obtained.
• The PBI/dicationic IL membranes are good candidate for application in HT-PEMFC.

In this work, innovative proton exchange membranes containing dicationic ionic liquids are developed for elevated temperature fuel cells applications under anhydrous conditions. The composite membranes based on polybenzimidazole (PBI) and dicationic ionic liquid 1,6-di(3-methylimidazolium) hexane bis (hexafluorophosphate) (PDC6) or monocationic ionic liquid 1-Butyl-3-methylimidazolium hexafluorophosphate (PMC4) are prepared with solution casting method. The analyses of the results demonstrate promising characteristics such as high ionic conductivity and fuel cell performance of phosphoric acid (PA) doped PDC6 composite membranes in comparison with PA doped PMC4 and PA doped PBI membranes at high temperatures. Dicationic ionic liquid with high number of charge carriers provides suitable ionic channels for proton transfer in PA doped PDC6 composite membranes. The ionic conductivity of 78 mS cm−1 and power density of 0.40 W cm−2 (at 0.5 V) are achieved for PA doped PDC6 composite membranes with PBI/ionic liquid mole ratio: 4 at 180 °C under anhydrous condition.