Research on Properties of SPEEK Based Proton Exchange Membranes Doped with Ionic Liquids and Y2O3 in Different Humidity

For applications in proton exchange membrane fuel cells at low relative humidity, the composite membranes were prepared with ionic liquids and yttrium oxide (Y2O3). The conductivities of composite membranes were higher than that of the pure SPEEK membrane. The conductivity of composite membranes modified with 1-ethyl-3 methylimidazole tetrafluoroborate (EB) or 1-butyl-3-methylimidazole methanesulfonate (BS) and Y2O3 were 0.08 Sácm-1 and 0.11Sácm-1 at 80¼C, 100% relative humidity(RH) while were 0.07 Sácm-1 and 0.09 Sácm-1 at 80¼C, 50% relative humidity (RH), respectively. The water uptake property would be slightly improved when containing ionic liquids and Y2O3. Compared with pure SPEEK membrane, the thermal stability of composite membranes modified with ionic liquids and Y2O3 was slightly increased by thermal gravimetric analysis, showing the promise for the use at temperatures up to 200¼C. The tensile stresses at break of the composite membranes were respectively 2.61 MPa (EB51) and 2.33 MPa (BS51) at room temperature. The coordination of ionic liquids and Y2O3 was a good potential method for improving the conductivity at low relative humidity.