Properties improvement of SPEEK based proton exchange membranes by doping of ionic liquids and Y2O3

The membranes of sulfonated poly(etheretherketone) with 65% sulfonation degree were prepared by doping of Y2O3 and ionic liquids, such as 1-ethyl-3-methylimidazole tetrafluoroborate (EB) or 1-butyl-3-methylimidazole methanesulfonate (BS), respectively. And the properties, including conductivities, water uptake, thermal stability and mechanical properties, of pure SPEEK based proton exchange membrane and SPEEK based proton exchange membranes by doping of ionic liquids and Y2O3 have been studied in the present investigation. The experimental results showed that the conductivity of membranes increased with the temperature increased from 30 to 90 °C, except for that of pure SPEEK membrane increased with increasing temperature from 30 to 70 °C and decreased with increasing temperature from 70 to 90 °C. The conductivities of SPEEK/EB/Y2O3 and SPEEK/BS/Y2O3 composite membranes at 90 °C were 9.04×10−2 S cm−1 and 1.18×10−1 S cm−1 at 100% relative humidity (RH) and 8.04×10−2 S cm−1 and 1.02×10−1 S cm−1 at 50%RH, respectively. It has been also found that the water uptake and thermal stability of the membranes slightly improved by doping of ionic liquids and Y2O3. The tensile stress at break at room temperature was 2.61 MPa and 2.33 MPa, for SPEEK/EB/Y2O3 and SPEEK/BS/Y2O3, respectively. Therefore it may be considered that the modification with ionic liquids and Y2O3 is a good potential method for improving the properties of SPEEK proton exchange membrane.