Preparation and characterization of proton-conducting sulfonated poly(ether ether ketone)/phosphatoantimonic acid composite membranes

The solid proton conductor, phosphatoantimonic acid, HSbP2O8 · H2O was prepared by ion exchange of the corresponding potassium salt. The composite membranes of SPEEK with up to 40 wt% of HSbP2O8 · H2O were prepared by introducing the solid proton conductor from the aqueous suspension. The composite membranes were characterized using FT-IR, powder X-ray diffraction, SEM, DSC/TGA. Thermal stability of the composite membranes was slightly lower than that of SPEEK. The composite membranes had higher water uptake when compared with SPEEK and the membranes exhibited controlled swelling up to 50 °C. The proton conductivity of the membranes was measured under 100% relative humidity up to 70 °C. The composite membranes showed enhanced proton conductivity up to 20 wt% of HSbP2O8 · H2O and the conductivity was reduced with further increase of HSbP2O8 · H2O loading. A maximum of four-fold increase in proton conductivity at 70 °C was observed for the composite membrane with 20 wt% of solid proton conductor.