Phosphotungstic acid embedded sulfonated poly(arylene ether ketone sulfone) copolymers with amino groups for proton exchange membranes

Abstract

Sulfonated poly(arylene ether ketone sulfone) containing pendant amino groups (Am-SPAEKS)/phosphotungstic acid (HPW) composite membranes with different HPW content were prepared by the solution blend method as proton exchange membranes (PEM) for proton exchange membrane fuel cells (PEMFCs) that operate at medium–high temperatures. Am-SPAEKS was synthesized successfully by adjusting the molar feed ratio, which was confirmed by Fourier transform infrared (FT-IR) and ¹H NMR spectroscopy. FT-IR spectroscopy showed that there were acid–base interactions between the amino groups and HPW, as well as between HPW and the sulfonic groups. These interactions could stabilize HPW in the composite membranes, which was confirmed by SEM images. The water uptake and thermal stability of the composite membranes were improved compared with the Am-SPAEKS membranes. The water retention capacity and the mechanical property of the composite membranes also met the requirement for proton exchange membranes. The proton conductivity of the Am-SPAEKS/HPW30% composite membrane was as high as 0.091 S cm⁻¹ at 120 °C. These results indicate that the Am-SPAEKS/HPW composite membranes have potential to be used as alternative proton exchange membrane materials for proton exchange membrane fuel cells at medium–high temperature conditions.