Sulfonated polyethersulfone/polyetheretherketone blend as high performing and cost-effective electrolyte membrane for direct methanol fuel cells

Blended electrolyte membranes based on sulfonated Polyethersulfone (sPES) and sulfonated Poly(ether ether ketone) (sPEEK) were prepared in two different ratios (i.e. 50/50 and 25/75) via a simple, scalable and inexpensive solution casting process to investigate their suitability for direct methanol fuel cell (DMFC) applications. Thermo-mechanical analysis revealed higher flexibility and thermal resistance with the blending of these two macromolecules, without any evidence of phase-segregation, and with good chemical stability. Furthermore, the proton transport was facilitated while the methanol permeability was dramatically reduced. The DMFC tests confirmed outstanding performance by using the membrane with the blend ratio 25/75, reaching a power density of about 130 mW cm at 80 °C in 4 M methanol solution. These features and the cost-effectiveness of sPES-SPEEK membranes make them interesting candidates for use in next-generation DMFCs.