Improvement in silicon-containing sulfonated polystyrene/acrylate membranes by blending and crosslinking

Silicon-containing sulfonated polystyrene/acrylate-poly(vinyl alcohol) (Si-sPS/A-PVA) and Si-sPS/A-PVA-phosphotungstic acid (Si-sPS/A-PVA-PWA) composite membranes were fabricated by solution blending and physical and chemical crosslinking methods to improve the properties of silicon-containing sulfonated polystyrene/acrylate (Si-sPS/A) membranes. FTIR spectra clearly show the existence of various interactions and a crosslinked silica network in composite membranes. The potential of the composites to act as proton exchange membranes in direct methanol fuel cells (DMFCs) was assessed by studying their thermal and hydrolytic stability, swelling, methanol diffusion coefficient, proton conductivity and selectivity. TGA measurements show that the composite membranes possess good thermal stability up to 190 °C, satisfying the requirement for fuel cell operation. Compared to the unmodified membrane, the composites exhibit less swelling and a superior methanol barrier. Most importantly, all of the composite membranes have significantly lower methanol diffusion coefficients and significantly higher selectivity than those of Nafion® 117. The Si-sPS/A-20PVA-20PWA membrane is the best applicant for use in DMFCs because it exhibits an optimized selectivity value (5.93 × 105 Ss cm−3) that is approximately 7.8 times of that of the unmodified membrane and is 27.8 times higher than that of Nafion® 117.