Solid polymer electrolyte based on sulfonated polysulfone membranes and acidic silica for direct methanol fuel cells

Composite membranes based on sulfonated polysulfone and acidic silica filler were prepared and investigated for direct methanol fuel cells. A significant influence of nanosized acidic silica on composite membrane properties was observed. A better distribution of acidic silica than bare silica was found in the membranes as well as a higher ionic conductivity of acidic silica membrane. The composite membranes based on sulfonated polysulfone modified silica (SPSf–SiO2–S) and bare silica (SPSf–SiO2) showed also an increase of DMFC performance compared to bare SPSf. The best electrochemical performance was obtained with the composite SPSf–SiO2–S membrane that showed satisfactory proton conductivity, low methanol crossover and low swelling in comparison to bare SPSf membrane. Methanol crossover currents of 20, 25 and 31mAcm−2 were measured for SPSf–SiO2–S, SPSf–SiO2 and SPSf membranes, respectively. The highest DMFC performance of 60mWcm−2 was obtained with the composite acidic silica-SPSf membrane (SPSf–SiO2–S) at 60°C. ► Composite membranes based on acidic silica and sulfonated polysulfone (SPSf). ► The acidic silica SPSf membrane has lower methanol crossover than bare SPSf. ► The maximum DMFC power density is achieved with the acidic silica SPSf membrane. ► The DMFC performance is mainly influenced by methanol crossover.