Low methanol permeable crosslinked sulfonated poly(phenylene oxide) membranes with hollow glass microspheres for direct methanol fuel cells

Organic/inorganic composite membranes based on sulfonated poly(phenylene oxide) (SPPO) and hollow glass microspheres (HGMs) were prepared for use as proton exchange membranes in direct methanol fuel cells (DMFCs). First, SPPO was successfully introduced onto the surfaces of the HGMs (SPPO-HGMs) to increase dispersion of SPPO-HGMs in the SPPO matrix. The SPPO composite membranes were fabricated with varying amounts of SPPO-HGMs. Then the composite SPPO membranes were crosslinked to decrease the methanol permeability and increase the mechanical properties, and the crosslinking time was controlled to determine the optimal crosslinking time. As a result, a 12 h crosslinking time at 80°C was selected as the optimum. The SPPO-HGM composite membranes exhibited proton conductivities ranging from 0.0294 to 0.0201 S cm^-1 and methanol permeability ranging from 5.20 × 10^-7 to 1.99 × 10^-7 cm2 s^-1 at 20°C.