PREPARATION AND PROPERTIES OF SPAES-TiO_2 HYBRID MEMBRANES FOR DIRECT METHANOL FUEL CELL

 Sulfonated poly(arylene ether sulfone) (SPAES) copolymer with degree of sulfonation of 1.0 was synthesized and characterized. A series of SPAES-TiO₂ hybrid membranes with various contents of nano-sized TiO₂ particles were prepared and characterized through sol-gel reactions. Scanning electron microscopy (SEM) images indicated the TiO₂ particles were well dispersed within polymer matrix. These composite membranes were evaluated for proton exchange membranes (PEMs) in direct methanol fuel cell (DMFC). These membranes showed good thermal stability and mechanical properties. It was found that the water uptake of these membranes increased with the increase of the TiO₂ contents in the hybrid membranes. Meanwhile, the introduction of inorganic particles increased the proton conductivity and reduced the methanol permeability. The proton conductivities (0.118-0.162 S/cm) of SPAES-TiO₂ hybrid membranes with 8% TiO₂ particles are much higher than those of Nafion 117 membrane (0.095-0.117 S/cm) and pure SPAES membrane (0.100-0.124 S/cm) with degree of sulfonation of 1.0 at all temperatures (25-100°C). Especially, the methanol diffusion coefficient (8.4× 10^-7 cm²/s) of SPAES-TiO₂ hybrid membranes with 8% TiO₂ is much lower than that of Nafion 117 membrane (2.1 ×10^-6 cm²/s). SPAES-TiO₂ hybrid membranes were therefore proposed as candidates of material for PEM in DMFC.