Hybrid ion-exchange membranes for fuel cells and separation processes

摘要

This work reports the preparation and characterization of hybrid membranes cast from dispersions of inorganic fillers in sulfonated polystyreneblock-udpoly(ethylene-ran-butylene)-block-polystyrene solutions. Silica gel, SBA-15 and sepiolite, all of them functionalized with phenylsulfonicudacid groups, were used as fillers. For comparative purposes, the performance of composite membranes cast from dispersions of functionalizedudinorganic fillers in Nafion® solutions was investigated. Inspection of the texture of the membranes by using SEM techniques shows that the fillersudare better dispersed in sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene than in Nafion®. The value of the water uptakeudfor the membranes prepared from the former polyelectrolyte is in most cases at least three times that measured for hybrid Nafion® membranes. Theudconductivity of the membranes was measured at 80 ◦C by impedance spectroscopy obtaining values of 3.44, 6.90 and 3.54 Sm−1 for the hybridudmembranes based on the triblock copolymer containing functionalized silica gel, SBA-15 and sepiolite fillers, respectively. These results compareudvery favourably with those obtained at 80 ◦C for Nafion® hybrid membranes containing silica gel, SBA-15 and sepiolite, all of them fuctionalizedudwith phenylsulfonic acid groups, whose conductivities are, 2.84, 6.75 and 3.31 Sm−1, respectively. Resistance measurements carried out underudcontrolled humidity conditions show that the conductivity of sulfonated triblock copolymer membranes containing functionalized SBA-15 fillerudundergoes a rather sharp increase when they are conditioned under an atmosphere of 75%, or larger, relative humidity.