In-situ preparation of PSSA functionalized ZWP/sulfonated PVDF composite electrolyte as proton exchange membrane for DMFC applications

Abstract

A series of proton exchange electrolytes were synthesized by blending polystyrene sulfonic acid (PSSA) functionalized ZWP ion exchanger and sulfonated poly(vinylidene fluoride) (SPVDF) as base by using solution casting method. The poly(vinylidene fluoride) was sulfonated by employing a direct sulfonation technique demonstrated in the literature. Surface modification of the ZWP was done to obtain the PSSA-ZWP ion exchanger. The membranes were synthesized by using ZWP and PSSA-ZWP as ion exchangers in the SPVDF polymer matrix. The physicochemical characterization of the membranes was performed by using FT-IR and XRD. The scanning electron microscope (SEM) was used to investigate the surface morphology of the fabricated membranes for any possible defects. Important membrane parameters, such as water uptake (up to 26%), methanol uptake (up to 22%), chemical stability (7.4%) and mechanical stability (tensile strength of up to 44 MPa), were measured and are reported. The ion exchange capacity (max 0.62 meq g−1) and electrochemical characterization of the membranes was conducted and parameters such as transport number (max 0.84) indicating good ion selectivity of the membranes and proton conductivity (max 3.89 mS/cm) were also determined. The single cell DMFC performance of the SPVDF-ZWP-PSSA membrane was evaluated at three different operating temperatures of 30 °C, 60 °C and 90 °C, out of which the synthesized membrane performed best at 60 °C with maximum current density and power density of 49.8 mAcm−2 and 20.1 mWcm−2 respectively.