Fabrication and electrochemical properties of surface modified sulfonated poly(vinylidenefluoride-co-hexafluoropropylene) membranes for DMFC application

• Synthesis and blending of sPVdF-co-HFP with different charged surface modifying macromolecules
• PEM prepared from sPVdF-co-HFP/MDI-PEG200-HBS blends produced best overall performance.
• A methanol permeability of 2.04 × 10− 7 cm2 s− 1 was achieved by sPVdF-co-HFP/MDI-DEG-HBS blend membranes.
• The proton conductivity of 4.99 × 10− 3 S cm− 1 was achieved by sPVdF-co-HFP/MDI-PPG425-HBS blend membranes.
• Overall membrane performance of sPVdF-co-HFP/cSMM blends was superior compared to pure sPVdF-co-HFP and Nafion.

Surface modification of sulfonated poly(vinylidenefluoride-co-hexafluoropropylene) (sPVdF-co-HFP) membrane was attempted by blending with differently charged surface modifying macromolecules (cSMMs) with different polyols. The prepared membranes were characterized using Fourier transform infrared spectroscopy, thermal analysis, mechanical properties, ion exchange capacity, atomic force microscopy, contact angle, and water uptake. The ionic conductivities of the prepared membranes are in the order of 10 −3 S cm −1. The proton conductivity was found to be dependent upon the water uptake of the membranes. Among the modified membranes, the sPVdF-co-HFP/cSMM-1 (2 × 10 −7 cm2 s −1) blended membrane shows lower methanol permeability whereas the sPVdF-co-HFP/cSMM-4 (5 × 10− 3 S cm −1) blended membrane indicates the highest proton conductivity. However, the sPVdF-co-HFP/cSMM-2 (21.8 × 103 S cm −3 s) blended membrane exhibits the highest overall membrane characteristic value. These characteristics make the prepared membranes a promising electrolyte for direct methanol fuel cell application.

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