Preparation of PVdF/PSSA composite membranes using supercritical carbon dioxide for direct methanol fuel cells

Composite membranes were prepared using supercritical carbon dioxide (scCO2) impregnation and polymerization procedures and were optimized as electrolytes by controlling the amount of divinylbenzene (DVB) for polymerization. These poly(vinylidene fluoride)/polystyrene sulfonic acid (PVdF/PSSA) membranes were characterized by various methods. The cross-sectional superficial morphology and structure of the PVdF/PSSA membranes were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), FT-IR and small-angel X-ray scattering (SAXS). The ion exchange capacity (IEC), ion conductivity, methanol permeability and cell performance of PVdF/PSSA membranes were measured and compared with Nafion 115. As the concentration of added DVB increased, the ion conductivity and methanol permeability of the PVdF/PSSA membranes decreased. The PVdF/PSSA membrane containing 7.5 wt% DVB achieved 94% of the current density with Nafion 115.