Effect of solution casting temperature on properties of nafion composite membrane with surface modified mordenite for direct methanol fuel cell

Incompatibility between organic polymer and inorganic filler has been addressed as critical area of Nafion and mordenite composite membrane fabrication for direct methanol fuel cell (DMFC) application. It possibly brings about void leading to high methanol crossover. Incompatibility at the surface of the filler can be improved by using silane coupling agent. In this study, two coupling agents were used in order to improve interfacial property between filler and polymer matrix, including gamma-glycidoxypropyl trimethoxysilane (GMPTS) and 3-mercaptopropyl triethoxysilane (MPTES). Surfaced modified mordenite was used in Nafion/mordenite composite membranes fabrication by using solution casting method. Properties of composite membranes were investigated, including chemical resistance, water uptake, ion-exchange capacity (IEC), proton conductivity and methanol permeability. It was found that properties of the composite membrane were greatly affected by casting temperature in casting method. In this work, the most suitable solution casting temperature was 100 °C. The obtained membrane gave 0.59% soluble, 1.38% water uptake and 0.10 meq g− 1 IEC. With type of silanes, membrane fabricated with MPTES treated mordenite showed better properties than that of GMPTES giving 60% higher proton conductivity and 85% lower methanol permeability at 30 °C.