Nafion/PTFE composite membranes for fuel cell applications

The composite membranes were prepared by impregnation of porous poly(tetrafluoroethylene) membranes with a 5 wt% Nafion solution. Scanning electron microscope micrographs of composite membranes show the surface and cross section of poly (tetrafluoroethylene) membranes were covered and filled with Nation resin. Comparison of physical properties and fuel cell performance of composite membranes with those of Nation membranes (DuPont Co) is presented. The composite membrane has better thermal stability and gas barrier property but worse ionic conductivity than Nafion membrane. Though the composite membrane has a lower conductivity than Nation membrane, however, owing to the thinner thickness of composite membrane (in thickness of 20 +/- 5 mum) than Nafion- 115 (in thickness of 125 mum) and Nafion- 117 (in thickness of 175 mum) membranes, the composite membrane has a shorter H+ ion transporting pathway and thus a higher conductance (conductance = conductivity/membrane thickness) than Nation- 115 and Nation- 117 membranes. Thus the composite membrane has a better fuel cell performance than Nafion- 117 and Nation- 115 membranes. In this report, we show that our composite membrane has a fuel cell performance similar to Nation- 112 membrane (in thickness of 50 mum).