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 Nafion resin. Comparison of physical properties and fuel cell performance of composite membranes with those of Nafion 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 Nafion membrane, however, owing to the thinner thickness of composite membrane (in thickness of 20±5µm) than Nafion-115 (in thickness of 125µm) and Nafion-117 (in thickness of 175µm) membranes, the composite membrane has a shorter H⁺ ion transporting pathway and thus a higher conductance (conductance = conductivity/membrane thickness) than Nafion-115 and Nafion-117 membranes. Thus the composite membrane has a better fuel cell performance than Nafion-117 and Nafion-115 membranes. In this report, we show that our composite membrane has a fuel cell performance similar to Nafion-112 membrane (in thickness of 50µm).