Nafion-Teflon-Zr(HPO4)2 composite membranes for high-temperature PEMFCs

Nafion membranes suffer high resistance due to dehydration when they are used at elevated temperatures ( > 100DGC) and atmospheric pressures (Nafion 1135 > 0.6 Omega cm 2 at 120DGC and 31% relative humidity). Thinner composite membranes containing Nafion and zirconium hydrogen phosphate, Zr(HPO4)2, were prepared and showed lower resistance ( < 0.3 Omega cm 2) at these conditions. Thermogravimetric analysis showed that the composite membrane was stable below 200DGC in oxygen. Hydrogen crossover of a 18 mm thick composite membrane was only 2 mA/cm2 at 120DGC. When the temperature of a cell using this membrane was raised from 80DGC (100% relative humidity) to 120DGC (31% relative humidity), the main performance loss at the elevated temperature was from low protonic conductivity and low oxygen permeability in the cathode catalyst layer and dehydration of the membrane.