THERMAL-STABILITY OF NAFION(R) IN SIMULATED FUEL-CELL ENVIRONMENTS

Nafion(R) is an important polymer electrolyte for polymer electrolyte fuel cell applications due to its inertness and high proton conductivi ty. Operation of these fuel cells for extended periods of time at temp eratures approaching 100 degrees C introduces concerns of the thermal stability of the Nafion electrolyte. To simulate the conditions in a f uel cell, Nafion samples were loaded with fuel-cell grade platinum bla ck and heated under atmospheres of nitrogen, 5% hydrogen, or air in a thermal gravimetric analyzer. The products of decomposition were taken directly into a mass spectrometer for identification. In all cases, N afion was found to be thermally stable up to 280 degrees C, at which t emperature the sulfonic acid groups began to decompose. A mechanism fo r the decomposition is proposed which explains many of the evolved com pounds observed during heating.