Development and demonstration of a higher temperature PEM fuel cell stack

Research and development was conducted on a proton exchange membrane (PEM) fuel cell stack to demonstrate the capabilities of Ionomem Corporation's composite membrane to operate at 120 °C and ambient pressure for on-site electrical power generation with useful waste heat. The membrane was a composite of polytetrafluoroethylene (PTFE), Nafion®, and phosphotungstic acid. Studies were first performed on the membrane, cathode catalyst layer, and gas diffusion layer to improve performance in 25 cm2, subscale cells. This technology was then scaled-up to a commercial 300 cm2 size and evaluated in multi-cell stacks. The resulting stack obtained a performance near that of the subscale cells, 0.60 V at 400 mA cm−2 at near 120 °C and ambient pressure with hydrogen and air reactants containing water at 35% relative humidity. The water used for cooling the stack resulted in available waste heat at 116 °C. The performance of the stack was verified. This was the first successful test of a higher-temperature, PEM, fuel-cell stack that did not use phosphoric acid electrolyte.