Question

Brad is working on proton-exchange membrane (PEM) fuel cells using Nafion and he is given a new membrane to test. The membrane is essentially the same chemistry as Nafion, but it is much thicker (300 microm vs 120 microm). Therefore, he expects the fuel cell to operate poorly with this new membrane. But, to his surprise, the open circuit voltage (OCV) with the new membrane is 1.1 V vs 1.05 V with Nafion. Why is the new membrane improving the OCV?

Answer 1

It is because to function, the new thicker membrane must have conducted hydrogen ions (protons) but not electrons as this would in effect "short circuit" the fuel cell. The membrane would also not have allowed either gas to pass to the other side of the cell, a problem known as gas crossover. Finally, the membrane must have been resistant to the reducing environment at the cathode as well as the harsh oxidative environment at the anode and thereby having greater OCV than Naflon