Analyzing the influence of high electrode potentials on intrinsic properties of catalyst coated membranes using impedance spectroscopy

When subjected to potentials higher than 1.2  V, an increased performance is observed for low ionomer loading CLs. It is found that by applying the high potential to the electrode a significantly increased proton conductivity is counteracting and superimposing the loss of electrochemical surface area (ECSA) due to carbon corrosion. After aging, the performance of the 15 wt% CL is at the same level as the 31−34 wt% ionomer content CLs at the beginning of life, even though the ECSA is reduced due to carbon corrosion or platinum dissolution. The findings indicate that for the optimization of the ionomer loading, either the changing wetting properties or the redistribution of ionomer during lifetime have to be taken into account.