Towards the understanding of proton conduction mechanism in PEMFC catalyst layer: Conductivity of adsorbed Nafion films

Thin adsorbed Nafion films, representing ionomer in the PEMFC catalyst layer, were prepared by spontaneous adsorption of Nafion on SiO2 model substrate. The conductivity of the thin films was examined over a wide range of temperature and relative humidity by electrochemical impedance spectroscopy. The activation energy of proton conduction was found to be twice and three-and-half times that of Nafion 112 membrane at high RH (80%) and low RH (20%), respectively. These results suggest that the mechanism of proton transport in the PEMFC catalyst layer is different than that in the membrane.

►This work is the first reported study on the conductivity of adsorbed Nafion films. ►Intrinsic protonic conductivity of adsorbed Nafion and membrane vary significantly. ►Activation energy for conduction in adsorbed Nafion and membrane are different. ►Proton conduction mechanism in PEMFC catalyst layer and membrane are different.