Two States of the Cathode Catalyst Layer Operation in a PEM Fuel Cell

Abstract

We measure impedance of a standard Pt/C-based PEM fuel cell for a series of current densities from 50 to 400 mA cm(-2). Using our recent model for extraction of spatially-resolved data from impedance spectra, we plot the dependence of the oxygen diffusion coefficient D-ox in the cathode catalyst layer (CCL) and D-b in the gas-diffusion layer (GDL) on the distance along the cathode channel. While the GDL oxygen diffusivity is fairly uniform over the cell active area, the shape of D-ox indicates that the cell is separated into two domains with high and low water contents in the CCL. We attribute this effect to the positive feedback loop between the rates of oxygen transport and liquid water evaporation in the CCL, leading to local CCL flooding. (C) The Author(s) 2018. Published by ECS.