Characterization of Gas Diffusion Layers for PEMFC

In proton-exchange membrane fuel cells, gas diffusion layers serve as current collectors that allow ready access of fuel and oxidant to the anode and the cathode catalyst surfaces, respectively. There is no electrochemical reaction in the gas diffusion layer, therefore the main polarization associated with it is due to mass transport limitation. Critical properties of in-house and commercial gas diffusion layers have been characterized and compared in this work in order to determine factors limiting the mass transport in the cathode gas diffusion layer. These properties are electrical conductivity, fraction of hydrophobic pores, gas permeability (Gurley number), pore size distribution, morphology, and the limiting current. Polarization curves for air and neat oxygen were collected to determine the limiting current at three operating temperatures, 80°C, 100°C, and 120°C, at atmospheric pressure. Linear empirical relationships for Gurley number versus limiting current were found at each of the three temperatures. Characterization of different gas diffusion layers through porosimetry provides a pore size distribution for each gas diffusion layer. Finally, an explanation of the correlation between Gurley number and limiting current tested is proposed, which relies on the pore size distribution of the gas diffusion layer associated with the data points.