Analysis and modeling of a membrane electrode assembly in a proton exchange membrane fuel cell

Abstract

In this study, a membrane electrode assembly of a proton exchange membrane fuel cell is modeled. Using the analytical model, a computational analysis has been conducted along with an extensive parametric study. Variation of ohmic losses, water content, and voltage drops from anode to cathode side of the membrane electrode assembly with many design/operation parameters such as thickness, temperature, pressure, and local/total humidity and conductivity, diffusivity, and resistivity have been evaluated at various current densities. Also, effect of molar concentration of hydrogen on hydrogen diffusive flux due to pressure change between the anode and cathode at different membrane thicknesses has been presented. Furthermore, variation of water uptake and concentration with the ratio of water and hydrogen fluxes, the current density, and membrane dry density have been studied along with their interrelation. It is observed that as the membrane thickness increases, its resistivity increases as well, causing higher ohmic losses. On the other hand, the water content increases with the thickness until a maximum point and then starts to decrease. Therefore, the membrane thickness should be optimized carefully to have desirable humidity levels with minimum crossover and losses.