Pore network modeling: Application to multiphase transport inside the cathode catalyst layer of proton exchange membrane fuel cell

A pore network modeling (PNM) approach is developed to study multiphase transport phenomena inside a porous structure representative of the Cathode Catalyst Layer (CCL) of Proton Exchange Membrane Fuel Cells. Two algorithms for predicting the invasion of the CCL by liquid water are proposed and compared. The effect of wetting is studied and a change in wettability, from hydrophilic to hydrophobic, is shown to have a significant influence. The total liquid saturation at the end of invasion is lower when the network is hydrophilic whereas the number of breakthrough points is greater. The simulations fully support the idea that water exits the CCL through a series of independent outlet points. Diffusion processes in the gas phase are also analyzed within the framework of the PNM. The results indicate that the Knudsen effect, and to a lesser extent the diffusion-slip effect must be taken into account. These results open up the route for the development of a full coupled PN model of transport phenomena occurring in the CCL.