Cross-scale study on water and gas transfer in proton exchange membrane fuel cell considering micro porous layer interfaces

Abstract

The maximum power density of a proton exchange membrane fuel cell (PEMFC) is most affected by mass transfer at high current densities, where water flooding hinders oxygen transfer. In this paper, the multiphase and mass transport lattice Boltzmann method (LBM) model is applied to cross-scale explore how water migrates from the catalyst layer (CL) to the flow channel through the micro porous layer (MPL), taking into account pressure and interfacial variations, and analyzing the structure factors (on water migration in-plane and through-plane), which can provide theoretical guidance for better mass transfer. Our simulations reveal that thicker transition layers (TL) lower water saturation in the gas diffusion layer (GDL) and on the MPL surface but reduce porosity, hindering oxygen transport and drainage. TL height exerts a significant influence on the timing of breakthrough, while an increase in crack width has the effect of reducing the influence of TL height. Crack width and spacing control where and how much water invades at the interface without affecting inner GDL flow channels. Moderate compression further reduces GDL saturation, with water breakthrough mainly under channels and higher saturation beneath channels than ribs. Low porosity is more sensitive to compression and increases the breakthrough time with increasing pressure, while high porosity is mainly affected by the thickness of the TL.