Impact of PTFE distribution on the removal of liquid water from a PEMFC electrode by lattice Boltzmann method

It is believed by many that polymer electrolyte membrane fuel cells (PEMFCs) will have a widespread application since they offer important features such as low operating temperature, high power density, and easy scale up. However, operation of PEMFCs is faced with some technical challenges including water management which may lead to flooding of the electrodes. Treatment of the gas diffusion layer (GDL) with a highly hydrophobic material such as PTFE is a common strategy for mitigating this issue. Several investigations have been done to clarify solely the effect of PTFE content. However, effects of PTFE distribution, which can be achieved through different treatment methods, has not been well studied yet. Lattice Boltzmann method (LBM) is one of the best choices for such numerical studies due to its capability of modeling multiphase flow in the complicated microstructure of a porous GDL considering its non-homogeneous and anisotropic transport properties. In the present study, droplet removal from four GDLs with different PTFE distributions through an interdigitated flow field is investigated using LBM. The results demonstrate that regardless of PTFE distribution, the interfacial forces between any untreated carbon fiber and a water droplet will strongly dominate over other forces and hence will prevent its removal. Therefore, it is concluded that an effective water management may be achieved by a suitable treatment method such that no carbon fiber inside the GDL remains uncoated.