Effect of spatial variation of gas diffusion layer wetting characteristics on through-plane water distribution in a polymer electrolyte fuel cell

Through-plane liquid water distributions recently visualized by Manahan et al. [1] and Turhan et al. [2] using the neutron radiography (NR) technique show that the peaks of the water distributions are located near the center of a gas diffusion layer (GDL). We suggest that the distinctive water profiles are caused by incomplete polytetrafluoroethylene (PTFE) treatment of the GDL and the resultant spatial variation of GDL wettability in the through-plane direction. Based on this hypothesis, we improve the macroscopic two-phase fuel cell model to describe two-phase transport through GDLs with variation of spatial wettability [3]. The proposed model successfully reproduces the shape of through-plane water profiles obtained from the NR experiments [1,2]. Therefore, the centrally located liquid saturation peak in the GDL can be attributed to incomplete PTFE treatment of the GDL. This occurs because liquid water is more easily accumulated in the relatively hydrophilic GDL pores encountered in the inner GDL region (rather than the outer GDL region) due to its incomplete PTFE treatment. Our results indicate that the overall characteristics of liquid water distribution in a GDL under an inhomogeneous wetting condition can be macroscopically predicted using the two-phase model presented here.