Improvement of polymer electrolyte fuel cell performance by gas diffusion layer with relatively hydrophilic surface

To improve the performance of polymer electrolyte fuel cells under high current density operation, the flooding problem in gas diffusion layers (GDLs) should be solved. In this study, a novel GDL with a relatively hydrophilic surface, consisting of hydrophilic and hydrophobic pores, which yielded a wettability distribution in the thickness direction, was proposed to achieve smooth water transport. First, we fabricated GDLs with surfaces partially hydrophilized by Nafion, and we demonstrated that the cell performance improved with this treatment. Cell performance tests suggest that a GDL with optimized surface treatment could reduce the water accumulation compared with the hydrophobic GDL used in this study; it could also improve cell performance owing to low mass transport losses. To verify the surface treatment-induced improvement in the oxygen diffusivity of the GDL, the water transport in the GDL was simulated using a lattice Boltzmann method. The results showed that the water accumulation in the GDL with surface treatment was small because the water flow was limited to the thin relatively hydrophilic region. Consequently, the oxygen diffusivity was higher than that of the hydrophobic GDL. Therefore, the flooding problem can be suppressed by the surface treatment, which yields a relatively hydrophilic surface.