Electrochemical performance and water management investigation of polymer electrolyte membrane fuel cell (PEMFC) using gas diffusion layer with polytetrafluoroethylene (PTFE) content gradients in through-plane direction

The water management capability and electrochemical performance of polymer electrolyte membrane fuel cell (PEMFC) using gas diffusion layers (GDLs) with polytetrafluoroethylene (PTFE) content variation in through-plane direction are investigated. Four PTFE content variation cases are considered by stacking GDLs with different amounts of PTFE content. Polarization curves and electrochemical impedance spectroscopy are experimentally obtained. The liquid water saturation and effective diffusion factor are numerically studied. In high humidity condition, a PEMFC containing a GDL without PTFE content variation and without PTFE treatment shows the best performance due to the highest effective diffusion factor and the lowest mass transport resistance. Despite the lowest liquid water saturation in a GDL with decreasing PTFE content toward channel, the effective diffusion factor of the GDL is not the highest because of the decreased porosity by PTFE treatment. In low humidity condition, a PEMFC containing a GDL with increasing PTFE content toward channel has the best performance because of the lowest ohmic resistance. The GDL has the largest liquid water saturation and the lowest effective diffusion factor, resulting in the better membrane hydration. In high current density, however, the performance of the PEMFC containing the GDL with increasing PTFE content toward channel drastically decreases due to large mass transport resistance.