Double-layer gas diffusion media for improved water management in polymer electrolyte membrane fuel cells

• New double-layer GDM with graded PTFE loading is demonstrated for PEMFCs.
• Double-layer GDM shows improved water management even under flooding conditions.
• Numerical model for saturation level in double-layer GDM is developed.
• Numerical predictions are validated by experimental measurements.
• Adding GDM layers with graded hydrophobicity can improve water management in PEMFCs.

Water management is an important consideration to improve the performance of polymer electrolyte membrane fuel cells (PEMFCs). Reactant gases are supplied to the catalyst layer through gas diffusion media (GDM) in PEMFCs. Under high current draw conditions, the GDM can flood with liquid water which is detrimental to fuel cell operation. In this paper, we investigate the effectiveness of a double-layer GDM with different polytetrafluoroethylene (PTFE) loadings to mitigate saturation with liquid water under flooding conditions. We developed a numerical model to predict the saturation field in the double-layer GDM, and showed that the overall saturation level is decreased when the layer with higher PTFE loading is placed adjacent to the catalyst layer. It was found that the interface between the two GDM layers plays a significant role in regulating the saturation level by lowering the driving saturation level for water transport inside the GDM. The numerical predictions of the model were validated by conducting experiments with the double-layer GDM which showed a higher limiting current density and more stable performance, thereby confirming that the new GDM architecture can improve water management in PEMFCs.