Experimental and theoretical study of a dual-layer gas diffusion layer in PEM fuel cells

The gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) functions as a diffuser and a current collector. The GDL typically consists of the microporous layer (MPL) and the macroporous substrate (MPS). The MPL reduces the ohmic losses and facilitates water removal in the MEA.;In this study, a novel method was developed to prepare a dual-layer GDL that enhances the catalyst utilization and the overall fuel cell performance. Several characterization techniques, including mercury porosimetry, water permeation measurement, electrochemical polarization and ac impedance spectroscopy were performed to investigate how carbon loading (or MPL thickness) and PTFE content in the MPL and in the MPS control the water management in PEM fuel cells.;An experimental study on carbon loading in the MPL showed that a relatively low carbon loading (0.5 mg cm-2 in this study) results in a balancing of water saturations in the catalyst layer and the GDL, thus improving the oxygen diffusion kinetics.;Experimental studies on PTFE content in the MPL and in the MPS indicated that effective water management is attributed to the trade-off between the pore volume and the hydrophobic property of each diffusion layer.;A theoretical study of a dual-layer GDL in PEM fuel cells demonstrated that saturation in the MPS is intimately coupled with both the fraction of hydrophilic surface and the average pore diameter. A thin and more hydrophobic MPL altered the pore geometry and the hydrophobic property of a MPS, resulting in better mass transport of reactants and products in the MEA.