Anisotropic Electrical Performance of Carbon Paper Type Gas Diffusion Layers in Proton Exchange Membrane Fuel Cells

The electrical resistance of gas diffusion layers (GDLs) contributes a major portion of the performance losses in proton exchange membrane fuel cells (PEMFCs). The anisotropic architecture of carbon-paper-based GDLs, coupled with the channel/rib configuration of bipolar plates (BPPs), results in complex current transport behavior. Understanding the structure–property relationship between the GDL microstructure and its anisotropic electrical properties is crucial for optimizing PEMFC performance. This work investigates the 3D anisotropic electrical performance of carbon paper type GDLs in both through-plane (TP) and in-plane (IP) directions. 2D and 3D morphological characterizations reveal the fundamental conduction mechanisms. An integrated mechanical–electrical model was developed to simulate the GDL deformation and current density distribution under realistic BPP compression conditions. Notably, TP resistance exhibits pronounced pressure dependence below 1 MPa, decreasing nonlinearly from 130 to 16 mΩ for GDL-240 and from 85 to 6 mΩ for GDL-340, consistent with surface morphology-controlled conduction. After three compression cycles, the TP electrical resistance stabilizes approximately 7 mΩ under 2 MPa for GDL-240 and 4 mΩ under 4 MPa for GDL-340, with pressure plateaus indicating microstructural saturation. These findings suggest material-specific optimal assembly pressures of 2 MPa for GDL-240 and 4 MPa for GDL-340 in PEMFC applications.