Synergistic Optimization of Cathode GDL Gradient Porosity and Dot-Matrix Flow Fields for Enhanced PEMFC Performance

Abstract The traditional gas diffusion layer has a single porosity distribution, and the flow field structure has limited capacity to regulate gas-liquid two-phase transport in proton exchange membrane fuel cells (PEMFCs). As a result, achieving an effective balance between oxygen supply and liquid water removal remains challenging during operation. This study investigates the effects of uniform and gradient porosity distributions in the cathode GDL on PEMFC performance and examines the synergistic interactions between different gradient porosity configurations and three cathode dot-matrix flow fields with rhombic, circular, and square geometries. The results show that, for GDLs with uniform porosity, the PEMFC exhibits the best overall performance at a porosity of 0.6, with the maximum current density increasing by 10.28% compared with that at a porosity of 0.4. The introduction of gradient porosity reduces cathode liquid water saturation and enhances oxygen diffusion. Among the gradient configurations examined, a linear porosity gradient along the thickness direction provides the greatest performance enhancement, yielding an approximately 8.92% increase in maximum current density relative to uniform porosity. Furthermore, the dot-matrix flow fields improve mass transport by enhancing flow disturbance and increasing the effective transport area. Among the three designs, the rhombic dot-matrix flow field achieves the highest performance, resulting in an approximately 19.21% increase in current density than the parallel flow field. When combined with the optimal linear porosity gradient, the current density is further improved by approximately 10.71% than the uniform porosity, while a more uniform temperature distribution is obtained.