Numerical investigation of performance of an interdigitated polymer electrolyte membrane fuel cell with a porous rib

Abstract

This numerical study evaluates a polymer electrolyte membrane fuel cell (PEMFC) with an interdigitated flow field and porous cathode rib using a 3D steady-state model. While the conventional interdigitated design with a solid rib enhances electrochemical reaction rates and mass transport, it requires a high pressure gradient to drive reactants, thereby increasing mechanical power consumption. The work underscores the trade-off between reaction efficiency and energy losses, guiding optimized flow field architectures to improve PEMFC net efficiency. The present study compares the features of the conventional interdigitated and porous-interdigitated designs under different conditions, including various stoichiometric ratios, cathode channel cross-section area, and the inlet humidity. The simulation results, presented as polarization curves, net power output, mechanical power consumption, and oxygen concentration profiles, indicate that the net power output of the porous-interdigitated model is similar to or slightly lower than that of the interdigitated model, due to oxygen diffusion into the porous rib without participating in electrochemical reactions. At a cathode stoichiometric ratio of 1.25, the porous-interdigitated model exhibits a 1.2% increase in power density at a current density of 1.05 A/cm² compared to the interdigitated model. Furthermore, at a stoichiometric ratio of 1.05 with 50% and 100% inlet relative humidity, the performance improvement exceeded 4.5% and 8%, respectively. The porous-interdigitated model also consistently shows a lower pressure drop than the standard interdigitated design at the same current density and all assumed operating conditions. Based on oxygen concentration profiles, the porous-interdigitated flow field design exhibits a more even oxygen dispersion, minimizing concentration losses and demonstrating enhanced efficiency at low flow rates and high current densities. Overall, the porous-interdigitated model demonstrates higher generated power and lower mechanical power consumption, particularly at high relative humidity and low stoichiometric ratios, making it a promising design for PEMFC performance enhancement.