Metal-foam-based cathode flow-field design to improve H2O retention capability of passive air cooled polymer electrolyte fuel cells

Two conceptional cathode flow field designs are proposed for preventing serious electrolyte dehydration and overcoming unstable performance issues in polymer electrolyte fuel cells (PEFCs) that are air-cooled and of the passive type. In one design, porous metal foam is selectively inserted into the parallel channels in contact with the cathode gas diffusion layer to suppress water transport from the cell, and the other design has a smaller cathode inlet area to reduce the amount of reactant air entering the MEA. The cathode flow field designs are evaluated through three-dimensional multiscale two-phase PEFC simulations. Compared with a conventional parallel flow-field configuration, the metal foam based design results in better water retention in the MEA when excess dry air is supplied. Furthermore, it shows more uniform distributions of species, temperature, current density, and higher cell performance. The modification of the cathode inlet area has a relatively small influence on the water content profile of the MEA and overall performance of the fuel cell. This study presents a new strategy for designing the cathode flow field for the optimal operation of passive air cooled fuel cells.