Effects of gradient porosity in the metal foam flow field on the performance of a proton exchange membrane fuel cell

Proton exchange membrane fuel cells have become promising electrochemical energy
conversion devices because of their high reliability, rapid response, and low pollutant
emissions. As a place for transporting reactants and removing products, the structure
of a bipolar plate flow field has an important effect on gas transportation and water
management in fuel cells. A well-designed flow field can effectively and quickly remove
the liquid water produced in a fuel cell and improve the overall output performance of
the fuel cell. This study investigated the effect of three different cathode metal foam
flow field structures on cell performance by constructing a three-dimensional
computational fluid dynamics model. During the process, the polarization curve,
oxygen distribution, liquid saturation, temperature distribution, and pressure drop of the
aforementioned three flow field structures were systematically analyzed. The
performance of the metal foam flow field was compared with that of the parallel flow
field. The results indicated that the heat and mass transfer ability of the metal foam
flow field was better than that of the traditional parallel flow field. The metal foam flow
field in the cross-streamwise direction with decreasing porosity possessed the optimum
performance. A better water management ability and a more uniform distribution of the
reaction gas were achieved when the porosity of the metal foam flow field decreased
cross-streamwise. The output current density of the metal foam flow field at 0.5 V with
decreased cross-streamwise porosity was 2.15% higher than that of the metal foam
flow field with uniform porosity. This study highlights the potential for optimizing fuel cell
design by manipulating cathode flow field gradients, offering insight for enhancing
performance.