Boosting the performance of polymer electrolyte membrane fuel cells with porous flow fields: Pros and cons

Abstract

The design of the cathode flow field plays a relevant role in the performance of proton exchange membrane fuel cells (PEMFC). Recently, porous flow fields have emerged as an alternative to conventional rib/channel flow fields (e.g., serpentine flow field) in an attempt to increase PEMFC performance. In this work, we aim to shed light on pros and cons of both bipolar plate types by analyzing transport through porous and rib/channel flow fields using experimental and numerical work. The experimental polarization curves and oxygen transport resistance data of a cathode porous flow field are used to validate the numerical model. Then, a comprehensive parametric study of the model is presented, involving both operating and constructive parameters. The results show that the main advantages of porous flow fields are: (𝑖) the improvement of oxygen transport, (𝑖𝑖) the decrease of flooding in the cathode MEA, and (𝑖𝑖𝑖) the increase of the distribution homogeneity in the in-plane direction of physical parameters (e.g., current density and temperature). In contrast, the main disadvantages are: (𝑖) the potential effect of electrical contact resistances between porous surfaces, and (𝑖𝑖) the decrease of the water removal drag force in the cathode channel. The above two issues can be mitigated using: (𝑖) thinly manufactured foams and/or increasing the assembly compression, and (𝑖𝑖) hybrid porous flow fields that incorporate a rib/channel pattern with fine pore-size porous ribs.