The interactive effect of heat and mass transport on water condensation in the gas diffusion layer of a proton exchange membrane fuel cell

Despite recent advancement in fuel cell technology, significant challenges remain in achieving high power density operation to meet the stringent targets of performance, durability and cost. This is due to the lack of fundamental understanding in interactive transports of oxygen, protons, heat, and water. In this study, we employed both experimental and analytical methods to study water onset condensation using Toray and Freudenberg diffusion media, which have different thermal and diffusion properties. Toray performs better under dry conditions, while Freudenberg has improved performance under wet conditions. The dry and wet effective diffusivities obtained using the in situ limiting current support the performance results. Neutron images show that liquid water exists throughout the layer of diffusion media for Toray material, but only under the land for Freudenberg keeping the area under the channel open for oxygen transport. To further understand this fundamental mechanism, we developed a 1-D model to simulate fuel cell performance. In addition, we identify the water condensation behavior is controlled by the product of thermal conductivity and the ratio of tortuosity to porosity. The findings provide new insights into improving material design and boosting energy conversion efficiency under a wide range of fuel cell operation conditions. © 2020 Elsevier B.V.