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Novel materials for gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFCs) are increasingly under investigation to improve high current performance. Metal gas diffusion layers are of interest as they provide high thermal and electrical conductivity as well as offering the possibility of integration of the flowfield and gas diffusion layer. These properties are all of importance to fuel cells as they should give increased volumetric power density and decrease resistive losses at higher current densities. Some recent studies have shown that these metal GDLs can outperform commercial carbon GDLs in the high current region [1]–[3]. The water dynamics of these types of GDL are poorly understood however, and there has been little or no research on this topic. We have performed a study using neutron imaging to study the movement of water in metal mesh GDLs and used EIS to study the consequent effect of mass-transport resistance at a number of current densities and humidities [4]. We have observed a number of interesting phenomena in the water transport in metal-mesh GDLs, which show quite different behavior to that of the normal carbon papers. When metal mesh is used as the anode and cathode GDL, there appears to be water accumulation in the areas of the channel, which also promotes the back-diffusion of water from the cathode to the anode side of the cell. With a carbon-paper GDL, liquid water accumulates in the land, and there does not appear to be significant back-diffusion compared to the metal mesh GDL. These behaviors also have significant effects on mass-transport and the performance of the cell. The insights provided by the neutron imaging, along with the EIS data will allow us to inform novel and future fuel cell designs. References [1] T. Yoshida and K. Kojima, “Toyota MIRAI Fuel Cell Vehicle and Progress Toward a Future Hydrogen Society,” Interface Mag., vol. 24, no. 2, pp. 45–49, Jan. 2015. [2] K. F. Fahy, J. Lapinski, and A. R. J. Kucernak, “Metal Mesh Gas Diffusion Layers for PEM Fuel Cells,” Meet. Abstr., vol. MA2016-02, no. 38, pp. 2569–2569, Sep. 2016. [3] N. Hussain, E. Van Steen, S. Tanaka, and P. Levecque, “Metal based gas diffusion layers for enhanced fuel cell performance at high current densities,” J. Power Sources, vol. 337, pp. 18–24, Jan. 2017. [4] R. S. Fu et al., “An Investigation of Thermally-Induced Water Transport in Polymer Electrolyte Fuel Cells with Neutron Radiography Imaging Technique,” in ECS Transactions, 2009, pp. 543–552. Figure 1 |
