Impact of cyclic compression of metal foam flow fields on the functional and structural properties of gas diffusion layer used in proton exchange membrane fuel cells

The proton exchange membrane fuel cell components experience severe stresses and deformations during assembly, and in service. The gas diffusion layer (GDL), which is made up of a macroporous substrate (MPS) and a microporous layer (MPL), must withstand such harsh operating conditions. This study reports the mechanical degradation of the MPS exposed to compression cycles owing to service loads and the expected performance variation. Fifty compression cycles with various pressure ranges were carried out on a GDL substrate with an open-cell nickel foam. The surface morphology of the compressed MPS displayed ruptured fibres due to intrusion of nickel foam struts and reduced porosity by 10 per cent due to fibre blockage and the power generated by 15 per cent. Further, the impact of strut intrusion into the MPL at high service loads is reported using extrapolation and analytical methods. The intrusion of struts into the MPL creates macropores, leading to water droplets obstructing oxygen diffusion paths. Besides, under severe loads and repeated compression cycles, the struts puncher MPL and substantially degrade the catalyst layer. At 8MPa contact pressure, the platinum load decreased by approximately by a factor ∼3.6. Unlike conventional graphite plates, the compression effect due to metal foam struts is localized.