Influence of different GDL compression on PEFC performance

problems one of the possible solution is to compress hardly the components together. Unfortunately, an excessive compression of the components, in particular the GDL, increases the mass transport problems with a consequent reduction of cell performance at high current density. Contrarily, a non optimal tightening of the cell does not warrant a perfect gases sealing and, moreover, it could cause an higher contact resistance between the MEA and graphite plates provoking a reduction of the cell performance. In this work, an evaluation, in single cell, of different gasket kinds with different thicknesses and torque momen~s was carried out. Because of the materials composing the gasket are subjected to a different deformation due to dlff~rent elastic modules, a different compression was obtained on the GDL as a function of the torque moment. Moreover, If the gaskets have not an appropriate thickness, especially too elevated, an increased contact resistance could be measured. These effects influence the cell performance, both the ohmic and the diffusive region of the polarisation curves, wh~re the problems related to the mass transport is more important. These problems are minimised when the cell is fed With gas pressurized at 3 abs bar, in fact at higher pressure the gas concentration is higher and the diffusion is favoured nevertheless the GDL compression and the consequent reduced porosity of it. Instead, with a pressure reduction at 1 abs. bar the effect of the GDL compression and the increasing of co.ntact resistance more influence the cell performance. In fact, at lower pressure the gas concentration is lower, due to an higher vapour phase, and the compression of the GDL has a more influence in the gas diffusion through it.