Impact of gas stoichiometry on water management and fuel cell performance of a sulfonated Poly(Ether Ether Ketone) membrane

Fuel cell tests have been performed on sulfonated Poly(Ether Ether Ketone) (sPEEK) membranes using dry gases. Impact of gas stoichiometry on performance evolution and membrane–electrodes assembly's water distribution optimization (water management) was studied. During the tests, output voltage evolution was recorded as well as impedance spectra, polarization curves and water amount collected at both sides.Fuel cell performances were observed to be influenced by water management which depends on both operating conditions and membrane intrinsic properties. Increasing either hydrogen or oxygen stoichiometry leads to a decrease of performance. This effect was more pronounced for hydrogen increase (anode). This has been ascribed to a global drying of the membrane along with the appearance of a heterogeneous hydration both through the MEA and along the gas channels.Cell performance characterization during the membrane lifespan was mainly based on Electrochemical Impedance Spectroscopy measurements and showed that water distribution heterogeneity increased with operating time for sPEEK membrane, leading to a drop of performance. This was mainly ascribed to the drying of the gas inlet and the increased hydration at the gas outlet. These behaviours were not observed for the better performing Nafion, which underlines the impact of membrane water transport properties on fuel cell performance.

► Water management depends on membrane's intrinsic water transport properties.
► For sPEEK increasing H2 or O2 stoichiometry leads to a decrease of performance.
► Slow back-diffusion in sPEEK leads to heterogeneous hydration of the MEA.
► Heterogeneous hydration of the MEA increases with time and stoichiometry.
► Nafion shows excellent water transport properties and performance compared to sPEEK.