Development of characterisation methods for the components of the polymer electrolyte fuel cell

Abstract: In this work characterisation methods and fuel cell hardwarewere developed for studying the components of the polymerelectrolyte fuel cell (PEFC). Humidifiers and other componentswere tested in order to develop reproducible and reliableexperimental techniques. A set-up for testing larger cells andstacks was developed.A new type of polymer electrolyte membrane fuel cell wasdeveloped for laboratory investigations. Current collectormaterial and gas flow channels can easily be modified in thisconstruction. The electrode potentials can be measured at thegas backing layers, thereby allowing measurement of contactresistances. The use of a reference electrode is alsopossible.Contact resistances were studied in situ as a function oftime, clamping pressure, gas pressure and current density.Ex-situ measurements were used to validate the in-situ contactresistance measurements. The validity and error sources of theapplied in-situ measurement methods with reference electrodesand potential probes were studied using both computersimulations and experiments.An in-house membrane electrode assembly (MEA) productionline was developed. In-house produced MEAs were utilised inboth membrane degradation and mass transport studies.The durability testing of PVDF based membranes membranes wasstudied both by fuel cell experiments and ex-situ testing.Raman spectra were measured for used membranes.A current distribution measurement method was developed. Theeffect of inlet humidification and gas composition at thecathode side was studied. In addition, two different flow fieldgeometries were studied. The results of current distributionmeasurements were used to validate a PEFC model.Methods for characterising gas diffusion layer (GDL)performance by fuel cell testing and ex-situ measurements weredeveloped. The performance of GDL materials was tested withvarying cell compression and cathode humidity. Porosity, poresize distribution and contact angle were determined. Electricalcontact resistance, thermal impedance and gas permeabilitieswere measured at different compression levels.Development work on a stack with stainless steel net wascarried out as well as characterisation studies of differentstack components. Thermal impedances and flow fieldpermeability were measured.Mass transport limitations in the cathodes were studied byvarying the electrode thickness, partial pressure and humidityof oxygen.Keywords:polymer electrolyte membrane fuel cell (PEFC),contact resistance, clamping pressure, stainless steel,membrane degradation, current distribution, gas diffusionlayer, stack, thermal impedance, permeability.