Study On The Membrane Electrode Ssembly For High Temperature Roton Exchange Membrane Fuel Ells

High-temperature (100-200℃) proton exchange membrane fuel cells(PEMFCs) have been considered the next generation of fuel cells because oftheir advantages over those operated at lower temperatures (usually below80℃).These advantages include:(1) faster electrochemical kinetics,(2)improved and simplified water management,(3) effective thermal managementand (4) improved contamination tolerance.To achieve high temperatureoperation of PEMFC,preferably under ambient pressure,acid–base polymermembranes represent an effective approach.The phosphoric acid-dopedpolybenzimidazole membrane seems so far the most successful system in thefield.It has in recent years motivated extensive research activities with greatprogress.Poly (2,5-benzimidazole)(AB-PBI) is the simplest type of thebenzimidazole polymer’s family,since it can be prepared easily by a singlemonomer,and the-N groups can be combined with acid by the hydrogenbond.So it possesses high proton conductivity.The membrane electrodeassembly (MEA) is the key component where fuel and oxidant react electrochemically to generate electrical power.MEA is the primary object tostudy if we want to research on fuel cells.In this paper,with the polarizations produced during the fuel cells runningas the breakthrough point,studied the effect of some factor (molecular weightof binder,pore former,catalyst loading and ratio both the anode and cathode)on the performance of differents MEA.Followings are the main contents:(1) In order to reduce the activation overpotential,AB-PBIs with differentmolecular weight were synthesized.The performances of the MEAs werestudied by polarization curves (I-V) and electrochemical impedancespectroscopy (EIS).The results showed that the best performance of MEA wasobtained when the MEA was prepared with AB-PBI of the least molecularweight.We also got another conclusion that the resistances of MEA weredecreased as the current density was increased.Also added pore former in thecatalyst layer to reduce the activation overpotential.Among the three poreformer we selected,the performance of the MEA with NH4NO3as poreformer was the best,followed by (NH4)2C2O4,(NH4)2SO4was the worst.(2) In order to reduce the ohmic overpotential,prepared MEA by CCM.Theoretically,contact resistance of the MEA prepared by CCM can decreasedsignificantly,thus the performance should be improved. But the performanceof MEA prepared by CCM had no obvious change.The specific reasons needto have a further research.(3) Optimized the process of MEA,obtained the optimum conditions for the preparation of MEA:anode catalyst loading is1mg/m2; cathode catalystloading is2mg/m2; anode polymer ratio is5wt.%;cathode polymer ratio for15wt.%.