Membrane Durability in a PEM Fuel Cell Studied Using PVDF Based Radiation Grafted Membranes** P.Gode 1 ,J.Ihonen 1 , A.Strandroth 2 ,H.Ericson 3 , G. Lindbergh 1,* ,M.Paronen 4 , F.Sundholm 4 ,G.Sundholm 1 ,andN.Walsby 4, x 1 DepartmentofChemicalEngineeringandTechnology,AppliedElectrochemistry,RoyalInstituteofTechnology,SE-10044Stockholm, Sweden 2 DepartmentofMaterialsChemistry,ngströmLaboratory,UppsalaUniversity,Box538,SE-75121Uppsala,Sweden 3 DepartmentofExperimentalPhysics,ChalmersUniversityofTechnology,SE-41296Göteborg,Sweden 4 LaboratoryofPolymerChemistry,UniversityofHelsinki,PB55,FIN-00014HY,Finland x Presentaddress:DepartmentofMaterialsandMedicalSciences,CranfieldUniversity,Shrivenham,SN68LA,UK Received12.12.02,accepted24.03.03 1 Introduction The polymer electrolyte fuel cell (PEFC) is one of the most promising types of fuel cell in transportation applications, consumer electronics and residential power units. The pro- gress in PEFC development has reduced the cost of the PEFC system, but it is still too high, especially for passenger vehicle applications [1]. The polymer electrolyte membrane in the PEFC will prob- ably constitute a minor part of the total PEFC system cost [2]. However, membranes currently available only work at tem- peratures < 100 C, thereby requiring complex and expensive auxiliary components, such as humidifiers and gas clean-up systems. A higher operating temperature would enhance cat- alyst activity and reduce the sensitivity to carbon monoxide poisoning. Recent developments and future prospects in PEFC membrane research have been summarised in several reviews [3 ± 8]. The general requirements for fuel cell membranes are low area resistance, low gas permeability, chemical, mechanical and thermal stability over long periods of use in the presence of oxidising and reducing species as well as reasonable cost. For direct methanol fuel cell applications low methanol per- meability is also required. Some of these properties, such as conductivity and gas permeability, can be measured reliably ex situ [9 ± 13]. In contrast, the degradation measurements ± [ * ] Corresponding author, goeran.lindbergh@ket.kth.se [ ** ] ThepaperhasbeenpresentedatSymposium8 oftheInternationalSocietyofElectrochemistry inDüsseldorf,Germany2002 Abstract The durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady-state and impedance measurements. The PEFC measurements, which are time consuming, have been compared to fast ex situ testing in 3% H 2 O 2 solution. For the direct assessment of membrane de- gradation micro-Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. By using low degrees of grafting, below about 35%, the durability of this type of membrane can be increased. Degradation in the fuel cell was found to be highly localised. It was found that in situ mea- surements in the PEFC alone are not sufficient. Measure- ment of the cell resistance via impedance is not always a reli- able indicator of changes in membrane resistance because other resistance changes in the cell can easily interfere and cannot be separated from those caused by the membrane. Micro-Raman is an ideal complementary method to in situ testing, but it is time consuming. For fast pre-screening of membrane durability mass loss measurements during expo- sure to 3% H 2 O 2 solution combined with the determination of changes in the IEC can be performed. Keywords: Membrane, Durability, Degradation, PEM Fuel Cell FUEL CELLS 2003, 3, No. 1±2  2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 21 ORIGINAL RESEARCH PAPER DOI: 10.1002/fuce.200320239