离子聚合物薄膜的埋藏界面结构及对质子传输的影响OA

Ionomers play a critical role in determining the performance of catalyst layers in polymer electrolyte fuel cells(PEFCs).Although sulfonated aromatic polyether ketone(SPEEK)and perfluorinated sulfonic acid(Nafion)ionomers are commonly employed,their structure-property relationships under operational conditions are not yet fully elucidated.In this work,we conducted a systematic investigation of platinum-supported SPEEK and Nafion ultrathin films(13 nm)using in situ ellipsometry,grazing-incidence wide-angle X-ray scattering(GIWAXS),and electrochemical impedance spectroscopy(EIS)to characterize their morphological features,water uptake behavior,and proton transport properties.In contrast to Nafion,the SPEEK films displayed dense and well-defined crystalline domains at the buried interface,which we attribute to their stronger affinity for the Pt substrate.Quantitative analysis indicated that at 90%RH,the interfacial layer of SPEEK retained a stable thickness of approximately 13.8 Å,whereas Nafion underwent more substantial swelling,expanding to around 18.7 Å.As a result,SPEEK films exhibited lower water uptake and reduced proton conductivity,especially under low-humidity conditions.Furthermore,proton conductivity measurements revealed significant anisotropy in SPEEK,with out-of-plane conductivity values 1-2 orders of magnitude lower than those in the in-plane direction.In comparison,Nafion showed less pronounced directional dependence.We suggest that intramolecular interactions among ether functional groups,combined with specific Pt-oxygen interactions within SPEEK repeat units,underlie the distinct structural attributes observed at the buried interface.