CHARACTERIZATION OF GDL TREATED WITH PERFLUOROPOLYETHERS FOR PEMFC BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS)

Two different gas diffusion layers (GDLs) having the same textile properties (i.e. density, warp, weft and weight), produced by an Italian Company (Saati), but coated with two different fluoro polymers, were investigated. Particurarly one of them was coated with a conventional fluoropolymers such as PTFE and was used as reference, the other was treated with a linear perfluoropolyether (PFPE) peroxide. The thermal decomposition of a linear PFPE peroxide produced linear PFPE radicals that covalently bonded the unsaturated moieties on the surface of GDL. Perfluorinated radicals can directly bond to the carbonaceous structure without any spacer that could decrease both thermal and chemical stability of the resulting materials [1]. Resulting material hydrophobicity has been verified by contact angle measurements. In order to evaluate electrochemical properties, the samples were tested in a cell assembly and Electrochemical Impedance Spectroscopy (EIS) was employed to assess ohmic resistances and the different nature of voltage losses [2].