Innovative PerfluoropolyetherFunctionalized Gas Diffusion Layers with Enhanced Performance in Polymer Electrolyte Membrane Fuel Cells

In this work, perfluoropolyether (PFPE) functionalization was used as hydrophizing treatment for gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFCs), instead of standard PTFE coatings, aiming to enhance the hydrophobicity of the gas diffusion media and to reduce the mass transfer limitations in the final device. Carbon cloth diffusion layers and carbon black were functionalized by decomposition of a PFPE peroxide. PFPE-functionalized carbon black was employed in the preparation of an ink suitable for obtaining microporous layers (MPLs) by deposition onto macroporous backing layers. Dual-layer gas diffusion media showing superhydrophobic behavior due to different hydrophobizing treatments were compared with conventional PTFE-based materials, by testing in a single PEMFC working at two different temperatures and at low and high relative humidity conditions. Such tests demonstrated improved performances over conventional GDLs for pure PFPE-based samples in terms of both overall electrical performance and reduced diffusive limitations in high current density conditions. The maximum output power achieved with the novel PFPE-based compounds was 460 mW cm-2 at 80 °C and RH 100 % while the best improvement (10 %) with respect to conventional GDLs was realized at 80 °C and RH 60 %.