New perfluorinated ionomer with improved oxygen permeability for application in cathode polymeric electrolyte membrane fuel cell

Proton Exchange Membrane Fuel Cells (PEM-FC) are considered an alternative to the internal combustion engine for transportation. Despite the existence of relevant demonstrations and few commercial fleets, there are still a series of issues such as the durability of the materials and the cost of platinum which limit a wider application in this field. To this regard, better utilization and consequently loading reduction of Pt in electrodes is of outstanding importance. Herein we report the synthesis, characterization and application of an ionomer in the cathode catalyst layer; thanks to its higher oxygen permeability the quantity of Pt may be minimized. This ionomer is a modification of commercial Aquivion® PFSA obtained by incorporation of a third monomer (2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, MDO). Results on cast membrane demonstrate a 20% higher oxygen permeability of the new ionomer compared to Aquivion PFSA E87-05S and Nafion NR212 at 100% RH. Furthermore, an improvement of the performance of a PEM-FC in automotive conditions (RH = 40-70%) is obtained with the assembly where this ionomer is used as cathode binder. In particular polarization curve at 70% RH shows improvement of 20% of power density peak and electrochemical impedance confirms higher oxygen permeability due to lower mass transport resistance than Aquivion.