Novel Fabrication Approach by Reversely Coating a Nafion Ionomer on Gas Diffusion Electrodes for High-Performance Membrane Electrode Assemblies

For optimal performance of proton-exchange membrane fuel cells (PEMFCs), it is necessary to optimize the interfacial contact between the proton-exchange membrane (PEM) and the catalyst layer (CL) in membrane electrode assemblies (MEAs). We have proposed a novel fabrication approach for the MEA of PEMFCs, whereby the perfluorosulfonic acid (PFSA) dispersion is coated on a substrate to form a wet film, and then a gas diffusion electrode (GDE) is placed on the wet PFSA film. After drying, separation from the substrate yields a PFSA membrane-coated electrode. In the traditional preparation method for membrane-coated electrodes, liquid PFSA ionomer suspension can easily penetrate into cracks and voids in the CL, resulting in its overfilling. This can hinder gas transmission and lead to the serious detriment of the electrochemical properties of the fuel cell. In our MEA method, the GDE floats on the wet PFSA film, avoiding excessive penetration of the liquid PFSA dispersion suspension into the CL as a result of gravity. That not only achieves excellent interfacial contact between the PEM and the CL but also prevents overfilling with the PFSA ionomer. Applying this novel MEA method, we have achieved a high peak power density of 2636 mW cm(-2) [O-2, 0.1 MPa, and 100% relative humidity (RH)], a reduced performance loss at a low RH, and the fabrication of extremely thin PEMs (down to 10-12 mu m).