A High-Performance Membrane Electrode Assembly with an Ultrathin Proton Exchange Membrane Based on a Wet-Combining Interface Forming Strategy

The preparation method of membrane electrode assemblies (MEAs) is a key factor that determines their electrochemical performance and lifespan. In this study, we develop a novel preparation method based on a wet-combining interface forming strategy for fabricating a high-performance MEA with an ultrathin proton exchange membrane (PEM). Through this method, an integrated MEA (R-MEA), assembled with an ultrathin (<10 μm) membrane reinforced with expanded polytetrafluoroethylene (ePTFE), is fabricated. In the wet-combining process, the liquid perfluorosulfonic acid (PFSA) ionomer sufficiently adheres to the surface of the three-dimensional (3D) catalyst layer (CL) of the gas diffusion electrode (GDE), thus forming a 3D coupling interface between the PEM and the cathode CL. Such a tight 3D PEM/cathode CL interface enlarges the contact area between the PEM and the cathode CL, thereby increasing the triple-phase boundary for the oxygen reduction reaction. On this basis, the novel R-MEA exhibits a significantly higher electrochemical surface area and a superior power performance compared to a conventional MEA (C-MEA) prepared by the catalyst-coated membrane method. Furthermore, the introduction of the ePTFE reinforcement in the PEM makes R-MEA possess a hydrogen crossover current close to that of C-MEA (which has a commercial GORE-SELECT membrane as its PEM). After 1000 cycles of wet/dry conditions, the R-MEA still maintains its superior power performance and a stable hydrogen crossover current, thus demonstrating its excellent mechanical durability.