Membrane electrode assemblies (MEAs) are critical components in influencing the electrochemical performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). MEA manufacturing processes are mainly divided into the catalyst-coated membrane (CCM) and the catalyst-coated substrate (CCS) methods. For conventional HT-PEMFCs based on phosphoric acid-doped polybenzimidazole (PBI) membranes, the wetting surface and extreme swelling of the PA-doped PBI membranes make the CCM method difficult to apply to the fabrication of MEAs. In this study, by taking advantage of the dry surface and low swelling of a CsH₅(PO₄)₂-doped PBI membrane, an MEA fabricated by the CCM method was compared with an MEA made by the CCS method. Under each temperature condition, the peak power density of the CCM-MEA was higher than that of the CCS-MEA. Furthermore, under humidified gas conditions, an enhancement in the peak power densities was observed for both MEAs, which was attributed to the increase in the conductivity of the electrolyte membrane. The CCM-MEA exhibited a peak power density of 647 mW cm⁻² at 200 °C, which was ~16% higher than that of the CCS-MEA. Electrochemical impedance spectroscopy results showed that the CCM-MEA had lower ohmic resistance, which implied that it had better contact between the membrane and catalyst layer.

Durability remains a primary bottleneck limiting the commercialization of proton exchange membrane fuel cells (PEMFCs). As a key functional component of the membrane electrode assembly (MEA), perfluorosulfonic acid (PFSA) ionomer is crucial for facilitating electrochemical reactions. While current research predominantly focuses on the degradation of the proton exchange membrane (PEM) or other catalyst layer (CL) components, the chemical degradation mechanisms of the ionomer within the CL and their consequent impacts have received relatively limited attention. In this study, a Fenton’s reagent-based accelerated stress test (AST) is employed to simulate radical attack conditions during PEMFC operation, enabling a systematic investigation into the chemical degradation of the ionomer within the CL. Physicochemical characterization revealed that radical attack generated by Fenton’s reagent induces a significant loss of fluorine, along with declines in ionomer crystallinity and CL hydrophobicity. Furthermore, concomitant carbon support corrosion and Pt nanoparticle agglomeration were observed. Electrochemical tests further reveal that the ionomer degradation leads to increased proton transport and charge transfer resistances, resulting in a decline in cell performance, particularly in the high current density region. This study highlights the pivotal role of ionomer degradation in the durability of the CL, providing valuable insights for enhancing the lifespan of PEMFCs.