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.

This work exhibits an effective approach to enhance the performance of membrane-electrode assembly (MEA) with KH₅(PO₄)₂-doped PBI membrane, by adding phosphoric acid (PA) in the catalyst layer (CL). The ohmic resistance and single-cell performance of the MEA, treated with PA, are reduced by ~80% and improved by ~800%, respectively, compared to that of untreated MEA. Based on the MEA pretreated with PA, the influence of humidity and temperature on the resistance and the single-cell performance are investigated. Under humidified gas conditions, the ohmic resistance of MEA is reduced but the charge transfer resistance is slightly increased. Regarding the effect of temperature, the ohmic resistance of MEA becomes lower as the temperature elevates from 140 to 180 °C, but increases at 200 °C. The maximum peak power density presents at 180 °C and 20% RH with 454 mW cm⁻². The peak power density is favored with temperature increase from 140 to 180 °C, but decreases with further increase to 200 °C. Moreover, when dry gas conditions are employed, the output performance is unstable, suggesting that humidification is necessary to inhibit degradation for a long-term stability test.

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For proton exchange membrane fuel cells(PEMFCs), the perfect interfacial contact between PEM and Catalyst layer in membrane electrode assemblies(MEAs) is desired. In this study, a novel fabrication approach of the MEA for PEMFCs is developed, for which the Nafion dispersion is coated on a substrate to form a wet film, then a gas diffusion electrode(GDE) is covered on the wet Nafion film, finally peeled off from the substrate after drying. For the traditional method, liquid Nafion ionomer suspension is easy to penetrate into the cracks and voids in CL, resulting in overfilling of Nafion ionomer and hindering gas transmission, seriously affecting the electrochemical properties. For the novel method, the GDE floats on wet Nafion film, avoiding excessive penetration of the liquid ionomer suspension into the CL due to gravity, so that it not only achieves good interfacial connection between PEM and CL with low interfacial resistance, but also does not cause overfilling of Nafion ionomer. This novel MEA method allows achievements of a high peak power density of 2.6W/cm 2 (O 2 , 0.1Mpa, 100% RH), a less performance reduction at low humidity, and the fabrication of extremely thin PEM (down to 10-12 mm in this study).