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The long‐term operation of polymer electrolyte membrane fuel cells (PEMFCs) relies heavily on the durability of the perfluorinated sulfonic acid (PFSA, e.g., Nafion) membrane against chemical and mechanical degradation. To mitigate mechanical degradation, the introduction of a reinforcing matrix, such as a porous PTFE sheet, is employed. However, completely impregnating the PFSA ionomer into the PTFE sheet through the conventional blade‐coating method using a highly viscous ionomer solution proves challenging. This limitation results in decreased mechanical and proton transport properties. To reduce proton transport resistance, thinner membrane thickness is desirable, although it increases the amount of gas crossover, which generates radicals and accelerates the chemical degradation of the membrane. In this study, a spraying process utilizing a low viscous‐solvent‐rich ionomer solution is experimentally optimized to construct a well‐impregnated PTFE/Nafion membrane and analyzed using a simple theoretical droplet‐spreading model. Furthermore, an ultrathin graphene oxide (GO) layer is introduced during the membrane fabrication process with the same spraying technique for reducing gas crossover while minimizing performance loss. The membrane electrode assembly (MEA) with the prepared PTFE/Nafion membrane‐incorporated ultrathin GO layer shows significantly greater durability and initial performance compared to the conventional MEA. [ABSTRACT FROM AUTHOR]

For achieving economically viable polymer electrolyte membrane fuel cells (PEMFCs) in the commercial market, simplifying the fabrication process and manufacturing of robust membrane electrode assembly (MEA) are important. Herein, a single spray‐coating method for developing a robust and free‐standing reinforced Nafion composite membrane and electrodes is reported. By comparing the fabricated membrane's morphology under diverse process conditions including the nozzle‐to‐substrate distance and solution‐loading rates, the optimized spray‐coating for uniformly deposited spray‐based membrane without any defects has been determined. To explain this optimized condition, a simple theoretical model based on the concept of the surface coverage of sprayed droplets is proposed. The fabricated multiwalled carbon nanotubes/CeO2‐reinforced Nafion composite membrane shows excellent mechanical properties with minimal proton‐conducting loss despite using additional fillers of total 4 wt% in the Nafion matrix. By successively depositing the catalyst layer on that membrane using the same spray‐coating device, an MEA with the reinforced spray‐based membrane has been successfully fabricated; moreover, diverse electrochemical measurements and durability tests have been conducted. The MEA with the reinforced membrane shows comparable initial performance and considerably higher performance after the durability test compared to the MEA with commercial Nafion membrane. [ABSTRACT FROM AUTHOR]

Summary: Improving the durability of the membrane electrode assembly (MEA) while obtaining high performance is required to further commercialize polymer electrolyte membrane fuel cells (PEMFCs). The durability of PEMFCs is improved by incorporating radical scavengers, such as CeO2 (ceria), into the MEA, especially the membrane. However, nanosized ceria particles are generally mixed with ionomers and are cast on substrates to fabricate composite membranes. In such a case, controlling their morphology and avoiding particle agglomeration is difficult. Herein, we report a novel method for constructing a robust membrane by incorporating ultrathin ceria barriers into the outermost sides of a commercial Nafion membrane to effectively alleviate radical attacks while ensuring the high uniformity and controllability of ceria layers. The improved durability of the composite membrane is confirmed via ex situ Fenton's test and in situ operation of a fuel cell. Moreover, we observe that the amount of fluoride ion emission and the loss of proton conductivity of the membranes decrease as the CeO2 density increases. The MEA comprises a modified membrane with CeO2 barriers that show proper areal density. It demonstrates excellent durability under accelerated environmental conditions (open circuit voltage test) and acceptable initial performance with an insignificant decrease in proton conductivity. [ABSTRACT FROM AUTHOR]

Incorporating inorganic fillers, such as SiO 2 , TiO 2 , and CeO 2 , into the electrolyte membrane via the conventional casting and evaporation process is proved to intensify the water retention, thus improve the proton conductivity of the polymer electrolyte membrane (PEM) under high temperature. However, this approach does not dramatically enhance the performance of the composite membrane due to the issue of proton pathway reduction and fillers agglomeration. Herein, uniformly patterned mesoporous TiO 2 microplates (PTMPs) are successfully embedded on the anode side surface of the Nafion® membrane by using micro-hole stencil for spatially localizing the PTMPs and well-controlled ionomer spray technique. Interestingly, the membrane comprised of PTMPs with a diameter of ∼50 μm and a height of ∼5.2 μm exhibits the maximum power density by more than 35.2% compared to the reference Nafion® membrane with the same thickness (∼25 μm) under 120 °C and relative humidity of 35% condition. The result indicates that suitably designed PTMPs-embedded Nafion® membrane is effective for improving the PEMFC performance under elevated temperature and low humidity conditions. [Display omitted] [ABSTRACT FROM AUTHOR]