The fabrication approach of a membrane electrode assembly (MEA) is closely related to the performance and durability of the fuel cell. In this work, we combine reinforcement-embedding technology with a direct membrane deposition approach to prepare a gas diffusion electrode (GDE) with an expanded poly­(tetrafluoroethylene) (ePTFE)-reinforced membrane and then assemble a reinforced MEA. Compared with the traditional MEA, the reinforced MEA exhibits higher performance, especially under low-humidity operating conditions. Under H2/air operating conditions, the cell performance of the reinforced MEA reaches 724 mW cm–2 (80 °C, 100% relative humidity (RH), normal pressure). With the addition of ePTFE reinforcement, the mechanical durability of the reinforced MEA is significantly improved. After 3000 cycles of alternative dry/wet conditions, the reinforced MEA exhibited lower hydrogen permeation and less performance degradation compared with the unreinforced MEA. This work provides a new and facile way for improving the mechanical durability of MEAs.

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As a key component of proton exchange membrane fuel cells (PEMFCs), the durability of the proton exchange membranes (PEMs) directly determines the service life of the PEMFCs. As state-of-the-art PEMs, perfluorosulfonic acid (PFSA) membranes suffer from critical mechanical and chemical degradation under actual working conditions. Considering this, we present a strategy to develop highly durable PEMs by intercalating double-layer expanded polytetrafluoroethylene (ePTFE) skeletons and doping CeO 2 radical scavengers into the PFSA membranes. The results reveal that the double-layer ePTFE reinforced membranes (DR-Ms) have significantly improved mechanical properties, lower swelling rates, and superior dimensional stability compared to single-layer ePTFE reinforced membranes (SR-Ms). After the wet/dry cycle durability test, DR-Ms show a lower hydrogen crossover increase, reduced power performance attenuation, and smaller membrane impedance increase than SR-Ms. After the open-circuit voltage (OCV) durability test (ODT), DR-Ms exhibit better chemical durability behaviors (such as membrane thinning and OCV decay rates). Furthermore, the 0.5 wt % CeO 2 -doped DR-M (Ce-DR-M1) imparts a further improved chemical durability during the ODT compared with DR-Ms. In short, the developed Ce-DR-M1 with double-layer ePTFE skeletons and CeO 2 radical scavengers is a promising candidate for advanced PEMs with high mechanical and chemical durability for PEMFC applications.

Intercalating expanded polytetrafluoroethylene (ePTFE) reinforcements and incorporating antioxidants (e.g., CeO2 and ZrO2) into perfluorosulfonic acid (PFSA) ionomers are typical methods used to improve the physical and chemical durability of PFSA-based proton exchange membranes, respectively. Nevertheless, these two popular methods still suffer from respective inherent limitations, including the poor interfacial binding between hydrophobic ePTFE and polar PFSA ionomers and the migration and loss of incorporated antioxidants. To solve these two issues simultaneously, we propose a solution based on a surface sol–gel process, by which the deposition of ZrO2 coating on polydopamine-modified ePTFE skeletons not only improves the interfacial bonding of the skeletons and PFSA ionomer but also restrains the migration and loss of antioxidant additives. The results show that the ZrO2-deposited ePTFE exhibits improved hydrophilicity and the reinforced composite membranes based on the modified ePTFE skeletons with one layer of ZrO2 coating are endowed with superior proton conductivity, mechanical properties, dimensional stability, and open-circuit voltage durability. In addition, the stability of the ZrO2 coating on the ePTFE skeletons is also verified.

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 [O2, 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 μm).

Electrolyte membranes loaded with KH 5 (PO 4 ) 2 are prepared by immersing SiO 2 /polybenzimidazole (PBI) matrices into molten KH 5 (PO 4 ) 2 . The morphologies, chemical structures, thermal properties, mechanical properties and proton conductivities of the electrolyte membranes are examined. The utilization of SiO 2 /PBI matrices ensures that the KH 5 (PO 4 ) 2 -loaded electrolyte membranes possess excellent mechanical properties. With the highest SiO 2 doping rate, the K/(3SiO 2 /7PBI) electrolyte membrane has favorable mechanical properties with a tensile strength of 55.83 MPa and an elongation of~5 5%, which satisfy the requirements for membrane electrode assemblies in intermediate temperature fuel cells. In addition, this electrolyte membrane possesses a superior conductivity of 0.139 S cm -1 at 180°C under an H 2 O/N 2 atmosphere and shows desirable conductivity stability at elevated temperatures. A fuel cell equipped with the K/(3SiO 2 /7PBI) electrolyte membrane exhibits an open-circuit voltage of 1.01 V and its peak power density reaches 36 mWcm -2 .

As a crucial factor dictating the power performance of proton exchange membrane fuel cells, the interface combination between the proton exchange membrane and the catalyst layer should be considered seriously. Herein, we propose a facile interface optimization strategy in which an expanded polytetrafluoroethylene (ePTFE) skeleton layer is biasedly embedded on the surface of the perfluorosulfonic acid (PFSA) membrane bulk to form three-dimensional surface structures naturally. The experimental results show that the biased ePTFE-reinforced membranes (BRMs) demonstrate significantly enhanced surface roughness compared with conventional central ePTFE-reinforced membranes (CRMs), thus providing an enlarged cathode membrane/catalyst layer contact area. With optimized membrane/catalyst layer interface bonding, the fuel cells equipped with BRM1 and BRM2 (ionomer concentrations of 10 and 20 wt %, respectively) exhibit markedly reduced interfacial resistance, increased electrochemical surface area, and improved power performance compared with conventional CRMs. Furthermore, this biased reinforcing process does not weaken the mechanical reinforcing and dimension constraint function of ePTFE skeletons in PFSA membranes. Instead, the BRM membranes demonstrate the same level of mechanical properties, swelling rates, and hydrogen crossover as CRM membranes. After the wet/dry cycle test, BRM1 exhibits less mechanical degradation than CRMs due to enhanced interface bonding, reflected in lower hydrogen crossover and interfacial resistance increase.