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For further commercializing proton-exchange membrane fuel cells, it is crucial to attain long-term durability while achieving high performance. In this study, a strategy for modifying commercial Nafion membranes by introducing ultrathin multiwalled carbon nanotubes (MWCNTs)/CeO2 layers on both sides of the membrane was developed to construct a mechanically and chemically reinforced membrane electrode assembly. The dispersion properties of the MWCNTs were greatly improved through chemical modification with acid treatment, and the mixed solution of MWCNTs/CeO2 was uniformly prepared through a high-energy ball-milling process. By employing a spray-coating technique, the ultrathin MWCNTs/CeO2 layers were introduced onto the membrane surfaces without any agglomeration problem because the solvent rapidly evaporated during the layer-by-layer stacking process. These ultrathin and highly dispersed MWCNTs/CeO2 layers effectively reinforced the mechanical properties and chemical durability of the membrane while minimizing the performance drop despite their non-ion-conducting properties. The characteristics of the MWCNTs/CeO2 layers and the reinforced Nafion membrane were investigated using various in situ and ex situ measurement techniques; in addition, electrochemical measurements for fuel cells were conducted.

Polystyrene-based polymers with variable molecular weights are prepared by radical polymerization of styrene. Polystyrene is grafted with bromo-alkyl chains of different lengths through Friedel–Crafts acylation and quaternized to afford a series of hydroxide-ion-conducting ionomers for the catalyst binder for the membrane electrode assembly in anion-exchange membrane fuel cells (AEMFCs). Structural analyses reveal that the molecular weight of the polystyrene backbone ranges from 10,000 to 63,000 g mol−1, while the ion exchange capacity of quaternary-ammonium-group-bearing ionomers ranges from 1.44 to 1.74 mmol g−1. The performance of AEMFCs constructed using the prepared electrode ionomers is affected by several ionomer properties, and a maximal power density of 407 mW cm−2 and a durability exceeding that of a reference cell with a commercially available ionomer are achieved under optimal conditions. Thus, the developed approach is concluded to be well suited for the fabrication of next-generation electrode ionomers for high-performance AEMFCs.

Reinforced polymer blend membranes with liposome-like morphology prepared for applications in polymer electrolyte membrane fuel cells from a sulfonated poly(ether sulfone) (BPSH), a hydroxylated poly(ether sulfone), and a hydroxylated sulfonated poly(ether sulfone) as a compatibilizer are characterized both experimentally and theoretically (by mesoscale and molecular dynamics simulations). Compared with those prepared from pristine BPSH, blend membranes exhibit improved mechanical strength, lower water uptake, and better dimensional stability, which is ascribed to the presence of hydroxylated polymers and the resulting hydrogen bonding between polymer chains. The blend membranes also show unusual morphologies; e.g., the 60-811 membrane exhibits a unique nanoscale phase-separated morphology similar to that of a liposome, featuring hydrophilic spherical ionic clusters (0.5 μm) with the small ionic domains of 15--20 nm at their cores. Hydrogen bonding between hydroxyl groups and sulfonic acid groups in this membrane results in enhanced water retention capability, high proton conductivity, and excellent single-cell performance superior to that of Nafion 212 under the conditions of both full and insufficient hydration. [ABSTRACT FROM AUTHOR]