Cross‐Linked Polyaryl Blend Membranes for Polymer Electrolyte Fuel Cells

Abstract

The preparation and characterization of different types of proton‐conducting polymer blend membranes are presented in this paper. The investigations are focused on the determination of the thermal stability of the membranes, because thermal stability is one of the important parameters for the application of the membranes in polymer electrolyte fuel cells. In addition to the thermal stability, chemical stability, proton conductivity and mechanical strength are required. The characterization of the membranes was performed by thermogravimetry (TGA), a combined TGA and FTIR analysis where infrared spectroscopy is used for the determination of decomposition products, and experiments on the dependence of water uptake (swelling) of the membranes on temperature. Ionically cross‐linked membranes have been investigated. The TGA‐FTIR coupling experiments showed clearly, that the decomposition of the membranes starts at ≈ 230 °C, and that in some cases the principal membrane component which is sulfonated polyaryletherketone splits off SO2 at slightly lower temperature in the membrane than in the pure substance. Most of the other polymeric components of the blend membranes were slightly more stable in the membrane than in the pure form. The ionically cross‐linked membranes were tested in direct methanol fuel cells as well as in a H2/air fuel cell and exhibit a performance which compares favorably with standard membranes.

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

“…Flexible ionomer networks can be prepared from acid-base polymers by ionically cross-linking of polymeric acids and polymeric bases [138][139][140][141][142], as recently reviewed by Kerres [16]. Basic polymers are typically PBI, but other polymers such as poly(4-vinylpyridine) (P 4 VP) [143], aminated PSF [144,145] and PEEK [146] and pyridine containing polymers [91,92] have also been used.…”

Transport in Proton Conductors for Fuel‐Cell Applications: Simulations, Elementary Reactions, and Phenomenology

“…The transport properties of the two materials are typical for these classes of membrane materials, based on perfluorinated and hydrocarbon polymers. This is clear from a compilation of D σ , D H 2 O , and D H 2 O P data for a variety of membrane materials, including Dow membranes of different equivalent weights, 226,255,260 Nafion/SiO 2 composites 243,244,[304][305][306] (including unpublished data from the laboratory of one of the authors), cross-linked polyarylenes, [307][308][309][310][311][312][313][314][315] and sulfonated poly-(phenoxyphosphazenes) 301 (Figure 19). The data points all center around the curves for Nafion and S-PEK, indicating essentially universal transport behavior for the two classes of membrane materials (only for S-POP are the transport coefficients somewhat lower, suggesting a more reduced percolation in this particular material).…”

“…318 The gas permeability is much . Transport coefficients of diverse membranes based on perfluorinated polymers (Dow 226,255,260 and Nafion/ silica composites 174,243,244,[304][305][306] ), polyarylenes (S-PEK/PSU blends, ionically cross-linked S-PEK/PBI), [307][308][309][310][311][312][313][314][315] and sulfonated poly(phenoxyphosphazene)s (S-POPs), 301 as a function of the water volume fraction X V . Lines represent data for Nafion and S-PEK (given for comparison); for data points, see Figure 14.…”

“…For DMFC applications (where the membrane is in contact with a liquid water/methanol mixture), this type of transport determines the crossover, which is only acceptably low for solvent volume fractions smaller than ∼20 vol % (see Figures 14 and 15). Consequently, recent attempts have been focused on strengthening the polymer, e.g., by cross-linking [307][308][309][310][311][312][313][314][315]321 or forming co-polymers of sulfonated arylenes and polyvinylidene difluoride (PVDF). 322 Initial fuel-cell tests are actually quite promising; 313 however, the brittleness of highly cross-linked polymers may cause mechanical failure of the membrane.…”

Properties of PEMs based on cross-linked sulfonated poly(ether ether ketone)

“…In [13] for instance, cross-linked sulfonated polyimides were prepared directly using a cross-linker containing sulfonic group and pre-sulfonated monomer. A series of studies focused on the development of covalently and ionically cross-linked polyarylenes has been carried out by Kerres et al [14][15][16]. The covalent cross-linking there was achieved through alkylation of sulfinate groups with ␣,-dihalogenoalkanes [14] which brought about thermally stable but brittle final products.…”