Enhancement in proton conductivity and methanol resistance of Nafion membrane induced by blending sulfonated poly(arylene ether ketones) for direct methanol fuel cells (original) (raw)
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Membranes
Nafion, a perfluorosulfonic acid proton exchange membrane (PEM), has been widely used in direct methanol fuel cells (DMFCs) to serve as a proton carrier, methanol barrier, and separator for the anode and cathode. A significant drawback of Nafion in DMFC applications is the high anode-to-cathode methanol fuel permeability that results in over 40% fuel waste. Therefore, the development of a new membrane with lower permeability while retaining the high proton conductivity and other inherent properties of Nafion is greatly desired. In light of these considerations, this paper discusses the research findings on developing Nafion-based membranes for DMFC. Several aspects of the DMFC membrane are also presented, including functional requirements, transport mechanisms, and preparation strategies. More importantly, the effect of the various modification approaches on the performance of the Nafion membrane is highlighted. These include the incorporation of inorganic fillers, carbon nanomateri...
Novel sulfonated poly(glycidyl methacrylate) grafted Nafion membranes for fuel cell applications
Polymer Bulletin, 2017
Nafion membranes have been modified by PGMA using persulphate initiation system, subsequent by sulfonation of PGMA graft branches, to convert the epoxy groups into sulfonic groups, which provide the modified membranes with more acidic sites to maintain its ionic conductivity. The grafting process and the sulfonation process have been confirmed by FT-IR, TGA and FT-IR, EDAX analysis and ion exchange capacity measurements, frequently. Moreover, the physicochemical properties of the modified membranes, such as water and methanol uptakes, and ion exchange capacity, have been studied. The results showed that the modified membranes have high water uptake. The ion exchange capacity measurements proved the conversion of the epoxy groups into sulfonic groups in the sulfonated grafted membranes since the sulfonated grafted membranes showed ion exchange capacity higher than that of grafted membranes. Also, the results showed that the modification process has no impact effect on the stability of the membranes dimensions in water and methanol. TGA analysis showed that the modified membranes exhibited high thermal stability than that of unmodified Nafion membranes. SEM analysis showed the homogeneity of the PGMA in the matrix of Nafion membrane. The methanol permeability of the modified membranes decreased with
Direct methanol fuel cell membranes from Nafion–polybenzimidazole blends
Journal of power sources, 2006
Proton conducting membranes for a direct methanol fuel cell (DMFC) were fabricated from blends of Nafion ® and polybenzimidazole (PBI) by solution casting. Prior to dissolution in the casting solvent, the sulfonic acid groups of the Nafion component of the blend were partially exchanged with sodium ions. The dependence of membrane proton conductivity and methanol permeability on the extent of proton substitution of Nafion during blending and on the PBI content of the final membrane was studied. It was found that membrane selectivity (the ratio of proton conductivity to methanol permeability) was the highest (four times that of Nafion 117) when fully protonated Nafion was used during blending and when the PBI content was 8%. DMFC performance of Nafion-PBI membranes (approximately 60 m in thickness) was found to be superior to that of Nafion 117 at 1.0 and 5.0 M methanol feeds.
International Journal of Hydrogen Energy, 2019
In the present work, three kinds of sulfonated poly(arylene ether ketones) (SPAEKs) with different structures are introduced into Nafion as blending modifiers to enhance the properties of Nafion, especially methanol resistance. Characterizations such as transmission electron microscope (TEM), proton conductivity, methanol crossover, and single cell performance, are carried out to evaluate these composite membranes (SPAEK@Nafion) as prepared. Besides, recast Nafion membrane is prepared and characterized for comparison via the same method. By investigating the microstructure of SPAEK@Nafion membranes, p-BPAF@Nafion membrane is found to have the most homogeneous distribution and Nafion-like phase separation among these membranes. The pendent sulfobutyl side-chain and fluorinated main chain of p-BPAF make it most similar structure with Nafion among three modifiers, and such Nafion-liked structure provides p-BPAF a good compatibility with Nafion, which can facilitate its enhancement for Nafion. Consequently,
Nafion/polyaniline/silica composite membranes for direct methanol fuel cell application
Journal of Power Sources, 2007
This work investigates the characterization and performance of polyaniline and silica modified Nafion membranes. The aniline monomers are synthesized in situ to form a polyaniline film, whilst silica is embedded into the Nafion matrix by the polycondensation of tetraethylorthosilicate. The physicochemical properties are studied by means of X-ray diffraction and Fourier transform infrared techniques and show that the polyaniline layer is formed on the Nafion surface and improves the structural properties of Nafion in methanol solution. Nafion loses its crystallinity once exposed to water and ethanol, whilst the polyaniline modification allows crystallinity to be maintained under similar conditions. By contrast, the proton conductivities of polyaniline modified membranes are 3-5-fold lower than that of Nafion. On a positive note, methanol crossover is reduced by over two orders of magnitude, as verified by crossover limiting current analysis. The polyaniline modification allows the membrane to become less hydrophilic, which explains the lower proton conductivity. No major advantages are observed by embedding silica into the Nafion matrix. The performance of a membrane electrode assembly (MEA) using commercial catalysts and polyaniline modified membranes in a cell gives a peak power of 8 mW cm −2 at 20 • C with 2 M methanol and air feeding. This performance correlates to half that of MEAs using Nafion, though the membrane modification leads to a robust material that may allow operation at high methanol concentration.
Materials Today: Proceedings, 2020
This paper presents the effect of polyvinyl alcohol (PVA) coated Nafion membranes on their water uptake, swelling and proton conductivity for various PVA coating thicknesses. These studies show that the optimum coating thickness of PVA on Nafion is 2 mm. Methanol permeation studies show that 2 mm thick PVA coating forms a barrier for methanol and significantly reduces methanol permeation through the membranes. Further, passive methanol fuel cells are tested with 2 mm thick PVA coat on Nafion as proton exchange membranes and their polarization plots show a significant enhancement in power as compared to the methanol fuel cells with pristine Nafion due to reduction in methanol crossover.
The surface of Nafion 117 membrane was modified by dip-coating of a blend of polybenzimidazole (PBI) and partially sulfonated polyvinylidinefluoride-co-hfp (SPVDF-co- HFP) polymer without any significant change in the thickness of the membrane. The dipcoated membranes were characterized by FTIR spectroscopy, thermogravimetry and rheology; ion exchange capacity (IEC), proton conductivity and methanol permeability were also measured to find the suitability of these membranes in the direct methanol fuel cell (DMFC), especially keeping in view with a reduced methanol crossover and improved electrical efficiency. The IEC and proton conductivity of the membranes were observed to be lower than pristine Nafion 117 membrane. On the other hand, the methanol permeability of coated membranes was found to be very less than the pristine Nafion 117 membrane. Although, a very thin coat of the blends of PBI and SPVdF-co-HFP was applied on Nafion117, the dynamic rheological studies indicated that the glass transition temperature of nafion117 shifted to a higher temperature, leading to higher stability of coated membranes at higher temperature in comparison to the stability of Nafion. The high thermal stability of the coated membranes compared to Nafion was also corroborated from the thermogravimetric analysis. All these results indicated that the coated Nafion117 membrane could be electrically efficient at high temperature for DMFC applications. From the DMFC performance test, it was observed that the Nafion 117 membrane coated with 70:30 PBI and SPVDF-co-HFP showed the best electrical performance (39mW/cm2 at 0.2 V) at the temperature of 90 °C, whereas for pristine Nafion 117 membrane, the maximum electrical performance of the DMFC was observed to be 36 mW/cm2 at the same voltage and at 60 °C.
European Polymer Journal, 2008
Poly-(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP)/Nafion ionomer/aluminum oxy hydroxide nanocomposite membranes were prepared by phase inversion technique. The resultant membranes were subjected to protonic conductivity, methanol permeability, infra-red and thermogravimmetric analysis. The infra-red spectroscopic measurements revealed the presence of sulfonic acid groups in the composite membranes. The thermal stability and ionic conductivity of the polymer membranes have been greatly varied upon the addition of AlO[OH] n . Although the PVDF-HFP/Nafion/AlO[OH] n composite membranes have moderate protonic conductivity it has lower methanol permeability and may be considered as a candidate for DMFC applications.
Nafion/Analcime and Nafion/Faujasite composite membranes for polymer electrolyte membrane fuel cells
Chemical Engineering Research & Design, 2010
The Nafion/zeolite composite membranes were synthesized for polymer electrolyte fuel cells (PEMFCs) by adding zeolite in the matrix of Nafion polymer. Two kinds of zeolites, Analcime and Faujasite, having different Si/Al ratio were used. The physico-chemical properties of the composite membranes such as water uptake, ion-exchange capacity, hydrogen permeability, and proton conductivity were determined. The fabricated composite membranes showed the significant improvement of all tested properties compared to that of pure Nafion membrane. The maximum proton conductivity of 0.4373 S cm−1 was obtained from Nafion/Analcime (15%) at 80 °C which was 6.8 times of pure Nafion (0.0642 S cm−1 at 80 °C). Conclusively, Analcime exhibited higher improvement than Faujasite.