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Sulfonated PEEK-WC membranes for possible fuel cell applications
Abstract
Sulfonated polyetheretherketones are polymers of some interest for preparing membranes as alternative to the expensive perfluorinated membranes (e.g. Nafion) presently used for fuel cell applications. Sulfonated poly(oxa-p-phenylene-3,3-phtalido-p-phenylene-oxa-p-phenilene-oxy-phenylene) (PEEK-WC) with various degrees of substitution (DS) was prepared and then characterized by FT-IR analyses. Sulfonated PEEK-WC dense membranes were tested for their permeability to various gases and vapors. At 60 °C, the permeability coefficient of methanol in a sulfonated PEEK-WC membrane with 70% DS was about two orders of magnitude lower in comparison with that in a Nafion 117 membrane. Conductivity measurements were carried out by the impedance technique as a function of relative humidity (RH), at 100 °C, and as a function of temperature, in the range 50–115 °C, at 100% RH. The proton conductivity strongly increases with temperature and DS and reaches 2.5×10−2 S cm−1 at 115 °C and 100% RH for DS=0.82. The hydration of the sulfonated polymer was also determined under the same conditions used for conductivity measurements.
... Les noms sont donnés en anglais ou en français selon les abréviations ou noms les plus usuels. MMT 9 MontMorillonite Na + -MMT (Southern Clay Co. 8 1.5 Zirconium Phosphate (ZrP) 17,24 α Zirconium Hydrogen Phosphate(α -ZrP) 25 (Zr(HPO 4 ) 2 nH 2 O) Sulfonated poly(oxa-p-phenylene-3,3-phtalido-p-phenyleneoxa-p-phenilene-oxy-phenilene) 52 PEEK-WC ...
... • Système de mesure La plupart des études actuelles utilisent des analyseurs en fréquence 8,9,13,14,16,20,23,41,46,47,[51][52][53]62,63,114,115,121,126,224,241 , sur une large gamme de fréquences 242 L'erreur, sur l'épaisseur de la membrane ou l'espace interélectrode, est de 10 µm mais il est souhaitable de connaître la valeur la plus précise à laquelle nous appliquons cette erreur accidentelle. Ce système peut fonctionner à force constante et le schéma de principe en est représenté ci-dessous. ...
... Les polysulfones sulfonés ont des conductivités notables puisque nous avons pris en compte pour notre moyenne tous les taux de sulfonation. Or, d'une façon géné-_________________________________________________________________ rale, les polyélectrolytes sulfonés voient leur conductivité augmenter avec le taux de sulfonation16,20,52 . Malgré ce choix contestable, nous avons ainsi une représentation inédite et constructive des valeurs de conductivité de ces familles. ...
The research works reported in the manuscript are a contribution to the study of polyelectrolytes for Proton Exchange Membrane Fuel Cells (PEMFC). They are supported by two investigation tools, i.e. the study of model molecules and accurate conductivity measurements. With regard to the material science domain, the optimization of polysulfone sulfonation procedure allows chain breakings to be reduced and even eliminated while obtaining reproducible sulfonation degrees. It is thus possible to improve the mechanical properties of the dense membrane elaborated with these polyelectrolytes before performing the tests on the MEA (Membrane Electrode Assembly). In parallel, the fonctionnalisation of microporous silicon made it possible to prepare polyelectrolytes reinforced by the mechanical strength of the silicon separator. With regard to the physicochemical and electrochemical characterizations, the model molecules, with the same functions and groups than for associated polymers, make it possible to amplify the electrochemical or thermal phenomena vs. the corresponding polymers. Thus, they simulate an accelerated ageing of the polye-lectrolytes. The development of a new conductivity measurement set allows conductivity to be obtained with a great accuracy, in a wide range of temperature and relative humidity.
... Supersaturation of salts is also crucialand in this case a desired phenomenonin the membrane crystallizers. It has been shown that in a membrane contactor producing supersaturated solutions, crystals with extremely high purity can be obtained, as shown in Fig. 1 for NaCl (Drioli et al. 2004). Similar results can be obtained for CaCO 3 and MgSO 4 Á 7H 2 O as solid products. ...
... The reaction is carried out in homogenous phase and in shorter times compared to that of the traditional PEEK. For example, the reaction of PEEK with concentrated sulfuric acid at room temperature for 192 h gives a polymer with DS = 0.85 (Nunes et al. 2002), while for PEEK-WC the same DS can be obtained by reaction in 4 h (Drioli et al. 2004). ...
... Supersaturation of salts is also crucialand in this case a desired phenomenonin the membrane crystallizers. It has been shown that in a membrane contactor producing supersaturated solutions, crystals with extremely high purity can be obtained, as shown in Fig. 1 for NaCl (Drioli et al. 2004). Similar results can be obtained for CaCO 3 and MgSO 4 Á 7H 2 O as solid products. ...
... The reaction is carried out in homogenous phase and in shorter times compared to that of the traditional PEEK. For example, the reaction of PEEK with concentrated sulfuric acid at room temperature for 192 h gives a polymer with DS = 0.85 (Nunes et al. 2002), while for PEEK-WC the same DS can be obtained by reaction in 4 h (Drioli et al. 2004). ...
... Supersaturation of salts is also crucialand in this case a desired phenomenonin the membrane crystallizers. It has been shown that in a membrane contactor producing supersaturated solutions, crystals with extremely high purity can be obtained, as shown in Fig. 1 for NaCl (Drioli et al. 2004). Similar results can be obtained for CaCO 3 and MgSO 4 Á 7H 2 O as solid products. ...
... The reaction is carried out in homogenous phase and in shorter times compared to that of the traditional PEEK. For example, the reaction of PEEK with concentrated sulfuric acid at room temperature for 192 h gives a polymer with DS = 0.85 (Nunes et al. 2002), while for PEEK-WC the same DS can be obtained by reaction in 4 h (Drioli et al. 2004). ...
... Supersaturation of salts is also crucialand in this case a desired phenomenonin the membrane crystallizers. It has been shown that in a membrane contactor producing supersaturated solutions, crystals with extremely high purity can be obtained, as shown in Fig. 1 for NaCl (Drioli et al. 2004). Similar results can be obtained for CaCO 3 and MgSO 4 Á 7H 2 O as solid products. ...
... The reaction is carried out in homogenous phase and in shorter times compared to that of the traditional PEEK. For example, the reaction of PEEK with concentrated sulfuric acid at room temperature for 192 h gives a polymer with DS = 0.85 (Nunes et al. 2002), while for PEEK-WC the same DS can be obtained by reaction in 4 h (Drioli et al. 2004). ...
... Poly(oxa-p-phenylene-3,3-phtalido-p-phenylene-oxa-p-phenilene-oxy-phenylene) is cheap and chemically inert polymer. The sulfonated PEEK-WC (SPEEK-WC) was used to prepare the proton exchange membranes for possible fuel cell applications [7][8][9][10]. The membranes based on SPEEK-WC show a good chemical and mechanical stabilities, high proton conductivity, and both reduced methanol permeability and a lower cost with respect to those of Nafion Ò membrane. ...
... The sulfonated PEEK-WC (SPEEK-WC) membranes have been developed for possible fuel cell application [7][8][9][10]. It was found that the proton conductivity and water uptake increases with increasing degree of sulfonation. ...
... Instead of modifying the Nafion membrane material, other authors prepared less expensive membrane materials as alternatives to Nafion. Examples of such materials are the sulfonated poly(oxa-p-phenylene-3,3-phtalido-pphenylene-oxa-p-phenilene-oxy-phenylene) (PEEK-WC) membranes, where a reduction of about two orders of magnitude of the methanol crossover was obtained in comparison with Nafion-117 [76], and the sulfonated poly(ether ether ketone) (sPEEK) membranes, where a reduction of 92 % on the methanol crossover was observed [28]. ...
... Despite the fact that crossover of gases, present as reagents and/or reaction products in DMFCs, may be also considered as an important factor influencing the efficiency of a DMFC, strategies to reduce gas crossover have attracted a relatively lower attention when compared to methanol crossover. Strategies for gas crossover reduction were studied for alternative membrane materials with modest results [28,76,85,86]. Drioli The approach followed in this work was the design of modified Nafion membranes by partially replacing their protons with ionic-liquid (IL) cations, in order to assess the influence of this modification in both the methanol and gas crossover. ...
... However, population growth and environmental pollution arising from the consumption of nonrenewable resources pose several challenges, resulting in an urgent need for alternative energy sources to meet our rising demands. 1 Fuel cells are considered as feasible energy conversion devices because of their (i) high efficiency, (ii) environmentfriendly approach, (iii) sustainable energy conversion and storage systems, and (iv) various commercial, industrial, and automobile applications. Further, fuel cells can be primary sources of power generation for vehicles, transportation, and other portable devices. 2 The electrolyte membrane functions as a barrier between the two electrode systems and is a key component in polymer electrolyte membrane fuel cells (PEMFCs). ...
A new series of polymer composite membranes was fabricated using a linear sulfonated poly(ether ether ketone) (SPEEK) polymer with zinc cobalt oxide (ZCO) as an inorganic filler and evaluated for fuel cell applications. SPEEK was obtained by the direct sulfonation of PEEK using concentrated sulfuric acid, and appropriate quantities of ZCO were loaded into it to yield the polymer composites.Proton nuclear magnetic resonance studies revealed the degree of sulfonation of SPEEK to be 55%, while morphological studies confirmed the successful incorporation of inorganic fillers into the polymer matrix. To evaluate the suitability of the prepared composite membranes for fuel cell applications, their physicochemical properties were studied in detail. The pristine SPEEK membrane exhibited a proton conductivity of 0.009 S cm−1 at 30°C, whereas the values for the composite membranes loaded with 2.5 to 10 wt% of ZCO were in the range 0.012–0.020 S cm−1. Moreover, the composite membranes showed excellent thermal stability up to 370°C. Indeed, the membranes obtained by the incorporation of ZCO into the SPEEK polymer show potential for fuel cell applications.
... However, population growth and environmental pollution arising from the consumption of nonrenewable resources pose several challenges, resulting in an urgent need for alternative energy sources to meet our rising demands. 1 Fuel cells are considered as feasible energy conversion devices because of their (i) high efficiency, (ii) environmentfriendly approach, (iii) sustainable energy conversion and storage systems, and (iv) various commercial, industrial, and automobile applications. Further, fuel cells can be primary sources of power generation for vehicles, transportation, and other portable devices. 2 The electrolyte membrane functions as a barrier between the two electrode systems and is a key component in polymer electrolyte membrane fuel cells (PEMFCs). ...
A new series of polymer composite membranes was fabricated using a linear sulfonated poly(ether ether ketone) (SPEEK) polymer with zinc cobalt oxide (ZCO) as an inorganic filler and evaluated for fuel cell applications. SPEEK was obtained by the direct sulfonation of PEEK using concentrated sulfuric acid, and appropriate quantities of ZCO were loaded into it to yield the polymer composites. Proton nuclear magnetic resonance studies revealed the degree of sulfonation of SPEEK to be 55%, while morphological studies confirmed the successful incorporation of inorganic fillers into the polymer matrix. To evaluate the suitability of the prepared composite membranes for fuel cell applications, their physicochemical properties were studied in detail. The pristine SPEEK membrane exhibited a proton conductivity of 0.009 S cm ⁻¹ at 30°C, whereas the values for the composite membranes loaded with 2.5 to 10 wt% of ZCO were in the range 0.012–0.020 S cm ⁻¹ . Moreover, the composite membranes showed excellent thermal stability up to 370°C. Indeed, the membranes obtained by the incorporation of ZCO into the SPEEK polymer show potential for fuel cell applications.
... This separation represents the aromatic C-C ring between the two ether bonds. The sulfonic acid groups were attached only to the 1, 2, 4-substituted aromatic ring between the two ether linkages [30]. When the MB loaded sPEEK sample was examined, it was seen that the 3400 cm −1 band -which is attributed to the O-H vibrations of the sulfonic acid groups formed by the sulfonation process-was destroyed. ...
The elimination of organic compounds from drinking water is considerable due to trace levels of organic pollutants have adverse effects on human health and environment. Methylene blue (MB), a cationic dye, was selected hereby because of its extensive usage in textile industry. The long term exposure of organism to MB may result in vomiting, anemia and hypertension. Various physical, chemical, and biological methods use for remediation of dyes from wastewaters. In contrast to the complex and time-consuming methods, adsorption is simple, efficient, and cost-effective, thus, it is currently the favored approach for wastewater treatments.
In this work, sulfonated poly(ether ether ketone) (SPEEK), which was priorly used as polymer electrolyte, was used as an adsorbent for the first time in cationic azo type dye methylene blue removal from aqueous solutions. The effect of contact time, initial concentration and temperature were inspected, and the adsorption capacity, isotherm, kinetic and thermodynamic parameters on the adsorption were determined. According to results, the kinetic of MB adsorption on SPEEK fits pseudo second order kinetic model. The equilibrium was reached in 40 minute, and k2 value was calculated as 0.013. The adsorption showed Langmuirian character with the maximum adsorption capacity of 98.04 mg/g. The thermodynamic parameters, ΔH (38.51 kJ/mol K) and ΔGo (at 298 K -13.38 kJ/mol K and at 313 K -15.83 kJ/mol K) were calculated. Adsorbent characterizations were investigated by FT-IR, SEM, TGA and BET analysis. Consequently, SPEEK can be used as a suitable adsorbent for methylene blue removal from aqueous solutions.
... The proton conductivities of the neat SPEEK membrane, the SP/Cr-fa-SPA membranes, the SP/fa-SPA-40 membrane and Nafion117 as a function of temperatures were determined at 100% relative humidity [38]. As shown in Fig. 3a, proton conductivities of the SP/Cr-fa-SPA membranes were gradually decreased with the increase of the Cr-fa-SPA content due to the reduced IEC values (Table S1). ...
The current direct methanol fuel cells are still largely limited to the neat methanol operation due to the high methanol permeation of the currently used Nafion membranes. To achieve high methanol concentration DMFC application of the sulfonated poly(ether ether ketone) (SPEEK)-based proton exchange membrane, the neat SPEEK membrane is here modified by blending with the designed cross-linked fully aromatic sulfonated polyamide (Cr-fa-SPA). As the similar fully aromatic features of the SPEEK and the Cr-fa-SPA and the formed hydrogen bonding interactions between the SPEEK and the Cr-fa-SPA, the SPEEK/Cr-fa-SPA membranes show good compatibility, which is beneficial for the construction of the uniform and contact morphology of the membrane. In addition, the cross-linking network and the hydrogen bonding interactions in the SPEEK/Cr-fa-SPA membranes are favorable for enhancing the dimensional stability and reducing the methanol permeation. In particular, the lowest methanol permeability of 0.46 × 10⁻⁷ cm²/s is successfully obtained by blending 40 wt% Cr-fa-SPA in the SPEEK/Cr-fa-SPA membrane, which is almost two magnitudes lower than that of the Nafion 117 membrane. Finally, the SPEEK/Cr-fa-SPA DMFC devices were successfully demonstrated with the highly concentrated 20 M methanol fuels with remarkable performance.
... PEEK has shown many outstanding properties: excellent mechanical strength (tensile strength 141 MPa) [2], high chemical resistance especially for acid and alkali corrosion, and low thermal conductivity (0.23 W/m·K) [3], which could be used as an outstanding thermal insulator with good thermal stability, and its extraordinary biocompatibility made it suitable for medical applications such as implanting tooth and prosthesis. PEEK therefore has attracted huge research interest in various applications including aircraft, automotive, fuel cell energy, and medical implants [4][5][6][7][8][9][10]. New members of the PEEK family with specific features have been developed to suit a broad range of applications, in terms of properties, processability and cost [1,11]. ...
We report a simple and effective method to fabricate PEEK (Poly Ether Ether Ketone)/IF-WS2 (Inorganic Fullerene Tungsten Sulphide) nanocomposites with IF-WS2 content up to 8 wt%. We have used electron microscopies to characterise the morphology and structural features of the nancomposites, and FTIR and XPS to show that some chemical interface bondings were formed between the PEEK and IF-WS2. We demonstrate that the resulting PEEK/IF-WS2 nanocomposites showed an extraordinary 190% increase in thermal conductivity, 50°C higher in degradation temperature, and mild improvements in strength and hardness. The increased degradation activation energy from 64 to 76 kJ/mol for neat PEEK and PEEK/IF-WS2 nanocomposites, respectively, is attributed to the synergistic interface between the PEEK matrix and IF-WS2 nanoparticles. The enhancements in both the mechanical and thermal properties will significantly expand the capacities of PEEK-based nanocomposites towards applications where thermal conductivity and stability are important.
... Sulfonated aromatic polymers (SAPs) are being largely investigated due to their potential applications in specific areas, such as catalytic coatings electrodialysis, rechargeable batteries, light-emitting diodes, junc- tion devices, enzymatic activity, corrosion protection, fuel cells, ionophores and absorbents towards heavy metal ions ( Huang et al., 2014;Pradeep, Arunraj, & Dhatchinamurthy, 2014). Thus, several aromatic polymers have been sulfonated over the last few years, such as polyaniline (PAN) ( Mav et al., 2000;Mav-Golež et al., 2011;Tsuchida et al., 1970), polyimides (Genies et al., 2001), polysulfones ( Drioli et al., 2004), poly(etherketones) ( Gil et al., 2004), polyamides (Nolte, Ledjeff, Bauer, & Mülhaupt, 1993), polyarylene(ether sulfones) , substituted poly(1,4-phenylenes) (Benavente, Garcıá, Riley, Lozano, & de Abajo, 2000), poly(phenylene sulfides) (Qi, Lefebvre, & Pickup, 1998). The percentage of sulfonation which is defined as the molar ratio of sulfur to nitrogen in sulfonated aromatic copolymers can be controlled by selecting varying of experimental conditions and by choosing various molar proportions of the two monomers. ...
The sulfonation of poly(p-phenylenediamine) (P(pPD)) polymer was accomplished by oxidative copolymerization of p-phenylenediamine (pPD) with 2,5-diaminobenzenesulfonic acid (DABSA) and 2-aminobenzenesulfonic acid (2ABSA) monomers with 50/50 mol% ratios, using ammonium persulfate ((NH4)2S2O8) as an oxidant. The pPD-co-DABSA and pPD-co-3ABSA copolymers obtained were fully characterized and compared by Fourier transform infrared spectroscopy (FT-IR), ¹H nuclear magnetic resonance spectroscopy (¹H NMR), Gel permeation chromatography (GPC), Wide-angle X-ray diffraction (WAXD) and Thermogravimetric analysis (TGA). The yield, molecular weight, solubility, degree of sulfonation, molecular structure and thermal stability of the copolymers were shown to be dependent on the type of comonomer. The solubility of pPD-co-DABSA and pPD-co-2ABSA copolymers was significantly improved compared to the P(pPD) polymer in most solvents. Conversely, the yield and molecular weight values obtained for the pPD-co-DABSA and pPD-co-2ABSA copolymers were lower than those obtained for P(pPD) polymer. The TGA results showed that P(pPD), pPD-co-DABSA and pPD-co-2ABSA copolymers have good thermal stability and decompose above 200°C in nitrogen.
... The growing need for the development of low emission power sources has attracted research interest on fuel cell technology [1][2][3][4][5][6]. Polymer electrolyte fuel cell is now used as energy sources for portable, stationary and automotive devices [7][8][9]. ...
... Selectivity. The IEC of the membranes was determined quantitatively by titration [24]: sample membranes were first boiled in 1.0 M sulfuric acid for 1 hr to guarantee the acid form. Over 0.3-0.4 ...
Nafion 212 membrane was subjected to swelling-dehydration (SD) cycles, as a relevant operation condition for direct methanol fuel cells (DMFCs). The major degradation mechanism due to the treatment was found to be sulfonic group contamination with trace ion, rather than formation of sulfonic anhydride, which is a well-known degradation mechanism for Nafion® membranes under hydrothermal (HT) aging condition. The consequences of the degradation include decreasing water content, thickness, and surface fluoride and increasing resistance, dry weight, and a changed surface morphology. Ion selectivity of the sulfonic group was studied toward different fuel cell relevant conditions. It turned out that the sulfonic groups have much higher selectivity toward cations rather than neighbor sulfonic groups. Trace impurities in the liquid methanol feed in DMFC may therefore represent an important contamination source.
... One of the alternatives is the modification of perfluorosulfonic acid membranes by crosslinking, improving water retention properties [7,8]. Other approaches involve modification by forming composites with hygroscopic oxides or inorganic proton conductors [9]; or by selecting rigid chain p ol y m e r s ca pa bl e o f b ei ng s u l f o na t e d s uc h a s polyetheretherketones (PEEK), polyetherketones (PEK), polyarylene ethersulfone (PES), polysulfoamides, and polybenzimidazole [10][11][12]. ...
Non-woven nanofiber mats of poly(styrene sulfonic acid-co-maleic anhydride) (PSSAMA) and poly(vinyl alcohol) (PVA) were prepared by electrospinning using water as solvent. Composite membranes were prepared by casting a poly(methyl methacrylate) (PMMA) chloroform solution over the PSSAMA/PVA nanofibrous mats. Scanning electron microscopy (SEM) showed that these composite membranes are dense structures formed by fibers with average diameter of about 300 nm which acts as composite filler and proton conducting channels. The proton conducting behavior of these membranes were evaluated by impedance spectroscopy in dry atmosphere and in deionized water. The best proton conductivity of this new type of composite electrolyte membrane was 1.67 mS/cm in a dry state, value which is lower than that of commercial Nafion membrane, in the same condition (9.24 mS/cm). Proton conductivity increased with temperature increase, up to 50 °C, when it reached the maximum value.
... This behaviour is indicated in Figure 2. This is consistent with literature [15,[20][21][22][23][24][25] where the added sulfonate groups provide the formation water-mediated pathways for cation transfer. Preliminary investigations found that sulfonation temperatures below 40 °C were too low to effectively sulfonate the PEEK polymer within a reasonable time frame. ...
A low cost cation exchange membrane to be used in a specific bioelectrochemical system has been developed using poly(ether ether ketone) (PEEK). This material is presented as an alternative to current commercial ion exchange membranes that have been primarily designed for fuel cell applications. To increase the hydrophilicity and ion transport of the PEEK material, charged groups are introduced through sulfonation. The effect of sulfonation and casting conditions on membrane performance has been systematically determined by producing a series of membranes synthesized over an array of reaction and casting conditions. Optimal reaction and casting conditions for producing SPEEK ion exchange membranes with appropriate performance characteristics have been established by this uniquely systematic experimental series. Membrane materials were characterized by ion exchange capacity, water uptake, swelling, potential difference and NMR analysis. Testing this extensive membranes series established that the most appropriate sulfonation conditions were 60 °C for 6 h. For mechanical stability and ease of handling, SPEEK membranes cast from solvent casting concentrations of 15%-25% with a resulting thickness of 30-50 µm were also found to be most suitable from the series of tested casting conditions. Drying conditions did not have any apparent impact on the measured parameters in this study. The conductivity of SPEEK membranes was found to be in the range of 10-3 S cm-1, which is suitable for use as a low cost membrane in the intended bioelectrochemical systems.
... Sulfonated PEEKs were explored extensively in the field of PEMFCs due to the ease of chemical modification by sulfonation and ready availability of a wide range of reagents such as concentrated sulfuric acid, fuming sulfuric acid, and so on. [7][8][9][10][11] Apart from chemical modification of the polymers by direct sulfonation, efforts were made to chemically graft functional group containing pendent chains onto the backbone of other polymers. 12,13 Direct polymerization of sulfonated monomers was also adopted to synthesize the sulfonated polymers. ...
Incorporation of phosphonic acid groups in the polymer backbone by direct phosphonation or by polymerization of prefunctionalized monomers requires harsh reaction conditions. The present research work reported an easy synthesis strategy of phosphonic acid-containing diphosphonated polyether ether ketone (P-PEEK) by polycondensation of difluoro benzophenone and phosphonated bisphenol A (BPA). Phosphonation of BPA was carried out by monophosphoazylation followed by rearrangement in the presence of organolithium compound at −78°C. Nuclear magnetic resonance (NMR) imaging, Fourier transform infrared, and electrospray ionization mass spectrometry were performed to acquire complete structural information about the synthesized monomer and polymer. Degree of phosphonation of the synthesized polymer calculated from proton NMR spectra was as high as 70%. Thermal properties of the P-PEEK were checked using a differential scanning calorimeter (DSC) and a thermogravimetric analyzer. Moderate increase in melting point and glass transition temperature (T g) were observed from the DSC analysis. Solubility of the polymer was improved significantly in the common organic solvents that permitted the polymer to be solution casted. Solid electrolyte membrane exhibited through plane proton conductivity of 7.5 × 10−5 S cm−1 at 25°C under fully hydrated conditions.
... The sulfonated PEEK was hydrophilic and therefore it showed a broad band at 3430 cm À1 owing to the OeH stretching vibration for water. This result was also consistent with the explanation given by Drioli et al., who studied the potential ability of sulfonated poly (oxa-p-phenylene-3, 3-phtalido-pphenylene-oxa-p-phenilene-oxy-phenylene) (PEEK-WC) at different DSs as PEM for fuel cells [23]. ...
In this paper, the performance of two common and two self-fabricated proton exchange
membranes were compared. Nafion 112 and Nafion 117, which are two of the most common
proton exchange membranes that can be used in all fuel cell systems, were compared
to SPEEK and SP/CC/TAP. The results showed that at lower COD such as 2000 mg/l, Nafion
117 has the highest performance in terms of power production and COD removal, while
once the COD of wastewater goes up to 5000 mg/l, SP/CC/TAP has approximately the same
performance as Nafion 117. The membranes were characterized by FESEM, while the degree
of sulfonation was measured by NMR. The oxidation activity of microorganisms was
measure by cyclic voltammetry (CV). Also, the attachment of bacteria onto the anode
electrode was observed by SEM, which showed that different bacteria from the media with
a mixed culture inoculum had attached to the anode electrode.
... The proton conductivity of the membrane based on the sulfonated polymer increases with increasing degree of sulfonation (DS) [14][15][16][17] . However, the sulfonation increase swelling, even soluble in water and therefore mechanical strength is decreased [18] . ...
The proton conducting membrane was prepared by cross-linking highly sulfonated and sulfinated poly(etheretherketone) (SsPEEK). The cross-linked membrane is low cost due to its use of non-expensive chemical and simple production procedure. The membrane exhibited high proton conductivity (0.04 S/cm at 60 °C), extremely reduced water uptake, enhanced strength and stability compared with that of non-cross-linked membrane. These results suggested that the cross-linked PEEK membrane is a suitable candidate of proton conducting membranes for polymer electrolyte membrane fuel cell (PEMFC) applications, particularly promising to be used in direct methanol fuel cell (DMFC) due to its lower methanol crossover.
... These water-filled channels containing SO 3 groups endow Nafion with its high proton conductivity. There are alternative PEMs based on styrene 12 , poly(arylene ether)s such as poly(arylene ether ether ketone) (PEEK) 13 , poly(imide)s 14 , and other materials. Nafion and other PFSA membranes are by far the most commonly used membranes for PEMFCs. ...
... 170 The stability and longevity of these modified membranes has been considered a key issue blocking them from mainstream use. Many different types of polymers have been investigated to reduce crossover including random copolymers containing sulfonic acid [171][172][173] , grafted SPS or PSSA on hydrophobic polymers 174,175 and block copolymers [176][177][178] . Impregnating nano-scale catalytic metals in Nafion that react with the crossover methanol as it travel through the membrane have helped the issue of polarization but not fuel efficiency. ...
... IEC of SPEES was determined quantitatively by the titration method according to the previously described procedure in literature [21]: 0.2-0.3 g of dried sulfonated sample was immersed into the 50 mL of saturated NaCl solution at 50 C for 48 h to exchange H þ with Na þ . ...
... Poly(oxa-p-phenylene-3,3-phtalido-p-phenylene-oxa-p-phenilene-oxy-phenylene) (PEEK- WC) is cheap and chemically inert polymer. The sulfonated PEEK-WC (SPEEK-WC) was used to prepare the proton exchange membranes for possible fuel cell applications78910. The membranes based on SPEEK-WC show a good chemical and mechanical stability, high proton conductivity, and both reduced methanol permeability and a lower cost with respect to those of the Nafion ® membrane. ...
The low cost proton exchange membrane was prepared by cross-linking water soluble sulfonated-sulfinated poly(oxa-p-phenylene-3,3-phthalido-p-phenylene-oxa-p-phenylene-oxy-phenylene) (SsPEEK-WC). The prepared cross-linked membrane became insoluble in water, and exhibited high proton conductivity, 2.9 × 10<sup>-2</sup> S/cm at room temperature. The proton conductivity was comparable with that of Nafion<sup>®</sup> 117 membrane (6.2 × 10<sup>-2</sup> S/cm). The methanol permeability of the cross-linked membrane was 1.6 × 10<sup>-7</sup> cm<sup>2</sup>/s, much lower than that of Nafion<sup>®</sup> 117 membrane. © 2009 Professor T. Nejat Veziroglu.
Ion-containing polymers have continued to be an important research focus for several decades due to their use as an electrolyte in energy storage and conversion devices. Elucidation of connections between the mesoscopic structure and multiscale dynamics of the ions and solvent remains incompletely understood. Coarse-grained modeling provides an efficient approach for exploring the structural and dynamical properties of these soft materials. The unique physicochemical properties of such polymers are of broad interest. In this review, we summarize the current development and understanding of the structure-property relationship of ion-containing polymers and provide insights into the design of such materials determined from coarse-grained modeling and simulations accompanying significant advances in experimental strategies. We specifically concentrate on three types of ion-containing polymers: proton exchange membranes (PEMs), anion exchange membranes (AEMs), and polymerized ionic liquids (polyILs). We posit that insight into the similarities and differences in these materials will lead to guidance in the rational design of high-performance novel materials with improved properties for various power source technologies.
The sulfonated spindle-like carbon derived from metal-organic framework, MOF-C-SO3H, has been employed as a filler for the SPEEK membrane. The obtained MOF-C-SO3[email protected] membrane shows improved properties as a PEM for DMFCs. In particular, with the presence of 3.0 wt% of MOF-C-SO3H, the MOF-C-SO3[email protected] membrane can exhibit higher proton conductivity and much lower methanol permeability than Nafion 115. The specific porous and sulfonated carbon structure is believed to play an important role in the high performance of the MOF-C-SO3[email protected] membrane. It helps the good dispersion of MOF-C-SO3H in the SPEEK matrix, decreasing the swelling ratio and methanol permeability of the membrane, and promotes the transport of protons through the membrane, improving the proton conductivity of the membrane. More interestingly, when used in the DMFCs, it can give maximum power density of 83.91 mW cm⁻², which is ∼50% higher than that of Nafion 115. This, together with its higher stability of the DMFC the MOF-C-SO3[email protected] membrane than that with Nafion 115, suggests that the MOF-C-SO3[email protected] membrane is a promising proton exchange membrane for fuel cells.
Poly(ether ether ketone) is a semicrystalline organic polymer. It has widely been used as high-performance engineering plastic owing to its high melting point (343 °C), excellent mechanical strength, and outstanding chemical resistance. Therefore, poly(ether ether ketone) and its composites have shown lots of applications in aerospace and medical fields. However, its application is restricted due to poor strength at the mechanically joint components. Thus, this scope leads us to study an alternative method of the joint process that will lead to finding a new joining process for poly(ether ether ketone)-based materials. In this study, a solid-state joining process was conducted to join two poly(ether ether ketone) rods by a friction welding process. Here, we statistically optimized the values of forge load, friction load, and friction welding time as 100 N, 450 N, and 8 s, respectively, which have more influence on tensile stress and hardness of the material after the friction welding process. It has been found that the forge load had the highest influence and the forge time had the least influence on tensile strength. Their optimal values were calculated after considering the trend in hardness values by statistical analysis using Minitab software. However, after the optimal values, the above parameter showed a negative effect on the high tensile stress due to the change in crystallinity of the friction welding processed poly(ether ether ketone) as confirmed by X-ray diffraction and thermal analyses.
The aim of this study is to investigate the methylene blue (MB) and basic violet 16 (BV16) as cationic organic dyes adsorption on sulfonated poly(ether ether ketone) (sPEEK) in aqueous solution. sPEEK was synthesized, then characterized by FTIR, SEM, TGA, BET/N2 surface area analysis, particle size and zeta potential measurements. Batch experiments were performed to analyze the effects of key parameters such as contact time, initial concentration and pH on MB and BV16 adsorptions. Additionally, temperature effect was investigated for MB adsorption. Kinetic data revealed that cationic dyes adsorptions were well-fitted by pseudo-second order kinetic model. The required times to achieve equilibrium were determined as 40 and 20 min for MB and BV16, respectively. The adsorptions showed Langmuirian character, and the maximum adsorption capacities were found to be 98.04 mg/g (0.29 mmol/g) for MB, and 181.8 mg/g (0.50 mmol/g) for BV16. The thermodynamic data showed that the MB adsorption was an endothermic process occuring spontaneously at room temperature. Desorption and recycling experiments showed that the adsorption efficiency decreased from 99.6% to 99.2% after the fifth cycle, pointing out sPEEK reusability for MB removal. Low desorption percentage of BV16 loaded sPEEK shows that sPEEK may be used for immobilizing of BV16.
A composite adsorbent coating on Al6061 aluminum substrate, based on SAPO34 zeolite filler and sulfonate poly (ether-ether ketone) (S-PEEK) matrix is proposed for sustainable energy saving technologies. The effect of sulfonation degree on the mechanical and physical chemical properties of the composite coating was assessed by synthesizing four batches with a degree of sulfonation of the matrix ranging from about 40%–50%. The degree of sulfonation was measured by titration and confirmed by thermogravimetry and FTIR analysis. For each batch of S-PEEK four coatings at increasing SAPO-34 filler content (in the range 80−95 wt.%) were realized. The composite coatings were homogenous and almost defect free. The mechanical performances, evaluated by scratch and pull-off tests, highlighted that all batches exhibited a suitable behavior for adsorption heat pumps application in mobile systems. Best results were observed by using a relatively high sulfonation time of S-PEEK. Obtained coating exhibited indeed very good adhesive and cohesive properties as well as high water vapor uptakes.
Blocky sulfonated poly(ether ether ketone) (SPEEK) ionomers were synthesized by postpolymerization functionalization in the gel state. Matched sets of blocky and random SPEEK with ion contents between 3 and 11 mol % were prepared, and the thermal transitions and crystallization kinetics were examined using differential scanning calorimetry (DSC). At similar ion contents, the blocky SPEEK exhibited higher crystallizability and faster crystallization kinetics than random SPEEK. Reduced scattering contrast in the USAXS/SAXS/WAXD analysis of the blocky SPEEK copolymer membranes, relative to the random analogues, suggested that the ionic aggregates in blocky SPEEK were distributed in close proximity to the crystalline domains. Despite similar water uptake values for the low ion content random and blocky SPEEK membranes, the blocky SPEEK exhibited higher proton conductivities than their random analogues. At significantly higher ion contents (45 mol %), the blocky SPEEK membranes remained semicrystalline, showed controlled water uptake, and exhibited a 2.5 times higher conductivity over that of the amorphous, random analogues. Moreover, these new blocky, semicrystalline SPEEK membranes were found to exhibit a proton conductivity that was comparable to that of the benchmark 1100 EW Nafion.
The DS 68% SPEEK composite membranes were prepared by post-sulfonation. Using diethylenetriamine as the epoxy cross-linking agent, which is uniformly distributed in the grafted SPEEK to form SPEEK/epoxy semi-interpenetrating network structure and explore the semi-interpenetrating network on the impact of membrane performances. Graphene oxide was synthesized according to Hummers method and organic in γ-chloropropyl triethoxysilane. Sulfonated graphite oxide doped SPEEK were prepared and optimized the formulation. Finally a series of SPEEK/epoxy/graphene oxide proton exchange membranes were prepared. With the increasing content of epoxy resin semi-interpenetrating network structure, the thermal properties of the proton exchange membrane are also increased. Covered with crosslinked network structure, the more long chain of SPEEK and graphene oxide particles, the more thermal performance improved. The methanol permeabile concentration is relatively close with pure SPEEK proton exchange membrane. The concentration of methanol permeability decreases with the increase of epoxy resin content. The semi-interpenetrating network structure increase the interaction with the matrix bonds and reduce the sulfonic acid groups on the excessive absorption of water molecules. But the membrane structure still exist problems such as density, which due to the loss of doped sulfonated graphene oxide. But there are only semi-interpenetrating network cannot be fully resolved.
Crystallite formation in membranes cast from sulfonated poly(etheretherketone) (SPEEK) dispersions in dimethylacetamide has been investigated by differential scanning calorimetry. The crystallites melt at 220 °C and the melting enthalpy (ΔHm) is strongly influenced by environmental conditions of solvent evaporation. When solvent is evaporated in air, ΔHm decreases with increasing the evaporation temperature so that no crystallites are formed above 45 °C. The study of crystallite formation at 30 °C, under controlled relative humidity (RH) and solvent evaporation rate, has shown that ΔHm decreases i) with decreasing RH from 75% to 5%, at constant evaporation rate, and ii) with increasing evaporation rate, especially at low RH. The exchange of protons with sodium ions results in an increase of the crystallite melting temperature thus indicating the presence of sulfonic groups in the crystallites. In comparison with crystallite-free SPEEK membranes, the presence of crystallites turns out in enhanced membrane mechanical properties, reduced hydration in liquid water above 75 °C, strongly anisotropic swelling (occurring mainly in the through-plane direction) and better performance in H2/air fuel cell at 70 °C.
The DS 68% SPEEK composite membranes with were prepared by post-sulfonation. Using diethylenetriamine as the epoxy cross-linking agent, which is uniformly distributed in SPEEK, to form SPEEK/epoxy semi-interpenetrating network structure and explore the impact of semi-interpenetrating network on the performances as proton exchange membrane. The contents of epoxy resin are 10 wt.%, 15 wt.% and 20 wt.%, respectively. The thermal properties of the proton exchange membranes are increases with the increase of crosslinking structure of epoxy resin. But the conductivity proton performances are slightly declined with the increase of semi-interpenetrating network. Crosslinking increased the density of proton exchange membrane, improved the anti-water swelling property and avoided the proton conductivity rising slowly at high temperature. With the increases of epoxy resin, the methanol permeability coefficient decreases.
Design of polymeric membranes for fuel cells application requires suitable selection and modification of polymers. This review accounts the various polymeric membranes available for use in fuel cells, advantages of sulphonation of polymers, various sulphonation methods and the characterization techniques. Presently, SPEEK finds extensive application as polymeric membrane in fuel cells. The advantages of SPEEK include good mechanical properties, thermal stability, and toughness and some conductivity depending on degree of sulphonation.
The general properties of polymer electrolyte membranes (PEMs) are discussed in terms of ion-exchange properties, sorption phenomena, and durability under fuel cell working conditions. For their good stability, particular attention is paid to morphology, water uptake, conductivity, and mechanical properties of perfluorinated ionomers, including Nafion, Aquivion, and their composite membranes. The main physicochemical properties of nonfluorinated polymers (including poly(benzimidazole), poly(arylene ether)s, poly(imide)s, and poly(phosphazene)s) are shortly reviewed and compared to those of perfluorinated ionomers.
Membrane technology can be used to recover high purity water from power station flue gas streams. In this work, the effect of temperature on water vapour and CO2 permeation properties of Sulphonated Poly (Ether Ether) Ketone (SPEEK) with two different ion exchange capacities were investigated (IEC 1.6 meq/g and 1.9 meq/g). It was found that both permeabilities increased with increasing water activity due to increased water solubility as water concentration increased. SPEEK with IEC 1.9 meq/g exhibited higher water permeability and selectivity than IEC 1.6 meq/g. At humidities greater than 50%, both water vapour and CO2 permeabilities also increased as temperature increased up to 50 °C due to the increase in diffusion of the penetrating molecules. However as temperature increased further, a significant drop in the permeability of both water and carbon dioxide occurred. This decrease was attributed to the formation of water clusters that filled the free volume in the polymer and hindered the diffusion of isolated molecules. This decrease in diffusion coupled with a reduction in solubility with increasing temperature resulted in the performance decline.
Polyethersulfone (PES) hollow fiber membrane was surface-modified for application as a separation membrane to recover water vapor from the flue gas. Hydrophilic sulfonated PES (SPES) was prepared by introducing a sulfonic acid group in PES structure and was used for the layer-by-layer (LbL) coating solution with polyallyamine hydrochloride (PAH). The surface characteristics of the modified PES membranes were observed by XPS, SEM, ζ-potential and contact angle measurements. The formation of hydrophilic nano-coating layer with 50∼80 nm in thickness on the surface of PES hollow fiber membranes by the LbL coating method led to relatively lower contact angle and higher water vapor permeance. As a result, the LbL coating method could be considered as a useful method for surface-modification of PES hollow fiber membrane to enhance their surface hydrophilicity and water vapor permeance.
Aromatic polymers are a very important group of high-performance engineering materials, which have been subjected to intense academic and industrial research. This chapter aims to provide a review on the history and recent advances in the synthesis, reactions, physical and chemical properties, and applications of certain aromatic polymers, with emphasis on poly(arylene ether)s, polyetherketones, polysulfones, and polysulfides. Specific published examples are adapted in this chapter for illustration concerning these four high-performance polymer families.
Export Date: 26 January 2015
The present work addresses the development of economic membrane material with superior proton conductivity and less methanol crossover. Sulfonated poly(ether ether ketone) (SPEEK) composite membranes with various loading of zirconium titanium phosphate (ZTP) have been prepared by solution casting method. The structural and thermal properties of the ZTP powder are evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area measurement, Fourier transform infrared spectroscopy (FTIR), and Thermo gravimetric analysis (TGA). The produced composite membranes are also characterized by evaluating the ion exchange capacity (IEC), water uptake, methanol uptake, thermal stability, proton conductivity, and methanol crossover as a function of ZTP loading. The proton conductivity of composite membrane is fourfold higher than that of the pure SPEEK membrane and also increases with an increase in the ZTP loading. The methanol permeability of the composite membrane containing 15% ZTP decreases by 264% (and 21%) when compared with pure SPEEK (and commercial Nafion 117 membrane). Over all, the selectivity of the SPEEK/ZTP composite membrane is found to be 15- and 3-fold higher than the pure SPEEK membrane and Nafion 117 membrane, respectively. Hence, the synthesized SPEEK composite membrane could be utilized as low cost alternative for the high cost commercial membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
In this work dense polymer electrolyte membranes (PEM) were prepared by casting and solvent evaporation from homogeneous solutions of the sulfonated derivative of an amorphous polyetheretherketone, known as SPEEK-WC. In order to obtain stabilized PEMs, the SPEEK-WC membranes were modified by following three different strategies: thermal annealing, chemical cross-linking with a diamine and blending with Nafion ionomer. Various ex situ characterizations were carried out on the modified and reference SPEEK-WC membranes, including: ion exchange capacity, proton conductivity, liquid water uptake, counter elastic index, chemical resistance in oxidative conditions, and gas permeability. The results indicated that the first two methodologies are able to increase hydrolytic and oxidative stability of the SPEEK-WC membranes at a temperature higher than 100 °C.
Sulfonated poly(ether sulfone)s (PESs) with a network structure were prepared by heat-induced crosslinking of the allyl-terminated telechelic sulfone polymers using a bisazide and their structure was analyzed by NMR. Having both uniform distribution of the hydrophilic conductive sites and controlled hydrophobic nature by minimized crosslinking, the crosslinked polymer (PES-60) membrane offered excellent proton conductivity at high temperature with a good thermal stability. In addition, selectivity of the crosslinked membrane (PES-60) was more than three times than that of Nafion.
Solid Polymer Electrolyte Membranes (SPEMs) play a vital role in polymer electrolyte fuel cell systems. The high cost (US$70-150/ft2) and/or poor performance of the existing membranes prompted many industrial and university research groups world-wide to develop very specific and low cost (US$2-50/ft2) polymer-based electrolyte membranes. This paper is discussing progress on these key topics and the openings for the future. The advantages and disadvantages of the already developed perfluorinated ionomer membranes (Nafion, Flemion, Aciplex, Dow or Asahi Chemical) are described. The development of SPEMs during the last ten years is investigated and analysed in terms of methods of preparation, properties and potential uses in polymer electrolyte fuel cell systems. The SPEMs, which are in development, has been classified as perfluorinated polymer, partially perfluorinated polymer and non-perfluorinated membranes. The advantages and disadvantages for each type of SPEMs are addressed. The openings for industrial applications of the various SPEMs are discussed including their limits and the future studies which may be done to improve their performance in practical systems.
A series of composite membranes based on sulfonated polyether ether ketone with embedded powdered heteropolycompounds was prepared and their electrochemical and thermal properties were studied. An increase in degree of sulfonation as well as introduction of these fillers resulted in increased Tg and enhanced membrane hydrophilicity, bringing about a substantial gain in proton conductivity. The conductivity of the composite membranes exceeded 10−2 S/cm at room temperature and reached values of about 10−1 S/cm above 100°C.
The thermal, mechanical and electrochemical characterisation of sitlfonated polyetherketone, including fuel cell tests in hydrogen/ oxygen and hydrogen/air are described. In thermogravimetric analysis, PEEK-S membranes lose water up to 150°C and degradation of the sulfonic acid groups takes place at ca. 240°C. Thermomechanical analysis of a PEEK-S membrane of 60 μm thickness and equivalent weight 625 g/mole shows that the membrane undergoes a shrinkage of 1.5 % up to 140°C. Reversible elongation of 0.6 % occurs thereafter up to 180°C. The conductivity, measured by impedance spectroscopy, on non-reinforced and on woven-polymer reinforced PEEK-S, is reported as a function of temperature and of relative humidity (RH), and compared with that of Nafwn®-117. At 100°C and 100% RH the conductivity of PEEK-S is 2 5.10-2 Scm-1 (depending on thermal history), increasing to 0.11 Scm-1 at 150°C. Polarisation characteristics of a non-reinforced PEEK-S membrane of 18 ®m thickness at temperatures up to 110°C under conditions of hydrogen/air and hydrogen/oxygen are compared. The results of fuel cell (H2-O2) tests on composite, reinforced membranes are reported.
Sulfonated polyethylene membranes have been obtained by reacting flat sheets of commercial polyethylene with a gaseous mixture of chlorine and sulfur dioxide with subsequent hydrolysis of the sulfonyl chloride groups. Polyethylene materials with various densities have been utilized. Depending on the polyethylene density and on the operating conditions of the chlorosulfonation reaction, membranes with various contents of acidic sulfonate groups have been produced. These membranes have been characterized for the ion-conduction and also for the permeation properties of methanol molecules at various temperatures between 25 and 60 °C. Some of these membranes showed hydrogen ion conductivity near at room temperature.
The past 10 years have witnessed a tremendous acceleration in research devoted to non-fluorinated polymer membranes, both as competitive alternatives to commercial perfluorosulfonic acid membranes operating in the same temperature range and with the objective of extending the range of operation of polymer fuel cells toward those more generally occupied by phosphoric acid fuel cells. Important requirements are adequate membrane mechanical strength at levels of functionalization (generally sulfonation) and hydration allowing high proton conductivity, and stability in the aggressive environment of a working fuel cell, in particular thermohydrolytic and chemical stability. This review provides an overview of progress made in the development of proton-conducting hydrocarbon and heterocyclic-based polymers for proton exchange and direct methanol fuel cells and describes the various approaches made to polymer modification/synthesis and salient properties of the materials formed, including those relating to proton transport and proton conductivity, e.g., water diffusion and electro-osmotic drag. The microstructure, deduced from small angle X-ray and neutron diffraction measurements of representative non-fluorinated polymers is compared with that of perfluorosulfonic acid membranes. Different degradation mechanisms and aging processes that can result in chemical and morphological alteration are considered, and recent characterization of membrane-electrode assemblies (MEAs) in direct methanol and hydrogen-air (oxygen) fuel cells completes this review of the state of the art. While several types of non-fluorinated polymer membrane have demonstrated lifetimes of 500-4000 h, only a limited number of systems exist that hold promise for long-term operation above 100oC.1
Perfluorosulfonated ionomer (PFSI) dispersions in various solvents, usually mixtures of organic compounds and water, were used to prepare the membrane-electrode system in polymer electrolyte membrane fuel cells (PEMFC), the aim being to increase performance by improving the triple contact of graphite (electron conducting material), Pt (hydrogen dissociation catalyst) and ionomeric membrane (proton conducting). When using PFSI dispersions in water-organic solvent mixture, care must be taken not to poison the Pt catalyst through organic decomposition products, a consequence of the thermal treatment of the electrode-polymer system bonded with PFSI dispersion. In the present study some procedures for preparing Nafion water dispersion, starting from a Nafion-117 membrane, are described. The morphological characteristics of the prepared dispersions were compared with Nafion commercial dispersion (NCD). Moreover, membranes with a thickness of 5–20 μm were prepared and characterised, using both the obtained and the NCD dispersions. The obtained data showed that Nafion water dispersion, which can be used to prepare the membrane/electrode system, results in thin membranes that absorb more water than NCD membranes, and have equal and/or higher proton conduction than the NCD.
This article reviews progress made over the past years in the functionalisation of polybenzimidazole and polyetherketones with a view to increasing their proton conduction properties without detriment to their thermohydrolytic and chemical stability such that corresponding membranes may be employed in hydrogen oxygen (air) or direct methanol fuel cells. The approaches include complexation of polybenzimidazole with acids, grafting of groups containing sulfonic acid moieties on to polybenzimidazole by N-substitution, and direct sulfonation of polyetherketones. A further approach concerns the incorporation of inorganic proton conducting particles in the polymer matrix, and this is developed in detail for the case of hybrid sulfonated polyetheretherketone–metal(IV) phosphate membranes.
In this contribution an overview is given about the state-of-the-art at the membrane development for proton-conductive polymer (composite) membranes for the application membrane fuel cells, focusing on the membrane developments in this field performed at ICVT.For preparation of the polymers, processes have been developed for sulfonated arylene main-chain polymers as well as for arylene main-chain polymers containing basic N-containing groups, including a lithiation step. Covalently cross-linked polymer membranes have been prepared by alkylation of the sulfinate groups of sulfinate group-containing polymers with α,ω-dihalogenoalkanes. The advantage of the covalently cross-linked ionomer membranes was their dimensional stability even at temperatures of 80–90°C, their main disadvantage their brittleness when drying out, caused by the inflexible covalent network. Sulfonated and basic N-containing polymers (commercial polymers as well as self-developed ones) have been combined to acid–base blends containing ionic cross-links. The main advantage of these membrane type was its flexibility even when dried-out, its good to excellent thermal stability, and the numerous possibilities to combine acidic and basic polymers to blend membranes having fine-tuned properties. The main disadvantage of this membrane type was the insufficient dimension stability at T>70–90°C, caused by breakage of the ionic cross-links, where the ionic cross-links broke as easier as lower the basicity of the polymeric base was. Some of the acid–base blend membranes were applied to H2 membrane fuel cells and to direct methanol fuel cells up to 100°C, yielding the result that these membranes show very good perspectives in the membrane fuel cell application.
The novel polytheretherketone (PEK-C) prepared from phenolphthalein in our institute is an amorphous, rigid, tough material with good mechanical properties over a wide temperature range. To improve its water vapor permeability for the application of gas drying, PEK-C was sulfonated with concentrated sulfuric acid and transferred in sodium, cupric, and ferric salt forms. Sulfonation degree can be regulated by controlling the temperature and reaction time. Characterization of sulfonated PEK-C in sodium form was made by infrared spectroscopy. Some properties of the sulfonated PEK-C, such as solubility, glass transition temperature, thermal stability, mechanical properties, and transport properties to nitrogen and water vapor, are also discussed. © 1996 John Wiley & Sons, Inc.
Poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene) (PEEK) and poly(4-phenoxybenzoyl-1,4-phenylene, Poly-X 2000) (PPBP), were sulfonated with sulfuric acid by incorporating sulfonic acid moieties in order to convert these polymers to proton-conducting polymers. The sulfonated polymers containing 65 mol% sulfonic acid showed a high proton-conductivity of 10−2–10−4 Scm−1 at room temperature. Sulfonated PPBP showed a much higher and more stable proton conductivity than sulfonated PEEK, which is in agreement with the strong water absorption of the former compound.
The products of methanol crossover through the acid-doped polybenzimidazole polymer electrolyte membrane (PBI PEM) to the cathode of a prototype direct methanol fuel cell (DMFC) were analyzed using multipurpose electrochemical mass spectrometry (MPEMS) coupled to the cathode exhaust gas outlet. It was found that the methanol crossing over reacts almost quantitatively to COâ at the cathode with the platinum of the cathode acting as a heterogeneous catalyst. The cathode open-circuit potential is inversely proportional to the amount of COâ formed. A poisoning effect on the oxygen reduction also was found. Methods for the estimation of the methanol crossover rate at operating fuel cells are suggested.
Layered zirconium sulfoarylphosphonates of the α- and the γ-type are proton conductors thermally stable up to at least 180°C. In these materials, the sulfophenyl groups are bonded through the phosphorus atoms to an α- or a γ-inorganic framework made of oxygen and zirconium atoms. Compounds where the sulfonic function is attached to a phenyl, benzyl or to a fluorinated benzyl group were characterized for their conductivity as a function of temperature and relative humidity (r.h.). Independent of the layer type, the highest conductivities were found for the sulfophenylphosphonates. The conductivity is strongly affected by the r.h. reaching values of 5×10−2Scm−1 at 100°C (100% r.h.) and 2×10−2Scm−1 at 150°C (80% r.h.). Due to their ability to undergo infinite swelling in appropriate solvents, these materials can be incorporated into polymeric proton conducting membranes. The possible advantages of these membranes for increasing the efficiency of indirect or direct methanol fuel cells working at medium temperature are discussed.The use of these membranes in gas sensors working at medium temperatures are also discussed. Preliminary results for the detection of hydrocarbons at 300°C by means of a sensor based on the protonic conductivity of zirconium phosphate are reported.
The basic principles of the various aspects of membrane technology are reviewed. Polymers used as membrane material are surveyed and factors determining material properties described. Various preparation techniques are overviewed and the phase-inversion process is discussed in detail. Characterization techniques are included, both for porous and nonporous membranes. Types of driving forces, transport processes and concentration polarization are described together with membrane fouling. Aspects of module and process design are given together with some process calculations. (P.M.T.)
PROMISES OF ENERGY-EFFICIENT, economical, and environmentally sound sources of electrical power have sparked an explosion in fuel-cell research and development during the past decade. With eyes fixed on applications in transportation and stationary and portable power, industries and governments have poured big bucks into the future of these electrochemical power generators. Market observers say that fuel-cell R&D budgets have climbed three orders of magnitude in the past several years and that annual spending in the industry has now reached the billion-dollar range. A steady flow of fuel-cell success stories in the news media tells the public that the electrochemical devices are on their way to market. But for the most part, they're not yet there. Nonetheless, the number and variety of demonstrations are growing quickly. In the meantime, scientists and engineers continue to work on fuel-cell materials, fueling issues, manufacturing methods, and other topics. Their aim is to boost efficiency, ...
Sulfonated poly(oxa-p-phenylene-3,3-phthalido-p-phenylene-oxa-p-phenylene-oxy-phenylene) (PEEK-WC) with various degrees of substitution was obtained by reaction of polyetheretherketone with neat chlorosulfuric acid. Highly sulfonated PEEK-WC was freely soluble in cold water. By working under suitable reaction conditions, no degradation of the polymeric chain was detected. The modified PEEK-WC was able to form asymmetric membranes. The expected chlorosulfonated derivatives were never achieved. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 477–482, 1998
Mixed Nafion®/silicon oxide membranes with non-uniform Si/S concentration ratio profile were prepared by allowing tetraethoxysilane (TEOS) and HF to diffuse simultaneously from isopropanol solutions located at opposite sides of the ionomer membrane. This was made possible by using a specially designed cell where the Nafion® membrane is used to define two different and non-contacting volumes containing the solutions. The presence of a Si/S intensity ratio profile with a maximum located near the center of the membrane is confirmed by point-by-point EDX measurements along the thickness of the membrane. These mixed Nafion®/inorganic membranes with unmodified surfaces are expected to have applications in polymer electrolyte fuel cells.
The performance and the efficiency of direct methanol fuel cells (DMFCs) are affected by the methanol permeation from the anode to the cathode. A widely used method to measure the methanol permeation in a DMFC is the analysis of the carbon dioxide content of the cathode exhaust. During the operation of a DMFC large amounts of carbon dioxide are produced in the anodic catalyst layer which can diffuse partially to the cathode. As a consequence the carbon dioxide in the cathodic exhaust gas stream is expected to consist of two fractions: the carbon dioxide resulting from the oxidation of the permeating methanol and the carbon dioxide diffusing from the anode to the cathode. In this work we describe a way to separate the distribution of the two fractions under real DMFC operating conditions. As a results we found that with low methanol concentrations (<1 M) and high current densities the amount of carbon dioxide passing from the anode to the cathode can even be higher than the amount of carbon dioxide formed at the cathode by methanol oxidation.
The transport properties and the swelling behaviour of NAFION and different sulfonated polyetherketones are explained in terms of distinct differences on the microstructures and in the pKa of the acidic functional groups. The less pronounced hydrophobic/hydrophilic separation of sulfonated polyetherketones compared to NAFION corresponds to narrower, less connected hydrophilic channels and to larger separations between less acidic sulfonic acid functional groups. At high water contents, this is shown to significantly reduce electroosmotic drag and water permeation whilst maintaining high proton conductivity. Blending of sulfonated polyetherketones with other polyaryls even further reduces the solvent permeation (a factor of 20 compared to NAFION), increases the membrane flexibility in the dry state and leads to an improved swelling behaviour. Therefore, polymers based on sulfonated polyetherketones are not only interesting low-cost alternative membrane material for hydrogen fuel cell applications, they may also help to reduce the problems associated with high water drag and high methanol cross-over in direct liquid methanol fuel cells (DMFC). The relatively high conductivities observed for oligomers containing imidazole as functional groups may be exploited in fully polymeric proton conducting systems with no volatile proton solvent operating at temperatures significantly beyond 100°C, where methanol vapour may be used as a fuel in DMFCs.
The availability of stable polymeric membranes with good proton conductivity at medium temperatures is very important for the development of methanol PEM fuel cells. In view of this application, a systematic investigation of the conductivity of Nafion 117 and sulfonated polyether ether ketone (S-PEEK) membranes was performed as a function of relative humidity (r.h.) in a wide range of temperature (80–160°C). The occurrence of swelling/softening phenomena at high r.h. values prevented conductivity determinations above certain temperatures. Nevertheless, when r.h. was maintained at values lower than 80%, measurements were possible up to 160°C. The results showed that Nafion is a better proton conductor than S-PEEK at low r.h. values, especially at temperatures lower than 120°C. The differences in conductivity were, however, leveled out with the increasing r.h. and temperature. While at 100°C and 35% r.h. the conductivity of S-PEEK 2.48 was about 30 times lower than the conductivity of Nafion, both membranes reached a comparable conductivity (4×10−2 S cm−1) at 160°C and 75% r.h. The effect of superacidity and crystallization of the polymers on the conductivity, as well as the possibility of using Nafion and S-PEEK membranes in medium temperature fuel cells, are discussed.
The resistance of the Nafion® 117 membrane in and polymer electrolyte fuel cells (PEFCs) has been measured in situ using fast current pulses. The dependence of the membrane resistance on current density, temperature, pressure and flow-field design was investigated. It was found that, independent of other variations, the resistance increases with increasing current density. When the current density in the cell is increased from 0.2 to 0.7 A cm−2, the membrane resistance increases by up to 22%. Even on open circuit the resistance at 60°C is 15%–35% higher than that measured ex situ, indicating that the membrane is not fully hydrated under the fuel cell operating conditions. The resistance on open circuit also depends on the design of the flow field. In a design with forced gas convection the resistance at 60°C is substantially higher (210 mΩ cm2) than in a design without forced convection (186 mΩ cm2).
The direct methanol fuel cell (DMFC) has been discussed recently as an interesting option for a fuel-cell-based mobile power supply system in the power range from a few watts to several hundred kilowatts. In contrast to the favoured hydrogen-fed fuel cell systems (e.g. the polymer electrolyte membrane fuel cell, PEMFC), the DMFC has some significant advantages. It uses a fuel which is, compared to hydrogen, easy to handle and to distribute. It also comprises a fairly simple system design compared to systems utilising liquid fuels (like methanol) to produce hydrogen from them by steam reforming or partial oxidation to filially feed a standard PEMFC. Nevertheless. many severe problems still exist for the DMFC, hindering its competitiveness as an option to hydrogen-fed fuel cells. This work reviews the major research activities concerned with the DMFC by highlighting the problems (slow kinetics of the anodic methanol oxidation, methanol permeation through the membrane, carbon dioxide evolution at the anode) and their possible solutions. Special attention is devoted to the steady state and dynamic simulation of these fuel cell systems.
Quality of life (QOL) as an outcome for cancer treatment has been studied primarily in urban populations. Yet, descriptions of rural dwellers suggest that their perception of QOL may differ from that of their urban counterparts. The purpose of this study was to examine QOL in people with a cancer diagnosis of at least 1 month duration in two similar rural northeastern states. The Functional Assessment of Cancer Therapy General (FACT G) scale was completed by 344 respondents. The mean QOL score was 89.41 +/- 16.55. State of residence, gender, known recurrence, and marital status were significant predictors of QOL, explaining 18.3% of the variance in this study. Age, education level, income, type of cancer, living arrangements, and time since diagnosis were not predictive. The QOL scores in this rural sample were higher than those reported earlier for predominantly urban dwellers. Future research is needed to understand these differences.