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1.
Sulfonated poly(ether ether ketone)s (SPEEKs) are substituted on the main chain of the polymer by nitro groups and blended with Nafion® to attain composite membranes. The sulfonation, nitration and blending are achieved with a simple, inexpensive process, and the blended membranes containing the nitrated SPEEKs reveal a liquid-liquid phase separation. The blended membranes have a lower water uptake compared to recast Nafion®, and the methanol permeability is reduced significantly to 4.29 × 10−7-5.34 × 10−7 cm2 s−1 for various contents of nitrated SPEEK for S63N17, and 4.72 × 10−7-7.11 × 10−7 cm2 s−1 for S63N38, with a maximum proton conductivity of ∼0.085 S cm−1. This study examines the single-cell performance at 80 °C of Nafion®/nitrated SPEEK membranes with various contents of nitrated SPEEK and a degree of nitration of 23-25 mW cm−2 for S63N17 and 24-29 mW cm−2 for S63N38. Both the power density and open circuit voltage are higher than those of Nafion® 115 and recast Nafion®.  相似文献   

2.
In the present study, a series of the crosslinked sulfonated poly(ether ether ketone) (SPEEK) proton exchange membranes were prepared. The photochemical crosslinking of the SPEEK membranes was carried out by dissolving benzophenone and triethylamine photo-initiator system in the membrane casting solution and then exposing the resulting membranes after solvent evaporation to UV light. The physical and transport properties of crosslinked membranes were investigated. The membrane performance can be controlled by adjusting the photoirradiation time. The experimental results showed that the crosslinked SPEEK membranes with photoirradiation 10 min had the optimum performance for proton exchange membranes (PEMs). Compared with the non-crosslinked SPEEK membranes, the crosslinked SPEEK membranes with photoirradiation 10 min markedly improved thermal stabilities and mechanical properties as well as hydrolytic and oxidative stabilities, greatly reduced water uptake and methanol diffusion coefficients with only slight sacrifice in proton conductivities. Therefore, the crosslinked SPEEK membranes with photoirradiation 10 min were particularly promising as proton exchange membranes for direct methanol fuel cell (DMFC) applications.  相似文献   

3.
Novel main-chain-type and side-chain-type sulphonated poly(ether ether ketone)s (MS-SPEEKs) are synthesised by reacting the sulphonic acid groups of pristine SPEEKs with 2-aminoethanesulphonic acid to improve the nano-phase separated morphology of the material. 1H NMR and FT-IR spectroscopy are employed to determine the structure and composition of main-chain-type and side-chain-type sulphonated polymers. Flexible and tough membranes with reasonable thermal properties are obtained. The MS-SPEEKs show good hydrolytic stability, and water uptake values ranging from 15% to 30% are observed. Compared to Nafion 117®, the methanol permeability of the MS-SPEEKs is dramatically reduced to 8.83 × 10−8 cm2 s−1 to 3.31 × 10−7 cm2 s−1. The proton conductivity increases with increasing temperature, reaching 0.013-0.182 S cm−1. A maximum power density and open circuit voltage of 115 mW cm−2 and 0.830 V are obtained at 80 °C, respectively, which is significantly greater than the values generated with Nafion 117®. The introduction of pendent side-chain-type sulphonic acid groups increases the single-cell performance by more than approximately 20%; thus, the lower water diffusivity, methanol permeability, electro-osmotic drag coefficient and high cell performance indicated that MS-SPEEK is a promising candidate for DMFC applications.  相似文献   

4.
In this paper, the blend membranes based on sulfonated poly(ether ether ketone) and sulfonated cyclodextrin as the proton conducting membranes for DMFCs usage are prepared and investigated. The incorporation of sulfonated cyclodextrin in SPEEK membranes is evaluated by the characteristic absorptions of FT-IR spectra. Thermal stability and micro-morphology of the blend membranes are determined by thermogravimetry analysis and scanning electron microscope tests. The properties of the blend membranes are investigated such as swelling behavior, methanol permeability and proton conduction as function of the fraction of sulfonated cyclodextrin. The methanol crossover could be suppressed by the incorporation of sulfonated cyclodextrin and the methanol permeability decreases when the methanol concentration increases from 2.5 M to 20 M. Proton conduction is also promoted by the introduction of sulfonated cyclodextrin and the proton conductivity increases with the increase of sulfonated cyclodextrin content. The calculated activation energy for proton conduction of the blend membranes is very low and the maximum value is 4.20 kJ mol−1, which is much lower than that of Nafion 115 (9.15 kJ mol−1, measured in our experiments). These data indicate that proton can transport easily through the blend membranes. The selectivity of the blend membranes, a compromise between proton conductivity and methanol permeability, is much higher than that of Nafion 115 at the sulfonated cyclodextrin content above 15 wt.%. The blend membranes with 15, 20, and 25 wt.% of sulfonated cyclodextrin are assembled in the practical DMFCs and their polarization curves with 2.5 M and 8.0 M methanol solution are determined, respectively. The membrane with 20 wt.% sulfonated cyclodextrin reaches the highest power density of 29.52 mW cm−2 at 120 mA cm−2 and 8.0 M methanol solution. These results suggest the potential usage of the SPEEK membranes incorporating with sulfonated cyclodextrin in DMFCs.  相似文献   

5.
A series of cross-linked membranes based on SPEEK/Nafion have been prepared to improve methanol resistance and dimension stability of SPEEK membrane for the usage in the direct methanol fuel cells (DMFCs). Sulfonated diamine monomer is synthesized and used as cross-linker to improve the dispersion of Nafion in the composite membranes and decrease the negative effect of cross-linking on proton conductivity of membranes. FT-IR analysis shows that the cross-linking reaction is performed successfully. The effects of different contents of Nafion on the properties of cross-linked membranes are investigated in detail. All the cross-linked membranes show lower methanol permeability and better dimensional stability compared with the pristine SPEEK membrane. SPEEK-N30 with the 30 wt % Nafion shows a methanol permeability of 0.73 × 10−6 cm2 s−1 and a water uptake of 24.4% at 25 °C, which are lower than those of the pristine membrane. Meanwhile, the proton conductivity of SPEEK-N30 still remains at 0.041 S cm−1 at 25 °C, which is comparable to that of the pristine SPEEK membrane. All the results indicate that these cross-linked membranes based on SPEEK/Nafion show good prospect for the use as proton exchange membranes.  相似文献   

6.
Sulfonated poly(ether ether ketone) containing hydroxyl groups (SPEEK-OH) has been prepared for use as a proton exchange membrane (PEM) by reducing the carbonyl groups on the main chain of the polymers. With the goal of reducing water uptake and methanol permeability, a facile thermal-cross-linking process is used to obtain the cross-linked membranes. The properties of the cross-linked membranes with different cross-linked density are measured and compared with the pristine membrane. Notably, SPEEK-4 with the highest cross-linked density shows a water uptake of 39% and a methanol permeability of 2.52 × 10−7 cm2 s−1, which are much lower than those of the pristine membrane (63.2% and 5.37 × 10−7 cm2 s−1, respectively). These results indicate that this simple approach is very effective to prepare cross-linked proton exchange membranes for reducing water uptake and methanol permeability.  相似文献   

7.
Sulfonated titania submicrospheres (TiO2-SO3H) prepared through a facile chelation method are incorporated into sulfonated poly(ether ether ketone) (SPEEK) to fabricate organic-inorganic hybrid membranes with enhanced proton conductivity and reduced methanol permeability for potential use in direct methanol fuel cells (DMFCs). The pristine titania submicrospheres (TiO2) with a uniform particle size are synthesized through a modified sol-gel method and sulfonated using 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt as the sulfonation reagent. The sulfonation process is confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS). The hybrid membranes are systematically characterized in terms of thermal property, mechanical property, ionic exchange capacity (IEC), swelling behavior, and microstructural features. The methanol barrier property and the proton conductivity of the SPEEK/TiO2-SO3H hybrid membranes are evaluated. The presence of the fillers reduces methanol crossover through the membrane. Compared with the unsulfonated TiO2-doped membranes, the TiO2-SO3H-doped ones exhibit higher proton conductivity due to the additional sulfonic acid groups on the surface of TiO2. The hybrid membrane doped with 15 wt.% TiO2-SO3H submicrospheres exhibits an acceptable proton conductivity of 0.053 S cm−1 and a reduced methanol permeability of 4.19 × 10−7 cm2 s−1.  相似文献   

8.
Sulfonated poly(ether ether ketone)s (SPEEKs) were further substituted on the polymer main chain by nitration. All sulfonation and nitration were achieved with an inexpensive and simple post substitute reaction. The nitrated SPEEKs have a high glass transition temperature and thermal decomposition temperature, and a lower water uptake than SPEEK, which provides sufficient mechanical strength without swelling in the direct methanol fuel cell (DMFC) application. The methanol permeability of nitrated SPEEKS is reduced to 1.76 × 10−7 cm2 s−1 for S53N22 and 1.86 × 10−7 cm2 s−1 for S63N17 with no loss of conductivity in the DMFC application, and a proton conductivity that reached 0.026 S cm−1. The nitrated SPEEK membranes satisfy the requirements of proton-exchange membranes for the DMFC.  相似文献   

9.
Sulfonated poly(ether ether ketone) has been investigated as an ionomer in the catalyst layer for direct methanol fuel cells (DMFC). The performance in DMFC, electrochemical active area (by cyclic voltammetry), and limiting capacitance (by impedance spectroscopy) have been evaluated as a function of the ion exchange capacity (IEC) and content (wt.%) of the SPEEK ionomer in the catalyst layer. The optimum IEC value and SPEEK ionomer content in the electrodes are found to be, respectively, 1.33 meq. g−1 and 20 wt.%. The membrane-electrode assemblies (MEA) fabricated with SPEEK membrane and SPEEK ionomer in the electrodes are found to exhibit superior performance in DMFC compared to that fabricated with Nafion ionomer due to lower interfacial resistance in the MEA as well as larger electrochemical active area. The MEAs with SPEEK membrane and SPEEK ionomer also exhibit better performance than that with Nafion 115 membrane and Nafion ionomer due to lower methanol crossover and better electrode kinetics.  相似文献   

10.
To prepare a cross-linked proton exchange membrane with low methanol permeability and high proton conductivity, poly (vinyl alcohol) is first blended with sulfonated poly (arylene ether ketone) bearing carboxylic acid groups (SPAEK-C) and then heated to induce a cross-linking reaction between the carboxyl groups in SPAEK-C and the hydroxyl groups in PVA. Fourier transform infrared spectroscopy is used to characterize and confirm the structure of SPAEK-C and the cross-linked membranes. The proton conductivity of the cross-linked membrane with 15% PVA in weight reaches up to 0.18 S cm−1 at 80 °C (100% relative humidity), which is higher than that of Nafion membrane, while the methanol permeability is nearly five times lower than Nafion. The ion-exchange capacity, water uptake and thermal stability are investigated to confirm their applicability in fuel cells.  相似文献   

11.
In the present study, the self-humidifying nanocomposite membranes based on sPEEK and Cs2.5H0.5PW12O40 supported Pt catalyst (Pt-Cs2.5H0.5PW12O40 catalyst or Pt-Cs2.5) and their performance in proton exchange membrane fuel cells with dry reactants has been investigated. The XRD, FTIR, SEM-EDXA and TEM analysis were conducted to characterize the catalyst and membrane structure. The ion exchange capacity (IEC), water uptake and proton conductivity measurements indicated that the sPEEK/Pt-Cs2.5 self-humidifying nanocomposite membranes have higher water absorption, acid and proton-conductive properties compared to the plain sPEEK membrane and Nafion-117 membrane due to the highly hygroscopic and acidy properties of Pt-Cs2.5 catalyst. The single cells employing the sPEEK/Pt-Cs2.5 self-humidifying nanocomposite membranes exhibited higher cell OCV values and cell performances than those of plain sPEEK membrane and Nafion-117 membrane under dry or wet conditions. Furthermore, the sPEEK/Pt-Cs2.5 self-humidifying nanocomposite membranes showed good water stability in aqueous medium. After investigation of several membranes such as sPEEK and sPEEK/Pt-Cs2.5 membranes, the self-humidifying nanocomposite membrane with sulfonation degree of 65.12% for its sPEEK and 15 wt.% of catalyst with 1.25 wt.% Pt within catalyst was found to be the best proton exchange membrane for fuel cell applications. This self-humidifying nanocomposite membrane has a higher single cell performance than the Nafion-117 which was frequently used as a proton exchange membrane for fuel cell applications.  相似文献   

12.
The proton exchange membrane (PEM) was synthesized using polyethersulfone (PES), sulfonated poly (ether ether ketone) (SPEEK) and nanoparticles. The metal oxide nanoparticles such as Fe3O4, TiO2 and MoO3 were added individually to the polymer blend (PES and SPEEK). The polymer composite membranes exhibit excellent features regarding water uptake, ion exchange capacity and proton conductivity than the pristine PES membrane. Since the presence of sulfonic acid groups provides by added SPEEK and the unique properties of inorganic nanoparticles (Fe3O4, TiO2 and MoO3) helps to interconnect the ionic domain by the absorption of more water molecules thereby enhance the conductivity value. The proton conductivity of PES, SPEEK, PES/SPEEK/Fe3O4, PES/SPEEK/TiO2 and PES/SPEEK/MoO3 membranes were 0.22 × 10?4 S/cm, 5.18 × 10?4 S/cm, 3.57 × 10?4 S/cm, 4.57 × 10?4 S/cm and 2.67 × 10?4 S/cm respectively. Even though the blending of PES with SPEEK has reduced the conductivity value to a lesser extent, hydrophobic PES has vital role in reducing the solvent uptake, swelling ratio and improves hydrolytic stability. Glass transition temperature (Tg) of the membranes were determined from DSC thermogram and it satisfies the operating condition of fuel cell system which guarantees the thermal stability of the membrane for fuel cell application.  相似文献   

13.
In this article, novel branched sulfonated poly(ether ether ketone)s (Br-SPEEK) containing various amounts of 1,3,5-tris(4-fluorobenzoyl)benzene as the branching agent have been successfully prepared. Compared with the traditional linear polymer membranes, the membranes prepared by Br-SPEEK showed improved mechanical strength, excellent dimensional stability and superior oxidative stability with similar proton conductivity. Notably, the Br-SPEEK-10 membrane began to break after 267 min in Fenton's reagent at 80 °C, which was 4 times longer than that of the L-SPEEK. Although the proton conductivity decreased with the addition of the branching agent, satisfying methanol permeability value was observed (down to 6.3 × 10−7 cm2 s−1), which was much lower than Nafion 117 (15.5 × 10−7 cm2 s−1). All the results indicated that the novel branched sulfonated poly(ether ether ketone)s membrane was potential candidate as proton conductive membranes for application in fuel cells.  相似文献   

14.
A diamine-terminated polybenzimidazole oligomer (o-PBI) has been synthesized for introducing the benzimidazole groups (BI) into sulfonated poly(ether ether ketone) (SPEEK) membranes. SPEEK/o-PBI/4,4′-diglycidyl(3,3′,5,5′-tetramethylbiphenyl) epoxy resin (TMBP) composite membranes in situ polymerization has been prepared for the purpose of improving the performance of SPEEK with high ion-exchange capacities (IEC) for the usage in the direct methanol fuel cells (DMFCs). The composite membranes with three-dimensional network structure are obtained through a cross-linking reaction between PBI oligomer and TMBP and the acid-base interaction between sulfonic acid groups and benzimidazole groups. Resulting membranes show a significantly increasing of all of the properties, such as high proton conductivity (0.14 S cm−1 at 80 °C), low methanol permeability (2.38 × 10−8 cm2 s−1), low water uptake (25.66% at 80 °C) and swelling ratio (4.11% at 80 °C), strong thermal and oxidative stability, and mechanical properties. Higher selectivity has been found for the composite membranes in comparison with SPEEK. Therefore, the SPEEK/o-PBI/TMBP composite membranes show a good potential in DMFCs usages.  相似文献   

15.
Novel poly(arylene ether sulfone) copolymers containing different amount of pendant sulfonic acid groups have been synthesized by an aromatic substitution polymerization reaction. The properties of the synthesized sulfonated poly(diphenylsulfone-diphenol) (SDPS-DP) copolymers depend on the sulfonic acid group content in the copolymers. Although all the copolymers show good thermal stability, low liquid uptake, and low methanol crossover, they exhibit lower proton conductivity than Nafion or sulfonated poly(ether ether ketone) (SPEEK). Taking advantage of the low methanol crossover, multilayer membranes consisting of the SDPS-DP copolymer as a methanol-barrier center layer and SPEEK as the proton-conducting outer layers have been fabricated and characterized. The SPEEK/SDPS-DP-60/SPEEK multilayer membranes with an optimized center layer thickness are found to exhibit better performance and higher power density in DMFC than plain SPEEK and Nafion 115 membranes.  相似文献   

16.
In this paper, proton exchange membranes for direct methanol fuel cells were prepared by blending sulfonated poly(arylene ether sulfone) with poly (vinylidene fluoride-co-hecafluoropropylene)(PVdF-HFP) and polyethersulfone (PES) to decrease methanol permeability while maintaining high proton conductivity. The content of the second polymer, such as PES and PVdF, in the blend membranes was controlled at 10–40 wt% based on SPAES. In order to investigate the effects of the second polymer content in the blended membranes, parameters of the prepared membranes related to fuel cell performance were characterized, including their morphology, mechanical properties, methanol permeability, and proton conductivity. Surface roughness of the blend membrane was increased by the introduction of a hydrophobic polymer. Mechanical properties of the PES/SPAES blend membrane were improved owing to interaction between the sulfonic acid groups in SPAES and PES. However, the tensile strength of the PVdF/SPAES blend membrane was decreased by due to the poor compatibility of SPAES and PVdF. The methanol permeability in the blended membranes decreased with increasing content of PES and PVdF. The SPAES/PES blend membranes exhibited good proton conductivity and lower methanol permeability than the SPAES membrane. The SVdF15 blend membrane showed the highest selectivity due to the absence of methanol crossover and a small decrease of proton conductivity. These blend membranes are suitable for DMFC applications.  相似文献   

17.
An easy and effective method for producing low methanol-crossover membranes is developed by dispersing sulfonated graphene oxide (SGO) into a Nafion matrix. A SGO/Nafion mixture with low SGO content exhibits unique viscosity behavior and allows for better SGO dispersion within the Nafion. After film casting, the composite membranes show lower methanol and water uptakes, a reduced swelling ratio, improved proton conductivity in low relative humidity, and extremely high methanol selectivity, which can be implemented in direct methanol fuel cells (DMFCs). The regular backbone of the composite membrane shows a higher storage modulus, increased α-relaxation (transition temperature), and improved tolerance to pressure during membrane electrode assembly (MEA). The small angle X-ray spectra indicate the shrinkage of the ionic clusters in the composite membranes, which thus reduce methanol crossover. The hybrid membranes applied to DMFCs demonstrate performances superior to that of the commercial Nafion 115 in 1 M and 5 M methanol solutions.  相似文献   

18.
In this study, a new type of cross-linked composite membrane is prepared and considered for its potential applications in direct methanol fuel cell. Nafion and sulfonated poly(arylene ether ketone) bearing carboxylic acid groups (SPAEK-C) are blended and subsequently cross-linked by a Friedel-Craft reaction using the carboxylic acid groups in the SPAEK-C to achieve lower methanol permeability. The perfluoroalkyl sulfonic acid groups of Nafion act as a benign solid catalyst, which assist the cross-linking of SPAEK-C. The physical and chemical characterizations of the cross-linked composite membranes are performed by varying the contents of SPAEK-C. The c-Nafion-15% membrane exhibits appropriate water uptake (10.49-25.22%), low methanol permeability (2.57 × 10−7 cm2 s−1), and high proton conductivity (0.179 S cm−1 at 80 °C). DSC and FTIR analyze suggest the cross-linking reaction. These results show that the self-cross-linking of SPAEK-C in the Nafion membrane can effectively reduce methanol permeability while maintaining high proton conductivity.  相似文献   

19.
A reinforced composite membrane based on SPEEK (sulfonated poly ether ether ketone) and porous PTFE substrate (polytetrafluoroethylene) is fabricated and investigated for proton exchange membrane fuel cell application. In order to improve the combination between SPEEK polymer and PTFE matrix, PTFE substrate is hydrophilically pretreated by naphthalene sodium solution. The experimental results indicate that SPEEK can impregnate into treated PTFE substrate (abbreviated as trPTFE) more easily. The variation of PTFE surface property before and after treatment is characterized by water contact angle experiment and ATR-FTIR technique. The impregnated status of SPEEK polymer in PTFE matrix is also characterized by ATR-FTIR. According to the appearance photo of two composite membranes, it is showed that SPEEK/trPTFE composite membrane has more uniform and homogeneous morphology. Moreover, the mechanical property of SPEEK/trPTFE composite membrane also has an advantage over pristine SPEEK membrane. Due to the reinforced effect of trPTFE substrate, thinner composite membrane can be applied in single cell evolution and achieves better performance as a result.  相似文献   

20.
A series of sulfonated poly(fluorenyl ether nitrile oxynaphthalate) (SPFENO) copolymers with different degree of sulfonation (DS) are synthesized via nucleophilic polycondensation reactions with commercially available monomers. Incorporation of the naphthalanesulfonate group into the copolymers and their copolymer structures are confirmed by 1H NMR spectroscopy. Thermal stability, mechanical properties, water uptake, swelling behavior, proton conductivity and methanol permeability of the SPFENO membranes are investigated with respect to their structures. The electrochemical performance of a direct methanol fuel cell (DMFC) assembled with the SPFENO membrane was evaluated and compared to a DMFC with a Nafion 117 membrane. The DMFC assembled with the SPFENO membrane of proper DS exhibits better electrochemical performance compared to the Nafion 117-based cell.  相似文献   

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