Basicity‐based screening of aniline derivative for composite proton exchange membranes

The aim of this study was to find a suitable aniline derivative to develop composite sulfonated poly(ether ether ketone) (SPEEK) membranes and detail evaluation of their physico‐ and electrochemical properties. The hypothesis was high basicity of the aniline derivatives could form good composite membranes with better physicochemical and electrochemical properties. To assess the basicity we measured the zeta potentials of the polymers and correlated them with ion‐exchange capacities, water uptakes, transport numbers, water‐diffusion coefficients, conductivities, and methanol permeabilities. The obtained values of zeta potentials at pH 7 were 6.52, ?14.66, ?25.17, and ?28 for SPEEK/polynaphthalene (PNAPH), SPEEK/polyanisidine (PANIS), SPEEK/polyaniline (PANI), and SPEEK/polyxylindine (PXYL), respectively supports the hypothesis and strongly suggests polyaniline derivative's basicity‐dependent properties. Of the four derivatives (PNAPH, PANIS, PANI, and PXYL), the SPEEK/PXYL composite membrane had the lowest methanol permeability of 1 × 10^?4 cm²/s and highest proton conductivity of 161 mS/cm. These values are far better than the neat SPEEK and SPEEK/PANI composite. The suitability of SPEEK/PXYL can be explained by the high basicity of the PXYL composite membrane, which leads to the formation of effective Debye spheres, meaning that the ionic complex can interact with surrounding hydronium ions and form hydrophilic channels resulting in high proton conductivity and low methanol permeability. These results suggest that SPEEK/PXYL is a highly suitable membrane for methanol fuel cells or other electrochemical applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43978.     

Study of high-temperature proton exchange membrane through one-step encapsulation of ionic liquid in sulfonated poly(ether ether ketone)

The proton exchange membrane (PEM) is the core component of a high-performance proton exchange membrane fuel cell (PEMFC). Since the traditional PEM has the disadvantages of poor cell performance and high cost, a new kind of PEM with good proton conductivity, low cost and simple preparation should be explored. In this paper, several different binary hybrid membranes were successfully prepared through one-step encapsulation of different ionic liquids (ILs) in sulfonated poly(ether ether ketone) (SPEEK). The prepared membranes were characterized by scanning electron microscope (SEM), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), proton conductivity measurements and dynamic mechanical analysis (DMA). SEM images showed that ILs were fully doped into SPEEK. FT-IR and XPS proved that SPEEK and IL formed a new chemical bond combined with intermolecular hydrogen bonds. The TG results showed that the binary hybrid membranes could maintain stability even at 300°C. The water uptake and swelling ratio showed that the water absorption capacity of the binary composite membrane played a vital role in improving proton conductivity. The proton conductivity study showed that ILs doping also helped to improve the proton conductivity of the SPEEK membrane. When the doping amount of IL was maintained at 30 wt.%, it has the highest proton conductivity, 25 mS cm⁻¹ at 120°C. It was proved that anhydrous hybrid membrane tetraphenyl imidazole sulfate/SPEEK ([IM2][H₂PO₄]/SPEEK) could be used in PEMFC at medium temperature.     

The Preparation of Metal–Organic-Framework/Boron Phosphate Hybrid Materials for Improved Performances in Proton Exchange Membranes

New types of metal–organic framework based hybrid materials are designed and prepared, which involving the hybridization of various content of boron phosphate (BPO₄) with the precursor of HKUST-1. The structure of obtained HKUST-1/BPO₄ hybrid materials (HB) is fully investigated, and then applied to construct sulfonated poly (ether ether ketone) (SPEEK) based proton exchange membranes (SPEEK/HB). Owing to effective interactions between hybrid materials and SPEEK matrix, the achieved composite membranes reflect a considerable improvement in mechanical and thermal stability, oxidative stability, methanol permeation, and proton conductivity. In particular, the tensile strength of SPEEK/HB-20 composite membrane is 41.3 MPa, which is 1.5 times higher than pristine SPEEK, and the methanol permeability reduced to one-third of SPEEK at the same time. The SPEEK/HB-10 displays the highest proton conductivity of 37.4 mS cm⁻¹ at 80 °C, which is obviously higher than pristine SPEEK. These results reveal that the hybridization of HKUST-1 with BPO₄ provide a promising candidate in the modification of proton exchange membranes (PEMs), and this strategy also possess great application potential in other types of MOFs-based hybrid materials.     

Non-fluorinated hybrid composite membranes based on polyethylene glycol functionalized polyhedral oligomeric silsesquioxane [PPOSS] and sulfonated poly(ether ether ketone) [SPEEK] for fuel cell applications

Novel hybrid composite membranes were prepared by blending poly(ethylene glycol) functionalized polyhedral oligomeric silsesquioxane [PPOSS] as nanofiller in varying concentration ranging from 1 to 5% (w/w) into sulfonated poly(ether ether ketone) [SPEEK] with degree of sulfonation ～55% for proton exchange membrane fuel cells [PEMFCs]. The effect of incorporation of PPOSS into SPEEK matrix was investigated in terms of thermomechanical and morphological properties, water uptake and proton conductivity of SPEEK. All the composite membranes were thermally and mechanically stable up to 250 °C. Transmission electron microscopy (TEM) revealed that the smallest particle size (～100 nm) of PPOSS was found for SPEEK membranes containing 2% (w/w) PPOSS where as agglomeration (～300 nm) was observed at higher loadings of PPOSS. The proton conductivity was found to be dependent on the morphology and was independent of the amount of water present in the membranes. At 100 °C and 100% RH, the highest proton conductivity (47 mS/cm compared 34 mS/cm for neat SPEEK i.e. an increase of ～51%) was recorded at 2% (w/w) PPOSS contents followed by a decrease on further addition of PPOSS.The water uptake of composite membranes increased with concentration of PPOSS while maintaining their hydrolytic stability at 100 °C for more than 24 h.     

Sulfonated poly(arylene ether ketone)s prepared by direct copolymerization as proton exchange membranes: Synthesis and comparative investigation on transport properties

Sulfonated poly(aryl ether ketone)s (SPAEK) copolymers were synthesized by aromatic nucleophilic polycondensation from 3,3′, 5,5′‐tetramethyl‐4, 4′–biphenol, 1,4‐bis(4‐fluorobenzoyl) benzene, and disulfonated difluorobenzophenone. The SPAEK membranes did not exhibit excessive swelling in hot water and at the same time show the proton conductivities in the range of 0.030 S/cm to 0.099 S/cm at 80°C. The methanol diffusion coefficients of the SPAEK membranes were in the range of 4.7 × 10^?7 to 8.1 × 10^?7cm²/s measured at 25°C. The transport properties of this series of SPAEK copolymers were compared to poly(aryl ether ether ketone)s (SPEEK), poly(aryl ether ether ketone ketone)s (SPEEKK), and Nafion® membranes. It was found that the transport properties (including proton conductivity and methanol permeability) follows the trend of SPEEKK‐60 < SPAEK‐60 < SPEEK‐60 < Nafion® 117, the order of which is also attributed to the differences in the chemical structure of the polymers and the membrane morphology. In general, this novel series of SPAEK membranes possess various advantages, such as low cost of the initial monomers, high thermal and mechanical stability, and low methanol permeability while simultaneously possessing sufficient proton conductivity, which makes them notably promising as proton exchange membrane (PEM) materials in direct methanol fuel cell (DMFC) applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Sulfonated polyether ether ketone composite proton exchange membranes incorporated with a novel hierarchical-structure hybrid nanofiller consisting solid superacid zirconium phosphate and CNTs

How to simultaneously improved the proton conductivity and mechanical strength is a key problem facing currently used proton exchange membranes (PEMs). Herein, a solid inorganic superacid-zirconium phosphate (ZrP) with a two-dimensional layer structure was combined with one-dimensional carbon nanotubes (CNTs) to prepare hybrid nanofiller ZrP-CNTs by an in situ chemical deposition method. The new hybrid nanofiller was then applied to modify sulfonated polyether ether ketone (SPEEK), a widely used PEM matrix, to obtain a series of composite membranes. The structure and properties of the membranes were fully characterized by SEM, XRD, FTIR, TG, tensile properties, and proton conductivity. The results showed that the proton conductivities of the membranes were significantly improved due to the addition of super solid acid-ZrP that has abundant proton sources or proton sites. Moreover, the composite membranes exhibited better mechanical properties and thermal stability than those of pure SPEEK membrane, owing to the great interface interaction and good compatibility between ZrP-CNTs and SPEEK. The composite membrane (2 wt% ZrP-CNTs) demonstrated the optimal comprehensive performance. Its proton conductivity was 36.63 mS cm⁻¹ and its tensile strength was 37.56 MPa, which was 70% and 10%, respectively, higher than those of the pure SPEEK membrane under the same condition.     

A convenient crosslinking method for sulfonated poly(ether ether ketone) membranes via friedel–crafts reaction using 1,6‐dibromohexane and aluminum trichloride

In this study, sulfonated poly(ether ether ketone) (SPEEK) was very efficiently crosslinked via a Friedel–Craft reaction using 1,6‐dibromohexane and AlCl₃. The resulting crosslinked SPEEK (c‐SPEEK) membranes exhibited improved dimensional stability, thermal and chemical stability, and mechanical strength with slight reduction in the elongation. The methanol permeability was reduced by approximately two orders of magnitude by the crosslinking reaction. The proton conductivities of c‐SPEEK membranes were greater than Nafion‐212 in the temperature range of 30–90°C. Overall, this new crosslinking method can be conveniently and efficiently applicable to most aromatic hydrocarbon polymer membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40695.     

Solution‐blown SPEEK/POSS nanofiber–nafion hybrid composite membranes for direct methanol fuel cells

This study aims to develop novel hybrid composite membranes (NHMs) by impregnating Nafion solution into the porous sulfonated poly(ether ether ketone)/polyhedral oligomeric silsesquioxanes (SPEEK/POSS) nanofibers (NFs). The composite membrane was prepared by solution blowing of a mixture of SPEEK/POSS solution. The characteristics of the SPEEK/POSS NFs and the NHMs, including morphology, thermal stability, and performance of membrane as PEMs, were investigated. The performance of NHMs was compared with that of Nafion117 and SPEEK/Nafion composite membranes. Results showed that the introduction of POSS improved the proton conductivity, water swelling, and methanol permeability of membranes. A maximum proton conductivity of 0.163 S cm^?1 was obtained when the POSS content was 6 wt % at 80°C, which was higher than that of Nafion117 and SPEEK/Nafion. NHMs could be used as proton exchange membranes (PEMs) for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42843.     

Sulfonated poly(ether ether ketone)/epoxy/phenol novolac blend proton‐exchange membranes with low methanol permeability

A crosslinked epoxy [4,4′‐diglycidyl‐(3,3′,5,5′‐tetramethylbiphenyl) epoxy resin (TMBP)], cured by phenol novolac (PN), was introduced into a sulfonated poly(ether ether ketone) (SPEEK) membrane (ion‐exchange capacity = 2.0 mequiv/g) with a casting‐solution, evaporation, and heating crosslinking method to improve the mechanical properties, dimensional stability, water retention, and methanol resistance. By Fourier transform infrared analysis, the interactions between the sulfonic acid groups and hydroxyl groups in the blend membranes were confirmed. The microstructure and morphology of the blend membranes were investigated with atomic force microscopy. As expected, the blend membranes showed excellent mechanical properties, good thermal properties (thermal stability above 200°C), lower swelling ratios (1.4% at 25°C and 7.0% at 80°C), higher water retention (water diffusion coefficient = 9.8 × 10^?6 cm²/s), and a lower methanol permeability coefficient (3.6 × 10^?8 cm²/s) than the pristine SPEEK membrane. Although the proton conductivity of the blend membranes decreased, a higher selectivity (ratio of the proton conductivity to the methanol permeability) was obtained than that of the pristine SPEEK membrane. The results showed that the SPEEK/TMBP/PN blend membranes could have potential use as proton‐exchange membranes in direct methanol fuel cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nanostructure and properties of proton‐conducting sulfonated poly(ether ether ketone) (SPEEK) and zirconia–SPEEK hybrid membranes for direct alcohol fuel cells: effect of the nature of swelling solvent and incorporation of heteropolyacid

The influence, on membrane nanostructure and properties, of water or ethanol as swelling solvent of sulfonated poly(ether ether ketone) (SPEEK) and zirconia–SPEEK hybrid membranes prepared using the sol–gel process has been investigated. Independent of the solvent, small‐angle X‐ray scattering measurements reveal the existence of a two‐level hierarchical structure in SPEEK of greater sulfonation level, consisting of solvent‐swelled spatially correlated primary SO₃H‐rich ionic clusters of around 15 Å in size, forming larger secondary aggregates well dispersed in the PEEK matrix. The size of the primary nanodomains and the connectivity between domains are determining parameters for protonic conductivity, solvent swelling ability and permeability of the membranes. For both SPEEK and zirconia–SPEEK membranes containing ethanol, the pronounced affinity of ethanol molecules with SPEEK leads to an increase in the size of ionic clusters and of the number of connecting channels between clusters compared to membranes containing water. This promotes solvent swelling and proton conductivity. The increase in permeability to water induced by incorporation of ethanol in place of water in both polymeric and hybrid membranes is less in the hybrid membranes. This result suggests that the potential use of zirconia–SPEEK hybrid membranes in direct alcohol fuel cells is more promising than that of pure SPEEK, due not only to the less probable alcohol and water penetration in the membranes associated with their lower permeability, but also to the fact that an eventual penetration of alcohol in hybrid membranes should reduce the risk of cathode flooding compared to zirconia‐free SPEEK membranes. Copyright © 2011 Society of Chemical Industry     

Effect of clay modification on the structure and properties of sulfonated poly(ether ether ketone)/clay nanocomposites

Sulfonated poly(ether ether ketone) (SPEEK)/clay hybrid membranes were prepared using three types of commercially available clays, the sodium montmorillonite (IC), hydrophobic organo‐clay with long alkyl chains (OC), and organo‐clay with carboxylic acid end groups (HC). It was found that the SPEEK/HC hybrid membranes achieved the best clay dispersion, with the exfoliation of the clay nano‐platelets when the filler loading was < 10 wt%. The incorporation of the carboxylic acid groups in clay layers also improved the connectivity between the ionic clusters in the membrane, resulting in higher proton conductivity without compromising the dimensional stability of membranes. The selectivity higher than the pristine SPEEK membranes was obtained for the SPEEK/HC hybrid membranes at low filler loading (<10 wt%), with higher proton conductivity and similar methanol permeability. POLYM. COMPOS., 37:2632–2638, 2016. © 2015 Society of Plastics Engineers     

Polymer electrolyte membranes prepared by EB‐crosslinking of sulfonated poly(ether ether ketone) with 1,4‐butanediol

Crosslinked sulfonated poly(ether ether ketone) (SPEEK) membranes were prepared through the electron beam (EB)‐irradiation crosslinking of SPEEK/1,4‐butanediol under various irradiation conditions and used as a proton exchange membrane (PEM) for fuel cell applications. The crosslinked membranes were characterized by gel fraction, a universal testing machine (UTM), dynamic mechanical analysis (DMA), and small‐angle X‐ray scattering (SAXS). The gel fraction of the crosslinked membranes was used to estimate the degree of crosslinking, and the gel fraction was found to be increased with an increase of the crosslinker content and EB‐absorbed dose. The UTM results indicate that a brittle EB‐crosslinked membrane becomes more flexible with an increase in the crosslinker content. The DMA results show that the EB‐crosslinked membranes have well‐developed ionic aggregation regions and the cluster T_g of membranes decrease with an increase in the 1,4‐butanediol crosslinker content. The SAXS results show that the Bragg and persistence distance of crosslinked membranes increase with an increase in the crosslinker content. The proton conductivities of the EB‐crosslinked membranes were more than 9 × 10^?2 S/cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41760.     

Sulfonated poly(ether ether sulfone) copolymers for proton exchange membrane fuel cells

Novel aromatic sulfonated poly(ether ether sulfone)s (SPEESs) with tert‐butyl groups were synthesized by aromatic nucleophilic polycondensation of disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenylsulfone (SDCDPS), 4,4′‐dichlorodiphenylsulfone (DCDPS), and tert‐butylhydroquinone (TBHQ). The resulting copolymers showed very good thermal stability and could be cast into tough membranes. The morphology of the membranes was investigated with atomic force microscopy. The proton conductivity of SPEES‐40 membranes increased from 0.062 S/cm at 25°C to 0.083 S/cm at 80°C, which was higher than the 0.077 S/cm of Nafion 117 under the same testing conditions. These copolymers are good candidates to be new polymeric electrolyte materials for proton exchange membrane fuel cells. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1443–1450, 2007     

Sulfonated poly(ether ether ketone)/zirconium tricarboxybutylphosphonate composite proton-exchange membranes for direct methanol fuel cells

Sulfonated poly(ether ether ketone) (SPEEK) is a very promising alternative membrane material for direct methanol fuel cells. However, with a fairly high degree of sulfonation (DS), SPEEK membranes can swell excessively and even dissolve at high temperature. This restricts membranes from working above a high tolerable temperature to get high proton conductivity. To deal with this contradictory situation, insolvable zirconium tricarboxybutylphosphonate (Zr(PBTC)) powder was employed to make a composite with SPEEK polymer in an attempt to improve temperature tolerance of the membranes. SPEEK/Zr(PBTC) composite membranes were obtained by casting a homogeneous mixture of Zr(PBTC) and SPEEK in N,N-dimethylacetamide on a glass plate and then evaporating the solvent at 60°C. Many characteristics were investigated, including thermal stability, liquid uptake, methanol permeability and proton conductivity. Results showed significant improvement not only in temperature tolerance, but also in methanol resistance of the SPEEK/Zr(PBTC) composite membranes. The membranes containing 30 wt-% ∼ 40 wt-% of Zr(PBTC) had their methanol permeability around 10^-7 cm²·s^-1 at room temperature to 80°C, which was one order of magnitude lower than that of Nafion ^¯115. High proton conductivity of the composite membranes, however, could also be achieved from higher temperature applied. At 100% relative humidity, above 90°C the conductivity of the composite membrane containing 40 wt-% of Zr(PBTC) exceeded that of the Nafion ^¯115 membrane and even reached a high value of 0.36 S·cm^-1 at 160°C. Improved applicable temperature and high conductivity of the composite membrane indicated its promising application in DMFC operations at high temperature.     

Enhanced Proton Conductivity of Sulfonated Poly(ether ether ketone) Membrane Embedded by Dopamine‐Modified Nanotubes for Proton Exchange Membrane Fuel Cell

Design and fabrication of alternative proton exchange membrane (PEM) with high proton conductivity is crucial to the commercial application of PEM fuel cell. Inspired by the bioadhesion principle, dopamine‐modified halloysite nanotubes (DHNTs) bearing –NH₂ and –NH– groups are facilely synthesized by directly immersing natural halloysite nanotubes (HNTs) into dopamine aqueous solution under mild conditions. DHNTs are then embedded into sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare hybrid membranes. HNTs‐filled hybrid membranes are prepared for comparison. The microstructure and physicochemical properties of the membranes are extensively investigated. Fourier transform infrared analysis implies that ordered acid–base pairs (e.g., –S–O^–…⁺H–HN–, –S–O^–…⁺H–N–) are formed at SPEEK–DHNT interface through strong electrostatic interaction. In such a way, continuous surface‐induced ion‐channels emerge along DHNTs. Although the incorporation of DHNTs reduces the channel size, water uptake, and area swelling of the hybrid membranes, which in turn would reduce the vehicle‐type proton transfer, the acid–base pairs create continuous pathways for fast proton transfer with low energy barrier via Grotthuss mechanism. Consequently, DHNT‐filled hybrid membrane with 15% DHNTs achieves a 30% increase in proton conductivity and a 52% increase in peak power density of single cell when compared with SPEEK control membrane, particularly.     

Physical and electrochemical behaviors of directly polymerized sulfonated poly(arylene ether ketone sulfone)s proton exchange membranes with different backbone structures

Sulfonated poly(ether ether ketone sulfone) (SPEEKS) and sulfonated poly(ether ether ketone ketone sulfone) (SPEEKKS) copolymers with different degree of sulfonation (DS) were synthesized by aromatic nucleophilic polycondensation of disodium 3,3′‐disulfonate‐4,4′‐dichloro‐diphenylsulfone (SDCDPS), tertbutylhydroquione, and 4,4′‐difluorobenzophenone or 1,4′‐bi(4‐fluorobenzoyl) benzene. Prepared sulfonated copolymers were characterized by Fourier transform infrared spectra, thermogravimetric analysis, and differential scanning calorimetry. The transmission electron microscope was used to investigate the microstructure of membranes. The different distance between two adjacent sulfonic groups in two series of membranes resulted in different physical and electrochemical properties between two kinds of membranes with the same DS. The proton conductivity, ionic exchange capacity and water uptake of SPEEKS membranes were higher than those of SPEEKKS membranes while the mechanical strength of SPEEKS membranes was lower than that of SPEEKKS membranes at the same DS. Moreover, the SPEEKKS membranes with DS equals to 0.8 showed a good combination of a high proton conductivity (0.046 S/cm at 25°C, 0.061 S/cm at 80°C), acceptable water uptake (33–65 wt %), excellent mechanical strength (tensile strength reached 49.7 MPa), and good thermal properties (T_g above 250°C, T_d5% above 300°C). It suggested that this could be a promising membrane for proton exchange membrane fuel cell application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

DMFCs用SPEEK/SiOx-S复合质子交换膜

A sulfonated poly(ether ether ketone) (SPEEK) membrane with a fairly high degree of sulfonation (DS) can swell excessively and even dissolve at high temperature. To solve these problems, insolvable functionalized silica powder with sulfonic acid groups (SiOx-S) was added into the SPEEK matrix (DS 55.1%) to prepare SPEEK/ SiOx-S composite membranes. The decrease in both the swelling degree and the methanol permeability of the membranes was a dose-dependent result of addition of the SiOx-S powder. Pure SPEEK membrane swelled 52.6% at 80°C, whereas the SPEEK/SiOx-S (15%, by mass) membrane swelled only 27.3% at the same temperature. From room temperature to 80℃, all SPEEK/SPEEK/SiOx-S composite membranes had methanol permeability of about one order of magnitude lower than that of Nafion&#61650;115. Compared with pure SPEEK membranes, the addition of the SiOx-S powder not only leads to higher proton conductivity, but also increases the dimensional stability at higher temperatures, and greater proton conductivity can be achieved at higher temperature. The SPEEK/SiOx-S (20%, by mass) membrane could withstand temperature up to 145°C, at which in 100% relative humidity (RH) its proton conductivity exceeded slightly that of Nafion&#61650;115 membrane and reached 0.17 S&#8226;cm－1, while pure SPEEK mem-brane dissolved at 90°C. The SPEEK/SiOx-S composite membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.     

Synergistic effect of aluminium phosphate and tungstophosphoric acid on the physicochemical properties of sulfonated poly ether ether ketone nanocomposite membrane

This study explores the synergistic effect of aluminium phosphate (ALP) nanoparticles and tungstophosphoric acid (TPA) on the physicochemical properties of sulfonated poly ether ether ketone (SPEEK) nanocomposite membranes. SPEEK/TPA/ALP nanocomposite containing optimum TPA (10 wt %) and varying ALP content (3–10 wt %) are fabricated to investigate the effect of ALP nanoparticles on membrane properties. Experimental results reveal that nanocomposite membrane containing 3 wt % ALP nanoparticles and 10 wt % TPA exhibits 3.3 and 18.8 times higher proton conductivity compared to 10 wt % TPA filled SPEEK composite membrane and reference SPEEK membrane. ALP nanoparticles help in retaining water within the membranes and thus 59.4% reduction in water desorption rate is achieved compared to SPEEK/TPA membrane. The leaching of TPA is reduced by 34.5% which helps in retaining membrane properties. Membranes are thermally stable up to 200°C. Microstructure of the composite films is investigated by scanning electron microscope. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42952.     

Modified Sulfonated Poly(ether ether ketone) Based Mixed Matrix Membranes for Direct Methanol Fuel Cells

Mixed matrix membranes based on zeolite 4A‐methane sulfonic acid (MSA)‐sulfonated poly(ether ether ketone) (SPEEK) are evaluated as a potential polymer electrolyte membrane (PEM) for direct methanol fuel cells (DMFCs). Ion‐exchange capacity, sorption of water, and water–methanol mixture, proton conductivity, and methanol permeability for the mixed‐matrix membranes have been extensively investigated. The mixed‐matrix membranes are also characterized for their cross‐sectional morphology, mechanical, and thermal properties. DMFCs employing SPEEK‐MSA (20 wt.%) blend, zeolite 4A (4 wt.%)‐SPEEK‐MSA (20 wt.%) mixed matrix membranes deliver peak power densities of 130 and 159 mW cm^–2, respectively; while a peak power density of only 95 mW cm^–2 is obtained for the DMFC employing pristine SPEEK membrane at 70 °C. The results showed that these SPEEK based mixed matrix membranes exhibit higher DMFC performance and lower methanol permeability in comparison to Nafion‐117 membrane.     

Hydrophilic TiO2 decorated carbon nanotubes/sulfonated poly(ether ether ketone) composite proton exchange membranes for fuel cells

Sulfonated poly(ether ether ketone) (SPEEK) is currently considered to be one of the most potential candidates of commercial perfluorinated sulfonic acid proton exchange membranes. To balance the proton conductivity and mechanical properties of SPEEK, nano TiO₂ coated carbon nanotubes (TiO₂@CNTs) were prepared using a benzyl alcohol-assisted sol-gel method and then used as a new nanofiller to modify SPEEK to prepare SPEEK/TiO₂@CNTs composite membranes. The thick insulated TiO₂ coating layer can effectively avoid the risk of electronic short-circuiting formed by CNTs, while the hydrophilicity of TiO₂ can also reduce the polar difference between CNTs and SPEEK matrix, thus promoting the homogeneous dispersion of CNTs in the composites. As a result, the composite membranes demonstrated simultaneously improved strength and proton conductivity. Incorporating 5 wt% of TiO₂@CNTs exhibited 31% growth in mechanical strength when compared with pure SPEEK. Moreover, the maximum conductivity was 0.104 S cm⁻¹ (80°C) for the composite membrane with 5 wt% of TiO₂@CNTs, which was nearly twice as high as that of SPEEK membrane (0.052 S cm⁻¹).