Preparation of sulfonated polysulfone/sulfonated titanium dioxide hybrid membranes for DMFC applications

Sulfonated titanium dioxide (STiO₂) was prepared by the reaction of TiO₂ with 1,3-propanesultone. Novel STiO₂ incorporated sulfonated poly(aryl ether sulfone) (SPAES) nanocomposite proton exchange membranes (PEMs) were made by solution casting. Fourier transform infrared, X-ray photoelectron spectroscopy, and proton nuclear magnetic resonance indicated the successful preparation of STiO₂ and SPAES. The thermogravimetric analysis and oxidative stability testing results implied that SPAES/STiO₂ membranes had better stability than pristine SPAES membrane. Meanwhile, the scanning electron microscopy spectra exhibited that the introduction of sulfonated groups on the surface of TiO₂ significantly improved its dispersibility in SPAES matrix. More specifically, SPAES membrane incorporated with 2%STiO₂ exhibited higher proton conductivity (60 mS cm⁻¹), lower methanol permeability (2.1 × 10⁻⁷ cm² s⁻¹) and better proton selectivity (28.0 × 10⁴ S s cm⁻³) than that of pure SPAES and SPAES/1%TiO₂ membrane. The SPAES-1%STiO₂ membrane showed better performance in direct methanol fuel cell (DMFC) test than SPAES and Nafion 117 due to the reduction of methanol crossover. From these results, it is evident that SPAES/STiO₂ nanocomposite PEMs have great potential for applications in DMFCs. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48938.     

Random sulfonated poly(arylene ether sulfone) and sulfonated poly(arylene ether ketone) membranes for fuel cell applications

In this study, sulfonated poly(arylene ether sulfone) (SPAES) and sulfonated poly(arylene ether ketone) (SPAEK) were randomly synthesized, employing a presulfonation process. This presulfonation process resulted in a more controlled and reproducible sulfonation level. The respective polymers were prepared using 2,2-Bis(4-hydroxyphenyl) propane at 50% molar ratio, which also provided some membrane elasticity. The resulting polymers, each had 25% of the block containing the sulfonic domains (SPAES A 25 and SPAEK A 25). Better conductive membranes were achieved for the random sulfone polymers than for the random ketone polymers, with values, respectively, of 0.24 and 0.07 S cm⁻¹ at 80°C. The lower proton conductivity from the ketone-based polymer was compensated with very low methanol permeability (0.25 × 10⁻⁶ cm² s⁻¹) and outstanding oxidative stability. The selectivity of both polymer membranes exceeded the reported values for the state-of-the-art Nafion® 117 and other commercially available options. Both polymer membranes, with their unique combination of ionic domains, elastomeric blocks, and resulting morphology, could be viable candidates for fuel cell applications.     

Novel amphoteric ion exchange membranes by blending sulfonated poly(ether ether ketone) with ammonium polyphosphate for vanadium redox flow battery applications

A novel amphoteric ion exchange membrane for vanadium redox flow battery (VRFB) was explored by blending sulfonated poly(ether ether ketone) (SPEEK) and ammonium polyphosphate (APP). The high-stability flame retardant of cross-linked APP with a large number of NH₄⁺ groups was first introduced into SPEEK membrane. It was observed that the addition of APP with special structure could achieve a good balance between proton conductivity and vanadium ions permeability. The abundant NH₄⁺ in APP could block the penetration of vanadium ions by Donnan/Manning exclusion effect and ionic crossing networks due to the ionic bonds between cation and anion groups, and specially a small amount of APP within 5% could remarkably improve the proton conductivity of pristine SPEEK membrane might be ascribed to the unique fast proton transport channels formed by hydrogen bond networks and particular micro-phase separation as a result of interaction between SPEEK and APP. When 5% APP was blended, the SPEEK/APP-5% (S/APP-5%) amphoteric membrane showed a higher selectivity of 20.87 × 10⁴ S min/cm³ (with a good proton conductivity of 0.075 S/cm and a lower VO²⁺ permeability of 3.45 × 10⁻⁷ cm²/ min) and presented better thermal and chemical stability compared to Nafion115 and SPEEK membranes. The VRFB single cell assembled with S/APP-5% amphoteric membrane exhibited more excellent performance than that of Nafion115 and pristine SPEEK membranes, which revealed a higher coulombic efficiency of 96.3%–98.3%, comparable voltage efficiency of 88.4%–78.7% and higher energy efficiency of 85.1%–77.4% from 40 to 80 mA/cm², respectively, and showed relatively good stability of the efficiency up to 50 cycles at 60 mA/cm². The results demonstrated that the designed S/APP amphiprotic membrane of outstanding selectivity, high battery efficiency, and good durability is a prospected VRFB separator.     

Preparation and properties of bisphenol A‐based sulfonated poly(arylene ether sulfone) proton exchange membranes for direct methanol fuel cell

Novel bisphenol A‐based sulfonated poly(arylene ether sulfone) (bi A‐SPAES) copolymers were successfully synthesized via direct copolymerization of disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenylsulfone, 4,4′‐dichlorodiphenylsulfone, and bisphenol A. The copolymer structure was confirmed by Fourier transform infrared spectra and ¹H NMR analysis. The series of sulfonated copolymers based membranes were prepared and evaluated for proton exchange membranes (PEM). The membranes showed good thermal stability and mechanical property. Transmission electron microscopy was used to obtain the microstructures of the synthesized polymers. The membranes exhibit increased water uptake from 8% to 66%, ion exchange capacities from 0.41 to 2.18 meq/g and proton conductivities (25°C) from 0.012 to 0.102 S/cm with the degree of sulfonation increasing. The proton conductivities of bi A‐SPAES‐6 membrane (0.10–0.15 S/cm) with high‐sulfonated degree are higher than that of Nafion 117 membrane (0.095–0.117 S/cm) at all temperatures (20–100°C). Especially, the methanol diffusion coefficients of membranes (1.7 × 10^?8 cm²/s–8.5 × 10^?7 cm²/s) are much lower than that of Nafion 117 membrane (2.1 × 10^?6 cm²/s). The new synthesized copolymer was therefore proposed as a candidate of material for PEM in direct methanol fuel cell. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nafion® reinforced with polyacrylonitrile/ZrO2 nanofibers for direct methanol fuel cell application

Nafion® membrane blended with polyacrylonitrile nanofibers decorated with ZrO₂ was successfully fabricated. The composite membrane showed improved proton conductivity, swelling ratio, thermal and mechanical stability, reduced methanol crossover, and enhanced fuel cell efficiency. The nanocomposite membranes achieved a reduced methanol crossover of 5.465 × 10⁻⁸ cm² S⁻¹ compared to 9.118 × 10⁻⁷ cm² S⁻¹ of recast Nafion® membrane using a 5 M methanol solution at 80°C. The composite membrane also showed an ion conductivity of 1.84 compared to 0.25 S cm⁻¹ recast Nafion® at 25°C. The composite membranes showed a peak power density of 68.7 mW·cm⁻² at 25°C, these results show a promising composite membrane for fuel cell application.     

Preparation of composite membranes with polyimides and poly (amide-imide)s skin via interfacial condensation for air separation

Composite membranes were prepared by the interfacial condensation of water-soluble diamines with an organic solvent (dichloromethane)-soluble dicarbo-methoxy terephthaloyl chloride or carbomethoxy terephthaloyl chloride on top of a porous aluminum oxide support. The morphology of skin on the composite membranes is different in the two different procedures. The polyimide composite membranes with 40-times coatings provide a high gas permeation rate of oxygen and good permselectivity [α(O₂/N₂)]. The composite membrane with the polyimides skin at 40-times coatings had a gas permeation rate of oxygen range from 83 × 10⁻⁵ to 130 × 10⁻⁵ cm³(STP) s⁻¹ cm⁻² cmHg⁻¹, and a permselectivity [α(O₂/N₂)] range of 3.57 to 5.60. The composite membrane with poly (amide-imide)s skin at 40-times coatings had a gas permeation rate of oxygen range from 102 × 10⁻⁵ to 146 × 10⁻⁵ cm³(STP) s⁻¹ cm⁻² cmHg⁻¹, and the permselectivity (α(O₂/N₂)) range from 3.20 to 4.96.     

EB‐crosslinked Polymer Electrolyte Membranes Based on Highly Sulfonated Poly(ether ether ketone) and Poly(vinylidene fluoride)/Triallyl Isocyanurate

In this study, crosslinked polymer electrolyte membranes for polymer electrolyte membrane fuel cell (PEMFC) applications are prepared using electron beam irradiation with a mixture of sulfonated poly(ether ether ketone) (SPEEK), poly(vinylidene fluoride) (PVDF), and triallyl isocyanurate (TAIC) at a dose of 300 kGy. The gel‐fraction of the irradiated SPEEK/PVDF/TAIC (95/4.5/0.5) membrane is 87% while the unirradiated membrane completely dissolves in DMAc solvent. In addition, the water uptake of the irradiated membrane is 221% at 70 °C while that of the unirradiated membrane completely dissolves in water at above 70 °C. The ion exchange capacity and proton conductivity of the crosslinked membrane are 1.57 meq g⁻¹, and 4.0 × 10⁻² S cm⁻¹ (at 80 °C and RH 90%), respectively. Furthermore, a morphology study of the membranes is conducted using differential scanning calorimetry and X‐ray diffractometry. The cell performance study with the crosslinked membrane demonstrates that the maximum power density is 518 mW cm⁻² at 1036 mA cm⁻² and the maximum current density at applied voltage of 0.4 V is 1190 mA cm⁻².     

Chelate membrane from poly(vinyl alcohol)/poly(N-salicylidene allyl amine) blend. III. Effect of Mn(II) and Co(II) on oxygen/nitrogen separation

Facilitated transport of oxygen through Co(II) and Mn(II) chelate membranes from poly(vinyl alcohol)/poly(N-salicylidene allyl amine) was investigated. As the membranes became chelated, oxygen diffusivity decreased and the solubility toward oxygen was enhanced. The oxygen permeability of the base poly(vinyl alcohol)/poly(N-salicylidene allyl amine) membrane was 2.6 × 10⁻³ cm³(STP)cm/cm² cm Hg sec (barrer), and the selectivity toward oxygen was 2.2. As Co(II) was introduced into this membrane, oxygen permeability and oxygen selectivity increased to 2.82 × 10⁻² barrer and 8.5, respectively. The permeability and selectivity of Mn(II) chelate membrane were 3.28 × 10⁻² and 5, respectively. A major reason for the increased selectivity was the enhanced solubility of oxygen in chelate membrane upon chelation. The transport behavior of chelate membranes followed a dual-mode transport, and the parameters were estimated and compared between Co(II) and Mn(II) membranes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 483–490, 1997     

Sulfonated poly(phenylene ether ether sulfone) membrane tailored with layer-by-layer self-assembly of poly(diallyldimethylammonium chloride) and phosphotungstic acid for DMFC applications

Poly(diallyldimethylammonium chloride) (PDDA) and phosphotungstic acid (PTA) were used as cationic and anionic polyelectrolyte layers, respectively, in an alternating fashion to enhance the methanol barrier property and oxidative stability of sulfonated poly (phenylene ether ether sulfone) (SPEES) proton exchange membranes (PEMs). The multilayer PEMs were characterized by AFM, FTIR, and AC impedance spectroscopy. Methanol permeability of the multilayered membranes was found to be much lower than the bare SPEES membrane. The multilayered membranes displayed significantly improved oxidative stability and dimensional stability compared to pristine SPEES membrane. Conversely, the water uptake (%) and proton conductivity (S cm⁻¹) of the prepared membranes decrease to some extent with increasing the PDDA/PTA bilayers in comparison to the pristine SPEES membrane. The maximum relative selectivity (2.23 × 10⁴ S cm⁻³ s) and retained weight (88.9%) were observed for SPEES-[PDDA/PTA]₅ multilayered membrane. The obtained results exposed the possibility of SPEES-[PDDA/PTA]₅ multilayered membrane to serve as high-performance PEMs in direct methanol fuel cells. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47344.     

Sulfonated poly(ether ether ketone)/s–TiO2 composite membrane for a vanadium redox flow battery

The SPEEK/s-TiO₂ composite membrane was prepared by blending sulfonated poly(ether ether ketone) (SPEEK) and sulfonated titanium dioxide (s-TiO₂) nanoparticles. The important physiochemical parameters such as proton conductivity, water uptake, swelling degree and ion exchange capacity of the composite membrane were measured. The thermal stability and chemical stability were also tested. It was observed that the SPEEK/s-TiO₂ composite membrane exhibited the best selectivity (7.13 × 10⁴ S·min·cm⁻³) accompanying high proton conductivity (0.061 S·cm⁻¹) and low tetravalent vanadium ion (VO²⁺) permeability (8.55 × 10⁻⁷ cm²·min⁻¹) compared with Nafion117, SPEEK and SPEEK/TiO₂ membranes. The battery performance with these membranes was characterized by charge–discharge cycling tests and it was found that the SPEEK/s-TiO₂ composite membrane showed the highest energy efficiency (EE) up to 82.3%, indicating the SPEEK/s-TiO₂ composite membrane is a candidate for vanadium redox flow battery (VRFB) application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48830.     

Gel polymer electrolyte with semi-IPN fabric for polymer lithium-ion battery

A new type of semi-IPN gel electrolyte was prepared by thermal polymerization in this article. At first, the crosslinkable PEG200 (MXPEG) was prepared by condensation reaction, then the crosslinkable components were blent with PMMA and heated under vacuum to form polymer blends with semi-IPN fabric. Differential scanning calorimetry and X-ray diffraction spectroscopy were used to investigate the thermal properties and crystalline/amorphous structure of the prepared polymer blends. With semi-IPN fabric, they present amorphous absolutely. For semi-IPN gel electrolyte, the mechanical and the electrochemical properties are varied with the quantity of absorbed liquid electrolyte. Ion-conductivity behavior for semi-IPN gel electrolyte measured by means of AC impedance spectrum showed that the best data was 1.62 × 10⁻³S cm⁻¹ at room temperature, and Arrhenius-type relationship was obeyed in the temperature dependence of ionic conductivity. In addition, the electrochemical stability window of the semi-IPN gel electrolyte was 4.6 V. All the properties showed that the prepared semi-IPN gel electrolyte was expected to have applications of electrolyte for lithium-ion polymer secondary batteries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Pre‐Oxidized Acrylic Fiber Reinforced Ferric Sulfophenyl Phosphate‐Doped Polybenzimidazole‐Based High‐Temperature Proton Exchange Membrane

Pre‐oxidized acrylic fiber (POAF) and ferric sulfophenyl phosphate (FeSPP) are incorporated into polybenzimidazole (PBI) membrane for the first time to prepare high‐temperature proton exchange membranes (PEMs). The strong hydrogen bonds formed between PBI/POAF and FeSPP lead to good dispersion of POAF and FeSPP, facilitate the construction of proton channels, and enhance the dimensional and mechanical stability of the membranes. PBI/FeSPP (30 wt%) shows good proton conductivity (5.43 × 10⁻² and 4.13 × 10⁻² S cm⁻¹ at 180 °C at 50% and 0 relative humidity (RH), respectively) and improved dimensional and mechanical stability compared with pristine PBI. By incorporating 5 wt% POAF into PBI/FeSPP (30 wt%), the swelling ratios are halved and the mechanical strength is enhanced by almost 30% while the proton conductivity is slightly affected (3.84 × 10⁻² and 2.97 × 10⁻² S cm⁻¹ at 180 °C at 50% and 0 RH for PBI/FeSPP (30 wt%)/POAF (5 wt%), respectively). This work offers a new route in the preparation of high‐temperature PEMs with enhanced properties.

     

Gas permeation properties of new type asymmetric membranes

We have developed a new type of asymmetric membranes having a homogeneous hyperthin skin layer, which was used as a polyimide synthesized by 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis(4-amino phenyl) hexafluoro-propane (BAAF). The skin layer thicknesses of the 6FDA-BAAF polyimide asymmetric membranes were 40–60 nm, and the porosity was 10^-6% when a defect size was assumed as 5 nm. The permselectivity of 6FDA-BAAF polyimide asymmetric membranes after silicone coating had α of 40 for CO₂/CH₄ and a flux of 1.0 [Nm³/m²-h-atm] (=3.7 × 10⁻⁴ [cm³(STP)/cm² s cmHg]) for CO₂, α of 4.3 for O₂/N₂ and a flux of 2.0 × 10⁻¹ [Nm³/m²/h/atm] (=7.1 × 10⁻⁵ [cm³(STP)/cm²s cmHg]) for O₂. These values were constant for large-scale manufacturing. © 1996 John Wiley & Sons, Inc.     

Partially Fluorinated Multiblock Poly(arylene ether sulfone) Membranes for Fuel Cell Applications

Sulfonated poly(arylene ether sulfone) (SPAES‐F series) membranes, which are partially fluorinated multiblock polymers containing Bisphenol 6F (6F‐BPA), are synthesized. The membranes exhibit less water uptake and higher ion conductivity at similar ion exchange capacity (IEC) values compared to previous SPAES membranes containing identical hydrophilic blocks. This is attributed to the presence of 6F‐BPA in the hydrophobic block, which enhances hydrophobicity and promotes phase separation, as observed through transmission electron microscopy analysis. F4 (IEC = 2.4 meq g^?1) shows superior ion conductivity than Nafion NRE212 membrane irrespective of the humidity level. Furthermore, the SPAES electrolyte membrane of 1.5 meq g^?1 produces better performance than NRE212, yielding a current density of 488 mA cm^?2 at 80 °C, 80% RH, and 0.6 V. In 50% RH at 80 °C, SPAES with 1.5 meq g^?1 exhibits a cell resistance and fuel cell performance comparable to those of NRE212; clearly, regulating hydrophobicity and hydrophilicity is crucial for enhanced performance.     

New organic–inorganic hybrid membranes based on sulfonated polyimide/aminopropyltriethoxysilane doping with sulfonated mesoporous silica for direct methanol fuel cells

A series of novel composite methanol‐blocking polymer electrolyte membranes based on sulfonated polyimide (SPI) and aminopropyltriethoxysilane (APTES) doping with sulfonated mesoporous silica (S‐mSiO₂) were prepared by the casting procedure. The microstructure and properties of the resulting hybrid membranes were extensively characterized. The crosslinking networks of amino silica phase together with sulfonated mesoporous silica improved the thermal stability of the hybrid membranes to a certain extent in the second decomposition temperature (250–400°C). The composite membranes doping with sulfonated mesoporous silica (SPI/APTES/S‐mSiO₂) displayed superior comprehensive performance to the SPI and SPI/APTES membranes, in which the homogeneously embedded S‐mSiO₂ provided new pathways for proton conduction, rendered more tortuous pathways as well as greater resistance for methanol crossover. The hybrid membrane with 3 wt % S‐mSiO₂ into SPI/APTES‐4 (SPI/A‐4) exhibited the methanol permeability of 4.68 × 10^?6 cm² s^?1at 25°C and proton conductivity of 0.184 S cm^?1 at 80°C and 100%RH, while SPI/A‐4 membrane had the methanol permeability of 5.16 × 10^?6 cm² s^?1 at 25°C and proton conductivity of 0.172 S cm^?1 at 80°C and 100%RH and Nafion 117 exhibited the values of 8.80 × 10^?6 cm² s^?1 and 0.176 S cm^?1 in the same test conditions, respectively. The hybrid membranes were stable up to about 80°C and demonstrated a higher ratio of proton conductivity to methanol permeability than that of Nafion117. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

New composite membrane poly(vinyl alcohol)/graphene oxide for direct ethanol–proton exchange membrane fuel cell

This study investigated a simple synthesis of a crosslinked poly(vinyl alcohol)/ graphene oxide composite membrane with lower ethanol permeability membrane for passive direct ethanol–proton exchange membrane fuel cells (DE-PEMFCs). The chemical and physical structure, morphologies, ethanol uptake and permeability, ion exchange capacities, water uptake, and proton conductivities were determined and found that transport properties of the membrane were affected by the GO loading. The composite membrane with optimum GO content (15 wt %) exhibited the highest proton conductivity of 9.5 × 10⁻³ Scm⁻¹ at 30°C, 3.24 × 10⁻² Scm⁻¹ at 60°C, respectively and reduced ethanol permeability until 1.75 × 10⁻⁷ cm² s⁻¹. In the passive DE-PEMFC, the power density at 60°C were obtained as 5.84 mW cm⁻² higher than those by commercial Nafion 117 is 4.52 mW cm⁻². © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46928.     

In vitro cadmium removal from human serum by Cibacron Blue F3GA–thionein‐complex conjugated affinity membranes

A new membrane affinity biosorbent carrying thionein has been developed for selective removal of cadmium ions from human serum. Microporous poly(2‐hydroxyethyl methacrylate) (pHEMA) membranes were prepared by photopolymerization of HEMA. The pseudo dye ligand Cibacron Blue F3GA (CB) was covalently immobilized on the pHEMA membranes. Then, the cysteine‐rich metallopeptide thionein was conjugated onto the CB‐immobilized membrane. The maximum amounts of CB immobilized and thionein conjugated on the membranes were 1.07 µmol cm⁻² and 0.92 µmol cm⁻², respectively. The hydrophilic pHEMA membrane had a swelling ratio of 58% (w/w) with a contact angle of 45.8 °. CB‐immobilized and CB‐immobilized–thionein‐conjugated membranes were used in the Cd(II) removal studies. Cd(II) ion adsorption appeared to reach equilibrium within 30 min and to follow a typical Langmuir adsorption isotherm. The maximum capacity (q _m) of the CB‐immobilized membranes was 0.203 (µmol Cd(II)) cm⁻² membrane and increased to 1.48 (µmol Cd(II)) cm⁻² upon CB–thionein‐complex conjugation. The pHEMA membranes retained their cadmium adsorption capacity even after 10 cycles of repeated use. © 2000 Society of Chemical Industry     

Partially Sulfonated Poly(vinylidene fluoride) Induced Enhancements of Properties and DMFC Performance of Nafion Electrolyte Membrane

Partially sulfonated poly(vinylidene fluoride) (SPVdF) has been prepared by incorporation of sulfonic acid groups within poly(vinylidene fluoride), using chlorosulfonic acid as the sulfonating agent. The degree of sulfonation (DS) has been varied by modulating the duration of the sulfonation reaction. Blending of SPVdF (having DS = 36.78%) with Nafion at a constituent wt.% ratio of SPVdF:Nafion = 70:30 has resulted in the fabrication of polymer electrolyte membrane with superior properties compared to pristine Nafion‐117 membrane. This particular blend composition exhibited a proton conductivity value of 3.6 × 10⁻² S cm⁻¹ (i.e. ∼12.5% increase over Nafion‐117), a methanol permeability value of 6.81 × 10⁻⁷ cm² s⁻¹ at 6M methanol concentration (i.e. ∼99.31% decrease from Nafion‐117) and a corresponding membrane selectivity value of 5.29 × 10⁴ Ss cm⁻³ (i.e. an increase of approximately two‐orders of magnitude over Nafion‐117) at 20 °C. In addition, this blend composition has also exhibited (a) better heat stability at temperatures as high as 160 °C by virtue of it possessing higher glass transition temperature, (b) higher storage modulus, (c) higher stress relaxation at high angular frequency and (d) superior DMFC performance at high methanol feed concentration in presence of humidified, as well as, non‐humidified air as the catholyte, compared to Nafion‐117 membrane.     

Preparation and characterization of sulfonated block‐graft copolyimide/sulfonated polybenzimidazole blend membranes for fuel cell application

Polymer electrolyte blend membranes composed of sulfonated block‐graft polyimide (S‐bg‐PI) and sulfonated polybenzimidazole (sPBI) were prepared and characterized. The proton conductivity and oxygen permeability coefficient of the novel blend membrane S‐bg‐PI/sPBI (7 wt%) were 0.38 S cm^?1 at 90 °C and 98% relative humidity and 7.2 × 10^?13 cm³(STP) cm (cm² s cmHg)^?1 at 35 °C and 76 cmHg, respectively, while those of Nafion^® were 0.15 S cm^?1 and 1.1 × 10^?10 cm³(STP) cm (cm² s cmHg)^?1 under the same conditions. The apparent (proton/oxygen transport) selectivity calculated from the proton conductivity and the oxygen permeability coefficient in the S‐bg‐PI/sPBI (7 wt%) membrane was 300 times larger than that determined in the Nafion membrane. Besides, the excellent gas barrier properties based on an acid ? base interaction in the blend membranes are expected to suppress the generation of hydrogen peroxide and reactive oxygen species, which will degrade fuel cells during operation. The excellent proton conductivity and gas barrier properties of the novel membranes promise their application for future fuel cell membranes. © 2015 Society of Chemical Industry     

Novel Proton Conducting Membranes from the Combination of Sulfonated Polymers of Polyetheretherketones and Polyphosphazenes Doped with Sulfonated Single‐Walled Carbon Nanotubes

Intent on developing efficient proton exchange membranes used for direct methanol fuel cells as well as hydrogen fuel cells, a series of membranes based on sulfonated polyetheretherketone and sulfonated polyphosphazene‐graft copolymers is prepared by cross‐linking reaction because the former material has good enough mechanical property, while the latter is excellent in the proton transfer. The cross‐linked membranes combine the advantages of the two kinds of polymers. Among them, the membrane poly[(4‐trifluoromethylphenoxy)(4‐methylphenoxy)phosphazene]‐g‐poly {(styrene)₁₁‐r‐[4‐(4‐sulfobutyloxy)styrene]₃₃‐sulfonated poly(ether ether ketone)75 (CF₃‐PS₁₁‐PSBOS₃₃‐SPEEK75) shows a proton conductivity at 0.143 S cm⁻¹ under fully hydrated conditions at 80 °C and performs tensile strength about five times as much as did the sulfonated polyphosphazene membrane CF₃‐PS₁₁‐PSBOS₃₃. Further doping of sulfonated single‐walled carbon nanotubes (S‐SWCNTs) into the cross‐linked membranes on the screening of additives gives composite membrane CF₃‐PS₁₁‐PSBOS₃₃‐SPEEK75‐SWCNT possessing proton conductivity of 0.196 S cm⁻¹, even higher than that of Nafion 117 and a tensile strength comparable to that of Nafion 117. However, this significance of the composite membrane in the proton conduction is not observed in the test with a H₂/air fuel cell when it shows a maximal power density of 280 mW cm⁻² at 80 °C, whereas 294 mW cm⁻² is observed for CF₃‐PS₁₁‐PSBOS₃₃‐SPEEK75.