Poly(vinyl alcohol)-based polymer electrolyte membranes for direct methanol fuel cells

We have prepared polymer electrolyte membranes (PEMs) from poly(vinyl alcohol) (PVA) and modified PVA polyanion containing 2 or 4 mol% of 2-methyl-1-propanesulfonic acid (AMPS) groups as a copolymer. The PEMs of various AMPS content and cross-linking conditions were prepared to determine the effect of AMPS content and cross-linking conditions on PEM properties. Proton conductivity and permeability of methanol through the PEMs increased with increasing AMPS content, C_AMPS, and with decreasing cross-linker concentration, C_GA, because of the increase in the water content. The permeability coefficient of methanol through the PEM prepared under the conditions of C_AMPS = 2.7 mol% and C_GA = 0.35 vol% was about 30 times lower than that of Nafion^®117 under the same measurement conditions. The proton permselectivity of the PEM, which is defined as the ratio of the proton conductivity to the permeability coefficient of methanol, gave a maximum value of 66 × 10³ S cm⁻³ s. The value is about three times higher than that of Nafion^®117.     

燃料电池用碱性膜材料的研究进展

碱性膜直接甲醇燃料电池因为结合了质子交换膜燃料电池和液体碱燃料电池的优点而产生自身独特的性质,使其可以在一定程度上弥补质子交换膜燃料电池以及液体碱燃料电池的缺点而尤其引人关注。其中碱性膜电解质为碱性膜燃料电池的核心组件,其性能直接关系到燃料电池的性能及寿命。截至目前,关于碱性膜材料的制备及应用方面的报道较多,涉及的碱性膜电解质的种类也较多。本文以燃料电池用碱性膜电解质为综述内容,对国内外关于碱性膜电解质的研究报道进行系统的梳理和介绍。     

Preparation and characterization of blend anion-exchange membrane from quarternized hydroxyethylcellulose/quaternized poly(vinyl alcohol)

阴离子交换膜是碱性直接甲醇燃料电池（ADMFC）的核心。本文将季铵化羟乙基纤维素（QHEC）和季铵化聚乙烯醇（QPVA）共混制备了一系列不同配比的QPVA/QHEC阴离子交换膜并对其进行热交联,对膜进行测试和分析,结果表明：膜表面均匀致密,低于300 ℃膜基本稳定;QPVA/QHEC共混膜的导电率随着QPVA量的增大而增大,在（2.0～7.8）×10－2 s/cm范围内,随着使用温度的升高逐渐升高;QHEC膜对甲醇有很好的阻隔效果,在20 ℃时,甲醇渗透率最低为2.49×10－6 cm2/s;随QPVA量的增加,共混膜的甲醇渗透率会略有增加。     

Poly(vinyl alcohol) and poly(vinyl amine) blend membranes for isopropanol dehydration

Blended membranes of hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(vinyl amine) (PVAm) were prepared and crosslinked with glutaraldehyde. The prepared membranes were characterized using infrared (attenuated total reflection mode) spectroscopy, differential scanning calorimetry, X‐ray diffractometry, and scanning electron microscopy measurements. Pervaporation performances of the membranes were evaluated for the separation of water‐isopropanol (IPA) mixtures. As the PVAm content increased from PVAm0 to PVAm1.5, the flux through a 70 μm film increased from 0.023 to 0.10 kg/m² h at an IPA/water feed ratio of 85/15 at 30 °C. The driving force for permeation of water increased due to the temperature but it has no effect on IPA permeation. Activation energies for the permeation of IPA and water were calculated to be 17.11 and 12.46 kJ/mol, respectively. Controlling the thickness of the blend membrane could improve the permeation flux with only a marginal reduction in the separation factor. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45572.     

直接甲醇燃料电池用阻醇质子交换膜研究进展

直接甲醇燃料电池是近十年兴起的新型燃料电池,并以其独特的优点引起了人们广泛的关注。作为其重要组成部分的质子交换膜的性质是影响电池性能的关键因素。本文在介绍近两年质子交换膜研究最新进展的基础上,综述了天然聚合物用作质子交换膜材料的研究情况,并分析了其优劣势及应用前景。     

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 compositemembrane indicated its promising application inDMFC operations at high temperature. __________ Translated from Acta Polymerica Sinica, 2007, (4): 337–342 [译自:高分子学报]     

PWA/silica doped sulfonated poly(ether sulfone) composite membranes for direct methanol fuel cells

A novel sulfonated poly(ether sulfone) (SPES)/phosphotungstic acid (PWA)/silica composite membranes for direct methanol fuel cells (DMFCs) application were prepared. The structure and performance of the obtained membranes were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), water uptake, proton conductivity, and methanol permeability. Compared to a pure SPES membrane, PWA and SiO₂ doped membranes had a higher thermal stability and glass transition temperature (T_g) as revealed by TGA‐FTIR and DSC. The morphology of the composite membranes indicated that SiO₂ and PWA were uniformly distributed throughout the SPES matrix. Proper PWA and silica loadings in the composite membranes showed high proton conductivity and sufficient methanol permeability. The selectivity (the ratio of proton conductivity to methanol permeability) of the SPES‐P‐S 15% composite membrane was almost five times than that of Nafion 112 membrane. This excellent selectivity of SPES/PWA/silica composite membranes indicate a potential feasibility as a promising electrolyte for DMFC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemical and morphological effects of blended sulfonated poly(styrene-isobutylene-styrene) and isopentylamine for direct methanol fuel cell applications

In this study, blend membranes based on a combination of sulfonated poly (styrene-isobutylene-styrene) (SIBS) with isopentylamine (IPA) were synthetized as potential candidates for direct methanol fuel cell (DMFC) applications. The impact of sulfonation level (57–93 mol%) and percentage of IPA incorporation (1, 3, and 5 wt%) were analyzed via different properties of the resulting membrane. FTIR analysis showed that IPA was successfully incorporated into the sulfonated polymer matrix and also confirmed the interaction between the sulfonic and amine groups. This interaction generates significant morphological changes in the nanostructure of the membranes that are evident through results of small angle x-ray scattering and atomic force microscopy analysis. Proton conductivity and methanol permeability of the membranes were also analyzed. Proton conductivity was significantly enhanced with the incorporation of IPA at an optimum loading, creating additional paths for the conduction of protons through the membrane. It was also sensitive to the morphological changes produced after the IPA incorporation and the interconnection between the ionic domains. Methanol permeability increased slightly due to the additional water domains and the inability of the isopentyl groups of IPA to block the free-volume in the membrane. Despite this, the selectivity (proton conductivity over methanol permeability) of the membranes was comparable to the state-of-the-art Nafion®, especially at an optimum IPA incorporation of 3 wt%.     

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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115 membrane and reached 0.17 S•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.     

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     

Modification of Nafion membrane using poly(4‐vinyl pyridine) for direct methanol fuel cell

Perfluorinated membrane such as Nafion (from Du‐Pont) has been used as a polymer electrolyte membrane. Nafion 117 membrane, which was usually used as the electrolyte membrane for the polymer electrolyte membrane fuel cell (PEMFC), was modified by using poly(4‐vinyl pyridine) (P4VP) to reduce the methanol crossover, which cause fuel losses and lower power efficiency, by the formation of an ionic crosslink structure (sulfonic acid‐pyridine complex) on the Nafion 117 surface. Nafion film was immersed in P4VP/N‐methyl pyrrolidone (NMP) solution. P4VP weight percent of modified membrane was controlled by changing the concentration of P4VP/NMP solution and the dipping time. P4VP weight percent increased with increasing concentration of dipping solution and dipping time. The thickness of the P4VP layer increased with increasing concentration of dipping solution and dipping time when the concentration of the dipping solution was low. At high P4VP concentration, the thickness of the P4VP layer was almost constant owing to the formation of acid–base complex which interrupted the penetration of P4VP. FTIR results showed that P4VP could penetrate up to 30 µm of Nafion 117 membrane. Proton conductivity and methanol permeability of modified membrane were lower than those of Nafion 117. Both decreased with increasing concentration of dipping solution and dipping time. Methanol permeability was observed to be more dependent on the penetration depth of P4VP. Water uptake of the modified membrane, the important factor in a fuel cell, was lower than that of Nafion 117. Water uptake also decreased with increasing of P4VP weight. On the basis of this study, the thinner the P4VP layer on the Nafion 117 membrane, the higher was the proton conductivity. Methanol permeability decreased exponentially as a function of P4VP weight percent. Copyright © 2006 Society of Chemical Industry     

Cardo poly(arylene ether sulfone) block copolymers with pendant imidazolium side chains as novel anion exchange membranes for direct methanol alkaline fuel cell

A series of phenolphthalein-based cardo poly(arylene ether sulfone) (PES) block copolymers containing pendant imidazolium group (PI-PESs) were synthesized as novel anion exchange membranes for direct methanol alkaline fuel cells. These PI-PESs combine the advantages of pendant anion conductors on the polymer side chains with the thermochemical stabilities of the imidazolium group, showing high hydroxide conductivity, together with good physical and chemical stability under basic conditions. The hydroxide conductivity over 0.03 S/cm at 20 °C and 0.1 S/cm at 80 °C was obtained for the PI-PES membranes. In addition, PI-PES membranes show low permeability to methanol (below 6.74 × 10⁻⁸ cm²/s) and very high selectivity (over 3.7 × 10⁵ S·s/cm³). These properties make the PI-PESs promising candidate materials for anion exchange membranes for direct methanol alkaline fuel cells.     

Application of sodium conducting membranes in direct methanol alkaline fuel cells

A study of a direct methanol alkaline fuel cell (DMAFC) operating with sodium conducting membranes is reported. Evaluation of the fuel cell was performed using membrane electrode assemblies incorporating carbon supported platinum catalysts and Nafion^® 117 and 112 membranes. A membrane electrode assembly was also prepared by the direct chemical deposition of platinum into the surface region of the membrane. Evaluation of the chemically deposited assembly showed it to be less active than those based on carbon supported catalysts. SEM &; TEM analysis indicate that this behaviour is due to the low surface area of the chemically deposited catalyst layer. The fuel cell performance with Nafion membranes is reported and is not as good as achieved with hydroxide ion conducting membranes suggesting that Nafion may not be suitable for DMAFC operation.     

Effect of functionalized silica particles on cross-linked poly(vinyl alcohol) proton conducting membranes

A family of proton conducting membranes based on cross-linked poly(vinyl alcohol), PVA, has been synthesized and characterized. The influence of surface-functionalized silica particles on the membrane properties has been evaluated by means of ¹H-NMR, vibrational spectroscopy, thermal analysis and electrochemical characterization. The study revealed that the crystallinity of the polymer, the proton diffusivity and the water retention are strongly affected by the presence of the inorganic compound. Conductivity measurements and preliminary fuel cell tests agreed in determining the best PVA/silica ratio among the various compositions explored and demonstrated the potentiality of the selected membranes as electrolytes in fuel cell devices.     

Glycerol-modified poly(vinyl alcohol)/poly(ethylene glycol) self-healing hydrogel for artificial cartilage

Poly(vinyl alcohol) (PVA) hydrogels have shown potential applications in bionic articular cartilage due to their tissue-like viscoelasticity, good biocompatibility and low friction. However, their lack of adequate mechanical properties is a key obstacle for PVA hydrogels to replace natural cartilage. In this study, poly(ethylene glycol) (PEG) and glycerol were introduced into PVA, and a PVA/PEG–glycerol composite hydrogel was synthesized using a mixing physical crosslinking method. The mechanical properties, hydrophilicity and tribological behavior of the PVA/PEG–glycerol hydrogel were investigated by changing the concentration of glycerol in PEG. The results showed that the tensile strength of the hydrogel reached 26.6 MPa at 270% elongation at break with 20 wt% of glycerol plasticizer, which satisfied the demand of natural cartilage. In addition, the excellent hydrophilicity of glycerol provides good lubricating properties for the composite gel under dry friction. Meanwhile, self-healing and cellular immunity assays demonstrated that the composite gel could have good self-healing ability and excellent biocompatibility even in the absence of external stimuli. This study provides a new candidate material for the design of articular cartilage, which has the potential to facilitate advances in artificial joint cartilage repair. © 2022 Society of Industrial Chemistry.     

New modifications of poly(vinyl alcohol)s and their applications

Poly(vinyl alcohol) (PV-OH), prepared from poly(viny) acetate), is used widely in many industries. Various grades have been produced, with different degree of polymerization and degree of hydrolysis. Recently, novel modified (PV-OH)s with anion, cation, silanol or hydrophobic groups have been studied and developed. They have new properties in addition to those of ordinary PV-OH and have new applications. The methods of modification and the characteristics and some applications of the modified polymers are described.     

Alkaline polymer electrolyte membranes from quaternized poly(phthalazinone ether ketone) for direct methanol fuel cell

Quaternized poly(phthalazinone ether ketone)s (QPPEK)s were synthesized by the chloromethylation and quaternization of poly(phthalazinone ether ketone) (PPEK) with chloromethyl methyl ether in 98% concentrated sulfuric acid and following trimethylamine. The presence of ? CH₂Cl groups in chloromethylated PPEK was confirmed by ¹H‐NMR. An alkaline QPPEK membrane was prepared and its thermal and mechanical properties were tested. The alkaline QPPEK membrane had a methanol permeability 6.57 × 10^?7 cm²/s and the highest anion conductivity 1.14 × 10^?2 S/cm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Gas permeation through water‐swollen polysaccharide/poly(vinyl alcohol) membranes

The effect of Na‐alginate content on the gas permeation properties of water‐swollen membranes prepared by varying Na‐alginate and poly(vinyl alcohol) (PVA) content in membranes was investigated. The influences of water content and crystallinity of the membranes on the gas permeation performance of the water‐swollen membranes were studied. The gas permeation rate and selectivity of Na‐alginate/PVA water‐swollen membranes were compared with those of the dry membranes. The permeation rates of nitrogen and carbon dioxide through water‐swollen membranes were in the range of 0.4–7.6 × 10^?7 to 3.7–8.5 × 10^?6 cm³ (STP)/cm² s^?1 cmHg^?1, which were 10,000 times higher than those of dry‐state membranes. The permeation rates of mixture gases through water‐swollen Na‐alginate/PVA membranes were found to increase exponentially with the increase of Na‐alginate content, whereas carbon dioxide concentration in permeates was decreased linearly. It was found that the gas permeance of the water‐swollen membranes increased with increasing the Na‐alginate content in the membrane. Gas permeation rates of the water‐swollen Na‐alginate/PVA membranes increased with increasing the water content in the membrane and decreasing the crystallinity of the membrane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3225–3232, 2004     

Enhanced oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) blended with poly(acrylic acid) for packaging applications

To enhance the oxygen‐barrier and water‐resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m^?1 day^?1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content. © 2016 Society of Chemical Industry