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Electrochemical characterisation of sulfonated polyetherketone membranes
Abstract
The thermal, mechanical and electrochemical characterisation of sitlfonated polyetherketone, including fuel cell tests in hydrogen/ oxygen and hydrogen/air are described. In thermogravimetric analysis, PEEK-S membranes lose water up to 150°C and degradation of the sulfonic acid groups takes place at ca. 240°C. Thermomechanical analysis of a PEEK-S membrane of 60 μm thickness and equivalent weight 625 g/mole shows that the membrane undergoes a shrinkage of 1.5 % up to 140°C. Reversible elongation of 0.6 % occurs thereafter up to 180°C. The conductivity, measured by impedance spectroscopy, on non-reinforced and on woven-polymer reinforced PEEK-S, is reported as a function of temperature and of relative humidity (RH), and compared with that of Nafwn®-117. At 100°C and 100% RH the conductivity of PEEK-S is 2 5.10-2 Scm-1 (depending on thermal history), increasing to 0.11 Scm-1 at 150°C. Polarisation characteristics of a non-reinforced PEEK-S membrane of 18 ®m thickness at temperatures up to 110°C under conditions of hydrogen/air and hydrogen/oxygen are compared. The results of fuel cell (H2-O2) tests on composite, reinforced membranes are reported.
... Numerous recent studies indicate that proton-conducting hydrocarbon membranes are a promising alternative to Nafion-type perfluorinated sulfopolymers for use in hydrogen-air proton exchange membrane fuel cells (PEMFC) [1][2][3][4][5][6][7][8][9][10]. Moreover, recent studies demonstrate the fabrications of effective PEMFC using hydrocarbon membranes [11][12][13]. ...
... The morphology of hydrocarbon membranes is similar to that of Nafion [25][26][27][28] and can also be described by a system of nanoscale channels where three main water states can be assumed at high water content: bulk-like water in the central part of the channel, weakly bound (transition layer) water, and strongly bound (near wall) water. The volume fraction of these fractions will depend on the ratio of hydrophobic and hydrophilic blocks and the fraction of near-wall water on the concentration of sulfonic SO 3 2− groups. Measurements of the IEC value, which characterizes the concentration of sulfonic groups, show that this parameter is almost the same for all compositions studied [28] and is at a level of 2.5, so we can assume that for all compositions, the fraction of nearwall water is approximately the same. ...
... At the lowest studied value of λ ≈ 4, the crossover point disappears, and the diffusion coefficient is described by one activation energy over the entire temperature range. Thus, for water content λ < λ 0 , the measured diffusion coefficient can be related to the transport of surface protons bound to SO 3 2− groups. Springer Nature journal content, brought to you courtesy of Springer Nature Customer Service Center GmbH ("Springer Nature"). ...
Proton diffusion in the co-PNIS85/15 membrane was investigated in the temperature range from 200 to 363 K at different water contents (4 ≤ λ ≤ 21) using ¹H SFG NMR diffusometry. At high hydration values, above the threshold value λ0 = 10.5, the ln(DNMR(1/T)) dependences show two different activation modes, separated by a crossover point Tcr ≈ 250–260 K. At temperatures above Tcr, the activation energy is Ea ~ 0.20 eV, which is close to the value for bulk water (Ea ~ 0.17 eV). At temperatures below the crossover point, the ln(DNMR(1/T)) dependences for different water contents merge together into one straight line characterized by a much higher Ea = 0.46 eV. At low hydration values λ < λ0, the activation energies for the high-temperature and low-temperature modes converge, so that at λ = 4, the dependence ln(DNMR(1/T)) is described by one straight line throughout the studied temperature range with Ea = 0.38 eV. A model is proposed that phenomenologically describes the diffusion in the co-PNIS membrane at different moisture contents λ.
... Poly(ether ether ketone) (PEEK) has been widely reported for PEMs because of their low cost, high thermal stability, and excellent mechanical properties. Sulfonated PEEK (sPEEK) can be synthesized via aromatic nucleophilic substitution reactions [129]. Xing et al. [130] adopted sulfuric acid (95-98 wt%) as the sulfonating agent to prepare a series of sPEEKs. ...
... sPEEK membranes exhibit excellent thermal stability with sulfonic acid groups decomposed at 240°C [129]. Their proton conductivities can reach up to 0.11 S cm −1 at 150°C and 100% RH. ...
High-temperature proton exchange membrane (HT-PEM) fuel cells offer more advantages than low-temperature PEM fuel cells. The ideal characteristics of HT-PEMs are high conductivities, low-humidity operation conditions, adequate mechanical properties, and competitive costs. Various molecular moieties, such as benzimidazole, benzo-thiazole, imide, and ether ether ketone, have been introduced to polymer chain backbones to satisfy the application requirements for HT-PEMs. The most common sulfonated polymers based on the main chain backbones have been employed to improve the rties. Side group/chain engineering, includ crosslinking, has been widely applied to HT-PEMs to further improve their proton conductivity, thermal stability, and mechanical properties. Currently, phosphoric acid-doped polybenzimidazole is the most successful polymer material for application in HT-PEMs. The compositing/blending modification methods of polymers are effective in obtaining high PA-doping levels and superior mechanical properties. In this review, the current progress of various membrane materials used for HT-PEMs is summarized. The synthesis and performance characteristics of polymers containing specific moieties in the chain backbones applied to HT-PEMs are discussed systemically. Various modification approaches and their deficiencies associated with HT-PEMs are analyzed and clarified. Prospects and future challenges are also presented.
... In recent years, two types of sulphonate fillers, sulphonate poly arylene ether ketone (SPAEK), and sulphonate poly ether ether ketone (SPEEK) have been developed and used to modify the Nafion membrane in DMFCs. Both SPAEK and SPEEK have good attributes: high proton conductivity and methanol resistance for SPAEK [68,69]; good mechanical properties, proton conductivity and good processing capacity of SPEEK polymers [70,71]. Regarding the behaviour in a methanol fuel cell [72,73], an increase by at least 30% in OCV and by 10% in highest power density were observed. ...
... Power Density (mW cm −2 ) Temperature ( • C) RH% Nafion/Silica [144] 350 100 100 Nafion/Silica particles [139] 380 85 100 Nafion/Hafnium oxide [147] 336 100 -Nafion/Titanium oxide [152] 514 110 -Nafion/Titanium oxide nanotubes [156] 1020 80 -Nafion/Zirconium oxide [141] 400 130 85 Nafion/Sulphonated zirconium oxide [142] 609 70 83 Nafion/mesoporous zirconium pshosphate [146] 353 70 18 Nafion/ zirconium pshosphate [145] 450 130 -Nafion/GO [179] 212 100 25 Nafion/SGO [180] 300 70 20 Nafion/GO/TiO 2 [183] 324 0 Nafion/GO/Phosphotungstic acid [184] 841 80 20 Nafion/Phosphotungstic acid [202] 220 120 -PBI [169] PBI/SiO 2 [169] 200240 165165 -PBI/GO [190] 388 165 0 PBI/SGO [191] 600 175 0 SulfonatedPolysulfone [160] 160 85 -SPolysulfone/titanium oxide [160] 240 85 -SPEEK [164] 179 120 -SPEEK/GO [188] 378 80 30 SPEEK/silica [164] 246 120 -SPI/ionic liquid [210] 100 120 0 SPI/demaTfO [208] 100 80 0 Membranes with fillers that were functionalised (most commonly with sulphonic groups) displayed a better performance in terms of proton conductivity and cell polarisation at elevated temperatures. This is attributed to the water retaining capabilities of these functional groups. ...
Nafion membranes are still the dominating material used in the polymer electrolyte membrane (PEM) technologies. They are widely used in several applications thanks to their excellent properties: high proton conductivity and high chemical stability in both oxidation and reduction environment. However, they have several technical challenges: reactants permeability, which results in reduced performance, dependence on water content to perform preventing the operation at higher temperatures or low humidity levels, and chemical degradation. This paper reviews novel composite membranes that have been developed for PEM applications, including direct methanol fuel cells (DMFCs), hydrogen PEM fuel cells (PEMFCs), and water electrolysers (PEMWEs), aiming at overcoming the drawbacks of the commercial Nafion membranes. It provides a broad overview of the Nafion-based membranes, with organic and inorganic fillers, and non-fluorinated membranes available in the literature for which various main properties (proton conductivity, crossover, maximum power density, and thermal stability) are reported. The studies on composite membranes demonstrate that they are suitable for PEM applications and can potentially compete with Nafion membranes in terms of performance and lifetime.
... Another series of FuMA-Tech PFSA membranes incorporated a stabilizer (labeled as FX) to mitigate radical attack. FuMA-Tech also prepared blend membranes of various thicknesses based upon sulfonated polyetheretherketone, with only 30 µm thickness in one case (E-730) [12,22]. Another approach at FuMA-Tech was dealing with composite membranes based on a PFSA polymer where zirconium phosphate nanoparticles were integrated into the PFSA polymer matrix. ...
... Long side chain (Fumion ® ) PFSA blends with 1800 and 2300 equivalent weight (e.g., fumapem ® F-1850, F-18120, and F-2350), hydrocarbon membranes based on sPEEK (e.g., fumapem ® E-730 and E-750), composite membranes based on zirconium phosphate (ZrP = Zr(HPO4)2·H2O) and perfluorosulfonic acid polymer (e.g., fumapem ® FZP 960 and FZP 990), and cross-linked PFSA membranes (e.g., FX-7050) were prepared at Fumatech using procedures reported elsewhere [20][21][22][23]30,31]. The main characteristics of these Fumatech membranes in terms of composition, equivalent weight, and preparation methods are reported in Figure 7. ...
Sulfonic acid-functionalized polymer electrolyte membranes alternative to Nafion(®) were developed. These were hydrocarbon systems, such as blend sulfonated polyetheretherketone (s-PEEK), new generation perfluorosulfonic acid (PFSA) systems, and composite zirconium phosphate-PFSA polymers. The membranes varied in terms of composition, equivalent weight, thickness, and filler and were investigated with regard to their methanol permeation characteristics and proton conductivity for application in direct methanol fuel cells. The behavior of the membrane electrode assemblies (MEA) was investigated in fuel cell with the aim to individuate a correlation between membrane characteristics and their performance in a direct methanol fuel cell (DMFC). The power density of the DMFC at 60 °C increased according to a square root-like function of the membrane selectivity. This was defined as the reciprocal of the product between area specific resistance and crossover. The power density achieved at 60 °C for the most promising s-PEEK-based membrane-electrode assembly (MEA) was higher than the benchmark Nafion(®) 115-based MEA (77 mW·cm(-2) vs. 64 mW·cm(-2)). This result was due to a lower methanol crossover (47 mA·cm(-2) equivalent current density for s-PEEK vs. 120 mA·cm(-2) for Nafion(®) 115 at 60 °C as recorded at OCV with 2 M methanol) and a suitable area specific resistance (0.15 Ohm cm² for s-PEEK vs. 0.22 Ohm cm² for Nafion(®) 115).
... In recent years, efforts have been committed to developing less expensive membranes than Nafion-based ones. However, once high protonic conduction, as well as a low level of chemical instability to oxidation reactions, are required, the advances have been small; nevertheless, promising results have been obtained with non-fluorinated polymers [136][137][138][139], with zirconium sulfophenyl phosphonates [140,141], and with polyantimonic acid (PAA) [142,143]. ...
Proton conductors are ceramic materials with a crystalline or amorphous structure, which allow the passage of an electrical current through them exclusively by the movement of protons: H+. Recent developments in proton-conducting ceramics present considerable promise for obtaining economic and sustainable energy conversion and storage devices, electrolysis cells, gas purification, and sensing applications. So, proton-conducting ceramics that combine sensitivity, stability, and the ability to operate at low temperatures are particularly attractive. In this article, the authors start by presenting a brief historical resume of proton conductors and by exploring their properties, such as structure and microstructure, and their correlation with conductivity. A perspective regarding applications of these materials on low-temperature energy-related devices, electrochemical and moisture sensors, is presented. Finally, the authors’ efforts on the usage of a proton-conducting ceramic, polyantimonic acid (PAA), to develop humidity sensors, are looked into.
... (SPEEK) 1985 , [2 ] . , , SPEEK ( PBI) [3 ] , , Nafion . ...
... The fuel cell must achieve excellent performance and durability to efficiently use in electronic devices, electric vehicles, and other applications. The basic working principle of a fuel cell is based on an electrochemical reaction in which fed fuels such as methanol, hydrogen, oxygen, ethanol, and natural gas are oxidized and reduced to produce electricity, water, and heat byproducts [6], [8], [9]. Table 1, different types of fuel cells vary in terms of the electrolytes used and the operating conditions. ...
The membrane in a fuel cell plays an essential role in permeating the ionic charges of positive and negative ions without passing the fuels and electrons through it. The membrane's common materials are perfluorinated polymer, non-fluorinated or hydrocarbon polymer, and natural polymer. The physicochemical properties of the membrane have the most significant influence on the performance of fuel cells in terms of mechanical stability, ionic conductivity, power output, and cell operation longevity. The incorporation of nanoparticles into polymeric-based materials improved the membrane's properties by suppressing fuel crossover, improving water retention, and increasing ionic mobility across the membrane. The effect of incorporating nanoparticles is determined by their type, size, shape, surface acidity, and relationship to the polymer matrix. The blending, sol-gel, and infiltration methods are used to develop the nanocomposite membrane. Compared to a commercial membrane in a fuel cell application, most of these membranes demonstrated superior cell performance. Based on published literature, this review briefly described the design and influence of specific advanced nanomaterials incorporated in polymer matrix toward membrane performance.
... In this work, we design a new experiment for the in situ determination of water uptake (WU) and proton conductivity as a function of temperature and relative humidity based on a temperature-controlled air-tight chamber containing a mass-sensitive langasite resonator and a conductivity probe with interdigitated electrodes. To validate the technique, we investigate a particularly well-known ionomer, sulfonated poly(ether ether ketone) (SPEEK) (Bauer et al., 2000;Di Vona et al., 2009;Kaliaguine et al., 2003; Zhong et al., 2007), prepared by drop coating in thin-film form on the analysis platform. ...
Proton-conducting polymers, such as sulfonated poly(ether ether ketone) (SPEEK), are of great industrial interest. Such proton
exchange membranes show high tendencies for water and water vapor uptake.
The incorporation of water not only leads to mass and dimensional changes,
but also to changes in conductivity by several orders of magnitude. Both
properties highly impact the potential application of the materials and,
therefore, have to be known precisely. As hydration is diffusion controlled,
thin films may behave differently to bulk specimens. However, the
determination of small mass changes occurring in thin-film samples is very
challenging.
In this work, a new measurement setup is presented to simultaneously
characterize the mass change and the conductivity of thin polymer films. The
mass change is measured by resonant piezoelectric spectroscopy (RPS) with a
nanobalance, which is based on high-precision piezoelectric resonators operating in thickness-shear mode (TSM). The mass resolution of this
nanobalance is ±7.9 ng. Electrochemical impedance spectroscopy and
an interdigitated electrode array are used for conductivity measurements.
The approach is validated by comparing two SPEEK films with different
degrees of sulfonation (DS). The relative humidity (RH) in the measurement setup was changed stepwise within the range ∼ 2 % < RH < ∼ 85 %. For both material compositions,
DS = 0.5 and DS = 0.9, the mass uptake, the hydration number and the
proton conductivity are presented and discussed depending on RH.
This newly designed experimental setup allows for in situ characterization of the
properties mentioned above; it can monitor not only the data for the
stationary state, but also the dynamics of the hydration. To the authors'
knowledge this is the first simultaneous and in situ measurement device for
simultaneously sensing mass and conductivity change due to hydration of
polymeric thin-film materials.
... 24 Besides these, sulfonic acid groups may be activated functional groups. 24 For developing polymer electrolytes for fuel cells, the most widely investigated systems include various sulfonated polymers such as Polyetheretherketons (PEEK) [25][26][27][28][29] Polyimide (PI) [24][25] or Polyetheretherketones (PEEKK), 30 Polyethersulfone (PES), [31][32][33][34][35][36] Poly (4-Phenoxybenzoyl-1-4 Phenylene (PPBP), [37][38][39] Poly (p-Phenylenes) (PP). 38 High conductivity is achieved at high degrees of sulfonation, but unfortunately, high sulfonation results in higher swelling leading to poor mechanical properties. ...
As the world’s transportation is seeking to switch towards renewable and sustainable sources of energy, the research in fuel cell technology has gained momentum. Proton exchange membrane fuel cell (PEMFC) operating at temperature range 100–200°C (high-temperature proton exchange membrane fuel cells, HT-PEMFCs) has gained interest in their major application to electric power generation. The most promising material is polybenzimidazoles (PBI). Synthesis methods such as condensation polymerization, solid-state or melt polymerization, etc. give the polymer with different inherent viscosity. The monomer modifications both in tetramine and the diacid, reveal variations in glass transition value. Further insight into the membrane casting solvents and methods along with its proton conductivity has been reviewed. Review paper is comprising of Part 1: for the synthesis methods, structural changes, and applications of PBIs in HT-PEMFCs while, Part 2: for the various kinds of PBIs has been discussed.[Formula: see text]
... One can clearly observe the significant decrease of impedance after infiltration of SPEEK, given that the conductivity of SPEEK [27,[35][36][37] is much higher than that of the nanotubular ZrO 2 matrix [23]. ...
... Aiming for better water retention other approaches have also been explored [12]. LT-PEM are mostly based on a stable fluorinated or polyaromatic backbone polymer, e.g., poly(ethylene-alt-tetrafluoroethylene) (ETFE) [13][14][15][16], poly (vinylidene fluoride) (PVDF) [17][18][19] or poly(ether ether ketone) (PEEK) [20][21][22][23]. Protogenic functional groups such as sulfonic acid groups are ...
Polymer electrolyte membranes (PEM) for potential applications in fuel cells or vanadium redox flow batteries were synthesized and characterized. ETFE (poly (ethylene-alt-tetrafluoroethylene)) and PVDF (poly (vinylidene fluoride)) serving as base materials were activated by electron beam treatment with doses ranging from 50 to 200 kGy and subsequently grafted via radical copolymerization with the functional monomers 2-acrylamido-2-methylpropane sulfonic acid and acrylic acid in aqueous phase. Since protogenic groups are already contained in the monomers, a subsequent sulfonation step is omitted. The mechanical properties were studied via tensile strength measurements. The electrochemical performance of the PEMs was evaluated by electrochemical impedance spectroscopy and fuel cell tests. The proton conductivities and ion exchange capacities are competitive with Nafion 117, the standard material used today.
... The hydrophilic ion clusters are principally responsible for the water uptake. It has been reported that the proton conductivity of sulfonated PEMs depends on the pre-treatment of membrane, degree of substitution (DS), hydration state, temperature, and ambient relative humidity [17]. The percentage water of SPS membrane was found to be 12%. ...
This paper deals with the preparation and characterization of low-cost sulfonated polystyrene (SPS) proton exchange
membrane (PEM) as well as its application in a double-chambered microbial fuel cell by using glucose solution as a
substrate. Characterization of membrane has been done by diffraction scanning calorimetry (DSC), thermogravimetric
analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM)
(before and after the use of 1100 h), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance
(HNMR), and few other methods. Performance of SPS membrane is studied in microbial fuel cell (MFC) in terms of
voltage, power density generated, and organic material removal with variable process parameter initial chemical oxygen
demand (COD) concentration, initial pH, and temperature. Box-Behnken model with three factors (initial COD, initial
pH, and temperature) and three levels is used to fix the experimental conditions for optimization of voltage and current
density using Design Expert software. Maximum voltage and power density generation of 647 mVand 104.7 W/m3 have
been obtained at initial COD 1500 mg/L, anodic pH 7, and temperature 35 °C.
... One can prepare cation-conducting ionomers (including proton exchange membranes) by grafting various cation exchange groups, in the majority of cases sulfonic acid [13][14][15][16] , and anionconducting ionomers (including hydroxide exchange membranes) by anchoring typically quaternary ammonium groups [17][18][19][20] . The ionic conductivity is related to the ion exchange capacity of the polymers, but also to the solvation of the conducting ions and other factors such as the connectivity and tortuosity of the ion conduction channels in the ionomer 21 . ...
We studied the gravimetric and volumetric water uptake and ionic conductivity of two model ionomers, cation-conducting sulfonated poly(ether ether ketone) (SPEEK) and anion-conducting polysulfone-trimethylammonium chloride (PSU-TMA), after immersion in phosphate, acetate and citrate buffer solutions. The equilibrium swelling of SPEEK and PSU-TMA ionomer networks was determined as a function of pH and buffer composition. The hydration data can be interpreted using the osmotic swelling pressure dependence on the ion exchange capacity of the ionomers and the concentration of the electrolyte solutions. In the case of SPEEK, anisotropic swelling is observed in diluted buffer solutions, where the swelling pressure is higher. A large water uptake is observed for citrate ions, due to the large hydration of this bulky anion. The ionic conductivity is related to the conducting ions and, in the case of SPEEK, to sorbed excess electrolyte. The highest ionic conductivity is observed after immersion in phosphate buffers. Ionic cross-linking is for the first time observed in the case of an anion-conducting ionomer in presence of divalent citrate ions, which limits the volumetric swelling and decreases the ionic conductivity of PSU-TMA.
... PAEKs are typically obtained in two ways, namely, through nucleophilic aromatic substitution reactions that form ether bonds or by Friedel-Crafts electrophilic substitutions that form ketone bonds [1][2][3][4][5]. A variety of functional units, such as sulfonyl [6][7][8][9][10], carboxyl [11][12][13][14][15], hydroxyl [13], methyl [13], azobenzene [16], and phthalocyanine [17] groups, have been introduced in order to control the properties of PAEKs and expand their applications. These functionalized PAEKs are prepared through the co-polymerization of monomers bearing the desired functional groups or through the post functionalization of pre-prepared PAEKs. ...
Carboxylated poly(arylene ether ketone)s with hyperbranched and linear architectures were synthesized by the self-condensations of aromatic dicarboxylic anhydrides. A linear poly(arylene ether ketone) was obtained from an AB monomer, 4-phenoxyphthalic anhydride, while a hyperbranched poly(arylene ether ketone) was obtained using an AB2 monomer, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride. The method for the synthesis of the hyperbranched poly(arylene ether ketone) is notable because it provides a high ion-exchange capacity, above 7 mmol g−1, through a one-pot polycondensation.
... One can clearly observe the significant decrease of impedance after infiltration of SPEEK, given that the conductivity of SPEEK [27,[35][36][37] is much higher than that of the nanotubular ZrO 2 matrix [23]. ...
A nanocomposite solid ion conductor was prepared by infiltrating zirconia or titania nanotube arrays, made by electrochemical anodization of Zr or Ti metal, with proton-conducting sulfonated poly(ether-ether-ketone) (SPEEK) ionomer. The resulting material was characterized using scanning electron microscopy, X-ray diffraction, and infrared spectroscopy showing the successful filling of the nanotubular matrix with the ionomer. Impedance spectroscopy revealed a conductivity increase by several orders of magnitude after infiltration; furthermore, the impedance of the TiO2nt-SPEEK nanocomposite is very sensitive to the relative humidity. Possible applications of these ionic conducting nanocomposites include solid-state humidity sensors or heterogeneous catalytic materials.
Graphical abstractᅟ
... It is possible to add only one sulfogroup to the monomer unit. In the case of PEEK, the use of chlorosulfonic acid as a sulfurizing agent destroys the polymer see [34], therefore concentrated sulfuric acid is used for this purpose [35,36]. It is possible to achieve a degree of sulfonation of 30-100% without cross-linking and polymer degradation. ...
... The hydrophilic ion clusters are principally responsible for the water uptake. It has been reported that the proton conductivity of sulfonated PEMs depends on the pre-treatment of membrane, degree of substitution (DS), hydration state, temperature, and ambient relative humidity [17]. The percentage water of SPS membrane was found to be 12%. ...
This paper deals with the preparation and characterization of low-cost sulfonated polystyrene (SPS) proton exchange membrane (PEM) as well as its application in a double-chambered microbial fuel cell by using glucose solution as a substrate. Characterization of membrane has been done by diffraction scanning calorimetry (DSC), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM) (before and after the use of 1100 h), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (HNMR), and few other methods. Performance of SPS membrane is studied in microbial fuel cell (MFC) in terms of voltage, power density generated, and organic material removal with variable process parameter initial chemical oxygen demand (COD) concentration, initial pH, and temperature. Box-Behnken model with three factors (initial COD, initial pH, and temperature) and three levels is used to fix the experimental conditions for optimization of voltage and current density using Design Expert software. Maximum voltage and power density generation of 647 mV and 104.7 W/m³ have been obtained at initial COD 1500 mg/L, anodic pH 7, and temperature 35 °C.
... We found that cis-DSPEEK shows high repulsion for hydrogen transfer and moderate adsorption affinity for protons. Theoretical findings confirm that replace Nafion, various highly hydrophilic materials that are thermally stable at high temperatures have been studied [14][15][16][17][18][19][20][21][22]. Among various polymers, PEEK (polyether ether ketone), used in the PEM industry, is a high-performance engineering thermoplastic polymer with good solvent resistance, excellent thermal oxidation stability, and good mechanical properties [23][24][25][26]. ...
The introduction of a protogenic group such as sulfonic acid enables the operation of polymer electrolyte membrane for fuel cells at intermediate temperatures (> 100 °C) and very low humidity. It has been reported that the addition of a strongly acidic sulfonic acid group to hydrophobic polyether ether ketone (PEEK) creates the water permeability and proton transfer. In order to understand how sulfonic acid develops hydrophilicity, we conducted density functional theory calculations to determine the adsorption affinity of water for sulfonated PEEK (SPEEK), which represents the binding energy and band gap between HOMO (highest occupied molecular orbital) of SPEEK and LUMO (lowest unoccupied molecular orbital) of water molecules. Moreover, we designed disulfonated PEEKs (DSPEEK) with cis- and trans-conformations and found that cis-DSPEEK exhibits higher adsorption affinity for water with strong hydrogen bonds. This is attributed to the narrow energy gap of water molecules on cis-DSPEEK. Furthermore, we investigated proton adsorption in the presence of water to determine the effect of hydrophilic environment on the proton exchange in SPEEK. We found that cis-DSPEEK shows high repulsion for hydrogen transfer and moderate adsorption affinity for protons. Theoretical findings confirm that sulfonation ultimately yields hydrophilicity and developed proton transfer ability for PEEK, leading to a suitable structure for preferable proton exchange membrane.
... Much research in this domain has been devoted to the use of perfluorosulfonic acid (PFSA) ionomers [5][6][7][8], including composite/blend membranes [9][10][11] and alternative functionalized polyaromatic systems [12][13][14][15]. In this last approach, sulfonated polyether ether ketone (sPEEK) exhibits lower cost, lower fuel permeability and easier availability than PFSA [16,17] but, at high levels of sulfonation, presents poor dimensional stability [18,19]. However, it was demonstrated that tuning the degree of sulfonation [20] and above all the possibility of crosslinking the polymer are valuable strategies to increase the stability of sPEEK in fuel cell operation conditions, due to an increase in the mechanical strength and a decrease in swelling and water uptake [21][22][23][24][25][26]. ...
Nanocomposite proton exchange membranes based on fibrous sulfonated poly(ether ether ketone) (sPEEK) and Aquivion® have been prepared by a two-step procedure involving electrospinning and impregnation. The dependence of their proton conductivity, water uptake, dimensional swelling and mechanical strength on the sulfonation degree of the sPEEK fibers has been determined and compared to a pristine Aquivion® membrane. The preparation of a composite membrane where a highly sulfonated PEEK mat is crosslinked previous to Aquivion® impregnation was also investigated. In all cases, the composite membranes demonstrate a diminution in proton conductivity compared to the non-reinforced membrane, but enhanced mechanical properties and dimensional stability. In particular, the system comprising crosslinked sPEEK presented the best mechanical and swelling behaviors with a lower conductivity loss.
... Nafion was also found to release fluoride during fuel cell application that in turn affects the performance of the cell (Smitha et al. 2003). Other than Nafion, many composite polymers have been tested as potential PEM such as polyether ether ketone (PEEK), poly(arylene-ether-sulfone) (PSU), PVDF-graft styrene, acid-doped polybenzimidazole (PBI), and polyphosphazene (Wainright et al. 1995;Lehtinen et al. 1998;Bauer et al. 2000;Lufrano et al. 2000;Alberti et al. 2001;Carter et al. 2002;Jörissen et al. 2002). However, all these membranes do not possess the performance characteristics as compared to Nafion's. ...
... One of the approaches is based on the attachment of sulfonic acid groups through sulfonation or by direct polymerization of the sulfonated monomers to thermally stable aromatic polymers [173]. Sulfonated poly(arylenethersulfone) (sPES) membrane with 500 h durability at 100 • C [174,175] and sulfonated poly(etheretherketone) (sPEEK) membrane with durability about 300 h at above 90 • C [176,177] were reported. ...
Polymer electrolyte membranes are key components in electrochemical power sources that are receiving ever-growing demand for the development of more efficient, reliable and environmentally friendly energy systems. Ongoing research is focusing on materials with high ionic conductivity and stability, at low cost. Among different methods, radiation-induced grafting is a universal attractive method for preparation of polymer electrolyte materials with tunable properties for various energy conversion and energy storage applications. This review addresses recent advances in the application of radiation-induced grafting techniques for the preparation of polymer electrolyte membranes/separators for emerging electrochemical devices such as fuel cells, batteries and supercapacitors. The challenges associated with the current state-of-the-art materials are highlighted, together with \new directions that should be considered for future research.
... Part III Part II Part I Fig. 6 Cell performance (current density against power density) of 20 % glycidyl methacrylate cast membrane (PVA/GMA at 0.5 % titania nanoparticles) and compressed Nafion-1135 at 80°C temperature and 100 % RH 0.05 V due to the MEA not being optimized for water measurement and the fluctuation of the gas pressure in cell. The obvious decrease in cell voltage after a certain time (up to 450 h) was caused by a reactant crossover, which was confirmed by the membrane edge crack along the electrodes [37,38]. On the other hand, the cell voltage of the membrane under study progressively decreased from 0.65 to 0.28 V over the 450 h. ...
Gamma irradiation was used for cross-linking poly (vinyl alcohol) (PVA) and glycidyl methacrylate (GMA) mixtures of different compositions. Specifically, 0.5 wt% titanium dioxide (TiO2) nanoparticles were added and blended well with the casting mixture prior to exposure to the irradiation dose. Next, 10 kGy was found to be the optimum dose for achieving the desired physical and chemical properties of the membrane. Characterizations of the cast membranes were carried out by Fourier transformer infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and positron annihilation lifetime spectroscopy (PALS). The properties of the membrane were also characterized by ion exchange capacity (IEC), water uptake, and tensile strength and were assessed in relation to application in proton exchange membrane fuel cells (PEMFCs). A maximum proton conductivity of 7.3 × 10−2 S cm−1 was obtained for the membrane having 20 % GMA, 80 % PVA, and 0.5 % TiO2, and its activity and durability in a membrane electrode assembly (MEA) were compared to those of a commercial Nafion® 1350.
... SPEEK-inorganic (SiO 2 , zirconium phosphate, and sulfenylphosphonate) nanocomposite PEMs are prepared either by infiltration of ZrOCl 2 , followed by reaction with phosphoric acid, or by blending of mesoporous ZrP/SiO 2 [60][61][62][63][64]. The conductive inorganic component enhances membrane conductivity without the loss of flexibility. ...
This chapter focuses on the study of the development of sol-gel materials with application in proton exchange membrane fuel cells (PEMFCs) and solid oxide fuel cells (SOFCs). The sol-gel method is an excellent process to produce proton-conducting materials because the gels contain a large number of micropores filled with liquid that can be used for fast proton transport. The chapter also discusses the use of sol-gel materials in lithium ion batteries. It discusses two of the newest electrodes (Li4Ti5O12 and LiFePO4) and solid electrolytes. Sol–gel synthesis is a successful method to prepare hybrid electrolyte materials at low temperature using inexpensive precursors of metal salts (nitrates, acetates, or oxides) combined with metal alkoxides. The introduction of inorganic fillers to poly(ethylene oxide) (PEO)-based electrolytes, in order to design hybrid materials, improves the conductivity and mechanical properties of the electrolytes.
... 22,[39][40][41][42] Although polyaromatic PEMs normally show much less time-dependent behaviors, extensive hydrothermal treatments can cause a notable conductivity and 336 Y. S. Kim and K.-S. Lee morphological changes over time. 11,43,44 Other factors such as cell clamp pressure and water transport restraint by the gas diffusion layer and electrodes also can substantially alter the PEM ion conduction. Therefore, low RH conductivity of stand-alone PEMs can be substantially different and thus only serve as a general guideline. ...
Polymer electrolyte membranes (PEMs) play a crucial role for use in major polymer-based fuel cell applications. Key PEM properties such as ion conductivity, reactant permeability, and chemical/physical stability are strongly influenced by the chemical structure and processing conditions of PEMs. This paper presents the property measurement techniques of PEMs using stand-alone membranes and membrane electrode assembly (MEA) configurations. PEM properties such as ion exchange capacity, water uptake, ion conductivity, gas/liquid permeability, and chemical/physical stability are discussed with emphasis on measurement techniques. In addition, the measurement techniques for polymer electrolyte in the catalyst layer are briefly discussed. This review may give some insight to polymer scientists when novel PEM materials are designed, prepared, screened, or fine-tuned for advanced fuel cell systems.
... Studies on anionexchange membranes (AEMs) [11] and different perfluorocarbon cation-exchange membranes (CEMs) [12] using thermogravimetric analysis suggest that temperature may reach 150 1C before the membranes start to be affected. Sulfonic acid sites in CEMs are known to be lost around 240 1C [10,13]. However, this technique does not reproduce the real conditions of ED operations as membrane samples are heated under an inert atmosphere, and they are kept at high temperatures only for a few minutes. ...
In this paper, the physicochemical, structural and mechanical properties of an anion-exchange membrane were investigated, during its lifetime in industrial electrodialysis for whey demineralization. Several analytical techniques permitted to disclose the membrane structure and to describe the evolution with time of the membrane properties. The homogeneous anion-exchange membrane, AMX-SB, is constituted of a semi-interpenetrating polymer network of poly(vinyl chloride) and functional poly(styrene-. co-divinylbenzene). No significant loss of the ion-exchange capacity or degradation of the functional poly(styrene-. co-divinylbenzene) chains were detected. However, fouling caused a decrease in the counter-ion mobility within the membrane, which produced a reduction of the electrical conductivity. A progressive loss of poly(vinyl chloride), which was degraded or washed out from the membrane during the cleaning-in-place process, was clearly evidenced. This led to the formation of non-charged pores available for electroneutral electrolyte solution and large molecules, such as lactose and proteins. The occurrence of such pores resulted in an increase in electrolyte permeability through the membrane and a rebound of the conductivity at the last stage of electrodialysis. The microheterogeneous model was applied to well account for these changes. By means of tensile strength tests, it was possible to investigate the mechanical properties of the membrane, which turned gradually from a rigid and tough material, to a rigid and brittle one, due to the loss of poly(vinyl chloride), leading to the end of the membrane lifetime.
... The following text is an attempt to present recent achievements made by our group for the phenomenological description of hydration and ionic conductivity of ionomers and their relationship . We will take as practical examples sulfonated poly-etherether-ketone (SPEEK) and sulfonated polyphenylsulfone (SPPSU) for which numerous experimental properties have been published over the years (Bauer et al., 2000; Rikukawa and Sanui, 2000; Li et al., 2003; Robertson et al., 2003; Roziere and Jones, 2003; Xing et al., 2004; Reyna-Valencia et al., 2006; Di Vona et al., 2009, 2010 Sgreccia et al., 2010; Wu et al., 2011; Hou et al., 2012; Knauth et al., 2013) but the discussed relations are also valid for other ionomers. ...
The hydration of proton-conducting ionomers is described in terms of a simplified model, where only osmotic and elastic contributions to the Gibbs free energy of hydration are considered. Although only two physically meaningful parameters are used – the deformation parameter, inversely proportional to the elastic modulus of the ionomer, and the free volume parameter – simulated hydration isotherms are in good agreement with the experiment. The proton mobility u inside the electrolyte solution of the ionomer is calculated from the proton conductivity determined at various hydration numbers. Its variation with the proton concentration c reveals the percolation threshold of hydrated nanometric channels and the tortuosity of the membrane. Above the percolation threshold, a power law u ~ c−3 is observed, in agreement with the “universal” law for 3-dimensional percolation. The proton conductivity σ shows at 100°C a maximum of 0.2 S/cm at a hydration number ~90. The σ = f(c) plot allows to predict, which hydration conditions are necessary for a desired area specific resistance.
During the past decade proton exchange membrane fuel cells (PEMFCs) as one kind of the potential clean energy sources for electric vehicles and portable electronic devices are attracting more and more attentions. Although Nafion® membranes are considered as the benchmark of proton exchange membranes (PEMs), the drawbacks of Nafion® membranes restrict the commercialization in the practical application of PEMFCs. As of today, the attention is to focus on developing both high-performance and low-cost PEMs to replace Nafion® membranes. In all of these PEMs, sulfonated poly(arylene ether ketone)s (SPAEKs) and sulfonated poly(arylene ether sulfone)s (SPAESs) are the most promising candidates due to their excellent performance and low price. In this review, the efforts of SPAEK and SPAES membranes are classified and introduced according to the chemical compositions, the microstructures and configurations, as well as the composites with polymers and/or inorganic fillers. Specifically, several perspectives related to the modification and composition of SPAESs and SPAEKs are proposed, aiming to provide the development progress and the promising research directions in this field.
Fuel cell has become an emerging renewable energy device with potential to meet energy demand by portable and transport applications with zero-emission, easy operation, and compact design. The chapter provides an insight into design and development of membranes for PEMFCs and recent progresses made in membranes so far. Although majority of research has focused on fluorinated and non-fluorinated membranes, these polymeric membranes have showed deteriorated properties at elevated temperature (>80oC) and lower relative humidity (30%). Considering the major issues with polymeric membranes, the authors have reviewed inorganic-organic nanocomposite membranes showing improved physical and electrochemical properties at elevated temperature and lower relative humidity. Recently, metal-organic framework (MOF), a novel and unique material, has attracted tremendous attention due to their enhanced proton conductivity, easy functionality, and stability. MOFs have also exhibited excellent compatibility with different polymeric materials that are also discussed in this chapter.
Direct methanol fuel cells (DMFCs) are being considered as one of the highly valued renewable energy sources, as evident from enormous work being carried out on the development of these devices over the past three decades. DMFCs are devices that directly transform the stored chemical energy of methanol into usable electrical energy. For this purpose, the fuel methanol gets oxidized at the anode of a DMFC, and oxygen gets reduced at the cathode in the presence of suitable electrocatalysts. Both the electrooxidation and electroreduction processes require involvement of protons and electrons. These electrode reactions, along with the transport of protons through the membrane electrolyte separator, are the backbone of DMFC operation, and the efficiencies of these phenomena are critical in the ultimate performance of the DMFC device. Keeping this in mind, this article has been completely dedicated to discussion and analysis of in‐depth fundamental electrochemistry involved within the membrane electrode assembly of DMFCs. In this regard, the involved electrochemical reactions in both acidic and alkaline media have been systematically described, with precise emphasis on the methanol oxidation reaction and the oxygen reduction reaction. In addition, the membrane characteristics and the mixed potential arising due to methanol crossover through the membrane have also been explained. Finally, the fundamental electrochemical aspects of DMFCs have been discussed systematically for easy understanding of the readers.
The objective of this PhD thesis was to gain insight into the proton dynamics and water adsorption mechanisms in novel porous materials that have been identified experimentally as promising candidates for low temperature proton conduction and adsorption-based heat reallocation-related applications. This was achieved by combining advanced computational tools at the electronic (Density Functional Theory) and atomic (force field_based Monte Carlo and Molecular Dynamics) levels to (i) reveal the water-assisted proton migration pathway through the pores of the hybrid metal organic frameworks MIL-163(Zr) and KAUST-7’and the inorganic phosphonate TiIVTiIV(HPO4)4 materials at the origin of their outstanding proton conduction performances and (ii) explain the water adsorption behaviors of a series of metal organic frameworks CUK-1(Me), MOF-801(Zr) and MIL-100(Fe) that can be tuned by changing the nature of the metal center, creating defects and incorporating coordinatively unsaturated sites. Such a fundamental understanding is expected to pave the way towards a more efficient development of materials for the two explored applications.
Electrostatic forces greatly affect the overall dynamics and diffusional activities of suspended charged particles in crowded environments. Accordingly, the concentration of counter-, or co-ions in a fluid -- ``the salt" -- determines the range, strength and order of electrostatic interactions between particles. This environment fosters engineering routes for controlling directed assembly of particles at both the micro- and nano-scale. Here, we analyzed two computational modeling schemes that considered salt within suspensions of charged particles, or polyelectrolytes: discrete and continuum. Electrostatic interactions were included through a Green's function formalism, where the confined fundamental solution for Poisson's equation is resolved by the General Geometry Ewald-like method. For the discrete model, the salt was considered as regularized point-charges with a specific valence and size, while concentration fields were defined for each ionic species for the continuum model. These considerations were evolved using Brownian dynamics of the suspended charged particles and the discrete salt ions, while a convection--diffusion transport equation, including the Nernst-Planck diffusion mechanism, accounted for the dynamics of the concentration fields. The salt/particle models were considered as suspensions under slit-confinement conditions for creating crowded ``macro-ions," where density distributions and radial distribution functions were used to compare and differentiate computational models. Importantly, our analysis shows that disparate length scales, or increased system size presented by the salt and suspended particles, are best dealt with using concentration fields to model the ions. These findings were then validated by novel simulations of a semi-permeable polyelectrolyte membrane, at the mesoscale, from which ionic channels emerged and enable ion conduction.
This review is designed as a comprehensive source of research on polyimide and polyimide composite-based fuel cell membranes. Polyimide and modified polyimide-based nanocomposite fuel cell membranes have gained research attention due to high operation temperature of ∼ 150 °C. To increase lifetime of polyimide-based fuel-cell, water and dimensional stability of hydrated membrane have been studied. Nanofillers such as silica, titania, graphene, carbon nanotube, and polyhedral oligomeric silsesquioxane have been reinforced in polyimide to improve proton conductivity (at low humidity/high temperature) and water stability. Design of new polyimide composite membranes must be focused in future for high water, chemical, and mechanical stability.
Nafion has been the material of choice for polymer electrolyte membrane fuel cells (PEMFCs), but during the last two decades, considerable efforts have been made to find an alternative with similar or better physicochemical properties and with lower manufacturing cost. Developments over the last two decades have resulted to some novel membrane materials with improved properties. Among the materials researched and developed, sulfonated poly(ether ether ketone) (SPEEK) has been the most promising and has the potential for commercialization. In this chapter, the properties of SPEEK and its characteristics are discussed.
The degradation of high-temperature proton exchange membrane fuel cells with phosphoric acid-doped polybenzimidazole (PBI) based membranes is one of the key challenges for early commercialization. The aim of this work is to analyze the influence of different reinforcement strategies on the performance and degradation of PBI-based membranes. The effects on the membranes were analyzed by polarization curves, long term operation under constant load, electrochemical impedance spectroscopy, in-situ cyclic voltammetry and electron microscopy techniques. The results show that the molecular weight distribution of the PBI and the different types of reinforcement have a distinct influence on the poisoning of the cathode layer and the mass transport resistance of the cathode microporous layer. The reasons are discussed in detail and a new degradation mechanism is proposed. A significant reduction of the degradation was obtained by enhancing the interactions between the PBI polymer chains via cross-linking.
Researching on fuel cells is an important direction of developing new energy in the twenty-first century. Fuel cells present broad application in the aerospace, military, power stations, electric vehicles and portable power applications due to their high power conversion efficiency (40-60%), environmental friendliness and reliability, small size, low noise and so on. This review gives an introduction into the fundamental, characteristics and applications of various fuel cells. In addition, the development of increasing use of polymers in fuel cells is also prospected.
This chapter is dedicated to some significant applications of membranes in the field of energy, focusing on fuel cells and electrolytic cells. Both electrochemical devices are part of an international effort at both fundamental and demonstration levels and, in some specific cases, market entry has already begun. Membranes can be considered as separators between cathodes and anodes. As fuel cells are extremely varied, with working temperatures between 80°C and 900°C, and electrolytes from liquid to solid passing by molten salts, they are of particular interest for the research and development of new membranes. The situation is quite similar to the case of electrolysers dedicated to water electrolysis. The principal features of these devices will be outlined, with emphasis on the properties of the state-of-the-art membranes and on the present innovations in this area.
This paper presents the main results obtained during the European project (FCH-JU) "LoLiPEM - Long-life PEM-FCH & CHP systems". The paper describes significant improvements in the polymer electrolyte by tailored heat treatments for cross-linking of Sulfonated Poly(ether ether ketone) (SPEEK), obtained without any addition of cross-linker species. The reported properties of the ionomers include mechanical properties, gas permeability and ionic conductivity.Innovative gas-diffusion electrodes are fabricated by the electrochemical deposition of Pt catalyst; the fuel cell current-voltage characteristics are reported with Nafion and SPEEK-based binder.The fuel cell performances at 80 °C of membrane-electrode-assemblies containing a SPEEK membrane with a cross-linking degree of 32% are among the best in the literature compared with the PEMFC using membrane alternative than Nafion.
The synthesis, processing, crosslinking, and characterization of original proton conducting membranes are presented. First, fluorinated terpolymers were obtained from the radical terpolymerization of chlorotrifluoroethylene (CTFE), 2-chloroethyl vinyl ether (CEVE) and glycerine carbonate vinyl ether (GCVE) followed by two chemical modifications into poly(IEVE-alt-CTFE)x-g-1H-1,2,4-triazole-3-thiol-co-(GCVE-alt-CTFE)y terpolymer that bear dangling cyclocarbonate and triazole functions (where IEVE stands for 2-iodoethyl vinyl ether). The successful grafting (overall yields >80%) of these terpolymers was monitored by 1H and 19F NMR spectroscopy and by thermal analyses (DSC and TGA) and did not shown any opening of the cyclocarbonate ring. Such fluorofunctional terpolymers were involved in the preparation of blend membranes with sulfonated PEEK (sPEEK), followed by the crosslinking in the presence of two telechelic diamines of different chain lengths via cyclocarbonate/amine reaction. The characterizations of these resulting membranes (thickness=35-50μm) in term of thermal stability (>200°C under air), water uptake (as low as <20%), conductivity, and mechanical properties (strain-stress relationships and by dynamical mechanical analysis) were comprehensively investigated to understand the influence of the nature of the diamines, the crosslinking, and the presence of azole group on membrane microstructure. Proton conductivities of crosslinked blend membranes comprising such fluorinated polymer components functionalized with triazole at 140°C and at low relative humidity (<25%) reached 4.3mScm-1 for a blend membrane containing 60%-wt of s-PEEK and 40%-wt of poly(CTFE-alt-IEVE)82%-g-1H-1,2,4-triazole-3-thiol86%-co-(CTFE-alt-GCVE)18% terpolymer. They displayed glass transition temperatures, Young modulus and tensile strengths up to 223°C, 4MPa and 6%, respectively.
The research works reported in the manuscript are a contribution to the study of polyelectrolytes for Proton Exchange Membrane Fuel Cells (PEMFC). They are supported by two investigation tools, i.e. the study of model molecules and accurate conductivity measurements. With regard to the material science domain, the optimization of polysulfone sulfonation procedure allows chain breakings to be reduced and even eliminated while obtaining reproducible sulfonation degrees. It is thus possible to improve the mechanical properties of the dense membrane elaborated with these polyelectrolytes before performing the tests on the MEA (Membrane Electrode Assembly). In parallel, the fonctionnalisation of microporous silicon made it possible to prepare polyelectrolytes reinforced by the mechanical strength of the silicon separator. With regard to the physicochemical and electrochemical characterizations, the model molecules, with the same functions and groups than for associated polymers, make it possible to amplify the electrochemical or thermal phenomena vs. the corresponding polymers. Thus, they simulate an accelerated ageing of the polye-lectrolytes. The development of a new conductivity measurement set allows conductivity to be obtained with a great accuracy, in a wide range of temperature and relative humidity.
Devices such as fuel cells require the use of materials that allow proton conduction even at low relative humidities. The present work proposes the synthesis of new proton conductors by reaction of colloidal zirconium oxide with organically modified phosphates and phosphonates. Accurate NMR spectroscopy studies allowed to determine the distribution of protons among water and acidic sites grafted onto the zirconia surface. Macroscopic conductivity measurements demonstrate that the limiting step is the intergranular protonic transport. However, Nuclear Magnetic relaxation studies (T1, T2) and relaxometry allowed to study the proton diffusion mechanisms which are of vehicular type under hydrated conditions (simply H3O+ diffusion) and of Grothus-type in anhydrous conditions, associated to H+ hopping between adjacent basic sites built with grafted molecules.
A novel fluorene-containing poly(arylene ether ketone) were synthesized followed by sulfonating into a series of sulfonated fluorene-containing poly(arylene ether ketone)s using chlorosulfonic acid. The sulfonated polymers were thereafter cast into membranes from their solutions. The properties of the ionic exchange capacity, sulfonation degree, water-uptake, mechanical properties, thermal and oxidative stabilities as well as proton conductivities of the membranes were fully investigated. It was found that their proton conductivities increased continuously with increasing testing temperature up to 130 degrees C at 100% relative humidity. The membrane exhibited a higher proton conductivity and other comprehensive properties for proton exchange membrane than Nafion-117 at 130 degrees C under same testing conditions. (c) 2006 Elsevier Ltd. All rights reserved.
Sulfonated PVC (PVCs) membranes were synthesized first using an ethylenediamine solution to aminate the porous free-standing PVC membrane. This modified PVC was then reacted with sulfuric acid to form the PVCs material. The reaction time was varied to give PVCs materials of different degrees of sulfonation (DS). The membranes were characterized with FTIR and elemental analysis to confirm the presence of a -SO3H group. SEM was used to ensure the morphology had not changed during the reaction. Water-uptake and proton conductivity were measured and it was found that as the reaction time increased, both conductivity and water-uptake of the membranes increased compared to the unmodified PVC material. This study demonstrates a novel technique to impart increased water-uptake and proton conductivity to a PVC polymer without destroying the pre-existing membrane morphology.
The feasibility of sulfonated poly(ether ether ketone) (SPEEK) membranes reinforced with unmodified silica (SiO2) and modified silica (SiO2-SO3H) nanoparticles as proton exchange membranes (PEMs) was investigated here. The sulfonated membranes were characterized for degree of sulfonation, thermal stability, as well as water/methanol uptake properties. The incorporation of SiO2 increased the hydrophilic behavior thus allowing more water retention, which facilitated an easy pathway for proton transfer. However, a reduction in proton conductivity was observed. The strong -SO3H/-SO3H interaction between SPEEK chains and SiO2-SO3H led to ionic cross-linking in the membrane structure, which compensated for this decrement in proton conductivity. The fuel cell performance study revealed the potential of SPEEK/SiO2-SO3H nanocomposite membrane to act as an efficient PEM for fuel cell application.
Hydrogen is considered one of the most important energy vector of the future and fuel in transport sector. The Fuel Cells (FCs) Traction System present some advantages respect to the traditional traction engine, consisting in lower emissions and noise. The more suitable Fuel Cells in automotive applications are those that use Polymer Electrolyte Membrane (PEM). The main obstacles to the commercialization of PEM fuel cells are largely concerning the cost, mechanical weakness and low durability of the membranes with increasing temperature. This latter aspect in particular referring to the fact that water is present in the membranes, thereby limiting the operating temperature of a fuel cell, which on average is about 80 °C. This in turn results in lower performance of the fuel cells due to a slower kinetics of electrodes and essentially no CO tolerance. It can groped to improve the performance of a PEM increasing the temperature above 100 °C, changing the membrane type making it resistant to the natural increase in temperature of the system so as to improve the electrodes kinetics. The present work has the purpose of highlighting the orientation of the current research towards the development of specific types of membrane for the FC performance improvement.
In this study the ex-situ and in-situ behavior of acid-base blend membranes from sulfonated polyethersulfone and a partially fluorinated sulfonated polymer (prepared by condensation of decafluorobipenyl with bisphenol AF, followed by sulfonation of the obtained polymer) and two different polybenzmidazoles (F-6-PBI and PBIOO(R)) was investigated. Two types of acid-base blend membranes from the abovementioned polymers were prepared and characterized: acid-base blend membranes with a molar excess of acidic blend component for low-T H-2 fuel cells (LT-FC) where the proton conductivity is overtaken by the sulfonic acid groups, and blend membranes comprising a molar excess of basic blend component which were subsequently doped with phosphoric acid for the usage in intermediate-T H-2 fuel cells (IT-FC) where the network of phosphoric acid molecules in the membrane provides the proton conduction. For elucidation of the radical stability of the membranes, the membranes were subjected to Fenton's Reagent and were operated in a H-2-PEMFC. After these tests, the membranes were investigated via SEC for molecular weight degradation. As a result, correlations could be found between degradation of the blend membranes in the fuel cell and after Fenton's test. Moreover, at IT-FC membranes, a correlation could be found between doping degree and fuel cell performance which are discussed in this paper. One of the membranes, a H3PO4-doped base-excess membrane from sPSU and PBIOO showed an excellent performance in an IT-K at 180 degrees C of 0.85 A/cm(2)@0.5 V without pressurization of the reactant gases.
A new membrane material for polymer electrolyte fuel cells (PEFC), ETFE-graft-poly(alpha-methylstyrene-sulfonic acid-co-methacrylonitrile), is presented, Its preparation by radiation-induced grafting and the dependence of the reaction kinetics on the irradiation dose (3 and 15 kGy) and crosslinker concentration are reported. A series of divinylbenzene crosslinked and uncrosslinked membranes is characterised with respect to ion exchange capacity (IEC) (up to 2.1 mmol/g), proton conductivity (up to 92 mS/cm at room temperature), and water uptake (10-67%). Furthermore, the correlation between the dimensional stability of the membrane and the graft level is presented. The ex situ hydrolytic stability of the membranes was tested and analysed by infrared (IR) spectroscopy. In a hydrogen/oxygen PEFC at 80 degrees C, Nafion 212 and a 35 mu m thick grafted membrane showed the same performance, whereas the hydrogen permeability of the grafted membrane is only one third compared to that of Nafion 212, (c) 2013 Elsevier B.V. All rights reserved
The proton mobility in a new family of PEMFC blend membranes containing 1,2,4-triazole groups is studied by infrared spectroscopy and particularly by 1H Magic Angle Spinning Solid State NMR spectroscopy. These membranes are usually used for fuel cell operation at low relative humidity (RH < 25%). The studied membrane contains 40%-wt of a partially fluorinated alternating poly(2-iodoethyl vinyl ether-alt-chlorotrifluoroethylene)-g-1H-1,2,4-triazole-3-thiol95% copolymer (II) and 60%-wt of sulfonated poly(ether ether ketone), sulfonated PEEK (IEC = 1.3 meq g−1) (r = n-NH/n-SO3H = 1.7). In this study, the 1D 1H MAS spectrum of copolymer (II) was fully determined. Following acidification of a suspension of this copolymer leading to acidified (II′) copolymer, the 1D 1H MAS spectrum showed two populations corresponding to triazole and triazolium groups. The 2D 1H EXchange SpectroscopY spectrum of (II′) showed faster proton dynamics of the triazolium protonated form than in the copolymer containing only non protonated triazole groups. Inhomogeneity of (II′) sample was confirmed by the different spin dynamics of triazole and triazolium ring protons. In the homogeneous membrane, spin dynamics were further increased (i.e. very short mixing time to observe proton diffusion). Hence, this work provides confirmation that protonation acts in favour of proton mobility in the material at room temperature, and provides experimental evidence for the increase of proton mobility due to triazole protonation from the sulfonic acid groups of sPEEK.
This review describes main strategies for the development of sulfonated aromatic polymers (SAP) with optimal properties for medium temperature (90-120 degrees C) polymer electrolyte membrane fuel cell applications. SAP are promising economical polymer electrolytes, but there still exist some challenges about these materials due mainly to excessive swelling in water, poor mechanical strength and low dimensional stability. Here, the state-of-the-art of SAP is reviewed and the main focus will be directed to properties of SAP, including proton conductivity, water uptake, mechanical strength, permeability. Especially three approaches to improve the performances are addressed: the formation of copolymers, the formation of hybrid materials and the polymer reticulation.
A state-of-the-art in radiation-induced graft copolymerization of styrene and acrylic acid monomers into Teflon-FEP films is presented with a view to develop proton exchange membranes for various applications. This process offers an easy control over the composition of
a membrane by careful variation in radiation dose, dose rate, monomer concentration, and temperature of the grafting reaction. By varying the nature and the amount of the grafted content, it is possible to achieve a membrane with desired physico-chemical properties. In this paper, a correlation
among the degree of grafting, structural changes, and properties of graft copolymer membranes is discussed.
Two complementary methods were developed to produce sulphonated poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene) (SPEEK) with random, homogeneous compositions over the range of zero to one sulphonate group per repeat unit. The sodium salts (Na-SPEEK) were prepared from about 5 to 100% sodium sulphonate. They displayed excellent thermal stability. The behaviour of Tg, ΔTg and ΔCp at the glass transition as a function of composition suggested the onset of ionic clustering below 25 to 30% sodium sulphonate—an observation confirmed by preliminary SAXS studies. In particular, Tg increased sigmoidally from about 150°C for 5% Na-SPEEK to 415°C for 100% Na-SPEEK. No evidence of crystallinity was observed by d.s.c. in melted and quenched samples above 9% sodium sulphonate. The equilibrium water content at room temperature and 58% relative humidity was four molecules of water per sodium sulphonate group for all compositions. For immersed films, this value increased from 8 molecules of water per sodium sulphonate group for 38% Na-SPEEK to an indeterminably large number for 100% Na-SPEEK, which slowly dissolved. Upon re-equilibration at 58% relative humidity, the water content of the films decreased to about 5.5 molecules per sodium sulphonate group. A low temperature (−80°C to −60°C) mechanical relaxation peak was present in the films conditioned at 58% relative humidity.
A new proton conducting material, poly(vinylidene fluoride) (PVDF) grafted with polystyrene (PS) and sulfonated (PVDF–SPS), has been investigated with regard to water uptake and the state of water in the material. The water uptake was estimated for the materials exposed to liquid water, in the temperature range between 22 and 100°C, and to water vapour of different water activities. The water uptake from saturated water vapour was found to be close to that from liquid water. The state of the absorbed water has been studied by Raman spectroscopy. We found that in the porous materials the state of water is similar to that of bulk water whereas in the non-porous samples a significant part of the absorbed water differs from that of the bulk.
A new type of reinforced composite perfluorinated polymer electrolyte membrane, GORE-SELECT{trademark} (W.L. Gore & Assoc.), is characterized and tested for fuel cell applications. Very thin membranes (5-20 {mu}m thick) are available. The combination of reinforcement and thinness provides high membrane, conductances (80 S/cm{sup 2} for a 12 {mu}m thick membrane at 25{degrees}C) and improved water distribution in the operating fuel cell without sacrificing longevity or durability. In contrast to nonreinforced perfluorinated membranes, the x-y dimensions of the GORE-SELECT membranes are relatively unaffected by the hydration state. This feature may be important from the viewpoints of membrane/electrode interface stability and fuel cell manufacturability.
PEEK, chemically identified as poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene), is a melt processable aromatic polymer which has recently been introduced. This polymer is said to possess excellent thermal stability, chemical resistance, and electrical and mechanical properties. Additionally, chemical modifications of this polymer are of interest. A discription is given of the controlled sulphonation and neutralization of PEEK, the characterization of sulphonated PEEK, and the effect of this modification on crystallinity, the thermal transition behavior, and the thermal stability.
Proton exchange membranes for fuel cell applications were synthesized by pre-irradiation grafting of styrene/divinylbenzene mixtures into poly(fluoroethylene-co-hexafluoropropylene) films and subsequent sulfonation. Grafting of pre-existing films overcomes the problem of shaping the grafted polymer into thin membranes and makes this process a potentially cheap and easy technique for the preparation of solid polymer electrolytes.The grafted membranes were characterized by measuring their ion exchange capacity, swelling, specific resistivity and area resistance. Due to their thickness in the range 67–211 μm, some of the membranes have a considerably lower resistance than the most widely used membrane Nafion® 117 (DuPont). The short-term and long-term performance of these membranes was investigated in fuel cells. Thin (< 100 μm), highly crosslinked (12% divinylbenzene) membranes show the best performance in the fuel cells. Tests for periods of up to 1400 h were performed to examine membrane stability and the degradation of grafted membranes.
This project is an attempt to synthesize and fabricate proton exchange membranes for hydrogen production via water electrolysis that can take advantage of the better kinetic and thermodynamic conditions that exist at higher temperatures. Current PEM technology is limited to the 125–150 °C range. Based on previous work evaluating thermohydrolytic stability, several families of polymers were chosen as viable candidates: polyether ketones, polyether sulfones, polybenzimidazoles, and polyphenyl quinoxalines. Representatives of each were converted into ionomers via sulfonation and fashioned into membranes for evaluation. In particular, the sulfonated polyetheretherketone, or SPEEK, was examined by thermoconductimetric analysis and performance tested in an electrolysis cell. Results comparable to commercial perfluorocarbon sulfonates were obtained.
Sulfonated poly(arylene ether sulfones) with various sulfonation levels have been prepared and evaluated as solid polymer electrolytes in electrolysers and fuel cells. Solution and slurry sulfonation of poly(arylene ether sulfones) such as Udel® P-1700 (PSU) and Victrex® PES 5200P (PES) yield polyelectrolytes which have been characterized using FTIR and 1H-NMR spectroscopy, titration, thermal analysis, and electrochemical characterization such as resistivity, selectivity of ion permeation, current/voltage plot and life time test in an electrolysis cell. In contrast to the sulfonated PSU, the PES sulfonated in a slurry process was water insoluble, even at high sulfonation levels of 90 mol%, and gave significantly improved electrochemical properties similar to those of fluorine-containing polyelectrolytes used in commercial membrane systems. A versatile in-situ crosslinking technique has been developed to crosslink the sulfonated poly (arylene ether sulfone) electrolytes during membrane processing in order to substantially reduce water swelling without impairing other membrane properties such as proton conductivity.
Grafting of sulfonated aryl groups on to polybenzimidazole, PBI, leads to a proton conducting polymer. The synthetic route allows close control of the degree of sulfonation, and a range of samples have been prepared with degrees of sulfonation up to 75% of the available sites. Sulfonation increases the conductivity from ca. 10−4 S cm−1 in non-modified PBI to >10−2 S cm−1 at room temperature for highly sulfonated samples. The dependence of the conductivity both on the degree of sulfonation and on the conditions of membrane preparation are discussed.
Proton-exchange membranes were synthesised by electron beam irradiation of poly(vinylidenefluoride) (PVDF) films (80 μm) followed by styrene graft polymerisation and sulfonation. Physical and electrochemical properties of the membranes were investigated. The membranes were tested as electrolytes in fuel cell conditions (humidified H2/O2, T=20–60°C, ambient pressure); emfs of ca. 0.85 V were observed during operation for >150 h. The conductivity of PVDF-g-pssa (30% graft) electrolyte membranes at 23°C is 0.03 S cm−1 with an overall cell resistance of 6.5 ohm cm2 under fuel cell conditions.
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