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Development of ionomer membranes for fuel cells
Abstract
In this contribution an overview is given about the state-of-the-art at the membrane development for proton-conductive polymer (composite) membranes for the application membrane fuel cells, focusing on the membrane developments in this field performed at ICVT.For preparation of the polymers, processes have been developed for sulfonated arylene main-chain polymers as well as for arylene main-chain polymers containing basic N-containing groups, including a lithiation step. Covalently cross-linked polymer membranes have been prepared by alkylation of the sulfinate groups of sulfinate group-containing polymers with α,ω-dihalogenoalkanes. The advantage of the covalently cross-linked ionomer membranes was their dimensional stability even at temperatures of 80–90°C, their main disadvantage their brittleness when drying out, caused by the inflexible covalent network. Sulfonated and basic N-containing polymers (commercial polymers as well as self-developed ones) have been combined to acid–base blends containing ionic cross-links. The main advantage of these membrane type was its flexibility even when dried-out, its good to excellent thermal stability, and the numerous possibilities to combine acidic and basic polymers to blend membranes having fine-tuned properties. The main disadvantage of this membrane type was the insufficient dimension stability at T>70–90°C, caused by breakage of the ionic cross-links, where the ionic cross-links broke as easier as lower the basicity of the polymeric base was. Some of the acid–base blend membranes were applied to H2 membrane fuel cells and to direct methanol fuel cells up to 100°C, yielding the result that these membranes show very good perspectives in the membrane fuel cell application.
... The synthesis of new polymer proton-conducting electrolytes [1], which are one of the main components of fuel cells [2,3], attracts considerable attention from researchers [4]. Especially intensive work is underway to create proton-conducting electrolytes based on sulfonated aromatic condensation polymers, which can act as an alternative to commercial membranes of the Nafion type: different aromatic condensation polymers, poly(arylene oxides), polybenzimidazole, sulfonated PEEK [1][2][3][4][5][6][7][8]. ...
... The synthesis of new polymer proton-conducting electrolytes [1], which are one of the main components of fuel cells [2,3], attracts considerable attention from researchers [4]. Especially intensive work is underway to create proton-conducting electrolytes based on sulfonated aromatic condensation polymers, which can act as an alternative to commercial membranes of the Nafion type: different aromatic condensation polymers, poly(arylene oxides), polybenzimidazole, sulfonated PEEK [1][2][3][4][5][6][7][8]. ...
... The authors of [38] obtained heat-resistant film materials with high mechanical characteristics based on rigid-chain polynaphthoylenimidobenzimidazole and flexible-chain PPQ. It was shown that copolymers are characterized not only by an excess of tensile strength by additive values but also by a significant (2)(3)(4) times increase in their deformability in relation to homopolymers. ...
This paper briefly reviews the results of scientific research on the proton conductivity of sulfonated polyphenylquinoxalines. Synthesis, structure (IR spectroscopy, SEM, quantum-chemical modeling, molecular weight distribution), moisture capacity, thermal properties, and proton conductivity of sulfonated polyphenylquinoxalines (sulfur content 2.6, 4.2, 5.5, and 7%) were studied. The relative stable configurations of sulfonated polyphenylquinoxalines with different positions of benzene rings and sulfogroups with the help of quantum chemical modeling were modeled. Sulfonation of the starting polyphenylquinoxalines was confirmed by IR spectroscopy and elemental analysis. The SEM method was used to study the surface of sulfonated polyphenylquinoxalines, and sulfonation regions were found. It was shown that sulfonated polyphenylquinoxalines contain water and are stable up to 250 °C; on further heating, the decomposition of the sulfogroups occurs. The conductivity of the obtained polymer electrolytes was studied by impedance spectroscopy, and long-term tests were carried out. It is shown that the proton conductivity at an ambient humidity of 98 rel. % reaches values 10−6–10−3 S/cm depending on the degree of sulfonation. It was shown that even after long-term storage in air (7 years), samples of sulfonated polyphenylquinoxalines with a high sulfur content of 7% at 98% air humidity have a conductivity of 8 × 10−4 S/cm.
... Fuel cells, which electrochemically convert the chemical energy stored in fuels directly to electricity, are widely regarded as next-generation power sources because of their high efficiency and low pollutant emissions. [1] Polymer electrolyte membrane fuel cells (PEMFC) are one major fuel cell type that can operate under low temperatures ranging from À 40 to 120°C. [2] This energy generating device has been widely used in power generation such as power plant, [3,4] automotive applications [5][6][7] , mobile phones, laptop computers, houses, and public construction as a mobile and stationary energy source. ...
... [8] PEMFC primarily use high-purity hydrogen gas as fuel that can be produced from renewable resources such as water electrolysis from solar and wind power, potentially free of CO 2 emissions so it is environmentally compatible power sources. [1] Many researchers around the world still devote their attention to PEMFC because of the excellent energy density, low operation temperature, and fast start and response times. [9] The polymer electrolyte membrane is the core component that determines the efficiency of the electrolyte fuel cell performance. ...
Chemical modification of Sulfonated poly(arylene ether ketone) with carboxylate acid side chain (C‐SPAEK) membranes has been conducted through partially substitution of the 4,4‐bis(4‐hydroxyphenyl)‐valeric acid (DPA) with 4,4‐bis(4‐hydroxyphenyl)‐propane (BPA) at varies different compositions of sulfonate. FTIR and EDS analysis of the synthesized SPAEK revealed the presence of carboxylic acid, methyl, sulfonate groups and aromatic ether bonds in the SPAEK membrane. The effect of different compositions of carboxylic acid and sulfonate groups on mechanical strength, thermal stability, oxidative stability, water absorption, swelling ratio and proton conductivity of the membranes was studied. The SPAEK‐50/50 membrane exhibits superior properties with high mechanical strength, high thermal and oxidative stability, good water absorption, low swelling ratio, high dimensional stability and has a proton conductivity at 80 °C of 0.102 S/cm close to the Nafion‐117 membrane of 0.120 S/cm. This finding confirms that the partial substitution of the hydrophilic monomer of DPA with 50 % mole of BPA with a sulfonate group composition of 50 % resulted in an excellent SPAEK membrane.
... As mentioned before, water uptake is a key parameter relevant to proton conductivity. Methods to control water uptake involve polymer blending [184][185][186][187][188] and crosslinking, which can be carried out chemically [189][190][191][192][193][194][195][196] or ionically [197,198]. Other authors have also reported the possibility for an additional self-crosslinking reaction in SPEEK via interchain polymerization of the sulfonic acid groups at high temperatures under vacuum [199]. ...
... (e) Power density curves of the Nafion-impregnated SiO 2 /SPEEK composite nanofiber membrane, recast Nafion, and SPEEK film at a 75 • C and 100% RH. Reproduced by permission of Springer from reference [197]. ...
The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton exchange membrane fuel cells (PEMFCs) to work at low and moderate temperatures. The design of new conductive membranes and nanoparticles (NPs) whose morphology directly affects their catalytic properties is of utmost importance. Nanoparticle morphologies, like cubes, octahedrons, icosahedrons, bipyramids, plates, and polyhedrons, among others, are widely studied for catalysis applications. The recent progress around the high catalytic activity has focused on the stabilizing agents and their potential impact on nanomaterial synthesis to induce changes in the morphology of NPs.
... The hydroperoxide sites at the macromolecules can cause radical chain scission [31]. C-H bond of polystyrene is easily attacked by oxygen, forming hydroperoxide radicals [30]. ...
... The hydroperoxide sites at the macromolecules can cause radical chain scission. Ionomer crosslinked membranes show reduced brittleness when dried out, compared to uncrosslinked or covalently cross-linked ionomer membranes, which is possibly caused by the flexibleness of ionic cross-links [31]. We used the SSA which contains two types of hydrophilic groups, i.e., SO 3 H and COOH as the crosslink agent. ...
Sulfonated poly(styrene-ethylene-butylene-styrene) copolymer (S-SEBS) was prepared as an anion exchange membrane using the casting method. The prepared S-SEBS was further modified with sulfonic acid groups and grafted with maleic anhydride (MA) to improve the ionic conducting properties. The prepared MA-grafted S-SEBS (S-SEBS-g-MA) membranes were characterized by Fourier transform infrared red (FT-IR) spectroscopy and dynamic modulus analysis (DMA). The morphology of the S-SEBS and S-SEBS-g-MA was investigated using atomic force microscopy (AFM) analysis. The modified membranes formed ionic channels by means of association with the sulfonate group and carboxyl group in the SEBS. The electrochemical properties of the modified SEBS membranes, such as water uptake capability, impedance spectroscopy, ionic conductivity, and ionic exchange capacity (IEC), were also measured. The electrochemical analysis revealed that the S-SEBS-g-MA anion exchange membrane showed ionic conductivity of 0.25 S/cm at 100% relative humidity, with 72.5% water uptake capacity. Interestingly, we did not observe any changes in their mechanical and chemical properties, which revealed the robustness of the modified SEBS membrane.
... milieu parfaitement anhydre, -atmosphère inerte, -faible température, -utilisation de butyl lithium très concentré. Quelle que soit la voie réactionnelle de sulfonation [47,48], les performances en PEMFC de ces membranes ne sont pas à la hauteur de celles du Nafion ® [48,49]. [50]. ...
... milieu parfaitement anhydre, -atmosphère inerte, -faible température, -utilisation de butyl lithium très concentré. Quelle que soit la voie réactionnelle de sulfonation [47,48], les performances en PEMFC de ces membranes ne sont pas à la hauteur de celles du Nafion ® [48,49]. [50]. ...
... An alternate strategy that includes the use of acid-base membrane bases can limit this drawback by controlling the water uptake and swelling ratio with high proton conductivity. Several studies have been reported earlier which include synthesis of acid-base membranes by forming simple physical interactions between a base and stable polymer backbone, blending ionomers with polymer in which the ionomer can form a hydrogen bond, and by forming chemically covalent crosslinked structures [20][21][22][23]. Among the above strategies, covalent crosslink types of membranes possess a drawback of becoming brittle while drying. ...
... Among the above strategies, covalent crosslink types of membranes possess a drawback of becoming brittle while drying. The physical interaction by hydrogen bonding generates an advantage: the swelling degree could be markedly reduced and the flexible hydrogen interaction by protonated nitrogen in the base could become a leading key factor to limit the brittleness during membrane drying [18,20]. ...
A successful approach towards enhancement in ion cluster size of sulfonated poly (arylene ether sulfone) (SPAES)-based membranes has been successfully carried out by encapsulating basic pendent branches as side groups. Modified SPAES was synthesized by condensation polymerization followed by bromination with N-bromosuccinamide (NBS) and sulfonation by ring opening reaction. Various molar ratios of branched polyethyleneimine (PEI) were added to the SPAES and the developed polymer was designated as SPAES-x-PEI-y, where x denoted the number of sulfonating acid group per polymer chain and y represents the amount of PEI concentration. Polymer synthesis was characterized by 1H-NMR (Nuclear magnetic resonance) and FT-IR (Fourier-transform infrared spectroscopy) analysis. A cumulative trend involving enhanced proton conductivity of the membranes with an increase in the molar ratio of PEI has been observed, clearly demonstrating the formation of ionic clusters. SPAES-140-PEI-3 membranes show improved proton conductivity of 0.12 Scm−1 at 80 °C. Excellent chemical stability was demonstrated by the polymer with Fenton’s test at 80 °C for 24 h without significant loss in proton conductivity, owing to the suitability of the synthesized hybrid membrane for electrochemical application. Moreover, a single cell degradation test was conducted at 80 °C showing a power density at a 140 mWcm−2 value, proving the stable nature of synthesized membranes for proton exchange membrane fuel cell application.
... Polysulfone (PSF) as a backbone polymer has some advantages among other polymers, such as good mechanical strength, high thermal stability, low price, and ease of processing. [3][4][5] Moreover, introducing sulfonate groups into polymer chains to form SPSF, a strong negatively charged polyelectrolyte, leads to decrease the methanol permeability with respect to Nafion. 4 Thus, it also becomes a potential candidate as the membrane electrolyte in the direct methanol fuel cell (DMFC). ...
... An extensive sulfonation leads to swell the polymers and, even to some extent, can convert them into a water-soluble polymer. 5 Thus, the membrane made of this type of polymer, is only suitable for applications that require low mechanical strength. However, this type of polymer also has a high effective charge that might play important role to increase the proton conductivity of the membrane. ...
... Polyether ether ketone (PEEK) is a semicrystalline thermoplastic polymer that is used in industrial applications such as aircraft [4] and turbine blades [5,6], missile connectors and radomes, cable insulation, acid pipelines, valve and pump parts, bearings [6], orthopedic and spine implants [7][8][9] and recently, fuel cell membranes when it is sulfonated [10,11]. The distinctive properties that enable such applications can be listed as resistance to temperature, chemicals, radiation, and the environment [6]. ...
As a thermoplastic and bioinert polymer, polyether ether ketone (PEEK) serves as spine implants, femoral stems, cranial implants, and joint arthroplasty implants due to its mechanical properties resembling the cortical bone, chemical stability, and radiolucency. Although there are standards and antibiotic treatments for infection control during and after surgery, the infection risk is lowered but can not be eliminated. The antibacterial properties of PEEK implants should be improved to provide better infection control. This review includes the strategies for enhancing the antibacterial properties of PEEK in four categories: immobilization of functional materials and functional groups, forming nanocomposites, changing surface topography, and coating with antibacterial material. The measuring methods of antibacterial properties of the current studies of PEEK are explained in detail under quantitative, qualitative, and in vivo methods. The mechanisms of bacterial inhibition by reactive oxygen species (ROS) generation, contact killing, trap killing, and limited bacterial adhesion on hydrophobic surfaces are explained with corresponding antibacterial compounds or techniques. The prospective analysis of the current studies is done, and dual systems combining osteogenic and antibacterial agents immobilized on the surface of PEEK are found the promising solution for a better implant design.
... 8−11 In the presence of solvents and electric fields that are in the core of the many applications of these polymers, the domains adapt, affecting the structure and consequently the functionality and stability of the materials. 8,12,13 Controlling the structure and mobility of ionizable polymers is fundamental to their current and potential applications. However, the correlation between the characteristics of the ionic clusters and the structure of ionomers remains a critical open question. ...
Ionic assemblies, or clusters, determine the structure and dynamics of ionizable polymers and enable their many applications. Fundamental to attaining well-defined materials is controlling the balance between the van der Waals interactions that govern the backbone behavior and the forces that drive the formation of ionic clusters. Here, using small-angle neutron scattering and fully atomistic molecular dynamics simulations, the structure of a model ionomer, sulfonated polystyrene in toluene solutions, was investigated as the cluster cohesion was tweaked by the addition of ethanol. The static structure factor was measured by both techniques and correlated with the size of the ionic clusters as the polymer concentration was varied. The conjunction of SANS results and molecular insight from MD simulations enabled the determination of the structure of these inhomogeneous networks on multiple length scales. We find that across the entire concentration range studied, a network driven by the formation of ionic clusters was formed, where the size of the clusters drives the inhomogeneity of these systems. Tweaking the ionic clusters through the addition of ethanol impacts the packing of the sulfonated groups, their shape, and their size distribution, which, in turn, affects the structure of these networks.
... The electrolyte layer operates as a physical barrier between the hydrogen and the oxygen, which restricts the direct mixing of H 2 and O 2 but enables conduction of ionic charges between the cathode and anode and the complete cell electric circuit. Among the various types of fuel cells the proton exchange membrane fuel cells (PEMFCs) are significantly considered as the most attractive fuel cell technology due to their affordable application in automobile industries, portable power generation and stationary applications [32][33][34][35]. The PEMFC was first ever developed for the Gemini space vehicle. ...
Abstract: Polybenzimidazole (PBI) based membranes have evolved in literature as a popular membrane material for various applications in the past two decades because of their high temperature thermal durability, strong mechanical and tensile
properties, high glass transition temperature (Tg), ion conduction ability at elevated temperature (up to 200°C), oxidative or chemical durability along with robust network like structural rigidity, which make PBI membranes suitable for various potential applications in chemically challenging environments. Ion conducting PBI based membranes have been extensively utilized in high temperature proton exchange membrane fuel cells (HT-PEMFC). In addition, PBI based membranes have been vastly utilized for the development of gas separation membranes and organic solvent nanofiltration (OSN) membranes for their unique characteristics. This review will cover the recent progress and application of various types of flat sheet PBI
based membranes for HT-PEMFC, gas separation and OSN application.
... 8 So far, many kinds of nonperfluorinated polymers have been mostly composed of sulfonic acid and secondary amine groups. For instance, polyether ether ketone (PEEK), 9 polysulfone (PS), 10 poly-(arylene ether sulfone) (PAES), 11 polybenzimidazole (PBI), 12 poly(styrene) (PSt), 13 poly(phenylene sulfide) (PPS), 14 polyphosphazenes (PPs), 15 and polyimides (PIs) 16 have wonderful benefits. Their properties in PEMFC working environments include being very cheap, oxidative, thermally efficient, and chemically stable. ...
... 1−3 In those applications, their high ion conductivity can be utilized in membranes and electrodes. 4,5 Application-relevant ionomer properties include ...
... 6 Many promising polymers depend on polyaromatic thermoplastics, for example, poly(aryl ether ketone) (PAEK/PEEK), poly ether sulfone (PES), and polybenzimidazole (PBI), all of which have high rigidity and thermal stability, low cost, and simple handling. [7][8][9][10] The functionalization of these polymers by sulfonation prompts improved layer properties such as better wettability, higher water transition, and better perm selectivity, making sulfonated polymers an excellent candidate for PEMFCs. Another approach to investigate the alternatives for polymer composites in fabricating the best membranes is to utilize functionalized polymers either alone or blended with other polymers or nanoparticles or clay. ...
An electrolytic membrane for fuel cell application was fabricated by blending sulfonated poly ether sulfone octyl sulfona-mide (SPESOS) with montmorillonite (MMT) clay at different proportions (1 wt.%, 3 wt.%, and 6 wt.%). The structural functionality, surface morphology, and thermal stability of the resultant composite membranes were characterized using Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. Interestingly, the thermal properties of the composite membranes were improved compared to pristine SPESOS. Furthermore , proportions as low as 0.1 wt.% in the MMT/SPESOS composite membrane showed superior proton conductivity to the SPESOS membrane. Thus, we propose the MMT/SPESOS composite membrane as a promising material for the electrolytic membrane in fuel cells at temperatures above 100°C.
... Upon hydration, there is significant phase separation between hydrophobic and hydrophilic domains, thus providing well-defined channels for proton conduction. However, the special structure of Nafion ® results in high costs due to its complex synthesis procedure [4][5][6]. The main challenge for obtaining alternative electrolytes is the improvement of the stability under operational conditions (i.e., temperature and relative humidity) of the current commercial electrolytes [7,8]. ...
Free volume plays a key role on transport in proton exchange membranes (PEMs), including ionic conduction, species permeation, and diffusion. Positron annihilation lifetime spectroscopy and electrochemical impedance spectroscopy are used to characterize the pore size distribution and ionic conductivity of synthesized PEMs from polysulfone/polyphenylsulfone multiblock copolymers with different degrees of sulfonation (SPES). The experimental data are combined with a bundle-of-tubes model at the cluster-network scale to examine water uptake and proton conduction. The results show that the free pore size changes little with temperature in agreement with the good thermo-mechanical properties of SPES. However, the free volume is significantly lower than that of Nafion®, leading to lower ionic conductivity. This is explained by the reduction of the bulk space available for proton transfer where the activation free energy is lower, as well as an increase in the tortuosity of the ionic network.
... proton conductivity of PEM can be tuned widely by the synthesis approach, including hybrid organic-inorganic materials (Di Vona et al., 2007, 2008a, polymer blends (Kerres, 2001;Maier and Meier-Haack, 2008), or composite solid electrolytes (Alberti and Casciola, 2003;Di Vona et al., 2008b). ...
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.
... O grande desafio no desenvolvimento destes polímeros são a obtenção de membranas com custo adequado, que viabilize um consumo em grande volume, com propriedades físico-químicas e mecânicas estáveis em temperaturas acima de 100ºC e quiçá até 200ºC, principalmente condutividade elevada e alta estabilidade química (6) . ...
RESUMO Células a combustível, que utilizam como eletrólito uma membrana polimérica, do tipo PEMFC (Proton Exchange Membrane Fuel Cell) são fontes alternativas promissoras para geração de energia devido à possibilidade de produção de forma eficiente de alta densidade de corrente. Neste trabalho, precursores poliméricos à base de copolímeros estirênicos sulfonados (RHS) foram utilizados com o objetivo de desenvolver membranas para células PEMFC termicamente estáveis a 80ºC e temperaturas superiores. Foram produzidos filmes a partir de misturas do copolímero sulfonado e poli(álcool vinílico) (PVA) com diferentes concentrações do polieletrólito, utilizando-se glutaraldeído como agente de reticulação. Os filmes ou membranas de RHS/PVA foram analisados por espectroscopia de infravermelho e de impedância eletroquímica, calorimetria diferencial de varredura, termogravimetria e quanto ao grau de inchamento em água. Pode-se observar que membranas contendo dois terços do polímero polieletrólito (RHS66_G1) apresentaram maior condutividade iônica, sendo esta da ordem de grandeza da membrana Nafion avaliada sob as mesmas condições. Palavras Chave: congresso, resina hidrocarbônica, polímero polieletrólito, Membrana catiônica, Célula a combustível.
... For this purpose, titanium dioxide (TiO 2 ) is typically used as the catalyst support material. The hydrogen evolution reaction takes place at the cathode The second proton-conducting ionomer type chosen for this study, ionically crosslinked blend ionomer membranes based on aromatic main-chain polymers, has been investigated by the Kerres group at ICVT Stuttgart for the last two decades due to their advantageous properties, such as increased proton conductivity, and improved chemical and mechanical stabilities, compared to their homo-ionomer analogs [28][29][30][31]. The acidbase blend membranes have been applied to low- [32] and intermediate temperature H2 fuel cells [33], perstractive alkene/alkane separation [34], and direct methanol fuel cells (DMFC) [35], as well as in H2-depolarized SO2 electrolysis [36] and redox-flow batteries [37]. ...
As an alternative to common perfluorosulfonic acid-based polyelectrolytes, we present the synthesis and characterization of proton exchange membranes based on two different concepts: (i) Covalently bound multiblock-co-ionomers with a nanophase-separated structure exhibit tunable properties depending on hydrophilic and hydrophobic components’ ratios. Here, the blocks were synthesized individually via step-growth polycondensation from either partially fluorinated or sulfonated aromatic monomers. (ii) Ionically crosslinked blend membranes of partially fluorinated polybenzimidazole and pyridine side-chain-modified polysulfones combine the hydrophilic component’s high proton conductivities with high mechanical stability established by the hydrophobic components. In addition to the polymer synthesis, membrane preparation, and thorough characterization of the obtained materials, hydrogen permeability is determined using linear sweep voltammetry. Furthermore, initial in situ tests in a PEM electrolysis cell show promising cell performance, which can be increased by optimizing electrodes with regard to binders for the respective membrane material.
... Conductivity of proton exchange membrane is highly related to proton conductivity. They are made to withstand a temperature of 100 • C [Kerres, 2001, ] and shows good proton conduction at such temperatures also. Conductivity of proton exchange membrane is directly related to water content. ...
This thesis deals to optimize the performance of PEMFC fuel cells, through the development of new flow-field plate designs. Tools such as water balance and electrochemical noise analysis have been used to diagnose water management within a PEMFC single cell. Optimal management of the water transport enables an increase of the performance and durability of fuel cells. Water balance method was used to measure and frame the value of the effective water diffusion coefficient within the membranes of fuel cells. New flow-flied plate geometries have been developed and characterized by conventional polarization curve and pressure measurements. The electrochemical noise technique was used to detect phenomena related to the behavior of water during fuel cell operation for each geometry developed. Electrochemical noise measurements have been associated with source mechanisms through an experimental approach and an appropriate signal processing based on frequency and time analysis. The descriptors obtained by time and frequency analysis shows that it possible to obtain the signature in normal operation of a fuel cell using a classical serpentine. This signature was compared to the new developed designs allowing to characterize the influence of these new geometries on the water transport. Finally, to complete the experimental approach carried out on the water diffusion coefficient within the membranes of PEMFC fuel cells, a model based on polarization curve, considering this coefficient, was developed and compared to the experimental curves of performances. In perspective, the impact of the new developed geometries has been extended in a stack utilization and a prognosis model based on artificial neural networks has been proposed.
... These developments are principally motivated to lower the material cost for low-temperature operation as recently reviewed. [17][18][19][20][21][22][23] Most of the sulfonated polymers were developed by postsulfonation of preformed polymers or copolymerization produced from sulfonated monomers. 24 Besides these, sulfonic acid groups may be activated functional groups. ...
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]
... Nafion is a widely used state-of-the-art proton exchange membrane (PEM). Moreover, there are other PEMs for fuel cell applications based on perfluorosulfonic acid (PFSA) derived from Nafion membrane such as Nafion 115, Nafion 117, etc. [1][2][3][4][5]. Nafion has been popular due to its unique properties such as flexibility, thermal and chemical stability, and conductivity when fully hydrated. ...
Proton exchange membranes (PEMs) suffer performance degradation under certain conditions—temperatures greater than 80 °C, relative humidity less than 50%, and water retention less than 22%. Novel materials are needed that have improved water retention, stability at higher temperatures, flexibility, conductivity, and the ability to function at low humidity. This work focuses on polyimide-poly(ethylene glycol) (PI-PEG) segmented block copolymer (SBC) membranes with high conductivity and mechanical strength. Membranes were prepared with one of two ionic liquids (ILs), either ethylammonium nitrate (EAN) or propylammonium nitrate (PAN), incorporated within the membrane structure to enhance the proton exchange capability. Ionic liquid uptake capacities were compared for two different temperatures, 25 and 60 °C. Then, conductivities were measured for a series of combinations of undoped or doped unannealed and undoped or doped annealed membranes. Stress and strain tests were performed for unannealed and thermally annealed undoped membranes. Later, these experiments were repeated for doped unannealed and thermally annealed. Mechanical and conductivity data were interpreted in the context of prior small angle X-ray scattering (SAXS) studies on similar materials. We have shown that varying the compositions of polyimide-poly(ethylene glycol) (PI-PEG) SBCs allowed the morphology in the system to be tuned. Since polyimides (PI) are made from the condensation of dianhydrides and diamines, this was accomplished using components having different functional groups. Dianhydrides having either fluorinated or oxygenated functional groups and diamines having either fluorinated or oxygenated diamines were used as well as mixtures of these species. Changing the morphology by creating macrophase separation elevated the IL uptake capacities, and in turn, increased their conductivities by a factor of three or more compared to Nafion 115. The stiffness of the membranes synthesized in this work was comparable to Nafion 115 and, thus, sufficient for practical applications.
... [6] In this context, several alternatives have been proposed in order to solve the problems concerning to these membranes, such as by incorporating non-aqueous additives in Nafion® membranes, building up new membranes with different ionomeric polymers and by using inert polymeric matrices impregnated with proton source conductive components. [7][8][9][10][11] In the latter case, polymeric composites containing ionic liquids as protonic carriers are one of the most promising alternatives for high temperature fuel cells in anhydrous conditions. Besides the membrane composition, RTILs have been used as electrochemical media to oxidation of molecular hydrogen for the application in hydrogen fuel cells. ...
Ionic Liquids (ILs) are considered as a new‐generation electrolyte for electrochemical devices such as fuel cells. When in contact with water, ILs can form a liquid | liquid interface due to their hydrophobicity. This feature allows us to build a conceptual membraneless device for energy generation by combining the oxygen reduction and hydrogen oxidation reactions in acid aqueous electrolyte and in [Bmim][PF 6 ], respectively. The IL | water interface serves as an ion‐exchange interface, allowing the proton transfer between the phases. The open circuit voltage (OCV) between the two half‐cells ((H 2 /H + ) (IL) | | (O 2 /H 2 O) (H2O) ) achieves 1.34 V with a maximum power density of 0.7 µW cm ‐2 at room temperature. Changes in the pH show no influence in the Galvani potential difference resulted from the IL | water interface and in the (H 2 /H + ) (IL) half‐cell, but exhibit a linear decrease of 63 mV dec ‐1 of the O 2 /H 2 O) (H2O) half‐cell potential. Besides the relative low fuel cell power the conceptual device, which is proposed here, has wide margin to improve, mainly in the cell design.
... One of the current research focuses is to improve the protonic conductivity of PFSA membranes at high temperatures [220]. Three technical pathways have been widely investigated: (i) adding hydrophilic inorganic materials [221][222][223], (ii) using non-aqueous and non-volatile solvents to replace water as the proton acceptor [224], and (iii) adopting proton conductors in solid states [225]. ...
Membrane is one of the most important components in proton exchange membrane fuel cells (PEMFCs), which determines the transport phenomena, performance, and durability. With the rapid development of novel membranes, many transport coefficients in membranes applied in numerical studies are outdated due to the lack of experimental data for new membranes. In this review, the fundamentals of commercially available membranes are scrutinized, followed by the fundamental working mechanisms. A detailed examination of the transport phenomena within the membranes, including transport mechanisms, mathematical description, and experimental methods, is conducted for protonic conduction, electro-osmosis drag, diffusion, hydraulic permeation, and gas crossover, which are urgently needed for theoretical and numerical studies. It is found that various empirical or analytical correlations have been established to predict the transport coefficients of the membranes. However, empirical models may not be accurate for all types of membranes since there is no sufficient experimental data for a solid correlation and validation. The experimental methods reviewed in the present study can be applied for new membranes, which is essential to quantify the transport phenomena and its further impact on cell performance and durability. The key transport-phenomena-related factors that affect the performance and failure modes of membranes are also reviewed in this study, which helps to develop strategies in improving membranes’ performance and durability during operation. This review deepens the understanding of the short-term and long-term performance of the membrane in PEMFCs and provides important insights into the further design of novel membranes.
... The loss of water at a higher temperature is another main disadvantage of this membrane [5,6]. These challenges pave the way for the researchers to think about developing new polyelectrolyte membranes which are free from the demerits shown by Nafion® [6,7]. As aromatic polymers are better in their oxidative stability and durability, these polymers may be the better candidates as alternative polyelectrolyte membranes for PEMFC. ...
A new unsymmetrical diamine, 4-(2-aminophenoxy)-4′-aminostilbene was successfully synthesized and used to synthesize stilbene-containing sulfonated polyimides. 2,2′-Benzidine-disulfonic acid, 1,4,5,8-naphthalene tetracarboxylic dianhydride and different mole ratios of 4-(2-aminophenoxy)-4′-aminostilbene and 2-bis(4-(4-aminophenoxy)phenyl) hexafluoropropane were used for the synthesis of stilbene-containing polyimides with sulfonic acid groups. The synthesized polymers were characterized using various physicochemical characterization techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis and electrochemical impedance spectroscopy. Furthermore, the viscosity, water uptake, ion exchange capacity, swelling ratio, hydrolytic stability, oxidative stability, mechanical properties and proton conductivity of the synthesized membranes were also analyzed. Sulfonated polyimide membranes showed a water uptake capacity of 18.93–28.89%, proton conductivity of 0.028–0.039 S cm−1 at 30 °C, ion exchange capacity of 1.469 meq g−1 and hydrolytic stability of 40–44 h at 80 °C. The solubility of the sulfonated polyimide membranes was improved when unsymmetrical diamine was used to prepare sulfonated polyimides.
... Peruorosulfonic acid (PFSA) ionomer-based membranes are commonly used as electrolytes for PEMFCs, due to their high H + conductivity as well as good thermal and mechanical stability. 2,3 The automobile industry has already commercialized PEMFC based vehicles, but their electrolyte membrane degradation still needs to be overcome to achieve a reasonable lifetime. 4 Among the different electrolyte degradation issues, chemical degradation is one of the major contributing issues that hamper the lifetime potential of polymer electrolyte membranes (PEMs). ...
The present investigation deals with the optimization of the concentration of lattice cerium(III) and oxygen vacancy concentration, over the surface of CeO2−δ nanoparticles by varying the processing parameters. The higher value was found to be in good agreement with the smaller grain size and transformation of tetravalent lattice cerium . This transformation explains the crucial mechanism behind the excellent scavenging behavior of CeO2−δ nanoparticles, towards degradation mitigation in the polymer electrolyte membrane (PEM). The overall degradation rate was suppressed 4.2 and 2.7 times after incorporation of CeO2−δ (100 °C, 24 hours) nanoparticles annealed in the hydrogen and oxygen atmosphere, respectively. It was estimated that the intrinsic lattice strain effect on the curved surface of nanoparticles could affect their surficial reactions. The presence of a high oxygen vacancy concentration inducing higher generation has a crucial effect on the exceptional durability of the hybrid CeO2−δ integrated Nafion film.
... L'amélioration de la tenue mécanique permet de réduire l'épaisseur de la membrane afin de diminuer la résistance protonique et ainsi augmenter la tension de cellule 23a) . La compagnie Gore a commercialisé une membrane sous le nom de Gore-Select ® composée de PTFE expansé qui assure la tenue mécanique et chimique, imprégné d'un polymère perfluorosulfoné 43 D'un polymère conducteur protonique greffé sur la silice. Ce polymère est le poly styrène sulfonate de sodium (PSSNa, Figure 17). ...
Fuel cells (FCs) have attracted widespread attention as a highly efficient, clean, and renewable energy conversion technology. Proton exchange membrane (PEM), as one of the core components of FCs, plays a crucial role, and a comprehensive summary of its development is essential for promoting rapid progress in the field of sustainable energy. This article provides a comprehensive review of the development status and research trends of PEMs over the past twenty-eight years, based on statistical analysis and data mining techniques. Price, sustainability, stability, and compatibility issues are the main challenges faced by current PEMs used in FCs research. The current research focuses mainly on the characterization, performance optimization, enhancement mechanisms, and applications of PEMs in FCs. This review provides a systematic summary of PEM materials, serving as a valuable reference for the development, application, and promotion of new PEM materials in FCs.
This paper delineates the design and fabrication of Nafion and Chlorophyll-Nafion membranes in originating the flexible supercapacitors and direct alcoholic fuel cells. Herein, the procedure for the extraction of Chlorophyll from the plant leaves is demonstrated. An advanced flexible membrane of Nafion-Chlorophyll is synthesized by a facile synthesis procedure. Here, we examine the Nafion-Chlorophyll membrane as a supercapacitor and its performance is enhanced in the absence of light using three-electrode setup. The chlorophyll intercalated membrane electrodes depict a specific capacitance of 0.237 \(\mu F\) \({cm^{-2}}\) when the light is just on from the dark and decreased to 0.15 \(\mu F\) \({cm^{-2}}\) after 60 min of light exposure. Moreover, the membrane electrode also exhibits capacitive retention of 89.04% after 1000 cycles. Furthermore, the excellent efficiency of the Nafion-Chlorophyll membrane is observed in methanol and ethanol oxidation reactions (MOR and EOR) along with the current density of 10 and 9.43 \(\mu A\) \({cm^{-2}}\) respectively. Thus, the fabricated flexible chlorophyll membrane shows huge proficiency in portable and flexible energy storage platforms.
Fuel cell is known as one of the most promising and potential clean energy technologies. Proton exchange membrane (PEM), as the core part of fuel cell, plays an important role in the performance of fuel cell. In view of the shortcomings of perfluorosulfonic acid PEM in high‐temperature and low‐humidity working environment, preparing inorganic composite PEM with low‐cost and high performance is an effective solution. In recent years, many methods have been tried to synthesize and improve inorganic composite PEMs. Based on the classification of the main inorganic fillers for the preparation of inorganic organic composite PEMs, in present chapter, we focused on the research progress and achievements of inorganic‐organic composite PEMs. The relationship between various inorganic fillers and the properties of composite PEMs was reviewed, and the researchers’ development direction in the future was prospected.
The activity of the catalyst layer is crucial for the performance of alkaline anion exchange membrane fuel cells (AEMFCs). However, the microscopic transport mechanism of active species (gas, H2O, OH⁻) in the triple-phase boundary (TPB), which is composed of gas, liquid, and solid catalyst particles, has not yet been elucidated so far. Herein, quaternized polyphenylene oxide (PPO) ionomers with different hydratability are synthesized and characterized by the electrochemical performance analysis and molecular dynamics simulations. The results indicate that the mass transport of active species in the TPB depends on the free flow of water and the “locked” water layer hinders the displacement and transport of active species on the catalyst surface. Furthermore, claw-shaped hydrophobic substituents of the ionomers are able to agitate the locked water transport layer on the catalyst surface in a manner that resembled the motion of a “paddle” and thus enhances active species transport in the TPB. The free-water-dominated active species transport mechanism and the “paddle effect” of the claw-shaped ionomer substituent lay the foundation for the construction of highly active catalyst layer.
In this work, metallic ions are introduced to polyacrylates to break the mutual limitation between damping peak width and height. It is found that all the ion‐coordinated polymers exhibit two loss peaks. With the increase of concentration, coordination strength, and steric hindrance, the temperature gap between two damping peaks can be broadened significantly while the peak height is slightly decreased. We are surprised to find that the effective damping temperature region (peak height ≥0.3) for poly (butyl acrylate) ionomers with 100% neutralization and weak coordination strength can be more than 200 K. Moreover, the damping peak area also increases after the introduction of metallic ions. Our result provides a new strategy for developing novel damping materials with high performance.
Membranes are considered a key component for PEM fuel cell performance. Numerous fluorinated and non-fluorinated hydrocarbon materials are explored as PEM membranes; however, new membrane materials are still being quested to overcome their existing challenges. In this context, NexarTM (non-fluorinated hydrocarbon) and its modified forms are investigated in the present work as a new and promising membrane material for PEM fuel cells. The pristine NexarTM is modified with graphene oxide (GO) and sulfonated graphene oxide (GO-SO3H) to prepare the nanocomposite membranes, which are later characterized through SEM, FTIR, and XRD. Membrane thickness, resistivity, and hydration number are determined. The prepared membranes are tested against water uptake, swelling ratio, IEC value, and proton conductivity necessary for PEM fuel cell membrane performance. The water uptake of GO modified (5 wt% loading) membrane increased up to ∼33%; however, it decreased by ∼50% in the case of the GO-SO3H membrane, still better than Nafion. Similar behavior is observed for the swelling ratio for both GO and GO-SO3H membranes. The IEC value of GO and GO-SO3H membranes decreased (∼25% for GO and ∼10% for GO-SO3H) compared with NexarTM membrane, while GO-SO3H membranes showed improvement in IEC values compared to GO-based membranes. The proton conductivity changes marginally, leading to a decreasing value (∼78%) for GO-membrane and an increasing value (∼12%) for GO-SO3H-membrane comparing NexarTM. Thus, GO-SO3H showed better performance comparing GO modified and pristine NexarTM.
El presente artículo expone una revisión del uso de las nuevas
tecnologías que miden la diabetes, que es una enfermedad donde el nivel de
azúcar en la sangre se encuentra aumentada, con una prevalencia creciente, con
menoscabo de la calidad de vida de la persona. Determinar el uso y percepciones
hacia las tecnologías de información y comunicación (TIC), en adultos mayores, del
barrio 18 de octubre Machala. Ecuador año 2018-2019.Se evaluó a 260 personas de
una población de estudio a 880 personas adultas mayores, del rango de 65 años a
79 años de edad, que vivan en el barrio 18 de octubre. Se procedió al procesamiento
de datos a partir de varias técnicas estadísticas para, así obtener resultados que
permitieron alcanzar las pertinentes conclusiones y recomendaciones, se pudo
concluir que, la utilización de las nuevas tecnologías, realizada sobre la diabetes, se
presenta como una tecnología factible y bien aceptada.
Herein, a proton exchange membrane fuel cell (PEMFC) equipped with phosphoric acid-doped polybenzimidazole (PA-PBI) membrane was exploited to determine the effects of changing type and stoichiometry of feed gas at operating temperature from 120 to 160 °C. Results show that maximum power density of proposed system increases as increasing temperature, and varying the type and stoichiometry of feed gas. For example, a typical power density of 0.254, 0.299 and 0.389 W/cm² was obtained when operating PEMFC at 120, 140 and 160 °C respectively with pure hydrogen (H2) as feed gas. By contrast, power density of only 0.128, 0.194 and 0.243 W/cm² was achieved when operating the PEMFC under identical condition with reformed H2 as feed gas. On the other hand, when varying oxygen (O2) stoichiometry from 2 to 6, power density of PEMFC vary from 0.330 to 0.472 W/cm² at 160 °C. At high temperature and high O2 diffusion rate, reaction kinetics of electrodes and membrane were boosted, resulting lower mass-transfer resistance and higher PEMFC performance. In addition, we conducted long-term operation of PEMFC at 160 °C for 500 h to examine durability of PA-PBI. PA-PBI membrane was not lose open circuit voltage (OCV) significantly, indicating its good PEMFC durability.
High–temperature proton exchange membrane fuel cells (HT–PEMFCs) are pursued worldwide as efficient energy conversion devices. Great efforts have been made in the area of designing and developing phosphoric acid (PA)–based proton exchange membrane (PEM) of HT–PEMFCs. This review focuses on recent advances in the limitations of acid–based PEM (acid leaching, oxidative degradation, and mechanical degradation) and the approaches mitigating the membrane degradation. Preparing multilayer or polymers with continuous network, adding hygroscopic inorganic materials, and introducing PA doping sites or covalent interactions with PA can effectively reduce acid leaching. Membrane oxidative degradation can be alleviated by synthesizing crosslinked or branched polymers, and introducing antioxidative groups or highly oxidative stable materials. Crosslinking to get a compact structure, blending with stable polymers and inorganic materials, preparing polymer with high molecular weight, and fabricating the polymer with PA doping sites away from backbones, are recommended to improve the membrane mechanical strength. Also, by comparing the running hours and decay rate, three current approaches, 1. crosslinking via thermally curing or polymeric crosslinker, 2. incorporating hygroscopic inorganic materials, 3. increasing membrane layers or introducing strong basic groups and electron–withdrawing groups, have been concluded to be promising approaches to improve the durability of HT–PEMFCs. The overall aim of this review is to explore the existing degradation challenges and opportunities to serve as a solid basis for the deployment in the fuel cell market.
Currently, hydrogen is considered as a promising energy carrier. However, it needs to be produced first using electrolysis, photo catalysis, thermochemical or biological processes. Then hydrogen is stored by compression, liquefaction, physisorption or chemisorption. Lastly, the conversion process occurs, which is based on using it as a product or a reactant in an application like Fuel Cells. Hydrogen fulfils the main characteristics to achieve the performance required for efficient energy carrier, but its low volume density remains a weak point. An extremely high energy-efficient compression is a necessary step. On the other hand, hydrogen purification step is also essential for several applications as mobility.The aim of this work is to investigate the Polymer Electrolyte Membrane (PEM) devices for hydrogen energy carrier. Specifically, PEM Water Electrolysis (PEMWE) for hydrogen production and Electrochemical Hydrogen Compressor/Concentrator (EHC) for hydrogen storage. First, a preliminary study was carried out using a dimensionless analytical steady state model of PEM electrolysis cells operating with large pressure gradient. This approach enables the estimation of performance using three dimensionless parameters that governed the electrochemical reaction at the catalyst layer and the mass transport through the membrane. The dimensionless numbers are: (i) a Wagner like numbers at the anode and cathode side which is the ratio between the protonic conductivity and the electrochemical kinetic at the catalyst layer, (ii) a number similar to Thiele modulus at the catalyst layers that describes the effective protonic conductivity and the operational current density, (iii) a dimensionless ratio describing the water transport process through the membrane. The model was applied to the PEMWE and it was in good agreement with the experimental data. Secondly, hydrogen compression and purification experiments were conducted using an EHC. During these tests, the compression was performed between 0 and 30 bars for different temperatures and relative humidity. In addition, an electrochemical impedance spectroscopy (EIS) measurement was also performed. These experiments ran on both pure hydrogen and hydrogen/nitrogen mixture. After the data entropy analysis and the postmortem characterization using FTIR and SEM imaging it was found that the azote is not a benign component for this application. Surprisingly, the N2 can lead to the degradation of the membrane due to local NH3 synthesis. Finally, an electrochemical impedance spectroscopy (EIS) model was developed. The EIS is a strong characterization method which inclines both theoretical and experimental approaches by modelling the different physics and electrochemical process into a very complexed system. The one-dimensional analytical model describes the electrochemical kinetics of the cell in EIS regime. This method allows to highlight the limiting process and to predict the artefacts.
Core–shell nanoparticles (NPs), which consist of foreign metal core NPs and Pt shells with one or two monolayers, are attractive cathode catalyst candidates for polymer electrolyte fuel cells (PEFCs), because the utilization of Pt is greatly improved, leading to the improved mass activity of Pt (MAPt) for oxygen reduction reaction (ORR). We have found that Pd core-Pt shell (Pt/Pd) NP catalysts whose core size was 3.3 and 4.2 nm were ca. 5.5 and 5 times as high in MAPt for ORR as commercial Pt NP-loaded carbon black (Pt/C) catalyst, respectively. In this study, to further improve MAPt, carbon-supported Pd100-xAux alloy core NPs with different compositions and core sizes were prepared. MAPt showed a volcano-type relationship with the Au content and core size, suggesting that the ORR activity could be optimized by these factors. The increase in MAPt was ascribed to that of SAPt which was influenced by the compressive strain of core–shell NPs or surface Pt–Pt distance of a Pt monolayer shell. The MAPt for the Pd90Au10 core-Pt shell-loaded carbon (Pt/Pd90Au10/C) electrode was ca. 8 and 1.5 times as high as that for the commercial Pt/C and Pt/Pd/C electrodes, respectively. In terms of durability, the Pt/Pd80Au20/C electrode was superior to the other electrodes because Au atoms segregated to the NP surfaces and protected defective sites on Pt monolayer shells.
Electrospinning technique was employed to fabricate composite nanofibers/nanoparticles of sulfonated polyether ether ketone, polyvinylpyrrolidone, and ruthenium oxide (sPEEK/PVP/RuO2). The samples were synthesized with different concentrations of hydrous ruthenium chloride of 2 wt%, 5wt%, and 10 wt%, and then annealed at a temperature of 300 oC for 4 hours to form the ruthenium oxide nanoparticles. Several characterization tests were conducted to study and compare the performance of the samples. Scanning electron microscopy (SEM) demonstrated the successful fabrication of nanofibers with diameter range of 140 nm to 240 nm as well as nanoparticles with average sizes within the range of 6 nm and 9 nm. The effect of annealing and RuO2 addition was illustrated by the decrease in fibers diameter. The vibration mode and structure of the samples were studied by Fourier transform spectroscopy (FTIR) along with Raman spectroscopy that revealed the strong interaction as well as crosslinking between the polymer blend and RuO2. The annealed samples exhibit enhanced thermal stability and less crystallinity as compared to the as prepared samples according to thermal gravimetric analysis (TGA) along with differential scanning calorimetry (DSC). Impedance spectroscopy tests were conducted to study the electrical properties of the samples as a function of ruthenium oxide concentration and temperature. The results illustrated the increase in resistivity as well as the activation energy with the increase of nanoparticle concentration due to the reduction in the free SO3H groups because of the strong ionic crosslinking. These observations revealed the enhancement of nanofiber properties at low temperatures, which make them suitable for different applications including supercapacitor as well as sensor applications at low temperatures.
Polybenzimidazole (PBI)-sulfonated nano titania (S-TiO2) polymer composite membranes have been prepared by solvent casting technique for high temperature polymer electrolyte membrane (HT-PEM) fuel cells. X-Ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy was used to characterize the polymer structure and confirm the complexation of the sulfonated titania inside the polymer matrix. The highest proton conductivity obtained was 0.091 S cm−1 at 160 °C. The temperature dependent proton conductivity of the phosphoric acid doped proton conducting polymer electrolyte exhibits an Arrhenius relation and Grotthuss mechanism. Thermal gravimetric analysis (TGA) showed that all the prepared proton conducting polymer membrane exhibit good thermal stability. The morphological behaviors of the prepared proton conducting polymer electrolytes were depicted by scanning electron microscope (SEM) micrograph. The prepared composite membranes were characterized by proton conductivity, durability and mechanical strength. The acid uptake of the PBI-sulfonated titania blended membrane was found to be higher than that of the pristine PBI. The fabricated composite membrane with the highest conductivity exhibited a maximum current density of 0.89 A cm−2 through the high proton conductivity.
The solid electrolyte membrane for a hydrogen-oxygen fuel cell was prepared and investigated from the potential of sulfonated poly(ether ether ketone) (SPEEK) embedded together with montmorillonite (MMT). Acid hydrophilized poly(ether ether ketone) (PEEK) and MMT with varying sulfonation levels of 25-70% prepared through solvent casting were investigated for their performance. The nuclear magnetic resonance (1 H NMR) spectra at 7.5 ppm affirmed the occurrence of sulfonation reaction, and its degree was studied by both 1 H NMR and titration method. The reaction time was varied to achieve sulfonation levels from 25 to 70%. The effect of incorporation of pristine and sulfonated MMT into SPEEK was examined. The membranes, prepared using solvent casting technique, were involved for water uptake over the wide range of temperature, thermal stability, and proton conductivity measurements. The cross-sectional surface arrangement of the membrane and clay dispersion was deliberated using SEM. The proton exchange membrane fuel cell (PEMFC) single cell's tests revealed that sulfonated PEEK membrane demonstrated service performance comparable to that of Nafion, as validated using MATLAB software.
A series of multiblock copolymers based on semi-crystalline hydrophobic poly(ether ketone) segments and partially fluorinated hydrophilic poly(arylene ether sulfone) segments were prepared for applications as proton exchange membranes. Through acidification, poly(ether ketimine) precursors were transformed into semi-crystalline acid form poly(ether ketone) segments. Nanophase separated morphologies were observed via small angle X-ray scattering with ion cluster dimensions ranging from 15.1 nm to 17.5 nm. Due to semi-crystalline domains within the polymer, these membranes exhibited outstanding chemical and mechanical stabilities as well as enhanced conductivities under fully hydrated and reduced humidity conditions. Moreover, film processing studies indicated that enhanced nanophase separation and desired membrane properties could be achieved via thermal annealing. All annealed PEK-6FBPSH membranes exhibited increased ion cluster dimensions ranging from 19.3 nm to 27.9 nm with significantly improved proton conductivities. Annealed membrane 4-b-14 were superior to Nafion 212 at low humidity and a wide temperature range.
Gamma radiation‐induced graft copolymerization of styrene monomer on a polyvinyl alcohol film has successfully prepared a proton exchange membrane based on polyvinyl alcohol/silicon nanoparticles (PVA/SiO2), for use in fuel cells. The physical and chemical properties of the prepared hybrid nanocomposite membranes were examined by the Fourier transformer infrared spectrometer (FTIR) and the hardness test. The electrochemical properties were studied as a function of the degree of grafting at different doses of gamma irradiation. Ion exchange capacity (IEC) was found to improve with rising in the degree of grafting and then slightly decrease because of styrene homo‐polymerizes as the dose of gamma irradiation intensifies. As the graft grade increases, the proton's conductivity rises to 30% of the degree of grafting and then begins to stabilize. The free volume hole size obtained from positron annihilation lifetime (PAL) experiments was found to increase by the further accumulation of the styrene graft content. The results of PAL support electrochemical results. Also, a strong link between the results of nanoscopic properties from PAL, and the results of chemical and physical properties (macroscopic results) has been successfully established. The prepared PVA/SiO2‐grafted sulfonated styrene seems to be a potential alternative to Nafion for fuel cell applications.
Blue energy as a renewable, substantial energy resource has attracted scientists who are interested in discovering abundant membrane materials to achieve high power density. For decades, ionomers have been used as ion‐exchange membrane to harvest this energy. Though extensive studies have been conducted, the underlying mechanism of ionic transmembrane behavior is still under debate. Here, the ionic transmembrane properties through membranes with 3D pores prepared by ionomers (polyphenylsulphone with pyridine pendants (PPSU‐Py)) are systematically studied. A series of PPSU‐Py with tunable porosities and surface charge densities is obtained simply by adjusting the percentages of the pendant. Nanoscale morphologies of the ionomers are simulated with the dissipative particle dynamic method, which is in agreement with the experimental data. Then, nanofluidic behaviors of as‐prepared porous membranes are studied, which exhibit anion selectivity, pH gating, and modulated transmembrane conductance. Furthermore, a series of salinity gradient power harvesters based on the ionomers are constructed, of which the output power density is improved by tuning the charge density with the maximum output power density that reaches up to 1.44 W m‐2. The impact of the ionomer on nanofluidic behavior is systematically discussed, and it is believed this work will shed light on nanofluidic materials and blue energy generator design.
In our contribution we present the preparation and characterization results of different types of acid-base ionomer blends. As acidic blend components sulfonated polyetherketone and sulfonated polysulfone have been applied, while as basic components PSU(NH2)(2), poly(4-vinylpyridine), and polybenzimidazole have been used. The thermal stabilities of the observed blend membranes ranged from 270 to 350 degrees C. Membranes showing low ionic resistances of <50 Ohm.cm were prepared. Some of the acid-base blend membranes were investigated in electronmicroscopy (TEM and SEM). The TEM micrographs showed a fine structure in the Angstrom size range, and at some of the membranes also structures in the 50-200 nm size range were observed. The FTIR analysis of the acid-base blends showed characteristic bands indicating ionic crosslink formation in the blends. Some of the membranes were applied to fuel cells. These membranes showed good performance both in H-2 and direct methanol fuel cells. The experiments yielded the result that the electrical power which is obtained with these membranes is comparable with the power obtained with Nafion(R) if the ion-exchange capacity of the membrane is high enough and if its thickness is in the range of 30-40 cm(2) The maximum power densitiy achieved with one of the acid-base membranes in a direct methanol fuel cell amounted to approximately 50 mW/cm(2) at 100 mA/cm(2) in air mode, which is a value comparable to that obtainable with Nafion(R).
A new process has been developed for the sulfonation of arylene polymers which can be lithiated, like polysulfone Udel®. The sulfonation process consists of the following steps: (1) lithiation of the polymer at temperatures from −50 to −80°C under argon, (2) gassing of the lithiated polymer with SO2; (3) oxidation of the formed polymeric sulfinate with H2O2, NaOCl, or KMnO4; (4) ion-exchange of the lithium salt of the sulfonic acid in aqueous HCl. The advantages of the presented sulfonation procedure are: (1) in principle all polymers which can be lithiated can be subjected to this sulfonation process; (2) by this sulfonation procedure the sulfonic acid group is inserted into the more hydrolysis-stable part of the molecule; (3) this process is ecologically less harmful than many common sulfonation procedures. The sulfonated polymers were characterized by NMR, titration and elemental analysis, by IR spectroscopy, and by determination of ionic conductivity. Also the hydrolytic stability of the sulfonated ion-exchange polymers was investigated. Polymers with an ion-exchange capacity of 0.5 to 3.2 mequiv SO3H/g Polymer have been synthesized and characterized. The following results have been achieved: membranes made from the sulfonated polymers show good conductivity, good permselectivity (>90%), and good hydrolytic stability in 1N HCl and water at temperatures up to 80°C. © 1996 John Wiley & Sons, Inc.
Gegenstand der Erfindung sind neue kompatible binäre und ternäre Kationenaustauscherpolymer- und Anionenaustauscherpolymer-Säure-Base-Blendmembranen.
The reaction of hypochlorite with aryl thiolsulfonates, ArSO2SAr, sulfinyl sulfones, ArS(O)SO2Ar, and α-disulfones, ArSO2SO2Ar, has been investigated. In the presence of sufficient hypochlorite the products of all these reactions are 2 mol of the sulfonate ArSO3- per mol of starting sulfur compound. This transpires because any sulfinate ArSO2- formed in intermediate stages is rapidly oxidized to ArSO3- by hypochlorite. The pH-rate profile for this sulfinate-hypochlorite reaction shows that OCl- reacts over 300 times faster with ArSO2- than does HOCl. The variation of the rate of the ArSO2- OCl- reaction with Ar and the reaction stoichiometry suggest a mechanism where there is nucleophilic attack of OCl- on the sulfur of ArSO2- to give a sulfurane-like intermediate, 5, which then decomposes rapidly to ArSO3- and chloride ion. Similarly, the fact that a small but significant amount of phenyl α-disulfone is isolated when PhS(O)SO2Ph is treated with just 1 mol of hypochlorite suggests that nucleophilic attack of OCl- on the sulfinyl sulfone leads to a sulfurane-like intermediate, 6, which breaks up either by loss of chloride ion to yield the α-disulfone, or by cleavage of the S-S bond to give sulfinate and ArS(O)OCl, and subsequently ArSO3-. After earlier inconclusive attempts to demonstrate the existence of intermediates on the reaction coordinate in simple substitutions of sulfinyl compounds, the apparent presence of 5 and 6 on the reaction coordinates of these two hypochlorite reactions is seen as providing significant support for the possible presence of sulfurane-like intermediates in many substitutions at sulfinyl sulfur, even though such intermediates may often break down so rapidly by expulsion of a leaving group as to make their detection extremely difficult.
The title sulfonated polyimides comprise repeating units I and II (Z1-2 = tetravalent group; Ar1-2 = arom. divalent group). The polymers are useful as ion-exchange membranes, esp. for fuel cells. The membranes have good durability and the fuel cells can be used in elec. vehicles. A polymer was prepd. by polymn.. of 4,4'-diamino-(1,1'-biphenyl)-2,2'-disulfonic acid, 4,4'-methylenebisbenzeneamine, and 5,5'-oxybis(1,3-isobenzofurandione)
Thermoreactive sulfur-containing poly(phenylquinoxaline)s were synthesized using two approaches: by sulfonation of poly(phenylquinoxaline)s prepared by conventional technique or by the synthesis of poly(phenylquinoxaline)s from monomers directly in the sulfonating medium. In both cases, sulfonation was performed in a sulfuric acid: oleum mixture (4:1) at 125°C. Cross-linked structures formed upon thermal treatment of sulfonated polymers at 320 - 360°C. Sulfonated poly(phenylquinoxaline)s can be processed by compression molding. High-strength thermally stable films showing high hydrolytic stability were cast from solution of sulfonated poly(phenylquinoxaline)s in DMF. Sulfonated poly(phenylquinoxaline)s can be used to prepare cation-exchange membranes.
The electrochemical oxidation of ethanol and methanol in a liquid‐feed solid polymer electrolyte fuel cell operating at was investigated. A composite membrane made of Nafion ionomer and silica was fabricated in order to maintain the advantageous water‐ retention properties of these materials at high temperature. A pressurized cell employing carbon‐ supported and catalysts with a loading of was investigated. The direct methanol fuel cell showed a peak power density of about at and . The power density approached in the innternal resistance‐free polarization curve, and the methanol crossover rate was about . The direct ethanol fuel cell showed a maximum power density of about at and with high selectivity toward formation (≈95%). ©1998 The Electrochemical Society
Recently, polybenzimidazole membrane doped with phosphoric acid (PBI) was found to have promising properties for use as a polymer electrolyte in a high temperature (ca. 150 to 200 C) proton exchange membrane direct methanol fuel cell. However, operation at 200 C in strongly reducing and oxidizing environments introduces concerns of the thermal stability of the polymer electrolyte. To simulate the conditions in a high temperature fuel cell, PBI samples were loaded with fuel cell grade platinum black, doped with ca. 480 mole percent phosphoric acid (i.e., 4.8 H{sub 3}PO{sub 4} molecules per PBI repeat unit) and heated under atmospheres of either nitrogen, 5% hydrogen, or air in a thermal gravimetric analyzer. The products of decomposition were taken directly into a mass spectrometer for identification. In all cases weight loss below 400 C was found to be due to loss of water. Judging from the results of these tests, the thermal stability of PBI is more than adequate for use as a polymer electrolyte in a high temperature fuel cell.
The polymer electrolyte membranes (AAc/SSS membrane) were synthesized by the radiation-induced graft polymerization of acrylic acid(AAc) and sodium 4-vinylbenzenesulfonate(SSS) on a polyethylene film. The single cells using the synthesized polymer films as the electrolyte were tested continuously. In the case of AAc/SSS membrane contacted directly with the oxidizing catalyst (Pt) in oxygen electrode at 55 °C, the cell voltage dropped significantly after only 5 h operation due to an oxidative degradation of the membrane. When the oxygen electrode was impregnated with an ionomer of perfluorocarbon-sulfonic acid to prevent the AAc/SSS membrane from its direct contact with Pt elec-trocatalysts, the cell worked continuously for 212 h at 55 °C and 71 h at 70 °C. When a thin fluorinated polymer electrolyte membrane (F-membrane, thickness=11 μm) was sandwiched between the AAc/ SSS membrane and the oxygen electrode impregnated with the ionomer, the significant degradation of the AAc/SSS membrane was delayed until 190 h at 70 °C. It is considered that the AAc/SSS membrane was oxidized by active oxygen (radical) species and/or hydrogen peroxide produced at the cathode side.
The sulfonic acid functionality has dominated as the ion-exchange component of virtually all polymeric materials that have been developed and commercialized for application as membranes in proton exchange membrane fuel cells (PEMFC). Over the years, phosphonic acid functionalized polymers have been proffered as potential candidates to augment the arsenal of available materials for use in PEMFC. This paper explores the synthesis of poly(trifluorostyrene)-based ionomers which contain as their ion-exchange functionality, the phosphonic acid grouping. Preparative details, materials characterization and early indications of fuel cell performance capabilities for these novel ionomers are discussed.
The influence of an in situ-grown, sol → gel-derived silicon oxide filler on mechanical, gas permeation and solvent affinity properties of Surlyn® materials, and melt processibility of Surlyn®/[silicon oxide] hybrid resin, was studied. Tensile modulus increases while elongation-at-break decreases with increasing silicon oxide uptake. He gas permeation vs. pressure profiles imply dual mode sorption. Swelling in n-hexane, 1-PrOH and xylene decreases as silicon oxide loading increases, the highest uptake being that of xylene. [Surlyn®Zn+2]/[silicon oxide] has better solvent resistance than the H-form hybrid for each solvent. Affinity of the Zn-form hybrid for xylene is considerably greater than that for 1-PrOH and n-hexane. Melt flow index of the filled H-form is lower than that of the unfilled H-form but higher than that of the partially Zn neutralized unfilled form. FTIR analysis of hybrids previously subjected to the melt flow index experiment shows that the silicon oxide phase remained intact but that the high temperatures drove condensation reactions between SiOH groups. After in situ sol–gel reactions and drying [Surlyn®-H]/[silicon oxide] flakes were passed through an extruder to assess the effect on silicon oxide structure of melt-processing conditions. All silicon oxide IR fingerprint bands for the processed hybrid persist, the spectrum closely resembling that of a nonextruded hybrid including the signature of Si–OH groups. 29Si solid-state NMR spectroscopy was used to probe degree of molecular connectivity within the silicon oxide phase. The spectrum is consistent with those of nonextruded hybrids in that Si atom coordination around SiO4 units is predominantly Q3 and Q4, the bias in the distribution toward Q3 being in harmony with the IR results. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 143–154, 1999
An improved preparation and handling procedure for the monomer is described. The polymer was prepared best by emulsion polymerization, although anionic polymerization was also found to be operable. A number of properties of the polymer are described, including solubility, the infrared absorption spectrum, x-ray diffusion (amorphous scattering), dielectric constant (2.56 ± 0.05), and dielectric loss tangent (0.0006 to 0.0035 over the range 102 to 1011 c.p.s.). Copolymerization with trifluorochloroethylene gave a copolymer containing 0.096 mole fraction of trifluorochloroethylene, and with styrene a copolymer containing 0.397 mole fraction. The copolymerization curve and constants for copolymerization with styrene are presented and discussed.
In order to predict hydroxy radical initiated degradation of new proton conducting polymer membranes based on polystyrene, polyethersulfone, polyetheretherketone, or on polymers obtained by radiation grafting of styrene on different fluoropolymers, eight sulfonated aromatics were chosen as model compounds for EPR experiments, aiming at the identification of products of HO/ radical reactions with these polymers. Photolysis of H
2
O
2
was employed as the source of hydroxyl radicals. A detailed investigation of the pH profile was carried out for p-toluenesulfonic acid. Besides benzyl- and hydroxy-cyclohexadienyl radicals at lower pH values, phenoxyl radicals were identified, predominating in the pH range 10.5-13.0. A large number of new radicals give evidence of multiple hydroxylation of the aromatic rings, confirming reaction mechanisms proposed on the grounds of product analysis, but no evidence of dimerisation was found. The result as regards stability of organic proton exchange membranes for fuel cells is, that all unsaturated bonds and weakly bound atoms are subject to immediate attack by HO/. Ether links open by HO/ ipso addition. Strategies for the reduction of membrane degradation should focus on a minimisation of HO/ formation and of its access to the interior of the membrane.
A stable reference electrode to be operated in a proton-exchange membrane direct methanol fuel cell (PEMDMFC) was strongly desired but is still lacking. Conventional reference electrodes known from aqueous systems are difficult to mount and to connect to the membrane electrolyte, and they introduce Donnan potentials into the system. It is shown in this study that a dynamic hydrogen electrode roughly maintains the thermodynamic hydrogen potential when operated at low cathodic current density sufficient to uphold the saturation with hydrogen of the electrode. Such a polarised auxiliary electrode allows the determination of a single electrode potential versus current density curves directly in the fuel cell, even during operation of the DMFC. A distinct determination of single electrode performance and fuel crossover is now possible.
In the presented work, PSU Udel® which is a chemically and thermally stable arylene main-chain polymer was modified via the metalation-sulfochlorination (-esterification,-sulfonamide formation) and the metalation/amination route. The aminated PSU was stepwise alkylated to yield PSU with (a) -secondary and (b) tertiary amino groups. PSU(SO2X) (XCl, OCH3, NHC3H7) was hydrolysed with hot water or hot diluted sulfuric acid. From the modified polymers membranes were formed by blending the polymers as follows: (a) unmodified PSU/sulfochlorinated PSU; (b) PSU/PSU-SO2OCH3; (c) PSU/PSU-SO2NHC3H7. At these blends only physical crosslinking between the polymers occurs by entanglement of the blend components. (d) Li-sulfonated PSU/aminated PSU (PSU-NH2). (e) Li-sulfonated PSU/monomethylaminated PSU (PSU-NH(CH3). (f) Li-sulfonated PSU/di-methylaminated PSU (PSU-N(CH3)2). At the blend membranes (d)–(f) specific interactions beween the polymer components occur by hydrogen bridges and - after acidic post-treatment (see below) -polysalt formation by proton transfer from the SO3H to the amino group. The PSU/nonionic sulfonic acid precursor membranes were subsequently hydrolyzed to yield PSU/PSU-SO3H blend membranes. It was observed that the membranes containing PSU-SO2NHC3H7 could be hydrolyzed only to a small extent to the sulfonic acid under the applied hydrolysis conditions. The blend membranes (d)–(f) were post-treated in 10% HCl to obtain the H+ form of the membranes. The ion-exchange capacity of the blends was adjusted by variation of the substitution degree of the modified polymers and by variation of the blend composition. The membrane-blends were characterized by impedance spectroscopy, thermogravimetry and by transmission and scanning electron microscopy. From the investigations it can be concluded that it is advantageous for the mechanical stability of the blends when there is not only entanglement between the polymeric chains of the blend components (as it is the case for the blend membranes (a)–(c)). The swelling degree of the acid-base blends (d)–(f) is lower than the swelling degree of the blends (a)–(c) at the same ion-exchange capacity, leading to better mechanical stability of the acid/base blend membranes (d)–(f).
The swelling properties of perfluorosulphonated ionomer (PFSI) membranes have been studied as a function of the solvent, the counterion and the temperature. The expansion of PFSI membranes has been measured in numerous solvents. Different solvent parameters have been considered and the donor number of the solvent is proposed as the relevant parameter. The influence of counterion is shown to be related either to the softness parameter of the cations for a very polar solvent or to the size of the cations for other solvents. Very large solvent uptake can be obtained by increasing the temperature, which remains in the sample on cooling back to room temperature. The material begins to dissolve even with low solvent uptake. The dissolution of the membrane depends only on the degree of swelling.
Crosslinked sulfonated PSU blend membranes have been produced via a new crosslinking process. The blends have been obtained from mixing of PSU Udeltm Na-sulfonate and PSU Udeltm Li-sulfinate in N-methyl pyrrolidone. The membranes have been crosslinked by S-alkylation of PSU sulfinate groups with dihalogenoalkanes The membranes produced via this process have been characterized in terms of ion-exchange capacity, electric resistance, swelling, ion-permselectivity. In addition, the thermal stability of the membranes has been determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and FTIR-spectra of the prepolymers and of the crosslinked blend membranes have been recorded. The new crosslinking procedure shows following advantages: (i) the preparative effort for crosslinking is very low; (ii) the properties of the crosslinked membranes are reproducible; (iii) the crosslinking proceeds with a high yield when applying suitable dihalogenoalkanes or other crosslinkers which are capable to S-alkylate the sulfinate group. The properties of the crosslinked PSU blend membranes are: (i) low electrical resistance at high IEC's; (ii) low swelling rate in practical temperature ranges from 20–70°C; (iii) excellent hydrolysis stability; (iv) excellent thermal stability.
In this contribution, the synthesis and characterization of novel ion-exchange blend membranes which contain the SO3Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag+ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the transport properties of the following blend membrane types are described: (1) acid–base blend membranes of ortho-sulfone-sulfonated polysulfone (PSU) with ortho-sulfone-diaminated PSU; (2) blend membranes of ortho-sulfone-sulfonated PSU with unmodified PSU; (3) blend membranes of ortho-sulfone-sulfonated PSU with ortho-sulfone disilylated PSU. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 422–427, 1999
Nafion-in situ sol-gel reactions were affected for Zr(OBu)4 that permeated low water content membranes unidirectionally. IR peaks reflecting ZrO2 and incomplete hydrolysis of ZrOBu groups near both surfaces were detected. Vibrations of Zr(OEt)4 detected near both sides arise from alkoxy exchange in the presence of the solvent EtOH. Unreacted alkoxy group bands are more distinct near the nonpermeated surface. An IR band for the ZnOBu group diminishes, whereas that for ZnOEt increases with increasing time near the permeated surface due to progressive alkoxy exchange. The ZrO2 band becomes more intense with time near the permeated surface. X-ray spectroscopy/scanning electron microscopy studies of Zr concentration across the membrane thickness verified compositional asymmetry. CO2 gas permeability versus upstream pressure plots are monotonically increasing, suggesting diffusion accompanied by complex plasticization.
The products of methanol crossover through the acid-doped polybenzimidazole polymer electrolyte membrane (PBI PEM) to the cathode of a prototype direct methanol fuel cell (DMFC) were analyzed using multipurpose electrochemical mass spectrometry (MPEMS) coupled to the cathode exhaust gas outlet. It was found that the methanol crossing over reacts almost quantitatively to COâ at the cathode with the platinum of the cathode acting as a heterogeneous catalyst. The cathode open-circuit potential is inversely proportional to the amount of COâ formed. A poisoning effect on the oxygen reduction also was found. Methods for the estimation of the methanol crossover rate at operating fuel cells are suggested.
Model compounds and radiatively grafted membranes were prepared in order to study the effect of tertiary hydrogens on the stability of membranes used in oxidatively aggressive environments. Sulfonated isopropylbenzene, which contains a tertiary hydrogen, yielded substantial amounts of degradation products when exposed to a strong oxidizing solution. Sulfonated t-butylbenzene, which is identical to sulfonated isopropylbenzene except that the tertiary hydrogen is replaced by a methyl group, yielded only minute amounts of degradation products when exposed to the same oxidizing solution. Styrene (contains a tertiary hydrogen) and α-methylstyrene (tertiary hydrogen has been replaced by a methyl group) were radiatively grafted onto poly (tetrafluoroethylene) films and sulfonated to form cationic membranes. The styrene-prepared membrane exhibited several times more weight loss during exposure to an oxidizing aging solution than did the α-methylstyrene prepared membrane. The energy efficiencies of styrene-grafted membranes decreased rapidly to less than 60% after 60 or 80 cycles in a cycling test cell. The energy efficiencies of α-methylstyrene grafted membranes were 82.6% and 83.0% for 700 test cycles and showed no effects of chemical degradation during this period.
The properties of imidazole (pyrazole) as a solvent for acidic protons in polymers and liquids are reported. The creation of protonic defects and the mobility of protons in these environments are found to be similar to the situation in corresponding water containing systems. The temperature stability is, however, increased and imidazole (pyrazole) is a stronger Bronstedt base compared to water, which may be useful for the application of such materials as electrochemical cells such as fuel cells and secondary batteries.
An organic—inorganic protonic polymer electrolyte (ormolyte—organically modified silane electrolyte) to be used as membrane in direct methanol fuel cells is presented. The synthesis, prepared by the sol—gel method, is based on several organically modified alkoxy silanes, chosen according to the particular properties needed in the final product. The membrane thus prepared exhibits a protonic conductivity of about 10−2 Ω−1 at room temperature.
A gas reaction fuel cell incorporates a thin catalyst layer between a solid polymer electrolyte (SPE) membrane and a porous electrode backing. The catalyst layer is preferably less than about 10 .mu.m in thickness with a carbon supported platinum catalyst loading less than about 0.35 mgPt/cm.sup.2. The film is formed as an ink that is spread and cured on a film release blank. The cured film is then transferred to the SPE membrane and hot pressed into the surface to form a catalyst layer having a controlled thickness and catalyst distribution. Alternatively, the catalyst layer is formed by applying a Na.sup.+ form of a perfluorosulfonate ionomer directly to the membrane, drying the film at a high temperature, and then converting the film back to the protonated form of the ionomer. The layer has adequate gas permeability so that cell performance is not affected and has a density and particle distribution effective to optimize proton access to the catalyst and electronic continuity for electron flow from the half-cell reaction occurring at the catalyst.
Polybenzimidazole films doped with phosphoric acid are being investigated as potential polymer electrolytes for use in hydrogen/air
and direct methanol fuel cells. In this paper, we present experimental findings on the proton conductivity, water content,
and methanol vapor permeability of this material, as well as preliminary fuel cell results. The low methanol vapor permeability
of these electrolytes significantly reduces the adverse effects of methanol crossover typically observed in direct methanol
polymer electrolyte membrane fuel cells.
Highly sulfonated poly(phenylene sulfide) prepared from the polysulfonium cation exhibits excellent thermal stability (T d = 265°C) and high conductivity (> 10 -2 S/cm). These properties arise from the two sulfonic acid groups substituted on one phenyl ring
The dynamic mechanical and infrared spectroscopic investigation of ionomer blends of poly(diacetylene)- and polystyrene-based ionomers has shown that miscibility of this usually incompatible polymer pair can be achieved through ion-ion interactions between the blend components. Microphase separation is prevented through ionic contacts generated during the blend formation; a schematic model of mixing in the blends is proposed.
Two new polyelectrolytes were synthesized by sulfonation of poly(2,2'-m-phenylene-5,5'-bibenzimidazole) with 1,3-propanesultone and sodium 4-(bromomethyl)benzene sulfonate, respectively. The new polymers exhibit a significantly higher solubility than the parent material but retain much of its thermal stability
The results of detailed studies of the ionic conductivity and ultrastructure of polymer blends complexed with LiClO4 are presented and discussed and include comparisons with undoped blends. These composite polymer electrolyte systems are studied over a temperature range -110 to 150 degrees C using differential scanning calorimetry (DSC), with room temperature FT-IR, and with -20 to 100 degrees C impedance analysis and consist of blends of poly(ethylene oxide) (PEG) or oxymethylene-linked PEO (OMPEO) with polyacrylamide (PAAM). The high molecular weight PAAM is found to inhibit the crystallization of PEO without impeding segmental motion. In fact the ionic conductivity is enhanced in the blends compared to the PEO-LiClO4, complex. Conductivities exceeding 10(-4) S/cm at room temperature were obtained for electrolytes prepared by the in situ polymerization of acrylamide in the polyether. Annealing the blends at 150 degrees C for 10-15 min makes the ultrastructure (recrystallization, melting, glass transitions) as initially observed by DSC less complex. Generally from DSC and FT-IR the ultrastructure appears to consist of emulsified PAAM complexed to itself and to polyether segments via Li+ cations surrounded by relatively uncomplexed polyether segments. At higher PAAM concentrations the PAAM-LiClO4 nonconducting cores increases in size, reducing the region of uncomplexed polyether; the ionic conductivity decreases. Assuming that the enhanced conductivity of these composite polymer electrolytes is associated with interphase phenomena, the conductivity results were analyzed in terms of a model based on effective medium theory.
In this contribution, the synthesis and characterization of novel ion-exchange blend membranes which contain the SO3Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag+ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the synthesis and characterization of following blend membrane types are described: (1) acid–base blend membranes of ortho-sulfone-sulfonated polysulfone (PSU) with ortho-sulfone-diaminated PSU; (2) blend membranes of ortho-sulfone-sulfonated PSU with unmodified PSU; (3) blend membranes of ortho-sulfone-sulfonated PSU with ortho-sulfone disilylated PSU. The differently modified PSU types were characterized via 1H nuclear magnetic resonance (1H-NMR). The acid–base blend membranes were characterized via Fourier transfer infrared (FTIR) spectroscopy. It could be indirectly proved that formation of PSU–SO3+H3N–PSU ionic crosslinks takes place. Transmission electron microscopy (TEM) investigations of (1) and (2) yielded the results that these blends are inhomogeneous at the microscopic scale. Mechanical stabilization of these blends is accomplished by physical entanglement of the different macromolecules. The blends (3) were macroscopically inhomogeneous due to the strong difference in hydrophilicity of the blend components. Only the blend 90% PSU–SO3H10% PSU[Si(CH3)3]2 formed a blended membrane. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 428–438, 1999
Nafion-in situ sol-gel reactions were affected for Zr(OBu)4 that permeated low water content membranes unidirectionally. IR peaks reflecting ZrO2 and incomplete hydrolysis of ZrOBu groups near both surfaces were detected. Vibrations of Zr(OEt)4 detected near both sides arise from alkoxy exchange in the presence of the solvent EtOH. Unreacted alkoxy group bands are more distinct near the nonpermeated surface. An IR band for the ZnOBu group diminishes, whereas that for ZnOEt increases with increasing time near the permeated surface due to progressive alkoxy exchange. The ZrO2 band becomes more intense with time near the permeated surface. X-ray spectroscopy/scanning electron microscopy studies of Zr concentration across the membrane thickness verified compositional asymmetry. CO2 gas permeability versus upstream pressure plots are monotonically increasing, suggesting diffusion accompanied by complex plasticization. © 1996 John Wiley & Sons, Inc.
Poly[bis(3-methylphenoxy)phosphazene] was sulfonated in a solution with SO3 and solution-cast into 100–200-μm-thick membranes from N,N-dimethylacetamide. The degree of polymer sulfonation was easily controlled and water-insoluble membranes were fabricated with an ion-exchange capacity (IEC) as high as 2.1 mmol/g. For water-insoluble polymers, there was no evidence of polyphosphazene degradation during sulfonation. The glass transition temperature varied from −28°C for the base polymer to −10°C for a sulfonated polymer with an IEC of 2.1 mmol/g. The equilibrium water swelling of membranes at 25°C increased from near zero for a 0.04-mmol/g IEC membrane to 900 % when the IEC was 2.1 mmol/g. When the IEC was < 1.0 mmol/g, SO3 attacked the methylphenoxy side chains at the para position, whereas sulfonation occurred at all available aromatic carbons for higher ion-exchange capacities. Differential scanning calorimetry, wide-angle X-ray diffraction, and polarized microscopy showed that the base polymer, poly[bis(3-methylphenoxy)phosphazene], was semicrystalline. For sulfonated polymers with a measurable IEC, the 3-dimensional crystal structure vanished but a 2-dimensional ordered phase was retained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 387–399, 1999
New mixed sulfinated/sulfonated polysulfone PSU Udel has been produced by partial oxidation of sulfinated PSU with NaOCl. From the mixed sulfinated/sulfonated PSU, thin crosslinked polymer films have been produced by S-alkylation of the residual sulfinate groups with ,ω-diiodoalkanes having 4–10 (CH2) units. The advantages of the partial oxidation process using NaOCl are as follows: (1) The desired oxidation degree can be adjusted finely. (2) No side reactions take place during oxidation. (3) The partially oxidized polymers is stable at ambient temperature. By variation of the oxidation degree of the sulfinated/sulfonated prepolymer and by variation of the chain length of the diiodo crosslinker, crosslinked membranes with a large range of properties in terms of ionic conductivity, swelling, and permselectivity have been produced. The partially oxidized polymers have been characterized by redox titration, 1H-NMR, and FTIR. The crosslinked membranes have been characterized in terms of ionic conductivity (resistance), permselectivity, and swelling in dependence on ion-exchange capacity and oxidation degree of the prepolymers. In addition, the thermal stabilities of the membranes have been determined by TGA, and FTIR spectra have been recorded on the crosslinked films. Selected membranes show low ionic resistances, low swelling, and good temperature stability which makes them promising candidates for application in (electro)membrane processes. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1441–1448, 1998
Polysulfone has been sulfonated to varying degrees using a sulfur trioxide–triethyl phosphate complex as the sulfonating agent. These conditions are suitable for surface sulfonation as well as solution sulfonation. The neutralized, sodium salt form is much more stable than the free acid form. The glass transition temperature of polysulfone is increased by as much as 130°C (i.e., to 310°C) by the introduction of SO3Na groups. Sulfonation also causes a major shift in the low-temperature (−100°C) transition of polysulfone. Compositions of intermediate degree of sulfonation, containing 0.5 SO3Na groups per polysulfone repeat unit, are melt processable. This composition also displays the best balance of properties. Water absorption, which exerts a large influence on mechanical properties, ranges from 1% to 61%, depending upon degree of sulfonation and sorption conditions. Water absorption and desorption curves show non-Fickian behavior. Compositions of intermediate degree of sulfonation display optimum reverse osmosis desalination behavior. Gas permeability is significantly reduced by sulfonation. Overall behavior is consistent with an ionomer-type structure.
The supermolecular structure and viscoelastic and diffusion properties of a perfluorinated polymer containing sulfonic acid (Nafion) were investigated. The breakdown of time–temperature super-position for the dry salt and and acid in the presence of 0.5 H2O/SO3H as well as the results of small-angle x-ray scattering suggest that the ions in this material are clustered. Above 180°C, the reestablishment of the time–temperature superposition in the salt suggests that ions in the clusters become mobile. Dynamic mechanical studies were performed over a temperature range from −190°C to above the glass transition temperatures Tg of the materials. The Tg of the salts is found at ca. 220°C, while in the acid it occurs at 110°C. A β peak in the acid is found at ca. 20°C, while in the salts it occurs between 140°C and 160°C. The β peak shifts to a lower temperature with the addition of water in both the acid and the salts, while the α and γ peaks are unaffected. The latter is located at ca. −110°C at 1 Hz. Dielectric behavior has also been studied as a function of water content for the acid sample and the potassium salt at frequencies of 100 Hz to 10 kHz. Two relaxations with different activation energies were observed. The position of both peaks shifts to a lower temperature as the water content increases. Finally, the diffusion of water in Nafion in the acid form has been determined. The diffusion coefficient can be represented by the equation
A new process has been developed for the sulfonation of arylene polymers which can be lithiated, like polysulfone Udel®. The sulfonation process consists of the following steps: (1) lithiation of the polymer at temperatures from −50 to −80°C under argon, (2) gassing of the lithiated polymer with SO2; (3) oxidation of the formed polymeric sulfinate with H2O2, NaOCl, or KMnO4; (4) ion-exchange of the lithium salt of the sulfonic acid in aqueous HCl. The advantages of the presented sulfonation procedure are: (1) in principle all polymers which can be lithiated can be subjected to this sulfonation process; (2) by this sulfonation procedure the sulfonic acid group is inserted into the more hydrolysis-stable part of the molecule; (3) this process is ecologically less harmful than many common sulfonation procedures. The sulfonated polymers were characterized by NMR, titration and elemental analysis, by IR spectroscopy, and by determination of ionic conductivity. Also the hydrolytic stability of the sulfonated ion-exchange polymers was investigated. Polymers with an ion-exchange capacity of 0.5 to 3.2 mequiv SO3H/g Polymer have been synthesized and characterized. The following results have been achieved: membranes made from the sulfonated polymers show good conductivity, good permselectivity (>90%), and good hydrolytic stability in 1N HCl and water at temperatures up to 80°C. © 1996 John Wiley & Sons, Inc.
Tetrafluoroethylene is copolymerized with a perfluorovinyl ether, containing a functional end group (-SO2F or -CO2CH3) to yield a melt fabricable precursor polymer. After fabrication into the desired shape, the polymer is treated with a solution of potassium hydroxide to convert the functional group to an ion exchange site.
The fundamental incompatibility of the ionic group with the perfluorinated polymer backbone results in a unique morphology, particularly in the presence of water or polar organic solvents. This has been the subject of extensive investigations by various research institutions.
The most important industrial use for these polymers is in the electrolysis of sodium chloride solutions. Initially introduced in order to eliminate the environmental problems of the amalgam process, their performance has now improved to the point where they offer substantial savings, particularly in terms of energy costs, over the two older processes.
An emerging, potentially very important use for perfluorinated ion exchange polymers is as an ionic conductor in fuel cells. Recent advances in this area will be discussed.
A brief description of the ion exchange membrane fuel cell, of important membrane properties and of some earlier membrane development work is given. We describe some results of membrane stability tests in electrolysis cells, which are important for fuel cell application, in context with fluorination degree and morphology of the membrane. These results demonstrate, that fluorinated membranes with “defined” morphology can be applied in these cells. Finally, we give evidence for asymmetric degradation of membranes at the H2-side.
In the presented paper, the preparation and characterization of new ionomer blend membranes containing sulfonated poly(etheretherketone) PEEK Victrex® is described. The second blend components were Polysulfone Udel®-ortho-sulfone-diamine, polymide PA Trogamid P (producer: Hüls) and poly(etherimide) PEI Ultem (producer: General Electric). In the blend membranes swelling was reduced by specific interaction, in the case of the blend components PA and PEI hydrogen bonds, and in the case of the blend component PSU–NH2 (partial) polysalt formation, leading to electrostatic interaction between the blend component macromolecules, and hydrogen bonds. The acid–base interactions also led to decrease of ionic conductivity by partial blocking of SO−3 groups for cation transport, compared with the ionic conductivity of the hydrogen bond blends. The acid–base blends showed better ion permselectivities than the hydrogen bond blends, even at high electrolyte concentrations, and thus better performance in electrodialysis. The thermal stability of the investigated blends was very good and in the case of the acid–base blends even better than the thermal stability of pure PEEK–SO3H. DSC traces of the blend membranes showed only one Tg. In addition, the membranes are transparent to visible light. But therefrom it cannot be concluded that the blend components are miscible to the molecular level: at the acid–base blend blends, the Tg of PEEK–SO3H is very similar to the Tg of PSU–NH2, and in the investigated hydrogen bond blends, the portion of PA or PEI, respectively, might be too low to be detected by DSC. The investigated blend membranes showed similar performance as the commercial cation-exchange membrane CMX in electrodialysis (ED) application. The performance of the acid–base blend membrane is better than the performance of the hydrogen bonded PEEK–PA blend, especially in the ED experiment applying the higher NaCl concentration. This is mainly due to the lower swelling and thus better ion permselectivity of the acid–base blend membrane, compared with the PEEK–PA blend. To get a deeper insight into the microphase structure of the investigated blends, dynamic mechanical analyses and TEM investigations of the prepared blend membranes are planned. In addition, due to their promising properties, the preparation of arylene main-chain acid–base blends with other polymeric acidic and basic components is planned. Furthermore, the acid–base blend membranes will be tested in H2 polymer electrolyte fuel cells and direct methanol fuel cells, because preliminary tests have shown that they have a good perspective in this application.
The permeability of Nafion®117 and some types of acid-base and covalently crosslinked blend membranes to methanol was investigated. The methanol crossover was measured as a function of time using a gas chromatograph with a flame ionization detector. In comparison to Nafion, the investigated acid-base and covalently crosslinked blend membranes show a significant lower permeation rate to methanol. Additionally, another method to reduce the methanol permeability is presented. In this concept a thin barrier layer is plasma polymerized on Nafion 117 membranes. It is shown that a plasma polymer layer with a thickness of 0.3 µm reduces the permeability to methanol by an order of magnitude. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 67–73, 1999
Ionic groups incorporated into a polymer have a decided effect on its physical properties. A number of ionomers and polyelectrolytes have been widely applied. In particular, sulfonated bisphenol-A polysulfone (SPSF) has been used as a composite or single-component membrane for the desalination of water. In this article, the synthesis and physical characteristics of sulfonated polysulfone are addressed. A detailed synthesis route is provided and methods that yield determinable levels of sulfonation are described. These ion-containing polymers retain an excessive amount of residual salts, which, of course, are impurities to the system. Therefore, before any analyses were made the polymers were subjected to a thorough soxhlet extraction process with boiling water, which appeared to be quite effective. The degree of sulfonation was assessed by several methods such as 1H NMR and FT-IR. A new 1H NMR method was derived because the method cited in the literature proved to be too inconsistent for our work. The new 1H NMR method used a quaternary ammonium counterion [N(CH3)4]. These methyl protons are easily measured and may be ratioed against the isopropylidene protons in the polymer backbone that act as an internal standard. Characterization of the physical properties of SPSF consisted of water uptake, differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and solubility studies. Its physical appearance and mechanical behavior were improved by the solution procedure. Also addressed were the effects of different counterions (Na+ & Mg++) with SPSFs of low levels of sulfonation. The variation in physical properties between the divalent and monovalent counterions is dramatic, especially when observed by TMA in the rubber plateau above the apparent glass temperature.
Nanocomposites were produced via sol–gel reactions for tetraethylorthosilicate within the cluster morphology of perfluorosulfonic acid films. Small-angle x-ray scattering revealed that the polar/nonpolar nanophase-separated morphological template persists despite invasion by the silicon oxide phase. Scanning electron microscopy (ESEM–EDAX) studies have indicated that the greatest silicon oxide concentration occurs near the surface and decreases to a minimum in the middle. Optical and ESEM micrographs revealed a brittle, surface-attached silica layer at high silicon oxide contents. © 1995 John Wiley & Sons, Inc.
Mauritz et al. exploited the polar/nonpolar nanophase-separated morphologies of Nafion® perfluorinated ionomer membranes, as well as a Nafion® ionomeric precursor film, as interactive templates that are capable of directing the condensation polymerizations of inorganic alkoxides and organoalkoxysilanes as well as the ultimate geometrical distribution of the inorganic oxide, or organically modified silicon oxide phases that result upon drying. This paper is a review of our extensive studies involving the in situ sol-gel reactions of the alkoxides of silicon, titanium, aluminum, zirconium and organoalkoxysilanes, as well as their mixtures and two step reactions involving these monomers. Throughout this presentation, we demonstrate how various spectroscopic (FTIR, 29Si solid state NMR, dielectric relaxation, pyrene (Py) fluorescence probe emission + UV absorption) microscopic, X-ray scattering, thermal (DSC, TGA, TGA-FTIR, DMA), mechanical tensile, and gas permeation tools were employed to interrogate the structures and properties of these heterogeneous materials over a range of dimensional scales ranging from the molecular to the macroscopic. Importantly, we established that these organic/inorganic materials are indeed structured on the scale of nanometers. Methods of tailoring the energetic environment, or polarity, within the cluster domains by the insertion of inorganic oxide or organically modified silicate nanostructures are presented. Finally, we discuss the potential for these nanocomposite membranes within a number of areas including gas and liquid separations technology as well as proton exchange membranes for fuel cell technology.
New modified PSU Udel® containing N-basic side groups like pyridine and dimethylamino groups have been developed. The modified PSU was synthesized via (i) lithiation of PSU ortho to the sulfone bridge and (ii) reaction of the lithiated PSU with aromatic ketones like 2,2′-bipyridylketone, 4,4′-dimethylaminobenzophenone, aromatic aldehydes like 2-, 3-, and 4-pyridinealdehyde, and 4-N,N-diethylaminobenzaldehyde, and aromatic carboxylic acid esters like isonicotinic acid ethyl ester and 4-N,N-dimethylaminobenzoic acid ethyl ester. The basic PSU polymers were characterized via NMR, elemental analysis, and thermogravimetry (TGA). Selected basic polymers were mixed with poly(etheretherketone) (PEEK) sulfonic acid to yield polymeric acid–base blends. The obtained blend membranes were characterized in terms of ionic conductivity by impedance spectroscopy, in terms of morphology by transmission electron microscopy (TEM), and in terms of thermal stability by TGA. The acid–base blends show good ionic conductivities at ion-exchange capacities of ≥1 meq/g, and good thermal stabilities. The TEM investigations yielded the result that the acid–base-blends are miscible-no polymer-microphase separation could be observed.
There is a strong relationship between the efficiency and economics of Proton Exchange Membrane (PEM) fuel cells. The fuel cell efficiency is not a single number; it is a function of power density at which the fuel cell is operating. Typically, the lowest efficiency is achieved at maximum power output. The optimum nominal efficiency that results in the least expensive electricity produced by the fuel cell is determined not only by the fuel cell performance characteristics, but also by its economics, i.e. capital cost of fuel cell and cost of hydrogen. The efficiency and economics of the fuel cells have been analyzed in various load profiles and for various development and cost scenarios. The results indicate that in the best case scenario the fuel cells can be produced at ~$100/kW, operate at 50% efficiency, and generate electricity at <$0.08/kWh if hydrogen can be supplied at $10/GJ.
Proton-exchange membranes, for possible use in H2/O2 and direct methanol fuel cells have been fabricated from poly[bis(3-methylphenoxy)phosphazene] by first sulfonating the base polymer with SO3 and then solution-casting thin films. The ion-exchange capacity of the membrane was 1.4 mmol/g. Polymer crosslinking was carried out by dissolving benzophenone photoinitiator in the membrane casting solution and then exposing the resulting films after solvent evaporation to UV light. The crosslinked membranes look particularly promising for possible proton exchange membrane (PEM) fuel cell applications. A sulfonated and crosslinked polyphosphazene membrane swelled less than Nafion 117 in both water and methanol. Proton conductivities in crosslinked and non-crosslinked 200 μm thick water-equilibrated polyphosphazene films at temperatures between 25°C and 65°C were essentially the same and only 30% lower than those for Nafion 117. Additionally, water and methanol diffusivities in the crosslinked polyphosphazene membrane were very low (≤1.2×10−7 cm2/s). Sulfonated/crosslinked polyphosphazene films showed no signs of mechanical failure (softening) up to 173°C and a pressure of 800 kPa and did not degrade chemically when soaked in a hot hydrogen peroxide/ferrous ion solution.
In this contribution novel acid–base polymer blend membranes are introduced. The membranes are composed of sulfonated poly(etheretherketone) sPEEK Victrex or poly(ethersulfone) sPSU Udel® as the acidic compounds, and of PSU Udel® diaminated at the ortho position to the sulfone bridge, or poly(4-vinylpyridine), poly(benzimidazole) PBI CELAZOLE®, or poly(ethyleneimine) PEI (Aldrich) as the basic compounds. The membranes showed good proton conductivities at ion-exchange capacities IEC of 1 (IEC=meq SO3H/g dry membrane), and they showed excellent thermal stabilities (decomposition temperatures >270°C). Two of the membranes were tested in a H2 membrane fuel cell and showed good performance. The specific interaction of the SO3H groups and of the basic N groups was investigated via FTIR for the sulfonated PSU/diaminated PSU and for the sulfonated PSU/poly(4-vinylpyridine) (Pyr) blend. It could be proved that in the dry membranes polysalt groups exist formed by the following acid–base reaction: PSU–SO3H+H2N–PSU→[PSU–SO3]−+[H3N–PSU], and PSU–SO3H+P→[PSU–SO3]−+[H–Pyr].