Anion Exchange Groups Research Articles

Communication—Anion-Conductive Perfluoroheteroaromatic Composite Membranes: High Chemical Stability under Strong Alkaline Conditions

Nafion is used as cation-conductive fluoropolymeric membranes in proton-exchange membrane fuel cells, flow batteries, etc. However, its fluoropolymer-based anion-exchange counterparts that are stable under strong basic conditions of alkaline membrane fuel cells have not yet been documented. In this communication, we report a fluoropolymer-based anion-conductive membrane comprised of perfluoro(phenyl-2,2′:6′,2″-terpyridine), 2,2′:6′,2″-terpyridine, and ZrO(ClO4)2, which was found stable in a 7 M KOH solution at 120°C for >2,200 h—unprecedented in literatures. Such high stability is due to its fluorinated polymeric structure, covalent C-C bonds that link the polymer side chains and the heteroaromatic ligands, and ZrO(ClO4)2 nanoclusters as anion-exchange groups.

Effect of Solvents on the Surface Modification of Hydrophilic Macro-Porous Particles with an Ion-Exchange Monomer Having Both Anion and Cation Exchange Groups

Effect of Solvents on the Surface Modification of Hydrophilic Macro-Porous Particles with an Ion-Exchange Monomer Having Both Anion and Cation Exchange Groups

Combination of OH– ions and –OH groups within QPPO/PVA hybrid membranes for acid recovery

Hybrid membranes are prepared from quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO), polyvinyl alcohol (PVA), monophenyl triethoxysilane, and tetraethoxysilane through sol–gel process. QPPO contains the anion-exchange groups which can be in the form of –N+(CH3)3OH−, –N+(CH3)3Cl−, or –N+(CH3)3Br−. The OH− ions can combine with PVA–OH groups to form weak interactions such as hydrogen bonds, and thus enhance the compatibility between QPPO and PVA phases and membrane stability. Hybrid membranes with the combination of OH−/−OH are generally homogenous and compact, with the lower water uptake of 57.6–67.4%, methanol content of 38.3–40.2%, and swelling degrees of 223–500% in 65°C water. The ion-exchange capacities are similar in the range of 1.04–1.08 mmol/g. Diffusion dialysis (DD) of HCl/FeCl2 solution shows that as the temperature increases from 15 to 55°C, the dialysis coefficients of HCl (UH) increase from 0.008 m/h to 0.014–0.018 m/h, while the separation factors decrease from 61–67 to 41–50. The UH values are similar to that of commercial membrane DF-120 (0.009 m/h at 25°C), and the separation factors are higher than those of reported membranes (lower than 48). The UH values can remain 87–95% after the erosion of HCl/FeCl2 system, with no significant reduction of selectivity. Hence, the combination of OH− ions and PVA–OH groups is effective to elevate membrane stability and selectivity, and the QPPO/PVA hybrid membranes can be potentially applied in DD process for acid recovery.

Proton and Metal Cage-Based Anion-Conductive Fluoropolymers for AMFCs

A new class of fluoropolymers (polymers 9 and 14) have been synthesized and tested as novel anion-conductive materials. Proton and lithium cages, which are alternative to conventional quaternary ammonium hydroxide are utilized as anion-exchange groups in these polymers. Such cage-based fluoropolymers can potentially be developed into chemically stable and anion-conductive membranes that can find applications in alkaline membrane fuel cells (AMFCs), metal-air batteries and many other electronic devices.

Preparation and electrochemical characterizations of anion-permselective membranes with structurally stable ion-exchange sites

ABSTRACT Novel semi-interpenetrating polymer network (semi-IPN) anion-permselective membranes are prepared via a facile monomer sorption method. The base membrane is prepared by in-situ copolymerization of N , N ’-dimethylaminoethyl methacrylate (DMAEMA) and divinylbenzene (DVB) in a non-porous poly(vinyl chloride) (PVC) substrate film ( i.e . poly(DMAEMA- co -DVB)/PVC). The successive quaternization reaction along with di-functional p -xylylene dichloride forms the structurally stable anion-exchange groups that are fused with one another. Various characterizations (measurements of the transport number, electrical resistance, I-V curves, and chronopotentiometry etc.) reveal that the electrochemical properties of the prepared membranes are almost comparable with those of a commercial anion-exchange membrane (AMX, Astom Corp., Japan). In addition, the structural stability of the anion-exchange sites is confirmed through the water-splitting experiments at a high applied current condition.

Proton and Metal Cage-Based Anion-Conductive Fluoropolymers for AMFCs

Alkaline membrane fuel cells (AMFCs) have attracted a great deal of attention due to its use of non-precious metal catalysts. However, the lack of chemically stable and highly ion-conductive anion-exchange polymer membrane has impeded the development and adoption of AMFCs by our society. Under strong alkaline conditions, hydroxide anions can be both a nucleophile and a strong base that degrade the hydrocarbon polymer backbones as well as the anion-exchange groups attached to the side chains of the polymer. Typically, positively charged quaternary amine or guanidinium groups are used for hydroxide transportation. Unfortunately, these functional groups are subjected to nucleophilic and elimination attacks by hydroxide anions. In this presentation, we will disclose a new class of chemically stable anion-exchange fluoropolymers that can be casted into AMFC membranes. The structure of a proton trap-based fluoropolymer is shown in the attached figure. This polymer was chemically synthesized from a perfluorosulfonic acid (PFSA) via a novel C-C coupling reaction. The highly fluorinated polymer backbone and side chains were known to tolerate chemical degradation while its proton cage group is robust against caustic conditions. In our polymer, a proton is encapsulated inside a three-dimensional cage and it is protected from hydroxide attacks. Such a polymer demonstrated remarkable stability in strong alkali media with good ion conductivity. In our talk, we will also discuss several other types of anion-exchange fluoropolymers including zirconium-based membranes and lithium cage-based electrolytes. Figure 1

A new polymeric ionic liquid-based magnetic adsorbent for the extraction of inorganic anions in water samples

In this work, a novel type of polymeric ionic liquid (PIL)-based magnetic adsorbent was successfully synthesized and applied for the extraction and determination of seven inorganic anions in water samples by coupling with ion chromatography. The new adsorbent was synthesized by simple free radical copolymerization of 1-ally-3-vinylimidazolium chloride, ethylene glycol dimethacrylate and silica-coated magnetite. The adsorbent exhibited well-defined core-shell structure and good magnetic response ability. Furthermore, due to the presence of abundant anion-exchange groups in the PIL, the adsorbent displayed expected extraction performance for anions including F−, Cl−, Br−, NO2−, NO3−, PO43− and SO42−. Various experimental parameters that could affect the extraction performance, such as the amount of adsorbent, desorption solvent, extraction and desorption time, the pH value of sample solution were investigated in detail. Under the optimized conditions, low limits of detection (S/N=3) and quantification limits (S/N=10) of the proposed method for the target anions were achieved within the range of 0.061–0.73μg/L and 0.19–2.41μg/L, respectively. The repeatability was investigated by evaluating the intra-day, inter-day precisions and batch-to-batch reproducibility with relative standard deviations (RSDs) lower than 11%. At the same time, the method also showed high extraction speed, simplicity, practicality and low cost for the extraction inorganic anions. Finally, the proposed method was used to detect anions in different water samples successfully. The recoveries were in the range of 71.0–111%, and the RSDs were below 12% in the all cases.

ICONE23-1872 Radioactive Cesium Removal from Seawater Using Adsorptive Fibers Prepared by Radiation-Induced Graft Polymerization

The meltdown of three reactors of the TEPCO Fukushima Daiichi nuclear power station (NPS) caused by the Great East Japan Earthquake on March 11th 2011 resulted in the emission of radionuclides such as cesium-137 and strontium-90 to the environment. For example, radioactive cesium exceeding the legal discharge limit (90 Bq/L, 2×10^<-13> M) was detected in the seawater of the seawater-intake area of the NPS at the end of September 2014. Adsorbents with a high selectivity for cesium ions over other alkali metal ions such as sodium and potassium ions are required for cesium removal from seawater because sodium and potassium ions dissolve respectively at much higher concentrations of 5×10^<-1> and 1×10^<-2> M than cesium ions (2×10^<-9> M). In addition, the simple operations of the immersion in seawater and the recovery of the adsorbents from seawater are desirable at decontamination sites. We prepared a cobalt-ferrocyanide-impregnated fiber capable of specifically capturing cesium ions in seawater by radiation-induced graft polymerization and chemical modifications. First, a commercially available 6-nylon fiber was irradiated with γ-rays. Second, an epoxy-group-containing vinyl monomer, glycidyl methacrylate, was graft-polymerized onto the γ-rayirradiated nylon fiber. Third, the epoxy ring of the grafted polymer chain was reacted with triethylenediamine to obtain an anion-exchange fiber. Fourth, ferrocyanide ions, [Fe(CN)_6]^<4->, were bound to the anion-exchange group of the polymer chains. Finally, the ferrocyanide-ion-bound-fiber was placed in contact with cobalt chloride to precipitate insoluble cobalt ferrocyanide onto the polymer chains. Insoluble cobalt ferrocyanide was immobilized at the periphery of the fiber. However, the impregnation structure remains unclear. Here, we clarified the structure of insoluble cobalt ferrocyanide impregnated onto the polymer chain grafted onto the fiber to ensure the chemical and physical stability of the adsorptive fiber in various contaminated waters. The adsorption rate and capacity of the fiber for cesium ions were compared with those of a zeolite as a conventional adsorbent.

Simultaneous Analysis of Inorganic Monovalent Anions/Cations Using Mixed-Bed Single-Column Ion Chromatography

The ion-exchange properties of a new mixed-bed ion-exchange column Scherzo SSC18 (Imtakt, USA) were investigated. This mixed-mode column is packed with two types of 3 µm spherical silica particles having either octadecyl- and strong cation-exchange functional groups or octadecyl- and strong anion-exchange functional groups. The regularities of the retention of alkali metal cations and inorganic anions were studied with diluted acids (sulfuric, perchloric to phosphoric, nitric, oxalic and citric acids) as eluents and direct conductivity for the detection. Eluent concentration, column temperature and organic solvent addition effects were investigated. The separations were achieved on the basis of ion-exchange interactions introduced by the strong anion and strong cation-exchange functionalities of the stationary phase; meanwhile, contribution of hydrophobic interactions was also evident for the hydrophobic iodide and thiocyanate. The simultaneous separation of 12 inorganic anions and cations in 20 min was obtained under isocratic conditions with 1 mM oxalic acid as eluent. The applicability of developed method to the determination of chloride, sodium, potassium as well as nitrite, nitrate and ammonium in soil extracts was demonstrated with good potential for nitrogen speciation studies.

A green approach for preparing anion exchange membrane based on cardo polyetherketone powders

Anion exchange membranes (AEMs) have attracted great attention due to their irreplaceable role in platinum-free fuel cell applications. The majority of AEM preparations have been performed in two steps: the grafting of functional groups and quaternization. Here, we adopted a simpler, more eco-friendly approach for the first time to prepare AEMs by atmospheric-pressure plasma-grafting. This approach enables the direct introduction of anion exchange groups (benzyltrimethylammonium groups) into the polymer matrix, overcoming the need for toxic chloromethyl ether and quaternization reagents. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and 1H NMR spectroscopy results demonstrate that benzyltrimethylammonium groups have been successfully grafted into the cardo polyetherketone (PEK-C) matrix. Thermogravimetric analysis reveals that the plasma-grafting technique is a facile and non-destructive method able to improve the thermal stability of the polymer matrix due to the strong preservation of the PEK-C backbone structure and the cross-linking of the grafted side chains. The plasma-grafted PG-NOH membrane, which shows satisfactory alcohol resistance (ethanol permeability of 6.3 × 10−7 cm2 s−1), selectivity (1.2 × 104 S s cm−3), thermal stability (safely used below 130 °C), chemical stability, anion conductivity (7.7 mS cm−1 at 20 °C in deionized water) and mechanical properties is promising for the construction of high-performance fuel cells.

Study of Chemical Modified Amphoteric Ion Exchange Membrane from Taurine

Fluorinated poly(aryl ether oxadiazole), synthesized by the copolymerization of 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole and diallylbisphenol A, was used as the main polymer chain (MP). 2-aminoethanesulfonic acid (taurine) was attached to brominated-MPs (Br-MPs) at mild conditions, serving as both cation and anion exchange groups. AIEM-0.6, AIEM-1.4 and AIEM-2.0 were obtained via solution-casting method. Quantum calculation and experiments verified the selective permeability of the membranes: high proton conductivities and low vanadium permeation parameters. Also the AIEMs demonstrate good acid resistance and thermal stability, showing potential in vanadium redox flow battery (VFB) fields.

Alkaline Durable 2-Methyl-1-Vinylimidazolium-Based Anion Exchange Membranes Prepared by Radiation-Induced Grafting for Hydrazine Hydrate Fuel Cells

Introduction An anion exchange membrane (AEM) is one of the key materials for alkaline-type fuel cells (AEMFC), which have potential advantages against proton exchange membrane fuel cells (PEMFC). In the AEMFC, electrochemical reactions are more facile than in acidic medium, and non-precious metals such as nickel, cobalt and iron can replace platinum as the catalyst.1,2 Because of high temperature and highly basic fuel cell operating condition, it is desirable to develop alkaline durable AEMs. In recent years, we have developed imidazolium-type AEMs by radiation-induced grafting for AEMFCs, especially in direct hydrazine fuel cells and found that poly(1-vinylimidazolium (VIm))-grafted and copoly(VIm/styrene)-grafted AEMs (AEM1 and AEM2) shows moderate alkaline stability; the AEMs degraded via the initial β-elimination and following ring opening reactions of the imidazolium unit.3,4 Therefore, we synthesized the AEM based on a poly(2-methyl-1-vinylimidazolium (MVIm)) grafts by radiation-induced grafting to improve long-term stability by suppressing β-elimination and ring opening reactions. Experimental The ETFE films were irradiated with a 60Co γ-ray source (JAEA Takasaki, Gunma, Japan) at room temperature in argon atmosphere with an absorption dose of 50 kGy. The pre-irradiated ETFE films were immediately immersed into the argon-purged monomer solution consisting of 50 wt% MVIm or a mixture of MVIm/stylene (8 : 2 weight ratio) in 1,4-dioxane. The imidazole groups in the grafted-ETFE were N-alkylated using methyl iodide. The resultant AEMs (an iodide form) were immersed in 1 M NaHCO3 solution at 60°C for 24 h to convert into a HCO3 - form, followed by the ion-exchange reaction with OH- in 1 M KOH solution at room temperature for 16 h to givethe anion forms of the AEMs (AEM3 and AEM4), as shown in Scheme 1. The ionic conductivity was measured by two-point probe AC impedance spectroscopy at 100% relative humidity in N2-purged deionized water. The ion exchange capacity (IEC) was measured using standard back titration methods. Results and discussion The poly(MVIm)- and copoly(MVIm/styrene)-grafted ETFE films (precursors of AEM3 and AEM4) were prepared with grafting degrees of 36 and 55%, respectively. The copolymer-type AEM4 was synthesized for reduction of steric and electrostatic repulsions between adjacent imidazolium cations. The N-alkylation for AEM3 proceeds quantitatively. Thus, molar ratio of MVIm and stylene in AEM4 determined from the weight gain after N-alkylation given that the N-alkylation of the imidazole groups proceeded in a quantitative maner was estimated as 1.0 : 1.4. AEM3 and AEM4 with IECs of 0.99 and 0.93 mmol g-1 showed ionic conductivities of 55 and 53 mS cm-1 at 60°C, respectively.The alkaline stability of AEMs was evaluated by monitoring the change in conductivity of AEMs in 1 M KOH at 80°C. Figure 1 shows the normalized conductivities of the AEMs on the basis of the initial conductance as a function of immersion time. The homopolymer-type AEM1 and AEM3 showed similar profiles for conductivity decreases, indicating the donimant β-elimination at an initial stage for homopolymer-type imidazolium grafts in the AEMs due to the steric and electrostatic repulsions. Copolymer-type AEM3, which had no 2-methyl group on the imidazolium group, showed a slower degradation rate after the fast decrease at the initial stage. Furthermore, copolymer-type AEM4, which had 2-methyl group on the imidazolium group, showed slower decreases at the initial stage and kept excellent long-term stability with keeping maintenance factor of 22% (12 mS cm-1) after 600 h immersion. The above results strongly indicate that the introducition of methyl group at 2-position of imidazolium unit drastically enhances the long-term durability in alkaline solutions at elevated temperatures due to the resistance of nucleophilic ring opening reactions of the imidazolium cations. Accordingly, the 2-methylimidazolium units in copolymer grafts in AEMs are promising an anion exchange group for highly alkaline durable direct hydrazine fuel cells. Acknowledgement This work was supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) from the Japan Science and Technology Agency (JST).

Electrodialytic properties of aromatic and aliphatic type hydrocarbon-based anion-exchange membranes with various anion-exchange groups

Anion-exchange membranes (AEMs) with various membrane structures were prepared by introducing various amines: trimethylamine (TMA), triethylamine (TEA), tri-n-propylamine (TPA) and tri-n-butylamine (TBA) into precursor membranes prepared from chloromethylstyrene (CMS)–divinylbenzene (DVB) and glycidyl methacrylate (GMA) – DVB. Their properties for ionic transport and anti-organic fouling were examined. Almost all of the prepared AEMs have excellent ionic transport properties: transport number of anions >0.94 and membrane resistance <4 Ωcm2. The voltage change through the AEMs during electrodialysis operation using solutions containing sodium dodecylbenzene-sulfonate as a foulant indicated that there are three cases of fouling mechanism being related to membrane structure: (a) aliphatic AEMs show lower fouling than aromatic ones; (b) the lower the water content of an AEM, the more remarkable the fouling; (c) the longer the chain length of the alkyl groups of the anion-exchange groups of an AEM, the more remarkable the fouling.

A novel ionic liquid-modified organic-polymer monolith as the sorbent for in-tube solid-phase microextraction of acidic food additives.

A novel ionic liquid-modified organic-polymer monolithic capillary column was prepared and used for in-tube solid-phase microextraction (SPME) of acidic food additives. The primary amino group of 1-aminopropyl-3-methylimidazolium chloride was reacted with the epoxide group of glycidyl methacrylate. The as-prepared new monomer was then copolymerized in situ with acrylamide and N,N'-methylenebisacrylamide in the presence of polyethylene glycol (PEG)-8000 and PEG-10,000 as porogens. The extraction performance of the developed monolithic sorbent was evaluated for benzoic acid, 3-hydroxybenzoic acid, cinnamic acid, 2,4-dichlorophenoxyacetic acid, and 3-(trifluoromethyl)-cinnamic acid. Such a sorbent, bearing hydrophobic and anion-exchange groups, had high extraction efficiency towards the test compounds. The adsorption capacities for the analytes dissolved in water ranged from 0.18 to 1.74 μg cm(-1). Good linear calibration curves (R(2) > 0.99) were obtained, and the limits of detection (S/N = 3) for the analytes were found to be in the range 1.2-13.5 ng mL(-1). The recoveries of five acidic food additives spiked in Coca-Cola beverage samples ranged from 85.4 % to 98.3 %, with RSD less than 6.9 %. The excellent applicability of the ionic liquid (IL)-modified monolithic column was further tested by the determination of benzoic acid content in Sprite samples, further illustrating its good potential for analyzing food additives in complex samples.

Methylated polybenzimidazole and its application as a blend component in covalently cross-linked anion-exchange membranes for DMFC

In the present work, the development and the characterization of new anion exchange membranes (AEMs) based on a methylated polybenzimidazole (mPBIOO) and their application in direct methanol fuel cell (DMFC) are described. For the preparation of methylated PBIOO (mPBIOO), a gentle methylation method was developed by using dimethyl carbonate (DMC) and 1,4-diazabicyclo[2.2.2]octane (DABCO). The synthesis of covalent cross-linked AEMs was achieved using the mPBIOO, sulfinated polysulfone (PPSU-SO2Li), DABCO and diiodobutane (DIB). The AEMs had IECs of more than 2.0meqg−1, which indicates a high concentration of anion-exchange groups. Depending on the cross-linking degree, the methanol gravimetric uptake reached a maximum of 43% (by mass) and all AEMs showed an excellent ex situ alkaline stability. After 10d in aqueous KOH (1M) at 90°C the IECs, ionic conductivities, and mechanical stabilities did not show a significant decrease. DMFC measurements show a performance improvement of a factor of three when the membranes were solvent (dimethylacetamide) extracted before integration into the fuel cell. With the usage of non-Pt catalysts, a maximum power density of 120mWcm−2 was achieved.

Performance analysis of aromatic adsorptive resins for the effective removal of furan derivatives from glucose

BACKGROUND Many countries have set goals to replace conventional energy sources with renewable energy sources. This has led to investigations into the use of lignocellulosic biomass as a feedstock for renewable fuels and base chemicals. Unfortunately hydrolysation of this biomass introduces impurities that are toxic to the fermentation bacteria. This study aims to find the key adsorber properties for the separation of toxic 5-hydroxymethylfurfural (HMF) from glucose. RESULTS Batch adsorption experiments on styrene based (anion exchange) adsorbers showed that a high surface area is a key property for effective HMF adsorption. Introduction of polar groups in the form of anion exchange groups appears to increase the HMF-affinity of the resin material, unfortunately these groups also introduce affinity for glucose. Competitive adsorption studies of HMF and glucose showed that glucose does not affect HMF adsorption in any of the resins. CONCLUSION Furan derivatives can be removed from water and sugar solutions with styrene based (anion exchange) polymeric resins. For efficient removal, a high surface area of the resin is a key property. Dowex Optipore L-493 shows the best specific HMF adsorption and no specificity for glucose, which makes it an excellent adsorber for HMF removal from hydrolysate for the fermentation of glucose. © 2013 Society of Chemical Industry

Synthesis of an Anion-Exchange Membrane Based on Imidazolium-Type Ionic Liquids for a Capacitive Energy Extraction Donnan Potential Device

Polymeric anion-exchange membranes (AEMs) were synthesized via the photocopolymerization of a vinyl imidazolium ionic liquid, with 1-butyl-3-(4-vinylbenzyl)imidazolium chloride ([BVBI][Cl]) as the anion-exchange group and styrene, acrylonitrile, and divinylbenzene as cross-linked agents. The physical, mechanical, and electrochemical properties of the prepared AEMs such as water uptake (%), swelling degree (%), ion-exchange capacity (mmol/g), thermal stability, tensile strength (Mpa), tensile modulus (Mpa), elongation (%), and ionic conductivity (S/cm) were evaluated. The synthesized AEMs were shown to have good physical, mechanical, and electrochemical properties for application of a capacitive energy extraction Donnan potential (CDP) device membrane. The CDP device was fabricated by using the synthesized AEM. The specific capacitance of the CDP device with AEM was determined as 2.53 F/g and 3.44 F/g by galvanostatic charge/discharge and cyclic voltammetry, respectively. The synthesized AEM with imidazolium ionic liquid can be applied as the CDP device membrane.

【原著】 グラフト鎖へのアニオン交換基の導入部位の制御によるアニオン交換多孔性中空糸膜の再生に要する緩衝液量の削減

【原著】 グラフト鎖へのアニオン交換基の導入部位の制御によるアニオン交換多孔性中空糸膜の再生に要する緩衝液量の削減

Preparation and characterisation of anion exchangers with dihydroxy-containing alkyl substitutes in the quaternary ammonium functional groups

Novel poly(styrene-divinylbenzene) (PS-DVB) based anion exchangers having one and two (2,3-dihydroxypropyl) substitutes in the quaternary ammonium functional groups are prepared and characterised by ion chromatography (IC). The introduction of bulky and hydrophilic substitutes to the anion-exchange groups allows the elimination of non-ionic interactions between the polarisable anions and the aromatic rings from the matrix and the improvement of separation selectivity as compared with the traditional trimethylammonium (TMA) functionalised ion exchangers. The synthesis of the ion exchangers includes acylation of PS-DVB particles with acetic anhydride followed by reductive amination either with methylamine hydrochloride or dimethylamine and further alkylation with oxiranes under varied conditions. The ion exchange selectivity and separation efficiency of nine adsorbents having different structure of bonded groups, ion exchange capacity (9–98μequiv.g−1) or particle size is studied for model mixture of inorganic anions (F−, Cl−, NO2−, Br−, NO3−, HPO42− and SO42−) using carbonate and hydroxide eluents. The adsorbents with more hydrophilic substitutes provided superior columns efficiencies and better peak symmetry as compared with analogues having hydrophobic functional groups. The calculated values of column efficiencies for polarisable NO3− and HPO42− are 18,500 and 29,000N/m, respectively, for anion-exchanger, having N-methyl-N′,N″-di-(2,3-dihydroxypropyl)ammonium groups which is significantly higher than 1800 and 12,000N/m obtained for these anions with anion exchanger bearing TMA functional groups.

A Dication Cross‐Linked Composite Anion‐Exchange Membrane for All‐Vanadium Flow Battery Applications

We report the fabrication and properties of a high-performance, inexpensive, composite, anion-exchange membrane (AEM) for an all-vanadium flow battery (VFB) application. The AEM was fabricated by dication cross-linking without the involvement of trimethylamine, and shows well-balanced anion conductivity and robustness due to imidazolium and imidazolium-ammonium functionalities, as well as a concomitantly achieved semi-interpenetrating network structure. The VFB single cell yielded a Coulombic efficiency of 99 % and an energy efficiency of 84 % at 80 mA cm(-2) , and operated for over 900 charge/discharge cycles. This work demonstrates the combined use of several favorable AEM design rationales, such as incorporating abundant and efficient anion-exchange groups, constructing a swelling- and oxidation-resistant structure, and facile fabrication; it provides an effective way of developing high-performance, low-cost AEMs for VFB applications.