Anion Exchange Membranes For Applications Research Articles

Enhanced performance of anion exchange membranes via crosslinking of ion cluster regions for fuel cells

Abstract Development of anion exchange membranes (AEMs) with high hydroxide conductivity, good dimensional and alkaline stabilities is still a challenge for the practical application of AEM fuel cells. In this study, we report a new strategy to prepare high-performance AEMs with crosslinked ionic regions. A series of phenolphthalein-containing poly(arylene ether sulfone)s crosslinked AEMs was synthesized by grafting ion groups selectively and densely on the phenolphthalein units to form ion clusters that are further crosslinked to generate the hydrophilic ionic regions. The crosslinking reaction not only improved the dimensional stability of the AEMs, but also increased the aggregation of the ion clusters leading to the formation of hydrophilic/hydrophobic phase-separated morphology and ion-conducting channels. As a result, enhancements in both ion conductivity and dimensional stability can be achieved. The crosslinked AEMs showed high hydroxide conductivities in the range of 52.2–143.4 mS cm−1 from 30 to 80 °C and a superb ratio of relative conductivity to relative swelling at 80 °C. Furthermore, the crosslinked AEMs also exhibited good mechanical properties, thermal and alkaline stabilities and desirable single cell performance. This work presents a promising strategy for the synthesis of high-performance AEMs for fuel cells.

Fluorenyl‐containing Quaternary Ammonium Poly(arylene ether sulfone)s for Anion Exchange Membrane Applications

AbstractA series of anion exchange membranes (AEM) based on block quaternary ammonium poly(arylene ether sulfone) (QA‐bPAES) were successfully synthesized from 9,9′‐bis(4‐hydroxyphenyl) fluorene, 4,4′‐(hexafluoroisopropylidene) diphenol and 4,4′‐difluorodiphenyl sulfone via block polymerization, chloromethylation, quaternization, alkalization and solution casting. Properties of the obtained QA‐bPAES membranes, including ion exchange capacity (IEC), water uptake, swelling ratios, methanol permeability and ion conductivity were investigated. The obtained QA‐bPAES membranes showed low water uptakes, high ion conductivities and good physical and chemical stability. For example, the membrane of QA‐bPAES(20/10)‐1.34 with IEC of 1.34 mmol g−1 exhibited swelling ratios of 5.0% and 5.1% in in‐plane and through‐plane direction, respectively, and ion conductivity of 15.6 mS cm−1 in water at 60 °C with low methanol permeability of 1.06 × 10−7 cm2 s−1 (25 °C). All the results indicated that this type of block membranes had good potentials for alkaline anion exchange membrane fuel cell applications.

Spirocyclic quaternary ammonium cations for alkaline anion exchange membrane applications: an experimental and theoretical study

Spirocyclic quaternary ammonium cation based alkaline anion exchange membranes were synthesized and studied by both experimental and theoretical analysis.

Polybenzimidazole-crosslinked poly(vinylbenzyl chloride) with quaternary 1,4-diazabicyclo (2.2.2) octane groups as high-performance anion exchange membrane for fuel cells

Development of anion exchange membrane (AEM) with high conductivity, good dimensional stability, desirable toughness and long life-time simultaneously is still a challenge for the practical application of AEM fuel cells. Herein, a novel AEM (denoted as PBI-c-PVBC/OH) is fabricated by applying polybenzimidazole (PBI) and 1,4-diazabicyclo (2.2.2) octane (DABCO) as the macromolecular crosslinker and quaternizing reagent for poly(vinylbenzyl chloride) (PVBC), respectively. With the aid of crosslinking by PBI, PBI-c-PVBC/OH exhibits good flexibility and strength both in dry and water-saturated state. Moreover, high hydroxide conductivity (>25 mS cm−1 at room temperature) and low swelling ratio (∼13%) is obtained, especially the swelling ratio nearly does not increase with temperature. The membrane is also advanced for the superior chemical stability in alkaline environment due to the stable polymer backbone and ionic conductive group (only one nitrogen atom in a DABCO molecule is quaternized). Furthermore, a peak power density of 230 mW cm−2 at 50 °C is obtained on the H2/O2 fuel cell using PBI-c-PVBC/OH, and the membrane presents high durability both in the constant current and continuous open circuit voltage testing. Therefore, it is considered that the PBI crosslinking together with DABCO quaternization can be regarded as a promising strategy in the development of AEM for fuel cells.

Novel imidazolium-functionalized anion-exchange polymer PBI blend membranes

The potential application of anion-exchange membranes (AEMs) in alkaline fuel cells has recently experienced renewed attention as an alternative to the cation-exchange membranes used in proton exchange fuel cell (PEMFC). To date, no commercial AEM is available that is chemically, mechanically and thermally stable while maintaining high conductivities. In order to further improve the chemical stability of the blended membranes developed within our research group, the addition of both imidazoles as quaternizing agents, as well as a polymeric sulfonic component to introduce ionic cross-links between blend components was investigated. For this purpose 1-methylimidazole (MIm) and 1-ethyl-2-methylimidazole (EMIm) were selected as quaternizing agents while sulfonated polyethersulfone (SAC) was added to further improve the chemical stability of the synthesized AEMs by formation of electrostatic interactions between the AEM and the SAC blend component. The novel AEMs were evaluated in terms of properties such as ion exchange capacity (IEC), ion conductivity, weight loss with extraction experiments, water uptake and thermal stability (TGA) with the main focus on monitoring the alkaline stability. The synthesized AEMs proved chemically much more stable than the benchmark Tokuyama A201 membrane, while the acid–base imidazolium-functionalized membranes׳ conductivities also exceeded those reported for Tokuyama at temperatures below 60°C while being comparable at temperatures from 60°C to 80°C.

Application of Anion-Exchange Membranes for Vanadium Redox Flow Battery

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Cross-linked, ETFE-derived and radiation grafted membranes for anion exchange membrane fuel cell applications

To develop a series of cross-linked anion exchange membranes for application in fuel cells, poly(ethylene- co-tetrafluoroethylene) (ETFE) films was radiation grafted with vinyl benzyl chloride (VBC), followed by quaternization and crosslinking with 1,4-Diazabicyclo[2,2,2]octane (DABCO), alkylation with p-Xylylenedichloride (DCX), and quaternization again with trimethylamine (TMA). These anion exchange membranes were characterized in terms of water uptake, ion-exchange capacity, ionic conductivity as well as thermal stability. The chemical structures of the membranes were examined by FT-IR. The anion conductivity of the resulting alkaline anion exchange membrane is as high as 0.039 S cm −1 at 30 °C in deionized water and the ionic conductivity increases with the increasing of temperature from 20 to 80 °C. The membrane is stable after being treated by 10 M potassium hydroxide solution at 60 °C for 120 h .The fuel cell performance with the final AAEM obtained in a H 2/O 2 single fuel cell at 40 °C with this AAEM was 48 mW cm −2 at a current density of 69 mA cm −2.

Potential application of anion-exchange membrane for hydrazine fuel cell electrolyte

A platinum electrocatalyst layer was directly bound to a perfluorinated anion-exchange membrane (AEM) by the electroless plating method and used for the characterization of AEM as a polymer electrolyte membrane for a direct hydrazine fuel cell. The crossover amount of hydrazine through AEM was much lower than that through the cation-exchange membrane (CEM) that did not depend on the applied current density. The fuel cell performance was far superior when using AEM than when using CEM.

Removal and recovery of phenol from FCC effluent

Effluent from the FCC process contains considerable concentrations of phenol, sulfide and ammonium ions. The pH of the effluent is around 9. In the present study, the possibility of the application of anion exchange membranes for its removal and recovery, was investigated. The equilibrium constant between phenol and hydroxide ions and the ion exchange capacity of a commercial anion exchange membrane were determined. The membrane was sandwiched between two glass cells filled with a phenol solution at pH 9, fed and withdrawn continuously to keep the phenol concentration constant, and a sodium hydroxide solution at various pH, respectively. The permeation rate increased with pH and reached a plateau at above pH 13. The permeation rate was measured for various concentrations of phenol in the feed side, keeping the pH of the strip side at 13. The rate linearly increased with the phenol concentration and reached a plateau at concentration greater than 1 mol/m 3. The apparent diffusion coefficient of phenol in the membrane was determined from the plateau value. At a concentration of less than 1 mol/m 3, the rate was found to be controlled by boundary film resistance. It was also found that the permeation rate of phenol was suppressed by the sulfide ion at a concentration comparable to or larger than that of phenol.