Study of Anion Exchange Membrane Properties Incorporating N-spirocyclic Quaternary Ammonium Cations and Aqueous Organic Redox Flow Battery Performance (original) (raw)
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2014
Pore-filled anion-exchange membranes (PFAEMs) with a thickness of about 25 μm have been prepared using porous polyethylene substrates and tested for diffusion dialysis (DD) application. The membranes possess strong mechanical properties (tensile strength and elongation at break of 125.8 MPa and 76.2%, respectively) as well as excellent electrochemical characteristics such as low electrical resistance ( o0.4 Ω cm 2 ), high anion transport number (4 0.97), and high fraction of conductive region on the membrane surface etc. Moreover, in order to further improve the diffusion dialysis performance of the PFAEMs, the surface of PFAEMs was modified by introducing a thin polypyrrole layer with good affinity to anions. As a result, the PFAEMs exhibited excellent DD performances (high acid permeability and selectivity) superior to that of commercial membrane (i.e. Neosepta-AFX, Astom Corp., Japan) by the surface-modification.
Membranes
Composite anion-exchange membranes (AEMs) consisting of a porous substrate and a vinyl imidazolium poly(phenylene oxide) (VIMPPO)/acrylamide copolymer layer were fabricated in a straightforward process, for use in redox flow batteries. The porous substrate was coated with a mixture of VIMPPO and acrylamide monomers, then subsequently exposed to UV irradiation, in order to obtain a radically cured ion-exchange coating. Combining VIMPPO with low-value reagents allowed to significantly reduce the amount of synthesized ionomer used to fabricate the mem- brane down to 15%. Varying the VIMPPO content also allowed tuning the ionic transport properties of the resulting AEM. A series of membranes with different VIMPPO/acrylamides ratios were prepared to assess the optimal composition by studying the changes of membranes properties—water uptake, area resistivity, permeability, and chemical stability. Characterization of the membranes was followed by cycling experiments in a vanadium RFB (VRFB...
ACS OMEGA, 2021
Anion exchange membrane fuel cells (AEMFCs) are encouraging electrochemical structures for the competent and complaisant conversion of energy. Herein, the development of brominated poly(2,6-dimethyl phenylene oxide) (BPPO)-based anion exchange membranes (AEMs) with different quaternary ammonium groups for AEMFCs was reported. The successful preparation of AEMs was proved by utilizing proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. They were explored in terms of water uptake (W R), ion exchange capacity (IEC), hydration number (λ), linear swelling ratio (LSR), morphology, tensile strength (TS), and elongation at break (E b). The alkaline stability of the prepared AEMs was assessed and compared with each other. The experimental outcomes demonstrated that the N-methylpyrrolidinium-based membrane (MPyPPO) exhibited higher alkaline stability, whereas the N-methylimidazolium-based membrane (MImPPO) showed the lowest alkaline stability among the prepared AEMs. Similarly, the hydroxide conductivity of the prepared AEMs was measured and compared with each other. The pyrrolidinium-based membrane (MPyPPO) exhibited higher hydroxide conductivity among the prepared AEMs.
Journal of Membrane Science, 2013
Anion exchange membranes (PE/VBC) are successfully synthesized by pore-filling a porous polyethylene (PE) substrate with poly(4-vinylbenzyl chloride) followed by amination with pyridyl functional groups for vanadium redox flow battery (VRFB) applications. The membrane crosslinked with 10% of DVB content (PE/VBC(10)), 33 mm in thickness, exhibits a low swelling ratio of 3.4% and a water uptake of 23%. In addition, the vanadium crossover rate of the PE/VBC(10) membrane is lower than Nafion 117 by 48% at a similar electrical area resistance. Electrochemical properties of the PE/VBC membranes are examined in terms of the transport number and migration of ions as well as the electrical area resistance. Transport numbers for anions of the PE/VBC(10) membranes are 0.96 and 0.97 in NaCl and NaOH solutions, respectively. In acidic solutions of HCl and H 2 SO 4 , the membrane shows remarkably higher cation transport numbers of 0.20 and 0.72, which imply that the membrane allows high proton permeation and it is advantageous in VRFB operations. Furthermore, the migration of ions reveals reasonably low fluxes of other cations through the anion exchange membrane. Finally, the energy efficiency of the PE/VBC (10) membrane is 90.2%, higher than Nafion 117 by 5.4%.
Polymers, 2020
In order to evaluate the performance of the anion exchange membranes in a vanadium redox flow battery, a novel anion exchange polymer was synthesized via a three step process. Firstly, 1-(2-dimethylaminoethyl)-5-mercaptotetrazole was grafted onto poly(pentafluorostyrene) by nucleophilic F/S exchange. Secondly, the tertiary amino groups were quaternized by using iodomethane to provide anion exchange sites. Finally, the synthesized polymer was blended with polybenzimidazole to be applied in vanadium redox flow battery. The blend membranes exhibited better single cell battery performance in terms of efficiencies, open circuit voltage test and charge-discharge cycling test than that of a Nafion 212 membrane. The battery performance results of synthesized blend membranes suggest that those novel anion exchange membranes are promising candidates for vanadium redox flow batteries.
ACS Appl. Polym. Mater, 2022
Two major challenges, namely, hydroxide conductivity and alkaline stability of the polymer membrane, are yet to be resolved adequately in spite of significant research outcomes on alkaline anion exchange membrane (AAEM) in the recent past. To address these challenges, in this work, the development of ionically cross-linked AAEMs has been achieved by blending pyridine-bridged polybenzimidazole (PyPBI) and Nspirocyclic quaternary ammonium spiro ionene polymer (SP). Further, membranes were converted to porous membranes by adding different weight percentages of porogen in the membrane matrix. Membranes were converted to hydroxide-conducting AAEMs by dipping into 1 M KOH solution, and under this condition, a part of the −NH− groups of PyPBI was deprotonated to form ammonium−imidazolate complexes with SP, which resulted in ionic cross-linking in the AAEM. Hydroxide ion conductivity of 129 mS/cm at 90°C was obtained in the case of the S70P30-OH membrane, which was a hydroxideform membrane obtained from the blend of 70 wt % SP and 30 wt % PyPBI, and this membrane showed the highest KOH uptake among all other AAEMs prepared in this study. On the other hand, among the porous ionically cross-linked membranes studied here, the S50P50-P25-OH (blends of 50 wt % SP and 50 wt % PyPBI with 25% porogen) membrane showed the highest hydroxide ion conductivity (117 mS/cm at 90°C). All the ionically cross-linked AAEMs displayed excellent alkaline stability and remained unaffected during alkaline stability test in 1 M KOH at 80°C for as long as the test was carried out (960 h). Observing the exceptional stability in 1 M KOH of S50P50-OH and S50P50-P25-OH membranes, OH − conductivity analysis and alkaline stability tests of these samples were carried out even in 2 M KOH, and we found that these membranes retained ∼80% of their OH − conductivity value even after 500 h of alkaline treatment in 2 M KOH at 60°C. Furthermore, membranes were found to be useful in alkaline water electrolysis, and the best performance was shown by the S70P30-OH membrane, which displayed a current density of 100 mA cm −2 at 2.6 V. Overall, these recently developed membranes retained hydroxide conductivity, structural and thermal stability even after harsh alkaline treatment for a longer period of time.
J. Mater. Chem. A, 2013
Synthesis of chloromethylated polysulfone (CMPSF) and PSF-TMA + Cl-. CMPSF was synthesized via the Friedel-Crafts reaction following the procedure described by Avram and coworkers. 1 Details describing the chloromethylation procedure and fabrication of PSF-TMA + Clused in our lab is given in our previously published work. 2 Note: higher molecular weight PSF (~75,000), Acros Organics, was used rather than the lower molecular weight PSF (~35,000) documented in our previous work. 2 The PSF-TMA + Clfilm was then ion-exchanged to sulfate form by immersing in 1 M Na 2 SO 4 solution at room temperature during 24 hours. The 1 M Na 2 SO 4 solution was changed several times over a 24 hour period to improve the ion exchange process. The PSF-TMA + in the sulfate form was immersed and rinsed with DI water for several hours (at least 3 hours) to remove excess ions. Ionic conductivity. Electrochemical impedance spectroscopy (EIS) was used to determine the in-plane conductivity of the membrane. A membrane (in sulfate form) was placed in the conductivity cell (Teflon ® cell) in contact with 4 platinum wires. The external wires were connected to the working and counter electrodes of the potentiostat and the inner electrodes were used as working sense and reference.
Journal of the Electrochemical Society, 2018
A sulfonated poly (ether ether ketone) (sPEEK) was tested as the separator in a full alkaline flow battery with 2,6-dihydroxyanthraquinone-ferro/ferricyanide, DHAQ-FeCy, redox couples. Cell performance was compared to that of an identical cell utilizing a perfluorosulfonic acid (PFSA) membrane. Replacement of the PFSA membrane with sPEEK resulted in a 10% power density increase, a 40% decrease in capacity loss per day and an 85-fold decrease in ferricyanide permeation. Though long-term stability of sPEEK in alkaline media requires improvement, these results highlight the potential to produce non-fluorinated membranes with better performance in organic redox flow batteries than the commercially available PFSAs.