Use Of Anion Exchange Membrane Research Articles

Towards High-Performance AEM Water Electrolyzers: Transitioning from PGM to Low-PGM and PGM-Free Electrocatalysts

Hydrogen, known for its high gravimetric energy density and low environmental impact, is widely regarded as a promising low-carbon energy carrier. The production of hydrogen via water electrolysis offers a valuable opportunity to efficiently utilize renewable energy resources – both as a storage and transport medium and to produce hydrogen that is a crucial feedstock for multiple industrial and manufacturing applications. Among various water electrolysis technologies, anion exchange membrane water electrolyzers (AEMWEs) are notable for their distinct and advantageous features. Their alkaline operational environment significantly reduces corrosion, allow for the possibility to use catalysts and cell component materials that are earth abundant and cost effective. Moreover, the use of anion exchange membranes (AEMs) as the electrolyte and zero-gap design enhance operational efficiency and hydrogen production rates compared to traditional alkaline electrolyzers. These benefits position AEMWEs as a compelling solution for efficient, cost-effective large-scale hydrogen production.To date, the development of lower-cost AEMWEs has been hindered by several challenges. A critical issue is the activity and durability of catalysts, particularly those that are platinum group metal (PGM)-free. This leads many researchers and electrolyzer manufacturers to lean on PGM catalysts at both the anode and cathode. These catalysts, while effective, significantly increase the cost and complexity of the system, posing a barrier to widespread adoption and commercialization of AEMEL technology in the burgeoning hydrogen economy. PGM-free anodes have been demonstrated for the AEMWE, but there have been fewer PGM-free options for the cathode.This study assessed the performance and durability of various low-PGM and PGM-free electrocatalysts for the oxygen evolution (OER) and hydrogen evolution (HER) reactions. We focused on Lanthanum Strontium Cobalt (LSC), Nickel Ferrite (NiFeOx), and Lead Ruthenate (PbRuOx) for the OER at the anode, and Nickel Molybdenum (NiMo), Nickel Rhenium (NiRe), and a low-PGM PtNi for the HER at the cathode. Furthermore, the performance of the NiMo HER catalyst was enhanced by optimizing the physical properties of both the catalyst powder and the electrodes. These experimental results offer crucial insights into developing PGM-free AEM water electrolyzer systems, marking a progressive step towards their commercial feasibility.

Crossover analysis in a commercial 6 kW/43kAh vanadium redox flow battery utilizing anion exchange membrane

The volumetric and species transport is a significant source of capacity decay in vanadium redox flow batteries (VRFBs). However, even with the prevalent use of anion exchange membranes (AEMs) in commercial systems, the understanding of the crossover mechanisms in this context remains limited. The primary objective of this study was to gain a deeper comprehension of these mechanisms through experimental investigations conducted on a 6 kW/43kAh VRFB system using AEMs. It is concluded that protons serve as the primary charge carriers, owing to the high ionic concentrations of the electrolyte. During normal operation, there was a consistent pattern of volume transfer from the positive to the negative half-cell (∼0.5 % of the total electrolyte per cycle/day). Experimental assessments performed at different states-of-charge (SoCs) revealed that the volumetric transport towards the anolyte increases with SoC. The osmotic effects are concluded to be the main contributors to the volumetric transport. The osmotic pressure difference is hypothesized to arise from the asymmetric diffusion coefficients of the vanadium ions, changes in pH affecting sulfate and bisulfate equilibrium alongside their different diffusion coefficients, and a likely predominance of the bisulfate concentration gradient in the water transport through the membrane.

Using a Tunable Triblock Cationic Polymer to Unravel Performance and Durability Effects in Anion Exchange Membrane Based Electrolysis

The use of anion exchange membranes (AEMs) as the polymer electrolyte membrane and related cationic polymers as ionomers in the electrodes of water splitting electrolyzers could lead to significant advantages including the elimination of precious metal electrocatalysts. Because oxygenated radicals in base have a very much lower half life than in acid these materials can be based on hydrocarbon backbones. This leads to an enormous possible variation in polymer chemistry and, while exciting from the point of view of the creation of new polymer chemistries, has led to a lack of detail in determining exactly how all of these many polymers really behave in terms of performance and durability. All of the new materials that are currently being commercialized are designed to be free standing films that are chemically stable to attack by the strongly nucleophilic hydroxide anion. Often these polymers have excessive swelling and poor mechanical properties and lack easy variation enabling their modification to the properties required for an ionomer. Studies where the effect of film processing on performance or durability are also lacking. There is a chronic lack of knowledge in how cationic polymers interact with catalyst particles, charge carrier and the AEM in electrodes. Further complicating these studies is whether the device is operated in water, carbonate or hydroxide solution. The first of which give unexpectedly low performance but may be more amenable to long durability and latter of which gives high performance and low durability.We have developed a triblock co-polymer, with polychlorostyrene blocks that can be quaternized to give a hydrophilic phase and a central hydrophobic polyethylene (pE) block that gives the material good mechanical properties. This seemingly simple system can show tremendous variations. We can control the polymer block lengths and overall molecular weight of the polymer. The material can be suspension cast or melt processed to obtain uniform films. The films are post-quaternized and we can control the degree of functionalization and the nature of the cation. What is interesting about these materials is that for all anions that we have studied their conductivity behavior indicates that they are fully dissociated. We hypothesize that the pE content of the films localizes the water, this has the effect of both promoting anion conduction and also not wetting much of the polymer and so improving the durability and mechanical properties. In a series of films where we systematically increase the pE content, the materials swell less but do not necessarily loose performance. They do however show durability improvements, where a material that is 50% pE will thin in an electrolysis test giving rise to a degradation rate of -23 mV/h, a material with 80% pE will show a degradation rate of +400mV/h, at 500 μA/cm2. Further understanding of these materials is likely to result in further durability improvements. Performance and durability can also be varied by the method by which the film is processed.By using an unsaturated version of the cationic triblock co-polymer in electrode formulations and post hydrogenating we can insolubilize the polymer (by creating an insoluble pE containing polymer insitu) as the ionomer in the electrode. This allows us to study, ionomer loading and to begin to control the positioning of the ionomer. We have baselined these materials using Ni supports, and studied Membrane electrode assemblies on our optimized membranes. These ionomers are surprisingly durable as they contain aromatic groups, leading to further speculation that the localization of the water in the material again gives performance and durability advantages. In this talk we will also show how ionomer chemistry can be used to improve the performance and durability of electrolysis electrodes with either silver, cobalt oxide, or manganese oxide.

Comparative Study of Different Ion-Exchange Membrane Types in Diffusion Dialysis for the Separation of Sulfuric Acid and Nickel Sulfate

The possibility of using various types of ion-exchange membranes in diffusion dialysis for the separation of sulfuric acid and nickel sulfate has been evaluated. The process of the dialysis separation of a real waste solution from an electroplating facility containing 252.3 g/L of sulfuric acid, 20.9 g/L of nickel ions and small amounts of zinc, iron, copper ions, etc. has been studied. Heterogeneous cation-exchange membrane containing sulfonic groups and heterogeneous anion-exchange membranes with different thicknesses (from 145 μm to 550 μm) and types of fixed groups (four samples with quaternary ammonium base and one sample with secondary and tertiary amines) have been used. The diffusion fluxes of sulfuric acid, nickel sulfate, and the total and osmotic fluxes of the solvent have been determined. The use of a cation-exchange membrane does not allow the separation of the components, since the fluxes of both components are low and comparable in magnitude. The use of anion-exchange membranes makes it possible to efficiently separate sulfuric acid and nickel sulfate. Anion-exchange membranes with quaternary ammonium groups are more effective in the diffusion dialysis process, while the thin membrane turns out to be the most effective.

Rigorous Evaluation of Liquid Products in High-Rate CO2/CO Electrolysis

In this work, the water crossover in CO2 electrolysis was systematically analyzed with hydrated ions transferring through ion-selective membranes as charge carriers in three-compartment devices. We demonstrate that the water crossover leads to a variation in the electrolyte volume, which plays an important role in the evaluation of the catalytic selectivity of liquid products. Without considering the water crossover, the catalytic selectivity of liquid products could be overestimated with the use of anion exchange membranes and underestimated with cation exchange membranes, especially when ions with large hydration numbers transport through membranes for long-term electrolysis. In addition, a protocol for reliably quantifying liquid products is proposed for high-rate CO2/CO electrolysis in three-compartment flow electrolyzers.

Seawater battery desalination with a reverse osmosis membrane for simultaneous brine treatment and energy storage

As it is typically disposed of to the ocean, naturally produced brine water has been an avoidable issue in seawater desalination technology, particularly in the reverse osmosis (RO) process. To address this issue, a seawater battery-desalination (SWB-D) system was used to reduce the concentration of RO brine while also storing electrical energy by harvesting sodium ions from the brine. The SWB equipped with an anion exchange membrane (AEM) can lower the RO brine concentration to seawater levels, but the use of AEM for brine treatment is costly and the slow kinetics of salt transport require long operation times. In this study, we present a proof of concept for using RO membrane as an alternative to AEM in the SWB desalination system. Owing to its low cost and unexpected support for salt removal via diffusion across the RO membrane, using RO membrane is a viable application. The effect of diffusion enables SWB-D with RO membrane to reduce the charging time by 36.8% (up to ∼40.5% salt removal) compared with SWB-D with AEM. In addition, ∼52.5 kWh m−3 of energy (assuming 80% energy recovery) was saved while lowering the concentration of brine to seawater levels (from 1.2 to ∼0.6 M).

Designing anion exchange membranes for CO2 electrolysers

New technologies are required to electrocatalytically convert carbon dioxide (CO2) into fuels and chemicals at near-ambient temperatures and pressures more effectively. One particular challenge is mediating the electrochemical CO2 reduction reaction (CO2RR) at low cell voltages while maintaining high conversion efficiencies. Anion exchange membranes (AEMs) in zero-gap reactors offer promise in this direction; however, there remain substantial obstacles to be overcome in tailoring the membranes and other cell components to the requirements of CO2RR systems. Here we review recent advances, and remaining challenges, in AEM materials and devices for CO2RR. We discuss the principles underpinning AEM operation and the properties desired for CO2RR, in addition to reviewing state-of-the-art AEMs in CO2 electrolysers. We close with future design strategies to minimize product crossover, improve mechanical and chemical stability, and overcome the energy losses associated with the use of AEMs for CO2RR systems. Carbon dioxide electroreduction is a promising approach to synthesize chemicals and fuels using renewable energy. This Review explores our understanding of anion exchange membranes — a key component of certain carbon dioxide electrolysers — and outlines approaches to design improved materials.

Production of a water disinfectant by membrane electrolysis of brine solution and evaluation of its quality change during the storage time

Anolyte solution produced by membrane electrolysis of NaCl solution contains a high level of available chlorine content (ACC) and other oxidizing compounds, rendering this solution a strong disinfectant property. In this paper, some process parameters affecting the anolyte production efficiency, such as total inlet flow (240–320 L/h), saline solution concentration (1.65–3.50 g/L), and the type of membrane (cation exchange, anion exchange, and bipolar membranes) were investigated in an electrolysis cell. Changes in the quality of anolytes produced at three initial concentrations of very high (ACC1 = 816.5 mg/L), relatively high (ACC2 = 461.5 mg/L), and medium (ACC3 = 355.0 mg/L) during storage (from the production up to 20 weeks) were examined by adjusting the total inlet flow, saline concentrations, and membrane types. Changes in the ACC of the produced anolyte solution were generally affected by the type of membrane used in the electrolysis cell. The use of anion exchange membrane resulted in the lowest durability of anolyte quality (60–80% ACC reduction after 4 weeks of storage) and the cation exchange membrane had the highest durability (less than 40% decrease after 4 weeks of storage). In addition, changes in the pH and the oxidation–reduction potential of the anolyte were investigated during the storage period, which had a different trend depending on the type of applied membrane.

Alkaline Stability of Pure Aliphatic-based Anion Exchange Membranes Containing Cycloaliphatic Quaternary Ammonium Cations

The alkaline stability of functional cations tethered to anion exchange membranes (AEMs) is essential for long-term operation in electrochemical devices. Here, we report the use of AEMs with pure aliphatic polymer backbones containing N-spirocyclic quaternary ammonium cation groups as highly conductive, crosslinked, and reinforced separators. Synthesizing these pure aliphatic-based AEMs via irradiation with ultraviolet (UV) light at room temperature avoids the use of carcinogenic solvents and the solution casting step generally used in AEM preparation. The resultant aliphatic-based AEMs have a chloride ion conductivity of 82 mS cm−1 at 70 °C with an ion exchange capacity (IEC) of 3.0 ± 0.2 mmol g−1. The aliphatic-based AEM retains 40% of its initial IEC after immersion in 1 M KOH at 80 °C for 30 d. A direct nucleophilic substitution degradation mechanism is proposed for such AEMs, based on FT-IR, solid state 13C-NMR spectroscopy, and XPS.

Reductive/Oxidative Sequential Bioelectrochemical Process for Perchloroethylene Removal

An innovative bioelectrochemical reductive/oxidative sequential process was developed and tested on a laboratory scale to obtain the complete mineralization of perchloroethylene (PCE) in a synthetic medium. The sequential bioelectrochemical process consisted of two separate tubular bioelectrochemical reactors that adopted a novel reactor configuration, avoiding the use of an ion exchange membrane to separate the anodic and cathodic chamber and reducing the cost of the reactor. In the reductive reactor, a dechlorinating mixed inoculum received reducing power to perform the reductive dechlorination of perchloroethylene (PCE) through a cathode chamber, while the less chlorinated daughter products were removed in the oxidative reactor, which supported an aerobic dechlorinating culture through in situ electrochemical oxygen evolution. Preliminary fluid dynamics and electrochemical tests were performed to characterize both the reductive and oxidative reactors, which were electrically independent of each other, with each having its own counterelectrode. The first continuous-flow potentiostatic run with the reductive reactor (polarized at −450 mV vs SHE) resulted in obtaining 100% ± 1% removal efficiency of the influent PCE, while the oxidative reactor (polarized at +1.4 V vs SHE) oxidized the vinyl chloride and ethylene from the reductive reactor, with removal efficiencies of 100% ± 2% and 92% ± 1%, respectively.

Functionalization of polybenzimidazole-crosslinked poly(vinylbenzyl chloride) with two cyclic quaternary ammonium cations for anion exchange membranes

The anion exchange membranes (AEMs) with both high ionic conductivity and good stability is always the research focus role for the long-term use of AEM fuel cells. A series of the mechanically and chemically stable PVBC/PBI crosslinked membranes, functionalized with N1-butyl substituted BDABCO groups, were designed, prepared and characterized. With the crosslinking by polybenzimidazole (PBI), the membranes showed good flexibility, strength and low swelling ratio (less than 18%). N1-butyl substituted doubly-charged BDABCO was introduced in the AEMs during the crosslinking reaction instead of the traditional dipping method, benefiting from the improvement compatibility between polymers and BDABCO groups. Attributing to the well-developed phase separation between hydrophilic domains and hydrophobic domains, the family of synthesized AEMs exhibited the higher conductivities than that of DABCO based membranes, which was proved by TEM and SAXS. The M-BDABCO-OH-1:3 with high BDABCO content displayed the highest ionic conductivity of 29.3 and 91.4mScm−1 at 20 and 80°C, respectively. The results of alkaline stability showed that the membranes had the superior chemical stability after immersing in a 1molL−1 KOH at 60°C solution for more than 550h. Furthermore, the peak power density of an H2/O2 single fuel cell using the optimized M-BDABCO-OH-1:3 was up to 340mWcm−2 at 0.492V with the EIS consisting of membrane resistance less than 0.1Ωcm2 which was much smaller than the other AEMs. Overall, the developed membranes demonstrated the superior performance and would be a promising candidate material for AEMFCs.

Performance and Durability Baselines in Alkaline Hydrogen and Oxygen Evolution Reactions

In the United States, 2% of energy uses hydrogen as an intermediate, to produce ammonia in agriculture and upgrade oil in transportation. [1, 2] While the majority hydrogen is produced by steam methane reformation, electrolysis can become cost-competitive through the use of renewable power sources. Further reductions in the cost of renewables may increase hydrogen use as an energy intermediate between the electric grid and transportation and industrial processes. [3] Since the cost of electrolysis-produced hydrogen is dominated by electricity cost, electrolyzers typically operate with high catalyst loadings to avoid durability losses. With a shifting focus toward hydrogen production cost, however, catalyst thrifting and durability become critical. [2, 4] The use of anion exchange membrane (AEM) electrolyzers are an attractive option, with potential durability benefits and an ability to use non-platinum group metal (non-PGM) catalysts in place of platinum and iridium. This study presents baseline performance in rotating disk electrode half-cell tests, in the hydrogen evolution and oxygen evolution reactions for alkaline electrolytes. PGM and non-PGM catalysts are evaluated, included polished metal electrodes and commercial nanoparticle catalysts, differentiating between surface area and specific activity as the source of mass activity. This work develops testing protocols, and examines the effect of the electrolyte manufacturer, the electrochemical cell, the counter electrode, and contaminants on performance and durability. Baselined catalysts were also evaluated for durability in alkaline hydrogen and oxygen evolution. While minimal hydroxide evolution losses are expected, durability in the oxygen evolution reaction is critical, to demonstrate a potential benefit to proton exchange membrane-based electrolyzers and to ensure non-PGM stability at elevated anode potentials. The modes of loss under specific testing protocols are presented and evaluated, and compared to performance and durability in single-cell electrolyzers. These types of studies are critical for establishing baseline catalyst performance within the electrocatalysis community. Figure caption. Summary of mass (red) and specific (blue) exchange current densities in the alkaline hydrogen evolution reaction, with platinum (Pt), Pt-ruthenium (Pt-Ru), palladium (Pd), and nickel (Ni) catalysts evaluated. Dashed blue lines corresponding to the specific activities of metal electrodes (Pt, Pd, Ni lines above respective commercial nanoparticles).

Thermochemical Stability Study of Alkyl-Tethered Quaternary Ammonium Cations for Anion Exchange Membrane Fuel Cells

The increased interest in the use of anion exchange membranes (AEMs) for applications in electrochemical devices has prompted significant efforts in designing materials with robust stability in alkaline media. Most reported AEMs suffer from polymer backbone degradation as well as cation functional group degradation. In this report, we provide comprehensive experimental investigations for the analysis of cation functional group stability under alkaline media. A silver oxide-mediated ion exchange method and an accelerated stability test in aqueous KOH solutions at elevated temperatures using a Parr reactor were used to evaluate a broad scope of quaternary ammonium (QA) cationic model compound structures, particularly focusing on alkyl-tethered cations. Additionally, byproduct analysis was employed to gain better understanding of degradation pathways and trends of alkaline stability. Experimental results under different conditions gave consistent trends in the order of cation stability of various QA small molecule model compounds. Overall, cations that are benzyl-substituted or that are near to electronegative atoms (such as oxygen) degrade faster in alkaline media in comparison to alkyl-tethered QAs. These comprehensive model compound stability studies provide valuable information regarding the relative stability of various cation structures and can help guide researchers towards designing new and promising candidates for AEM materials.

The effect of restriction membranes on mass transfer in an electrodialysis with filtration membrane process

In an electrodialysis with filtration membrane (EDFM) separation process, a pair of restriction membranes is used to prevent leakage of molecules into the electrode solution. Driven by the electrical potential gradient, ions transport across these membranes in different directions, resulting in concentration changes in the feed and permeate compartments respectively. However, the effects of these restriction membranes have not been systemically studied to date. In the present work, the performance of a non-charged polyacrylamide (PAm) membrane and two ion-exchange membranes were compared. PAm restriction membranes were found to give the most stable operation, with only slight concentration and pH changes in the feed and permeate compartments. The configurations with either cation or anion exchange membranes showed more significant changes in electrolyte concentration in opposing directions but the same pH trend, as the current density increased. The configuration with cation exchange membranes as restriction membranes resulted in the highest protein recovery, while the use of anion exchange membranes would appear as the best choice for separation of a protein with net positive charge. The results of this work provide important insights for the design and operation of EDFM processes and a better understanding of the transport phenomena that occur during the separation of bioactive compounds.

Highly stable pyridinium-functionalized cross-linked anion exchange membranes for all vanadium redox flow batteries

Abstract It has recently been demonstrated that the use of anion exchange membranes (AEMs) in vanadium redox flow batteries (VRFBs) can reduce the migration of vanadium ions through the membrane due to the Donnan exclusion effect among the positively charged functional groups and vanadium ions. However, AEMs are plagued by low chemical stability in harsh chemical environments. Here we propose and fabricate a pyridinium-functionalized cross-linked AEM for VRFBs. The pyridinium-functionalized bromomethylated poly (2,6-dimethyl-1,4-phenylene oxide) exhibits a superior chemical stability as a result of the strengthened internal cross-linking networks and the chemical inertness of the polymer backbone. Therefore, the membrane exhibits littler decay in a harsh environment for 20 days during the course of an ex situ immersion test. A cycling test also demonstrates that the VRFB assembled with the membrane enable to retain 80% of the initial discharge capacity over 537 cycles with a capacity decay rate of 0.037% cycle−1. Meanwhile, the membrane also shows a low vanadium permeability and a reasonably high conductivity in supporting electrolytes. Hence, all the measurements and performance tests reported in this work suggest that the membrane is a promising AEM for redox flow batteries to achieve excellent cycling stability and superior cell performance.

NMR As a Tool for the Study and Rational Design of Aems

The use of anion exchange membranes (AEMs) as separators in alkaline polymer electrolyte fuel cells (AFCs) has received considerable interest over the past decade. AFCs offer several advantages over more traditional PEM fuel cells, in particular operating at high pH enables the use of non-precious metal catalysts, drastically reducing the cost of the cells. However, widespread adoption of AEMs has been hampered due to poor stability, in part due to base-induced decomposition of the polymer backbone and cation group as well as conversion to carbonate form, all of which contribute to reduction of ion exchange capacity (IEC), conductivity, and mechanical strength. Furthermore, there is an insufficient understanding on how the polymer nanostructure and microstructure affects stability, transport, and cell performance. Nuclear magnetic resonance (NMR) spectroscopy is well suited to investigate these issues. We will demonstrate how 1D and 2D NMR spectroscopy may be utilized to characterize the degradation of AEMs using both model cations and ex situ membranes. Measurements of relaxation, e.g. T1, for a series of AEMs will be correlated with ionic conductivity. We also have used pulsed-field gradient NMR experiments to measure water self-diffusion to assist in deconvoluting how tortuosity, connectivity, and the mobility of water in hydrophobic and hydrophilic domains are governed by the nature of the cation and polymer backbone. The ultimate goal of this work is to develop a structure-activity relationship to assist in the design of novel materials with desirable properties.

(Invited) The Use of Broadband Electric Spectroscopy to Probe the Relaxations and Polarizations in Phase Seperated Polymer Electrolytes

There has been a recent surge in interest in the use of anion exchange membranes (AEMs) as the separator in many electrochemical conversion devices such as fuel cells, electrolyzers, redox flow cells, and for uses in electrochemical water purification processes. This is because electrocatalysis is generally more facile in alkaline conditions, and so these devices could potentially operate with non-precious metal catalysts and with catalysts capable of oxidizing or generating fuels beyond hydrogen. An AEM with high anionic conductivity would overcome many of the disadvantages of proton exchange membrane devices that need precious metal catalyst and work best with hydrogen. Improved AEMs are also required for water purification applications. Realization of AEM devices, therefore, would revolutionize electrochemical energy conversion, as inexpensive versatile devices could be made available. While much attention has been focused on generating new AEMs with stable cations and backbones, very little attention has been paid to the design of AEMs to maximize ionic conductivity and water transport. The work presented here represents the first detailed study of the thermomechanical, polarization, and dielectric phenomena related to morphology in a series of AEMs. In detail in this presentation, the micro-structure is studied by Small Angle X-ray Scattering (SAXS), the thermal stability and transitions are detected by High-Resolution Thermogravimetry (HR-TG) and by Modulated Differential Scanning Calorimetry (MDSC), respectively. The mechanical properties and transitions are investigated by Dynamic Mechanical Analysis (DMA). Broadband Electrical Spectroscopy (BES) is used to study the electric response and the conductivity mechanisms of the membranes in the frequency and temperature range of 0. 01—107 Hz and -105 — 100 °C, respectively. BES is a powerful technique, which allows us to fully understand the overall electric response and dielectric relaxations of the membranes, both in a completely dry state and after full hydration, thus allowing clarification of the role played by both ion solvation phenomena and water cluster structure on performance of these materials. The integration of the information acquired by the above techniques allows us to propose a reasonable mechanism for the long-range charge migration processes in polyvinylbenzyltrimethylamne bromide-block-polymethylbutylene [PVBTMA][Br]-b-PMB, it hydoxide analogue and the random polymers of the same chemistry crosslinked by UV and thermal methods. We have also extended this study to polyphenylene-b-[PVBTMA][OH] and the pentablock quaternary ammonium functioalized analogue of the sulfonated polymer, Nexar. In amny of these polymers we observe an order-disorder transition, Tδ, where dispersed cations aglomorate due to the interactions of their dipoles. As Tδ often occurs above 0°C this phenomenom is of nterset to the development of practical devices. This study has important consequences for the design of next generation revolutionary AEMs.

New Polymer Structures for Anion Exchange Membranes

There has been a strong and growing interest in the use of anion exchange membranes for electrochemical technologies. A key part of the research in this burgeoning sub-field is the search for polymeric anion exchange membranes that are stable, highly conductive, and scalable to quantities that are useful for cell engineering. Our group has been one of the pioneers in the design and scale-up of a number of different anion exchange membrane platforms based on commercially-relevant polymeric substrates. We have devised scalable post-polymerization modification chemistry to covert inexpensive polymers to performance-competitive anion exchange membranes and have used this platform to increase conductivity, improve mechanical properties and decrease water uptake. This range of new anion exchange membrane structures is currently being evaluated in cell testing for various devices and being evaluated for further scale-up activities.

Cross-Linked Anion Exchange Membranes for AEMFC

Anion-exchange membranes (AEMs) have attracted great interest for their operation in alkaline platinum-free fuel cells .However the use of AEMs in a wide range of devices has been limited due to various challenges. Two major obstacles are the membranes' low conductivity and poor stability in the highly alkaline environment required for fuel cells that necessitates generation of hydroxide anions and transport through the solid polymer membrane.The effect of cross-linker and its apparent impact on AEM properties will be the focus of this study. Two different cross-linkers were chosen, one has an amino-ether group and the other, has a trymethylhexadecyl amine group. These two crosslinkers have a fundamental difference, where the amino-ether is more hydrophilic and therefore would improve membrane's conductivity and may prevent membrane’s drying out. The properties and stability of the membrane with these two cross-linkers were investigated. Conductivity and swelling measurments were examined at various temperatures for both types of samples. Indeed, water uptake and conductivity were found to be higher for the amino-ether crosslinker. However, degradation measurements analyzed by FTIR and XPS, indicated that the membrane cross-linked by amino-ether group degraded faster at high temperature and pH conditions. Thus, the ether linkage in the cross-linker has a negative influence on the thermal and alkaline stability of the membrane.

Anion-exchange membranes in electrochemical energy systems

A detailed perspective on the use of anion-exchange membranes in fuel cells, electrolysers, flow batteries, reverse electrodialysis, and bioelectrochemical systems.