Development of advanced anion exchange membrane from the view of the performance of water electrolysis cell

Green hydrogen produced by water electrolysis combined with renewable energy is a promising alternative to fossil fuels due to its high energy density with zero-carbon emissions.Among water electrolysis technologies,the anion exchange membrane(AEM) water electrolysis has gained intensive attention and is considered as the next-generation emerging technology due to its potential advantages,such as the use of low-cost non-noble metal catalysts,the relatively mature stack assembly process,etc.However,the AEM water electrolyzer is still in the early development stage of the kW-level stack,which is mainly attributed to severe performance decay caused by the core component,i.e.,AEM.Here,the review comprehensively presents the recent progress of advanced AEM from the view of the performance of water electrolysis cells.Herein,fundamental principles and critical components of AEM water electrolyzers are introduced,and work conditions of AEM water electrolyzers and AEM performance improvement strategies are discussed.The challenges and perspectives are also analyzed.

Towards high-performance and robust anion exchange membranes(AEMs)for water electrolysis:Super-acid-catalyzed synthesis of AEMs

The increasing demand for hydrogen energy to address environmental issues and achieve carbon neutrality has elevated interest in green hydrogen production,which does not rely on fossil fuels.Among various hydrogen production technologies,anion exchange membrane water electrolyzer(AEMWE)has emerged as a next-generation technology known for its high hydrogen production efficiency and its ability to use non-metal catalysts.However,this technology faces significant challenges,particularly in terms of the membrane durability and low ionic conductivity.To address these challenges,research efforts have focused on developing membranes with a new backbone structure and anion exchange groups to enhance durability and ionic conductivity.Notably,the super-acid-catalyzed condensation(SACC)synthesis method stands out due to its user convenience,the ability to create high molecular weight(MW)polymers,and the use of oxygen-tolerant organic catalysts.Although the synthesis of anion exchange membranes(AEMs)using the SACC method began in 2015,and despite growing interest in this synthesis approach,there remains a scarcity of review papers focusing on AEMs synthesized using the SACC method.The review covers the basics of SACC synthesis,presents various polymers synthesized using this method,and summarizes the development of these polymers,particularly their building blocks including aryl,ketone,and anion exchange groups.We systematically describe the effects of changes in the molecular structure of each polymer component,conducted by various research groups,on the mechanical properties,conductivity,and operational stability of the membrane.This review will provide insights into the development of AEMs with superior performance and operational stability suitable for water electrolysis applications.

Electrochemical reconstruction of non-noble metal-based heterostructure nanorod arrays electrodes for highly stable anion exchange membrane seawater electrolysis

Direct seawater electrolysis for hydrogen production has been regarded as a viable route to utilize surplus renewable energy and address the climate crisis.However,the harsh electrochemical environment of seawater,particularly the presence of aggressive Cl^(-),has been proven to be prone to parasitic chloride ion oxidation and corrosion reactions,thus restricting seawater electrolyzer lifetime.Herein,hierarchical structure(Ni,Fe)O(OH)@NiCoS nanorod arrays(NAs)catalysts with heterointerfaces and localized oxygen vacancies were synthesized at nickel foam substrates via the combination of hydrothermal and annealing methods to boost seawater dissociation.The hiera rchical nanostructure of NiCoS NAs enhanced electrode charge transfer rate and active surface area to accelerate oxygen evolution reaction(OER)and generated sulfate gradient layers to repulsive aggressive Cl^(-).The fabricated heterostructure and vacancies of(Ni,Fe)O(OH)tuned catalyst electronic structure into an electrophilic state to enhance the binding affinity of hydroxyl intermediates and facilitate the structural transformation into amorphousγ-NiFeOOH for promoting OER.Furthermore,through operando electrochemistry techniques,we found that theγ-NiFeOOH possessing an unsaturated coordination environment and lattice-oxygen-participated OER mechanism can minimize electrode Cl^(-)corrosion enabled by stabilizing the adsorption of OH*intermediates,making it one of the best OER catalysts in the seawater medium reported to date.Consequently,these catalysts can deliver current densities of 100 and 500 mA cm-2for boosting OER at minimal overpotentials of 245and 316 mV,respectively,and thus prevent chloride ion oxidation simultaneously.Impressively,a highly stable anion exchange membrane(AEM)seawater electrolyzer based on the non-noble metal heterostructure electrodes reached a record low degradation rate under 100μV h-1at constant industrial current densities of 400 and 600 mA cm-2over 300 h,which exhibits a promising future for the nonprecious and stable AEMWE in the direct seawater electrolysis industry.

Electrochemical synthesis of trimetallic nickel-iron-copper nanoparticles via potential-cycling for high current density anion exchange membrane water-splitting applications

Hydrogen is known for its elevated energy density and environmental compatibility and is a promising alternative to fossil fuels.Alkaline water electrolysis utilizing renewable energy sources has emerged as a means to obtain high-purity hydrogen.Nevertheless,electrocatalysts used in the process are fabricated using conventional wet chemical synthesis methods,such as sol-gel,hydrothermal,or surfactantassisted approaches,which often necessitate intricate pretreatment procedures and are vulnerable to post-treatment contamination.Therefore,this study introduces a streamlined and environmentally conscious one-step potential-cycling approach to generate a highly efficient trimetallic nickel-iron-copper electrocatalyst in situ on nickel foam.The synthesized material exhibited remarkable performance,requiring a mere 476 mV to drive electrochemical water splitting at 100 mA cm^(-2)current density in alkaline solution.Furthermore,this material was integrated into an anion exchange membrane watersplitting device and achieved an exceptionally high current density of 1 A cm^(-2)at a low cell voltage of2.13 V,outperforming the noble-metal benchmark(2.51 V).Additionally,ex situ characterizations were employed to detect transformations in the active sites during the catalytic process,revealing the structural transformations and providing inspiration for further design of electrocatalysts.

Anion exchange membranes with a semi-interpenetrating polymer network using 1,6-dibromohexane as bifunctional crosslinker

An anion exchange membrane(AEM)is generally expected to possess high ion exchange capacity(IEC),low water uptake(WU),and high mechanical strength when applied to electrodialysis desalination.Among different types of AEMs,semi-interpenetrating polymer networks(SIPNs)have been suggested for their structural superiorities,i.e.,the tunable local density of ion exchange groups for IEC and the restrained leaching of hygroscopic groups by insolubility for WU.Unfortunately,the conventional SIPN AEMs still struggle to balances IEC,WU,and mechanical strength simultaneously,due to the lack of the compact crosslinking region.In this work,we proposed a novel SIPN structure of polyvinylidene difluoride/polyvinylimidazole/1,6-dibromohexane(PVDF/PVIm/DBH).On the one hand,DBH with two cationic groups of imidazole groups are introduced to enhance the ion conductivity,which is different from the conventional monofunctional modifier with only one cationic group.On the other hand,DBH has the ability to bridge with PVIm,where the mechanical strength of the resulting AEM is increased by the increase of crosslinking degree.Results show that a low WU of 38.1%to 62.6%,high IEC of 2.12—2.22 mmol·g^(-1),and excellent tensile strength of 3.54—12.35 MPa for PVDF/PVIm/DBH membrane are achieved.This work opens a new avenue for achieving the high-quality AEMs.

Durable poly(binaphthyl-co-p-terphenyl piperidinium)-based anion exchange membranes with dual side chains

Building well-developed ion-conductive highways is highly desirable for anion exchange membranes(AEMs).Grafting side chain is a highly effective approach for constructing a well-defined phaseseparated morphological structure and forming unblocked ion pathways in AEMs for fast ion transport.Fluorination of side chains can further enhance phase separation due to the superhydrophobic nature of fluorine groups.However,their electronic effect on the alkaline stability of side chains and membranes is rarely reported.Here,fluorine-containing and fluorine-free side chains are introduced into the polyaromatic backbone in proper configuration to investigate the impact of the fluorine terminal group on the stability of the side chains and membrane properties.The poly(binaphthyl-co-p-terphenyl piperidinium)AEM(QBNp TP)has the highest molecular weight and most dimensional stability due to its favorable backbone arrangement among ortho-and meta-terphenyl based AEMs.Importantly,by introducing both a fluorinated piperidinium side chain and a hexane chain into the p-terphenyl-based backbone,the prepared AEM(QBNp TP-QFC)presents an enhanced conductivity(150.6 m S cm^(-1))and a constrained swelling at 80℃.The electronic effect of fluorinated side chains is contemplated by experiments and simulations.The results demonstrate that the presence of strong electro-withdrawing fluorine groups weakens the electronic cloud of adjacent C atoms,increasing OH^(-)attack on the C atom and improving the stability of piperidinium cations.Hence QBNp TP-QFC possesses a robust alkaline stability at 80℃(95.3%conductivity retention after testing in 2 M Na OH for 2160 h).An excellent peak power density of 1.44 W cm^(-2)and a remarkable durability at 80℃(4.5%voltage loss after 100 h)can be observed.

Technical factors affecting the performance of anion exchange membrane water electrolyzer

Anion exchange membrane(AEM)electrolysis is a promising membrane-based green hydrogen production technology.However,AEM electrolysis still remains in its infancy,and the performance of AEM electrolyzers is far behind that of well-developed alkaline and proton exchange membrane electrolyzers.Therefore,breaking through the technical barriers of AEM electrolyzers is critical.On the basis of the analysis of the electrochemical performance tested in a single cell,electrochemical impedance spectroscopy,and the number of active sites,we evaluated the main technical factors that affect AEM electrolyzers.These factors included catalyst layer manufacturing(e.g.,catalyst,carbon black,and anionic ionomer)loadings,membrane electrode assembly,and testing conditions(e.g.,the KOH concentration in the electrolyte,electrolyte feeding mode,and operating temperature).The underlying mechanisms of the effects of these factors on AEM electrolyzer performance were also revealed.The irreversible voltage loss in the AEM electrolyzer was concluded to be mainly associated with the kinetics of the electrode reaction and the transport of electrons,ions,and gas-phase products involved in electrolysis.Based on the study results,the performance and stability of AEM electrolyzers were significantly improved.

Poly(Ionic Liquid) as an Anion Exchange Membrane for a 3.3 V Copper–Lithium Battery

Metal–metal battery bears great potential for next-generation large-scale energy storage system because of its simple manufacture process and low production cost.However,the cross-over of metal cations from the cathode to the anode causes a loss in capacity and influences battery stability.Herein,a coating of poly(ionic liquid)(PIL)with poly(diallyldimethylammonium bis(trifluoromethanesulfonyl)imide)(PDADMA^(+)TFSI^(−))on a commercial polypropylene(PP)separator serves as an anion exchange membrane for a 3.3 V copper–lithium battery.The PIL has a positively charged polymer backbone that can block the migration of copper ions,thus improving Coulombic efficiency,long-term cycling stability and inhibiting self-discharge of the battery.It can also facilitate the conduction of anions through the membrane and reduce polarization,especially for fast charging/discharging.Bruce-Vincent method gives the transport number in the electrolyte to be 0.25 and 0.04 for PP separator without and with PIL coating,respectively.This suggests that the PIL layer reduces the contribution of the internal current due to cation transport.The use of PIL as a coating layer for commercial PP separator is a cost-effective way to improve overall electrochemical performance of copper–lithium batteries.Compared to PP and polyacrylic acid(PAA)/PP separators,the PIL/PP membrane raises the Coulombic efficiency to 99%and decreases the average discharge voltage drop to about 0.09 V when the current density is increased from 0.1 to 1 mA cm^(−2).

Chemical Oxidation Effects on Anion Exchange and Nitrate Sorption Capacity of Biochar for Ruminal Methanogenesis Inhibition

The chemical composition of biochar is determined by the chemical profile of the material the by-product is made of and the pyrolysis conditions. Analysis of commercial biochar detected similarities to the chemical profile of hardwood, which was used as an object of pyrolysis for biochar production and showed the presence of bridge-forming cations, such as manganese, iron, and sodium. Despite frequently being reported in existing literature, the current study showed that the redox potential of biochar is not associated with biochar’s ability to recover certain anions. No association was detected between biochar’s redox potential and the material nitrate sorption capacity. In fact, higher redox potential values were associated with lower nitrate absorption. In the case of the anion exchange capacity of biochar, a direct association between this electrochemical property of the by-product and its redox potential was observed. However, redox potential’s impact on anion exchange capacity can be inhibited by the presence of organic compounds in biochar’s chemical profile. The chemical oxidation of biochar is a complex process and is a research priority for a potential role to mitigate enteric methanogenesis in livestock.

Investigation of Polyacrylate Anion-Exchangers for Separation of Rare Earth Element Complexes with EDTA

The rare earth complexes with EDTA, Ln(edta), show an unusual sequence of affinity for the anion exchangers. The sorption and chromatographic separation of Y 3+ for Nd 3+ complexes with EDTA was studied by using the strongly basic gel and macroporous polyacrylate anion exchangers, Amberlite IRA 458 and Amberlite 958, and the weakly basic gel polyacrylate anion exchanger, Amberlite IRA 68. The investigations on sorption and separation of rare earth complexes with EDTA on the polyacrylate anion exchangers applied mainly in the environment protection so far indicate that they can be applied in anionexchange separation of lanthanide complexes with aminopolycarboxylic acids. It was shown that the weakly basic polyacrylate gel anion exchanger Amberlite IRA 68 is the most effective in purification of Y 3+ from Nd 3+ in comparison with the strongly basic anion exchangers of this type.

Exchange Reaction Characteristics of Anion Exchange Resin for Diclofenac Sodium

Aim To study the exchange reaction characteristics of anion exchange resin for diclofenac sodium. Methods The drug-resin complexes were prepared by a batch method with diclofenac sodium as the model drug and the strong anion exchange resin (201 × 7) as the carrier. The effects of different forms (OH~ - and Cl~ - ) of the strong anion exchange resin, the particle size of the resin, and the reaction temperature on the exchange behavior were described. The exchange kinetic profiles were fitted. The related exc...

Thermodynamics of Cr(Ⅵ) adsorption on strong alkaline anion exchange fiber

Removal of Cr（VI） from aqueous solution by strong alkaline anion exchange fiber （SAAEF） was achieved using batch adsorption experiments. The effect of contact time, initial Cr（VI） concentration and pH was investigated. The results showed that the maximum adsorption capacity of SAAEF was 187.7 mg/g at pH=1.0. The adsorption capacity increased with Cr（VI） concentration but decreased with pH value when pH〉1.0. Adsorption isotherms at various temperatures were obtained. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models were adopted and the equilibrium data fitted best with the Langmuir isotherm. The constants of these models indicated that the adsorption process involved both chemisorption and physisorption. The values of thermodynamic parameters, including DH, DG and DS, suggested that the adsorption of Cr（VI） on SAAEF was a spontaneous, entropy-driven and endothermic process. Q（iso） was not a constant value, which indicated an inhomogenous energy distribution on SAAEF.

Cholangiocyte anion exchange and biliary bicarbonate excretion

Primary canalicular bile undergoes a process of fluidization and alkalinization along the biliary tract that is influenced by several factors including hormones, innervation/neuropeptides, and biliary constituents. The excretion of bicarbonate at both the canaliculi and the bile ducts is an important contributor to the generation of the so-called bile-salt independent flow. Bicarbonate is secreted from hepatocytes and cholangiocytes through parallel mechanisms which involve chloride efflux through activation of Cl- channels, and further bicarbonate secretion via AE2/SLC4A2-mediated Cl-/HCO3- exchange. Glucagon and secretin are two relevant hormones which seem to act very similarly in their target cells （hepatocytes for the former and cholangiocytes for the latter）. These hormones interact with their specific G protein-coupled receptors, causing increases in intracellular levels of cAMP and activation of cAMP-dependent Cl- and HCO3- secretory mechanisms. Both hepatocytes and cholangiocytes appear to have cAMP-responsive intracellular vesicles in which AE2/SLC4A2 colocalizes with cell specific Cl- channels （CFTR in cholangiocytes and not yet determined in hepatocytes） and aquaporins （AQP8 in hepatocytes and AQP1 in cholangiocytes）, cAMP-induced coordinated trafficking of these vesicles to either canalicular or cholangiocyte lumenal membranes and further exocytosis results in increased osmotic forces and passive movement of water with net bicarbonate-rich hydrocholeresis.

Using an Anion Exchange Membrane to Predict Soil Available N and S Supplies and the Impact of N and S Fertilization on Canola and Wheat Growth

A growth chamber study was conducted to determine the relationships between the supply of soil available nitrogen (N) and sulfur (S) and canola (Brassica napus) and wheat (Triticum aestivum L. 'Biggar') N and S uptake and yield in three Western Canadian soils. The suitability of one-hour burial with an anion exchange membrane (AEM) was assessed for its utility as a quick test of the available N:S balance in the soil. Canola and wheat were grown on a Luvisolic soil low in available S and on Brown and Black Chernozemic soils low in both available N and S, with different rates and combinations of N and S fertilizers applied. AEM burial was used to assess soil available nitrate and sulfate supply rates after fertilization. Dry matter yield and N and S concentrations in plant tissues were determined after 6 weeks of growth. The soil available N:S ratio determined by AEM burial closely reflected the relative supplies of available N and S as revealed in the N:S ratios of plant tissue dry matter. The highest yields were achieved where the available N:S ratio in soil and plant tissue ranged from 5 to 13. Thus, a one-hour burial of an AEM probe in the field may be a useful tool to quickly test if a balanced N and S supply is present in the soil for optimum crop yield.

Study of Sorption Properties of Anion Exchangers with Long-Chained Cross-Linking Agents for Tungsten Hydrometallurgy

The macroporous anion exchangers with long-chained cross-linking agents were investigated for the tungsten recovery from salt solutions.The physical-chemical characteristics of these sorbents were studied by means of sorption-desorption experiment aswell as electron and IR-spectroscopy.The anion exchangers on the basis of macroporous copolymers of methylacrylate and divinyl-ester of diethyleneglycol or tetravinyl-ester of pentaerythritol possess the exchange capacity to tungsten 2--5 times greater than the porous anion exchangers on the basis of styrene and divinylbenzene,therefore they can be used for selective tungsten recovery from comulex salt solutions.

Ternary layered double hydroxide oxygen evolution reaction electrocatalyst for anion exchange membrane alkaline seawater electrolysis

Anion exchange membrane(AEM)water electrolyzers are promising energy devices for the production of clean hydrogen from seawater.However,the lack of active and robust electrocatalysts for the oxygen evolution reaction(OER)severely impedes the development of this technology.In this study,a ternary layered double hydroxide(LDH)OER electrocatalyst(NiFeCo-LDH)is developed for high-performance AEM alkaline seawater electrolyzers.The AEM alkaline seawater electrolyzer catalyzed by the NiFeCo LDH shows high seawater electrolysis performance(0.84 A/cm^(2)at 1.7 Vcell)and high hydrogen production efficiency(77.6%at 0.5 A/cm^(2)),thus outperforming an electrolyzer catalyzed by a benchmark IrO_(2)electrocatalyst.The NiFeCo-LDH electrocatalyst greatly improves the kinetics of the AEM alkaline seawater electrolyzer,consequently reducing its activation loss and leading to high performance.Based on the results,this NiFeCo-LDH-catalyzed AEM alkaline seawater electrolyzer can likely surpass the energy conversion targets of the US Department of Energy.

Synthesis and Characterization of Two Binuclear Macrocyclic Zinc(Ⅱ) Complexes by Anion Exchange

Two macrocyclic zinc（Ⅱ） complexes {[ZnL（VO3）2]·0.33H2O}n（1） and [ZnL（H2O）2][Ni（CN）4]（2）（L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane） have been obtained from the reactions of [ZnL]（ClO4）2 with NH4VO3 and K2[Ni（CN）4], respectively, and structurally characterized by elemental analysis, IR, XRPD, TG and X-ray diffraction. Single-crystal X-ray diffraction analyses indicated that the Zn（Ⅱ） atom lies on an inversion center and is octahedrally coordinated by four nitrogen atoms of the tetradentate macrocyclic ligand in the equatorial plane and two oxygen atoms of [VO4] tetrahedra in the axial positions in 1, and two oxygen atoms of two water molecules in 2. Complex 1 shows a three-dimensional structure, which is constructed by the links of [VO3]nn- chains with [ZnL]2＋, forming one-dimensional channels occupied by guest water molecules. The monomers of [ZnL（H2O）2]2＋ and [Ni（CN）4]2- are connected through the intermolecular hydrogen bonds to form a two-dimensional sheet in complex 2.

Porous 2D Copper（Ⅰ） Complex of 1,3-Dicyanobenzene for Anion Exchange and Reversible Incorporation of Guest Molecules

The 2D porous copper（Ⅰ） complex with 1,3-dicyanobenzene （DCB）, [Cu（DCB）2]（PF6）（Me2CO） 1, exhibits channels along axis c, in which one molecule acetone and one anion PF6 per formula unit are included respectively. The reversible incorporation of guest acetone and acetonitrile, as well as the anion exchange from PF6^- to BF4^- or CF3SO3^-, was investigated by thermogravimetric （TG） analysis, ^1H NMR spectra and/or infrared absorption spectroscopy. Additionally, the incorporation of benzene and toluene into complex 1 was also discussed. Complex 1 exhibited size selectivity for guest inclusion or anion exchange.

One-Pot Synthesis of Chloromethylated Mesoporous Silica Nanoparticles as Multifunctional Fillers in Hybrid Anion Exchange Membranes

Chloromethylated mesoporous silica nanoparticles （CM MSN） were synthesized through co-condensation of tetraethoxysilane and （chloro） phenyltrimethoxysilane precursors using hexadecyl trimethyl ammonium bromide as template.With the addition of the particles into chloromethylated poly （ether ether ketone） （PEEK）,the hybrid membranes were prepared by a solution-casting method after complete quatemization of the casting solution.The successful synthesis of the particles was verified by transmission electron microscopy,X-ray diffraction and Fourier transform infrared spectroscopy while the effect of CM MSN incorporation on membrane performance including thermal stability,mechanical strength and hydroxide conductivity was investigated by thermal gravimetric analysis,electronic stretching machine,alternating-current impedance and so on.Owing to the large pore volume and high surface area of the particles,the hybrid membranes exhibited enhanced hydroxide conductivity （88.7% increase at 60 ℃,100% RH with 5.0 wt% filling content） due to an increase in ion concentration and optimization of the channel morphology.Besides,higher mechanical strength,thermal and dimensional stability of hybrid membranes were obtained compared with those of the imidazolium PEEK membrane.

Semi-interpenetrating network anion exchange membranes based on quaternized polyvinyl alcohol/poly(diallyldimethylammonium chloride)

The semi-interpenetrating network anion exchange membranes(AEMs)based on quaternized polyvinyl alcohol(QPVA)and poly(-diallyldimethylammonium chloride)(PDDA)are synthesized.The chemical cross-linking structure is formed between hydroxyl groups of QPVA and aldehyde groups of glutaraldehyde(GA),which makes PDDA more stable embed in the QPVA matrix and also improves the mechanical properties and dimensional stability of AEMs.Due to the phase separation phenomenon of AEMs swelling in water,a microporous structure may be formed in the membrane,which reduces the transmission resistance of hydroxide ions and provides a larger space for the transfer of hydroxide ions,thus improving the conductivity.The ring structure of PDDA is introduced as a cationic group to transfer hydroxide ions,and shields the nucleophilic attack of the hydroxide ions through the steric hindrance effect,which improves alkaline stability.The hydroxide conductivity of semi-interpenetrating network membrane(QPVA/PDDA0.5-GA)is 36.5 mS cm^(-1) at 60℃.And the membrane of QPVA/PDDA0.5-GA exhibits excellent mechanical property with maximum tensile strength of 19.6 MPa.After immersing into hot 3 mol L^(-1) NaOH solutions at 60℃ for 300 h,the OHconductivity remains 78%of its initial value.The semi-interpenetrating network AEMs with microporous structure exhibit good ionic conductivity,mechanical strength and alkaline durability.