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.

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.

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.

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.

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.

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.

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.

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).

Application of monodispersive anion exchangers in sorption and separation of Y^3＋ from Nd^3＋ and Sm^3＋ complexes with dcta

Rare earth complexes with trans-1,2-diaminocyclohexane-N,N,N ,N -tetraacetic acid （DCTA） of the Ln（dcta） type exhibited an unusual sequence of affinity on the polystyrene anion exchangers： pm^3＋〉Nd^3＋〉Sm^3＋〉Pr^3＋〉Ce^3＋〉Eu^3＋〉Gd^3＋〉La^3＋〉Sc^3＋〉Tb^3＋〉Dy^3＋〉 Ho^3＋〉Y^3＋〉Er^3＋〉Tm^3＋〉Yb3＋〉Lu^3＋[1]. Taking into account the position of Y^3＋, Sm^3＋, and Nd^3＋ in this affinity series, for the monodispersive polystyrene anion exchangers, Lewatit MonoPlus M 500, Lewatit MonoPlus M 600, Lewatit MonoPlus MP 500, Lewatit MonoPlus MP 64, and for the heterodispersive anion exchanger, Lewatit MP 62, the weight （Dg） and bed （Dv） distribution coefficients of these complexes and working ion exchange capacities （Cw） were determined. Based on these values, purifications of Y^3＋ from Nd^3＋ and Y^3＋ from Sm^3＋ in the macro-micro component system on these anion exchangers were studied. The application potential of this method was highlighted for the separation of Y^3＋ in the presence of Nd^3＋ and Sm^3＋. With 1 L of monodispersive and strongly basic polystyrene gel anion exchanger Lewatit MonoPlus M 500 in the acetate form, it is possible to obtain approximately 79 g Y2O3 purified from Nd2O3 and 70 g Y2O3 purified from Sm2O3 in the same process condition.

THERMODYNAMIC STUDY ON ADSORPTION OF AROMATIC SULFONIC ACIDS ONTO MACROPOROUS WEAK BASE ANION EXCHANGER FROM AQUEOUS SOLUTIONS

The adsorption equilibrium isotherms of three aromatic sulfonic acid compounds, 2-naphthalenesulfonic acid, p-toluenesulfonic acid and p-chlorobenzenesulfonic acid, from aqueous solutions by macroporous weak base anion exchanger within the temperature range of 293 K-313 K were obtained. Several isotherm equations were correlated with the equilibrium data, and the experimental data was found to fit the three-parameter Redlich-Peterson equation best within the entire range of concentrations. The study showed that the hydrophobicity of solute has distinct influence on adsorption capacity of the anion exchanger for the aromatic sulfonic acid. Moreover, estimations of the isosteric enthalpy, free energy, and entropy change of adsorption were also reported. The positive isosteric enthalpy and entropy change for adsorption indicate an endothermic and entropy driven process in the present study.

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 on the Use of the Weakly Basic Polyacrylate Anion-Exchanger Amberlite IRA-68 for Sorption and Separation of Iminodiacetate Complexes of Rare Earth Elements

Based on the determined affinity series of rare earth element complexes with IMDA for the anion-exchangers, purification of macroquantities of Nd 3+ from Y 3+, Sm 3+ from Ho 3+, La 3+ from Nd 3+ and La 3+ from Pr 3+ on the weakly basic gel anion-exchanger Amberlite IRA-68 was studied. Using the presented method on 1 L of Amberlite IRA-68 in the acetate form, it is possible to obtain about 240 g Nd 2O 3 purified from Y 2O 3. Great difference in affinity of La 3+ and Nd 3+ as well as Pr 3+ complexes for this anion-exchanger in the acetate form indicates the possibility of applying this process for purification of lanthanum on the increased scale. On 1 L of Amberilte IRA-68 in the acetate form it is possible to obtain about 1125 g La 2O 3 purified from Nd 2O 3. On the basis of these results it can be assumed that unique properties of polyacrylate anion-exchangers enable their application for separation of rare earth elements.

Preparation of a new anion exchanger by pre-irradiation grafting technique and its adsorptive removal of rhenium(Ⅶ) as analogue to ^(99)Tc

A new anion exchanger with pyridine groups was prepared by grafting of 2-vinyl pyridine onto polypropylene(PP) nonwoven fabrics by pre-irradiation grafting technique, followed by quaternization of pyridine rings in grafted chains in reaction with bromoethane. The results showed that the grafting yield increased with the monomer concentration and conversion ratio of quaternization increased with the time. The grafted and quaternized fabrics were characterized by FT-IR, DSC, SEM and ICP. The possibility of adsorption of perrhenate(ReO–4), a nonradioactive analogue to pertechnetate(99TcO–4), from aqueous solution by anion exchanger was investigated. The experiments performed at pH= 0.1–6 showed that p H = 2.2 was the optimal acidity for ReO–4adsorption, and an adsorption equilibrium was achieved in 30 min. The reaction enthalpy was-12.55 k J/mol,indicating that the adsorption process is exothermic. XPS tests indicated that the Re O–4uptake was a typical ion exchange between Cl–on anion exchanger and ReO–4.

Expression and Purification of Hydrophilic Domains of Bovine Anion Exchanger,Member 1 and Electrogenic Sodium Bicarbonate Cotransporter 1

[ Objective] To express and purify the intracellular hydrophilic domains of bovine membrane carrier proteins：anion exchanger, member 1 （AE1） and electregenic sodium bicarbonate cotransporter 1 （NBCel）, which were associated with bicarbonate ion transport. [ Method] The hydrophilic domains of bovine AE1 and NBCel were amplified by PCR and inserted into the prokaryotic expression vector pET-28a, respectively. The recombinant plasmids were transformed into the expression strain E. coli BL21 （DE3） and then induced by IPTG. The expressed proteins were purified by nickel ion affinity chromatography and analyzed by 15% SDS-PAGE. [Result] The hydrophilic domains of bovine AE1 and NBCel were amplified respectively by PCR and expressed by prokaryotic expression system with the induction of IPTG. They were mainly expressed in the cyto- plasm of E. coli and high-purity was achieved by nickel ion affinity chromatography. [Condusion] The expression of the hydrophilic domains of bovine AE1 and NBCel provides a major exit route for preparation of antibodies and the regulatory mechanisms of carrier proteins.

Uptake of Multi-Disperse Starch by Anion Exchangers

Demineralisation plants of power stations are not able to remove organics in all cases to a satisfied degree. The present work focuses on natural organic matter （NOM） and its interaction with anion exchanger and adsorber resins to optimize organics uptake. In this study, four different starches （one of them 14C-labelled） with different molecular size distributions were selected as model substances for the biopolymer fraction of NOM. Their uptake by various anion exchangers and adsorbers was measured in column experiments. Results are discussed in terms of size exclusion, anion exchange, adsorption, and hydrophilic/hydrophobic repulsion. In summary, at neutral pH, starch has been removed preferably by size-exclusion followed by adsorption, whereas anion exchange resins show higher uptake capacities than ＂pure＂ adsorber resins caused by stronger attraction between starch and polar functional groups of the anion exchangers. At acidic pH, the uptake of sulphate, as competitive adsorptive, leads to an earlier starch breakthrough at anion exchangers. Therefore, adsorbers are more effective. It was found that the higher the water content of the resins, the more effective the uptake is.

Study on Separation of Lanthanum from Praseodymium Complexes with IMDA by Gel and Macroporous Anion Exchangers

During our studies on separation of rare earth complexes with aminopolycarboxylic acids on anion-exchangers, it is found that the affinity series of these elements with IMDA (Ln 3+ ∶IMDA=1∶2) for the anion-exchanger Dowex 1 in the acetate and IMDA forms is non-typical: Dy 3+ > Ho 3+ > Gd 3+ >Eu 3+ >Er 3+ >Y 3+ >Sm 3+ >Tm 3+ >Nd 3+ >Pr 3+ >>La 3+ . In the affinity series La 3+ is characterised as the lowest affinity in comparison with other rare earth elements, which indicates possibility of purification of La 3+ from all remaining lanthanides as well as Pr 3+ in the macro-micro systems by the frontal analysis technique. In the investigations strongly basic gel anion-exchangers Dowex 1×8 (type 1) and Dowex 2×8 (type 2) and strongly basic and weakly basic macroporous anion-exchangers Dowex MSA-1 and Dowex MWA 1 were used. Macroporous ion-exchangers have a sponge-like matrix which contains pores larger than molecules in size and the exchange of large ions is faster. The studies indicate that both the gel and macroporous anion-exchangers are useful for purification of La 3+ from Pr 3+ complexes with iminodiacetic acid.

SORPTION OF PHENOL AND P-NITROPHENOL ONTO A WEAKLY ANION EXCHANGER: XPS ANALYSIS AND MECHANISM

X-ray photoelectron spectroscopy(XPS)was adopted to elucidate sorption mechanism of phenol and p-nitrophenol onto a weakly anion exchanger D301.The distribution of specific forms of tertiary amino group on D301 was obtained and effect of free tertiary amino group on phenol sorption onto D301 was discussed. The result indicated that the percent of the protonated tertiary amine group on polymeric matrix was much lower than the reference compound N,N-dimethylbenzylamine at an identical pH value in solution due to the much lower activity degree of hydrogen ion in inner resin phase than in the external solution. Less free amino group on D301 results in less sorption capacity of phenol and p-nitrophenol in an acidic solution. Under the experimental conditions both phenol sorption onto D301 can be explained as solid extraction and the distribution coefficient varies linearly with the content of free amino group on D301.

STUDIES ON THE POLYMERIZATION OF ACRYLONITRILE INITIATED BY METAVANADATE-CONTAININ G ANION EXCHANGER-THIOUREA REDOX SYSTEM

The polymerization of acrylonitrile (AN) in aqueous nitric acid initiated by metavanadate-containing anion exchange resin (PV)-thiourea (TU) redox system at 20—40℃. has been investigated. The overall rate of polymerization (R_p) is given byR_p=1.92×10~4e^(-6.860/RT) [AN]^(1.2) [PV]^(0.44) [TU]^(1.0)[HNO_3]^(1.0)The kinetic parameters differed from those of V^(5+)-TU system indicated that the generation of the primary radicals is mainly a difffusion-controlled reaction. The effect of macromolecular field arisen from the polymer matrix exerts a great influence on the polymerization process.