Commercial Anion Exchange Membrane Research Articles

Advanced CFD simulation of two-phase anion exchange membrane water electrolysis

Anion exchange membrane (AEM) water electrolysis is a promising and inexpensive solution for hydrogen production and environmental problems. Owing to its low technical proficiency, AEM electrolysis necessitates high fidelity to improve its durability, reliability, and efficiency. Therefore, a CFD-based model for AEM electrolysis was developed to analyze the three-dimensional and two-phase phenomena inside the cell. The temperature, pressure, and gas generation profiles inside the cell were studied by combining electrochemical models with mass, momentum, and heat transfer models. Parameters were estimated using the experimental data from a high-accuracy model. The results showed that the applied voltage, which determined the exothermic/endothermic mode, significantly influenced the water electrolysis performance. Specifically, in the exothermic mode, with voltages exceeding the thermo-neutral voltage (1.48 V), the amount of hydrogen generated (15.53, 25.05, and 28.82 mol/m3 at 1.6, 1.8, and 2.0 V, respectively) was higher than that in the endothermic mode (4.78 mol/m3 at 1.45 V). However, the increased gas generation caused a rapid increase in the temperature and pressure drop inside the cell, which adversely affected durability. The model developed in this study can be used in experiments of various scales to optimize serpentine designs and commercial AEM electrolysis stack developments.

A Stable Polymer-Blended Anion-Exchange Membrane for Enhanced Performance in Redox Flow Batteries

Redox flow batteries (RFBs) operate with a membrane, responsible for the separation of cationic active species and allowing the passage of counter-ions, to preserve electroneutrality on each side of RFBs. Commercial cation-exchange membranes (CEMs), such as Nafion®, possess excellent ionic conductivity and chemical stability. However, they face challenges in blocking cationic active species common in RFBs, leading to significant capacity loss over time. Anion-exchange membranes (AEMs) efficiently block active species with the assistance of the Donnan effect. Nevertheless, commercial AEMs lack acid stability and conductivity compared to their cationic counterparts.Polytetrafluoroethylene (PTFE)-reinforced quaternary ammonium cardo poly(ether)ketone (QPEK-C)-based membranes with Al2O3 additives (PQPAM), a heterogeneous AEM developed in our lab1, possess excellent ionic conductivity with low permeability of active species and good mechanical properties. PQPAM has demonstrated better acid stability than commercial AEMs. However, its acidic and oxidative stability require improvement, as evidenced by degradation after 250 hours of in-situ harsh RFB cycling due to the heterogeneous nature of PQPAM and the exposure of the susceptible QPEK-C-rich side to the electrolytes2. To address this issue, we propose a strategy to enhance the chemical stability of QPEK-C-based membranes by inhibiting the exposure of QPEK-C to oxidation agents through blending with a hydrophobic engineering thermoplastic like polybenzimidazole (PBI)3,4. Furthermore, PBI's known ability to protonate in acidic media will reinforce ionic conductivity and the separation of active species, thus improving the Donnan effect, in addition to enhancing chemical and mechanical stability.Elemental analyses and microscopy images confirm a homogeneous blending of PBI and QPEK-C, promising stability improvement. The results of ex-situ tests on ionic conductivity, cation permeability, and chemical stability align with the mentioned hypotheses, showcasing that blend of PBI/QPEK-C outperforms pure PBI and QPEK-C AEMs. Additionally, the mechanical properties of the PBI/QPEK-C blended AEMs are improved compared to pure QPEK-C AEMs and PBI/QPEK-C blended AEMs outperform pure PBI and QPEK-C AEMs in in-situ cycling tests with our patented titanium-cerium RFBs5. Moreover, this work will explore other strategies to improve the blended AEM properties, such as utilizing inorganic fillers or PTFE reinforcement.

Development and characterization of a quaternized polymeric anion exchange membrane reinforced with Mg–Al–NO3− LDH for direct borohydride fuel cells

Recently, direct borohydride fuel cell (DBFC) has gained widespread attention as a new type of direct liquid fuel cell due to its high theoretical voltage, high energy density, and ability to utilize non-precious metals as catalysts. In this study, a series of anion exchange composite membrane (QFPTP-x%) consisting of quaternized Poly (para-terphenyl piperidinium) (QFPTP) and Mg–Al layered double hydroxide (LDH) has been developed. Due to the hydrophilicity and OH− conductivity features of Mg–Al–NO3− LDH, QFPTP-x% exhibits enhanced ion exchange capacity, water uptake, and OH− conductivity. The interaction between LDH and copolymer at the interface between the organic and inorganic leads to the formation of hydrogen and covalent bonds, improving the mechanical properties. More importantly, the borohydride permeability can be effectively reduced by adding LDH. The optimal amount of LDH has been determined to be 1 % (QFPTP-1%) by evaluating the properties of QFPTP-x%. The assembled DBFC incorporating QFPTP-1% exhibits a remarkable peak power density, achieving 1218 mW cm−2 @ 2.9 A cm−2, which is higher than the commercial anion exchange membrane PiperION® based DBFC (1079 mW cm−2 @ 2.5 A cm−2). Such an enhancement is attributed to the superior OH− conductivity and diminished borohydride permeability presented by the QFPTP-1% membrane. Additionally, the DBFC incorporating QFPTP-1% presents excellent stability with a minimal voltage loss of 34.1 % after 10 h of operation, highlighting the potential of the composite membrane for practical DBFC applications.

Utilization of commercial anion exchange membrane DF-120 for adsorptive removal of eosin-B from wastewater

This study investigates the batch adsorption of eosin-B (EB) from wastewater onto the commercial anion exchange membrane (AEM) DF-120 at a temperature of 25 °C. The detailed influence of various operational factors on the percentage removal of EB is outlined. The EB removal percentage from wastewater demonstrates an increase with the mass of AEM DF-120 and contact duration. At the same time, the percentage removal of it decreases with the rise in temperature and concentration. Results from the adsorption kinetics studies reveals that EB adsorption conforms to pseudo second order (PSO) model, having a correlation coefficient (R2) value of 0.999. The adsorption isotherm analysis indicates that EB adsorption aligns with the Langmuir isotherm as the value of R2 approaches unity. Furthermore, the measured mean adsorption energy (E = 0.68 KJmol−1) suggests that this is a physical adsorption process. Thermodynamic assessments of adsorption reveal its exothermic nature, supported by the value of enthalpy (ΔH° = −56.09 KJ mol−1). Additionally, Gibb’s free energy (ΔG°) value signifies that the process is feasible. The regeneration of the commercial AEM DF-120B was also revealed.

Electrodepositing polydopamine and iron (III) complexed polyacrylic acid for monovalent selective anion exchange membrane fabrication

Monovalent selective anion exchange membranes were efficiently prepared by two-steps electrodeposition. Firstly, a polydopamine (PDA) interlayer was formed onto the surface of a commercial anion exchange membrane (AEM), followed by the deposition of a top layer of Fe3+ complexed polyacrylic acid (Fe-PAA). The PDA interlayer formation was investigated by reversing the polarity of the electric field applied. In particular, modified membrane prepared with PDA layer facing the cathode (labeled as FC-PDA-M) exhibited lower negative charge surface density compared to the membrane prepared with DA solution close to the anode (labeled as FA-PDA-M). This effect resulted in an increased deposition of PAA, due to the diminished electrostatic repulsion, when a solution of Fe3+ complexed polyacrylic acid with a Fe/PAA ratio of 1/4 was electrodeposited on the PDA layer. After eluting the Fe3+ with EDTA, the two manufacture membranes, labeled as FC-PDA/(Fe)PAA-M and FA-PDA/(Fe)PAA-M, were characterized. The former exhibited a higher Cl−/SO42− permselectivity than the latter, although the latter demonstrated better performance compared to both the pristine AEM and a PAA-PDA-M obtained without applying any current during the deposition process. The effect the Fe3+ addition and varied the Fe/PAA ratio was also investigated. The membranes obtained using the Fe/PAA ratio of 1/4 exhibited best separation performance. Finally, the stability of this membrane was assessed by conducting ten consecutive electrodialysis (ED) experiments, revealing consistent Cl−/SO42− permselectivity values within the 5–6 range.

Investigation of membranes-electrodes assemblies in anion exchange membrane fuel cells (AEMFCs): Influence of ionomer ratio in catalyst layers

Anion exchange membrane fuel cells (AEMFCs) have recently attracted significant attention as low-cost alternative fuel cells to traditional proton exchange membrane fuel cells because of the possible use of platinum-group metal-free electrocatalysts. Over the past decade, new materials dedicated to the alkaline medium, such as anion exchange membranes (AEMs) and anion exchange ionomers (AEIs), have been developed and studied in AEMFCs. However, only a few AEMs and AEIs are commercially available, and there are no ready-to-use membrane electrodes assemblies (MEAs) with the desired AEMs and AEIs. Consequently, the need to manufacture in-house CCMs or GDEs becomes a reality that we must face.This work deals with the influence of ionomer content on the prepared MEAs with the commercial anion exchange membrane and ionomer from Aemion™ Ionomr Innovations AF1–HNN8–2 and AP1–ENN8/HNN8 respectively and by varying the support (gas diffusion layer or membrane). The prepared MEAs were characterized morphologically by SEM and profilometry, as well as electrochemically by AEMFC polarization curves and cyclic voltammetry. In addition, an attempt to investigate water management was made with and without a reference electrode in the cell to understand the behavior of water in an operating AEMFC. Our results show that CCM-based MEAs can undergo deformation during the anion conversion step, leading to weakening of the membrane and hence faster degradation in the fuel cell. On the contrary, no deformation was observed for the GDEs during the anionic conversion, although the results are poorer due to (i) poor interface contact between membrane and GDE that depends on ionomer ratio in the ink and (ii) a high overpotential at the anode due to the production of water that cannot be effectively evacuated.

Removal of Eriochrome black-T from wastewater by utilizing the commercial DF-120 anion exchange membrane

This work describes the batch adsorption of Eriochrome black-T (EBT) an anionic dye onto the DF-120 commercial anion exchange membrane (AEM) from wastewater at 25 °C. The effect membrane dosage, temperature, ionic strength, contact time, pH and initail concentration on EBT adsorption was illustrated. Adsorption capacity (qe) was enhanced from 7.32 to 12.71, 1.77 to 12.71, 6.71 to 12.71, and 16.16 to 17.39 mg/g with membrane dosage (mass), initial concentration, contact time, and ionic strength respectively while decreased from 12.71 to 3.77 and 12.71 to 3.65 mg/g with temperature and pH of medium respectively. Adsorption of EBT was subjected to various adsorption isotherms including Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) models. It was noticed that EBT adsorption obeyed Freundlich isotherm because the value of correlation coefficient (R2 = 0.991) was close to unity. Several kinetics models were utilized to demonstrate EBT adsorption. Results showed that EBT adsorption fitted to pseudo-second order (PSO) model because the value of correlation coefficient (R2 = 0.997) was close to unity. Adsorption thermodynamics study represented that EBT adsorption onto the DF-120 commercial AEM was an exothermic process (ΔH°= −79.78 KJ/mol). In addition, the regeneration of DF-120 commercial AEM was also studied.

Influence of ionomer concentration and membrane thickness on membrane electrode assembly in alkaline fuel cell performance

AbstractThe alkaline fuel cell is subject to extensive research owing to its fast kinetic response relative to acidic media. However, the efficiency of the catalytic layer at the electrodes depends on the amount and distribution of ionomers present there. It is crucial to have the right ionomer concentration to have the best cell performance. Additionally, the membrane thickness is a significant parameter that affects the system performance in alkaline fuel cells. This research studies the best alkaline fuel cell performance using the membrane electrode assembly preparation parameters. The prepared membrane electrode assembly consists of catalyst layers containing Fumion, a commercial anion exchange ionomer, as a binding agent, sandwiched a Fumasep, a well‐known commercial anion exchange membrane. This work elucidates the single‐cell alkaline fuel cell performance by quantifying the influence of Fumion concentrations (~20–60 wt.%) within the catalytic layer and Fumasep thicknesses (30, 75 and 130 μm). The best concentration of Fumion was found to be 50 wt.%, culminating in the maximum peak power density of 67 mW cm−2 achieved by the FAA‐3‐PK‐75. Meanwhile, FAA‐3‐PK‐130 exhibited the highest open‐circuit potential with lowest power density at 53 mW cm−2. These findings may serve as a valuable guide for membrane electrode assembly preparation in alkaline fuel cells.

High-performance cation electrokinetic concentrator based on a γ-CD/QCS/PVA composite and microchip for evaluating the activity of P-glycoprotein without any interference from serum albumin.

The development of cation electrokinetic concentrators (CECs) has been hindered by the lack of commercial anion-exchange membranes (AEMs). This paper introduces a γ-cyclodextrin-modified quaternized chitosan/polyvinyl alcohol (γ-CD/QCS/PVA) composite as an AEM, which is combined with a microchip to fabricate a CEC. Remarkably, the CEC only concentrates cationic species, thereby overcoming the interference of the highly abundant, negatively charged serum albumin in the blood sample. P-Glycoprotein (P-gp) is recognized as an efflux transporter protein that influences the pharmacokinetics (PK) of various compounds. The CEC was used to evaluate the activity of P-gp by detecting the positively charged rhodamine 123 (Rho123 is a classical substrate of P-gp) with no interference from serum albumin in the serum sample. Using the CEC, the enrichment factor (EF) of Rho123 exceeded 105-fold under DC voltage application. The minimal sample consumption of the CEC (<10 μL) enables reduction of animal sacrifice in animal experiments. Here, the CEC has been applied to evaluate the transport activity of P-gp in in vitro and in vivo experiments by detecting Rho123 in the presence of P-gp inhibitors or agonists. The results are in good agreement with those reported in previous reports. Therefore, the CEC presents a promising application potential, owing to its simple fabrication process, high sensitivity, minimal sample consumption, lack of interference from serum albumin and low cost.

Surface-modified nanoclay incorporated anion exchange membrane facilitating performance in self-humidifying bipolar membrane fuel cell

Bipolar membrane fuel cell (BPMFC) undergoes self-humidification due to formation of water at the interface of proton exchange layer (PEL) and anion exchange layer (AEL). Ion conductivity and dimensional stability of individual layers (PEL/AEL) play crucial role in the ohmic resistance/interface resistance of the BPM. A series of polysulfone based composite anion exchange membranes (AEMs) were synthesized by varying 2, 4, 6, and 8 % w/w of surface modified montmorillonite (MMT) nano clay (SM-MMT), and their electrochemical/physiochemical properties were optimized and compared with commercial AEM fumasep®, FAS-50. The AEM with 6 wt% SM-MMT (AEM-SM-MMT-06) showed improved OH− conductivity (103.34 mS cm−1, 80 °C) compared to both AEM-pristine (72.68 mS cm−1, 80 °C) and commercial FAS-50 (86.61 mS cm−1, 80 °C), while dimensional stability (i.e. swelling ratio, %) of AEM-SM-MMT-06 (16.43 %) much higher compared to pristine AEM (47.37 %), but closer to fumasep® (FAS-50, at 80 °C, 15.78 %). Finally, BPM fuel cell test carried out without external humidification showed peak power density of 331.2 mW cm−2 with nafion-212 (PEL)/AEM-SM-MMT-06 (AEL), followed by other two BPMs (nafion-212/FAS-50, 270 mW cm−2; nafion-212/AEM-pristine, 246 mW cm−2).

Modulating Cation and Water Transports for Enhanced CO Electrolysis via Ionomer Coating.

Electrification of the chemical industry has been considered an enabler for energy transition on a massive scale. In this context, carbon monoxide electroreduction (COR) to produce multi-carbon (C2+ ) products is considered one of the forefront emerging technologies. The key challenge in COR comes from the excessive cation crossover to the cathode via electromigration and water diffusion, which limits CO availability and impedes product selectivity. Commercial anion exchange membrane (AEM) suppresses the electromigration of cations, however, suffers from water diffusion which facilitates cation crossover. Here, we tackled these problems emerging from cation crossover and water diffusion by directly depositing an ultrathin Nafion ionomer on the cathode (sputtered Cu) surface. Our approach enables full-cell energy efficiency of 21 % for converting CO into ethylene (C2 H4 ) at 100 mA/cm2 with over 200 hours of stable operation. We also exhibited record high energy efficiency for ethanol (C2 H5 OH) production with CO-to-C2 H5 OH electrolysis efficiency of 17 %. This approach to directly depositing ultrathin ionomer on the cathode to enhance system performance may benefit other electrochemical systems to overcome challenges associated with scalability, stability, and efficiency to produce high-value chemicals.

Alkaline-Stable, In Situ Menshutkin Coat and Curable Ammonium Network: Ion-Solvating Membranes for Anion Exchange Membrane Water Electrolyzers

Anion exchange membranes fabricated through a one-step Menshutkin reaction with down-selected multifunctional alkyl halides and multifunctional tertiary amines within an ion-solvating matrix, poly(ethylene-co-vinyl alcohol), yielded alkaline-stable ammonium network polymers. Due to the vast simplicity in fabrication due to the quaternization/Menshutkin reaction between tertiary amine and alkyl bromides, which does not evolve any by-products that require purification, alkaline-stable membranes were fabricated in one step through facile mixing and curing of alkaline-stable ammonium network forming monomers. Prepared membranes showed controllable ion exchange capacity (IEC), conductivity, and mechanical strength by controlling of poly(ethylene-co-vinyl alcohol) amount which is an ion-solvating polymer. The selection of ammonium network chemical structure allowed for flawless retention of IEC and conductivity under conditions of 70°C, 1M KOH of over 300 h. Anion exchange membrane electrolysis membrane electrode assembly tests with optimized membranes showed a greater performance (1.78 A/cm2 at 2.0 V) and more enhanced water electrolyzer durability than that of commercial anion exchange membrane.

Commercial Anion Exchange Membranes (AEMs) for Fuel Cell and Water Electrolyzer Applications: Performance, Durability, and Materials Advancement

The utilization of anion exchange membranes (AEMs) has revolutionized the field of electrochemical applications, particularly in water electrolysis and fuel cells. This review paper provides a comprehensive analysis of recent studies conducted on various commercial AEMs, including FAA3-50, Sustainion, Aemion™, XION Composite, and PiperION™ membranes, with a focus on their performance and durability in AEM water electrolysis (AEMWE) and AEM fuel cells (AEMFCs). The discussed studies highlight the exceptional potential of these membranes in achieving high current densities, stable operation, and extended durability. Furthermore, the integration of innovative catalysts, such as nitrogen-doped graphene and Raney nickel, has demonstrated significant improvements in performance. Additionally, the exploration of PGM-free catalysts, such as Ag/C, for AEMFC cathodes has unveiled promising prospects for cost-effective and sustainable fuel cell systems. Future research directions are identified, encompassing the optimization of membrane properties, investigation of alternative catalyst materials, and assessment of performance under diverse operating conditions. The findings underscore the versatility and suitability of these commercial AEMs in water electrolysis and fuel cell applications, paving the way for the advancement of efficient and environmentally benign energy technologies. This review paper serves as a valuable resource for researchers, engineers, and industry professionals seeking to enhance the performance and durability of AEMs in various electrochemical applications.

Moisture-driven CO2 pump for direct air capture

Direct Air Capture, the chemical separation of carbon dioxide (CO2) from air, is considered a necessary approach to generate negative carbon emissions and in turn limit global warming, though energetic and monetary costs must continue to decline to meet the needed gigaton scale. The promise of energy-efficient and continuous carbon dioxide membrane separation has only recently been investigated with the development of facilitated chemical transport and novel electrochemically driven methods. This work demonstrates the potential for continuous pumping of CO2 from air using commercial anion exchange membranes driven solely by a water vapor gradient. A reactive transport model that couples ionic transport with moisture sensitive bicarbonate chemistry in charged polymers, also termed moisture swing sorption, was developed alongside experimentally measured equilibrium and transport properties of CO2 and water vapor in Fumasep FAA-3 to determine the mass transport limits of such a system. The results show that the commercial membrane is kinetically limited by the moisture sensitive chemistry, enabling a CO2 current of 1.1 μmol/m2∙ s. In diffusion limited materials, a CO2 pumping flux can reach 11 μmol/m2∙ s in and peak performance is expected with a dry air relative humidity around 50% pumping into a saturated water vapor permeate. In all configurations, water loss becomes the major cost in such a separation and must be managed through optimal polymer design or water recovery mechanisms. The work demonstrates the applicability of a new driving force, the evaporation of water, to meet the energetic demand of CO2 separation from air.

Composite Anion Exchange Membranes Based on Quaternary Ammonium-Functionalized Polystyrene and Cerium(IV) Phosphate with Improved Monovalent-Ion Selectivity and Antifouling Properties.

The possibility of targeted change of the properties of ion exchange membranes by incorporation of various nanoparticles into the membranes is attracting the attention of many research groups. Here we studied for the first time the influence of cerium phosphate nanoparticles on the physicochemical and transport properties of commercial anion exchange membranes based on quaternary ammonium-functionalized polystyrenes, such as heterogeneous Ralex® AM and pseudo-homogeneous Neosepta® AMX. The incorporation of cerium phosphate on one side of the membrane was performed by precipitation from absorbed cerium ammonium nitrate (CAN) anionic complex with ammonium dihydrogen phosphate or phosphoric acid. The structures of the obtained hybrid membranes and separately synthesized cerium phosphate were investigated using FTIR, P31 MAS NMR, EDX mapping, and scanning electron microscopy. The modification increased the membrane selectivity to monovalent ions in the ED desalination of an equimolar mixture of NaCl and Na2SO4. The highest selectivities of Ralex® AM and Neosepta® AMX-based hybrid membranes were 4.9 and 7.7, respectively. In addition, the modification of Neosepta® membranes also increased the resistance to a typical anionic surfactant, sodium dodecylbenzenesulfonate.

Short term fouling tests on homogeneous and heterogeneous anion-exchange membranes from food and bio-based industrial streams: Foulant identification and characterization

Electrodialysis is used in food and bio-based industries for selective separation and recovery of target ions and neutral molecules. Anion exchange membranes (AEM) are prone to fouling due to their complex interactions with organics. Currently, research has focussed mainly on fouling tests using model organic foulants. In this study, three different complex industrial feed streams: corn steep liquor (CSL), citric acid by-product (CA), and cheese whey (CW), were used to foul two commercial AEM types: Fujifilm type-10 (homogeneous) and RALEX (heterogeneous). A 1.5 – 2.3 fold higher membrane resistance after fouling was a result of a difference in membrane structure, ion exchange capacity, water uptake, and thickness (depending on the feed used). Liquid Chromatography – Organic Carbon Detection (LC-OCD) analysis of feed revealed highly hydrophilic (CDOC) fractions in CSL (85%), CA (87%), and CW (100%). This analysis was extended to foulant desorption solutions (NaCl (35 g/L) and EtOH-water-H2SO4 mixtures), which revealed that > 90 % of humic substances (HS) and building blocks (BB) desorbed when using NaCl (35 g/L), following a (concentration wise) desorption order: HS > BB > LMWN > BP > LMWA. For the EtOH-water-H2SO4 solution, low molecular weight neutrals and acids (LMW(A + N)) were desorbed majorly (>60%) and followed a desorption order: LMWN > LMWA > BB > BP > HS. Desorption due to the ion-exchange mechanism was dominant for NaCl (35 g/L) solution, while foulant-desorbant polar interactions were prevalent for the EtOH-water-H2SO4 solution. Upon foulant desorption using NaCl (35 g/L) solution, RALEX AEM owing to the presence of nanovoids in them, showed a 1.5 – 4 fold higher concentration difference vs. FF10 AEM, while this difference was not dominantly observed when EtOH-water-H2SO4 mixture was used. This study revealed that LMW fractions could possibly enter into the membrane matrix whereas HS and BB fractions owing to their high molecular weight, majorly adsorbed on surfaces.

Removal of chromium (VI) by commercial anion exchange membrane BII from an aqueous solution: Adsorption kinetic, equilibrium and thermodynamic studies

Removal of chromium (VI) by commercial anion exchange membrane BII from an aqueous solution: Adsorption kinetic, equilibrium and thermodynamic studies

Superior diffusion dialysis anion exchange membranes from miscible polyether sulfone – poly(vinyl pyrrolidone-co-styrene) blends

Diffusion dialysis is a promising method for the recovery of titania waste acid due to its low energy consumption and ease of operation. However, the current commercial anion exchange membranes (AEMs) suffer from low acid permeability coefficient and high cost. To address this issue, the development of high-performance AEMs is crucial for the successful recovery of titania waste acid by diffusion dialysis. Previous studies [Journal of Membrane Science, 2022, 662, 120980] have shown that the dense polyether sulfone - poly(vinyl pyrrolidone) (PES-PVP) blend membranes can be converted into AEMs through the protonation reaction of the O atoms in pyrrolidone with H+ in sulfuric acid solution. This process enables the efficient separation of sulfuric acid from ferrous sulfate. The acid permeability coefficient of the blend membrane is influenced by the content and molecular weight of PVP. Higher content and molecular weight of PVP result in a greater acid permeability coefficient of the membranes. It is observed that due to the water solubility of PVP, the amount of PVP added to the blend membranes cannot exceed 60%, however this would restrict further improvement in the acid permeability coefficient of the membranes. Additionally, there is a concern regarding the long-term stability of the membranes as the PVP may get washed out from the membranes. To this, P(VP-co-St) copolymers with a certain hydrophobicity are synthesized through free radical copolymerization of hydrophilic monomer N-vinylpyrrolidone (VP) and hydrophobic monomer styrene (St). PES-P(VP-co-St) dense membranes are then prepared by mixing the P(VP-co-St) copolymers with PES. The objective of this study is to investigate the effects of P(VP-co-St) molecular weight, VP content, and composition of the casting solution on the physicochemical properties, mass transfer properties, and stability of the blend AEMs. The results show that homogeneous dense membranes can be prepared by completely mixing PES with P(VP-co-St) copolymers with 87–90 wt% VP content and 100–150 kDa molecular weight. The permeability coefficients of H2SO4 (PH2SO4) and FeSO4 (PFeSO4) increase with the VP content in the membrane phase. The ion exchange capacity of the PES-P(VP-co-St)-1# AEM varies in the range of 0.32–0.81 mmol/g dry membrane. For the PES-P(VP-co-St) blend membranes, synthesized by blending P(VP-co-St) with 90 wt% VP content with PES at a mass ratio of 7:3 (VP content of 61 wt% in the membranes), the PH2SO4, PFeSO4, and selectivity coefficient of the membranes are 692 × 10−9 m2/h, 5.8 × 10−9 m2/h, and 119, respectively. The PH2SO4 of the PES-P(VP-co-St) AEM is much higher than that of the commercial AEM Tianwei DF-120 while maintaining high selectivity. This study successfully develops AEMs with high performance in diffusion dialysis through a convenient method by blending P(VP-co-St) copolymers with PES.

Membrane Engineering Reveals Descriptors of CO2 Electroreduction in an Electrolyzer

Anion exchange membranes (AEMs) and ionomers are keys for electrochemical CO2 reduction (eCO2R), but their development and multiple roles have not been intensively investigated. This study demonstrates HQPC-tmIM, a polycarbazole-based anion-conducting material, as a commercially viable AEM and reveals through multiphysics model simulation key descriptors governing eCO2R by exploiting the extraordinary membrane properties of HQPC-tmIM. The mechanical/chemical stability of HQPC-tmIM showed superior eCO2R performance in a membrane electrode assembly electrolyzer (MEA) in comparison to a commercial AEM (Sustainion). The CO partial current density (jCO) of −603 mA cm–2 on HQPC-tmIM MEA is more than twice that of Sustainion MEA and is achieved by only introducing HQPC-tmIM AEM and binder. The mutiphysics model revealed that the well-constructed membrane morphology of HQPC-tmIM leads to the outstanding membrane conductivity, and it enables high jCO through the facilitated charge transfer in overall reactions. This research suggests guidelines for developing a commercially viable AEM and ionomer for eCO2R.

Efficiency of Neat and Quaternized-Cellulose Nanofibril Fillers in Chitosan Membranes for Direct Ethanol Fuel Cells.

In this work, fully polysaccharide based membranes were presented as self-standing, solid polyelectrolytes for application in anion exchange membrane fuel cells (AEMFCs). For this purpose, cellulose nanofibrils (CNFs) were modified successfully with an organosilane reagent, resulting in quaternized CNFs (CNF (D)), as shown by Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 (C13) nuclear magnetic resonance (13C NMR), Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC), and ζ-potential measurements. Both the neat (CNF) and CNF(D) particles were incorporated in situ into the chitosan (CS) membrane during the solvent casting process, resulting in composite membranes that were studied extensively for morphology, potassium hydroxide (KOH) uptake and swelling ratio, ethanol (EtOH) permeability, mechanical properties, ionic conductivity, and cell performance. The results showed higher Young's modulus (119%), tensile strength (91%), ion exchange capacity (177%), and ionic conductivity (33%) of the CS-based membranes compared to the commercial Fumatech membrane. The addition of CNF filler improved the thermal stability of the CS membranes and reduced the overall mass loss. The CNF (D) filler provided the lowest (4.23 × 10-5 cm2 s-1) EtOH permeability of the respective membrane, which is in the same range as that of the commercial membrane (3.47 × 10-5 cm2s-1). The most significant improvement (~78%) in power density at 80 °C was observed for the CS membrane with neat CNF compared to the commercial Fumatech membrane (62.4 mW cm-2 vs. 35.1 mW cm-2). Fuel cell tests showed that all CS-based anion exchange membranes (AEMs) exhibited higher maximum power densities than the commercial AEMs at 25 °C and 60 °C with humidified or non-humidified oxygen, demonstrating their potential for low-temperature direct ethanol fuel cell (DEFC) applications.