Ion Exchange Capacity Research Articles

Highly flexible SCOF proton exchange membrane reinforced with PTFE to enhance fuel cell power density

Sulfonated covalent organic frameworks (SCOFs) facilitate rapid proton conduction through densely ordered sulfonic acid groups, however, the brittleness of COFs self-supporting membranes often makes potential difficulty in fuel cell assembly and limits their power density. Herein, a highly flexible SCOF proton exchange membrane is developed through in-situ growth of a continuous BD(SO3H)2-COF microphase within porous PTFE networks. The strong hydrogen bonding between PTFE and BD(SO3H)2-COF contributes to the defect-free morphology of the BD(SO3H)2/PTFE membrane. The reinforce of PTFE network makes the membrane extremely high flexibility, achieving an elongation at break of 124.4% even with a remarkably high SCOF mass proportion of 90 wt.% (BD(SO3H)2/PTFE-0.9). This allows the membrane to be folded repeatedly, even in dry state. The swelling ratio in water at 80 °C is effectively restricted to 8.6%, even with a high ion exchange capacity of 3.6 mmol g-1 and a water uptake of 68.2%. The densely ordered sulfonic acid groups in continuous BD(SO3H)2-COF microphase contribute to a high proton conductivity up to 249.2 mSꞏcm-1 at 80°C, approximately 1.5 folds that of Nafion 212. As a result, the BD(SO3H)2/PTFE-0.9 membrane achieves a fuel cell power density of 1195.3 mWꞏcm-2 at 80°C, along with a high open circuit voltage of 1.01 V, surpassing the-state-of-the-art COF-based proton exchange membranes. This work provides a novel strategy to fabricate COFs into flexible and size scalable membranes, enhancing the performance of fuel cells.

Regeneration of a Fire‐Resistant Fluid‐Fouled Strong Base Anion Resin using a Caustic Solution with Citric Acid as a Surfactant

AbstractFire Resistant Fluid (FRF), used in turbine governing systems, transforms during operation, forming substituted phenol and phosphoric acid. The use of strong Base Anion Resin (SBA resin) to reduce the Total Acid Number (TAN) of FRF is widespread. However, the regeneration of these oil‐fouled resins is crucial due to their high cost and the challenges associated with their environmental disposal. In this study, we present a novel method for recovering exhausted resin by treating it with an aqueous solution of citric acid, followed by regeneration with a caustic soda solution. We optimized the recovery percentage in the ion exchange capacity by testing varying concentrations of the citric acid solution under different reaction conditions. The highest recovery of ion exchange capacity achieved was 55 % after soaking for 16 hours in a 5 % citric acid solution, followed by regeneration with a 5 % NaOH solution. The efficacy of citric acid in this research was further explored through a Density Functional Theory (DFT) study. This study is significant as it is the first to demonstrate the successful regeneration of oil‐fouled resins with high ion exchange capacity using citric acid, a more environmentally friendly and cost‐effective alternative.

Development of a potentiometric sensor for mercury (II) ion using cerium (IV) tinmolybdophosphate

ObjectivesThe primary objective of this report is to develop a heperopolyacid salt, Cerium (IV) tinmolybdophosphate (CeSnMoP), with distinctive attributes that significantly enhance its ion exchange capacity. Through deliberate adjustments in temperature, pH, and volume ratios, we have carefully prepared a range of CeSnMoP samples. One sample exhibiting an ion exchange capacity (IEC) of 5.06 ± 0.2 meq gm-1 has been identified for further extensive analysis. The second objective was to develop the potentiometric sensor by using the synthesised sample therefore it was transformed into an electrode incorporating PVC as binder material and validated as a potentiometric sensor for Mercury ions which can work as variable media.Data descriptionInstrumental analyses, such as XRD, IR, TGA, SEM and EDS, were used to elucidate the compound’s structural aspects. Distribution coefficient (Kd) studies highlighted the compound's pronounced selectivity towards Hg2+ ions. This catalyst was further utilized as an electro-active substance for detecting Hg2+ ions in an external solution. Epoxy resin played the role of a binder in the electrode formulations. The electrode, comprising a membrane with 50% exchanger material, demonstrated superior performance. This selected membrane exhibited a wide operational concentration range of 1 × 10–6 M – 1 × 10–1 M of Hg2+ ions for quantitative analysis of unknown samples of mercury ions. The lower detection limit for the calibration curve was recorded up to 2 × 10–8 M from 1 to 10–1 M. The electrode effectively sensed this metal ion within the pH range of 3.74–7.51 and exhibited a lifespan exceeding 8 months.

Influence of Bacterial Nanocellulose Consumption on the Content of Macronutrients and Trace Elements in the Organs of Rats.

Bacterial nanocellulose (BNC) prepared by the methods of "green" bionanotechnological synthesis is considered a promising food additive and food ingredient. At the same time, the risk of reducing the bioavailability of minerals due to their adsorption on BNC fibers having a high specific surface area and high adsorption and ion exchange capacity cannot be excluded. We studied the effect of oral administration of BNC on the accumulation of macronutrients and trace elements included in the diet in the liver and kidneys of laboratory animals. Male Wistar rats received BNC at doses of 0 (control), 1, 10, and 100 mg/kg body weight as part of their diet for 8 weeks. The content of 30 macronutrients and trace elements in the liver and kidneys was determined by inductively coupled plasma mass spectrometry. It was found that BNC at all doses did not significantly change the content of the main essential macronutrients and trace elements in the organs (Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, Se, and Zn), which indicates the absence of a negative effect on their bioavailability. Among other elements, a statistically significant decrease in the content of As, B, Cd, Co, and Pb in the liver and an increase in Al, B, Ba, Ni, and Pb in the kidneys were revealed (more than 20% of the control). The revealed decrease in the bioaccumulation of cobalt can indicate inhibition of assimilation of certain chemical forms of this trace element under the action of BNC.

Recent Progresses and Challenges to Determine Properties of Sulfonated Polyether Ether Ketone Based Electrolytes for Direct Methanol Fuel Cell Applications

AbstractThis review focuses on fillers, modifications, and methods used in the preparation and development of sulfonated poly(ether ether ketone) (sPEEK) membranes, specifically for direct methanol fuel cell (DMFC) applications as proton exchange membranes in recent years. The primary objective is to evaluate recent advancements by emphasizing key characteristics such as water uptake and swelling capacity, ionic conductivity, methanol permeability, and single cell polarization tests. Additionally, the review aims to provide insights for future researchers by discussing the preparation processes of electrolytes. It presents basic characterizations of membrane electrolytes, including evaluations of the sulfonation degree and ion exchange capacities of sPEEK. High performance of membrane electrolytes is essential for commercialization and to compete with established membranes like Nafion®, which has a perfluorosulfonic acid structure. Therefore, the review also covers detailed characterization methods for assessing long‐term stability when available in the related studies. Numerical results and indicators are categorized and tabulated for easy interpretation and comparative analysis.

Bipolar Membranes Via Divergent Synthesis: On the Interplay between Ion Exchange Capacity and Water Dissociation Catalysis.

Bipolar membranes (BPMs) enable the operation of electrochemical reactors with electrode compartments in different chemical environments or pH. The transport properties at the microscopic scale are dictated by the composition and morphology of the interfacial junctions as well as the specific chemistry of the ion-exchange layers that support the current of protons and hydroxide ions. This work elucidates the relation between water-dissociation efficiency and the physicochemical properties of the individual ion-exchange membrane layers in the poly(styrene-b-poly(ethylene-ran-butylene)-b-polystyrene) (SEBS)-based BPM. The optimal water dissociation performance of three previously reported water-dissociation catalysts in the SEBS-based BPM was examined, with junction thickness of graphene oxide > TiO2 > SnO2, resulting in disparate junction morphologies at the BPM's interface. A hybrid junction system, which included both the effective water dissociation catalyst SnO2 and direct contacting of the ion-exchange membrane layer, exhibited high water dissociation efficiency. This was likely due to the immediate ion transport pathway provided by direct membrane contact around the catalyst, which also improved the interfacial adhesion. A higher ion exchange capacity (IEC) in BPMs substantially enhanced the water dissociation performance in BPMs without water-dissociation catalysts. However, the incorporation of the effective SnO2 catalyst into the BPMs with a lower IEC significantly improved performance, an effect attributed to the hybrid junction system. Additionally, the increase in water uptake and ion conductivity of the cation exchange layer with higher IEC suggested that the cation exchange layer and its interface to the water-dissociation catalyst layer may play a key role in water dissociation. This study identifies the key parameters of individual BPM components and their interactions to water dissociation performance, offering new insights to guide in the construction of future BPMs optimized for enhanced water dissociation efficiency at high current densities.

MoS2 nanosheet assisted poly vinyl alcohol cross-linked with carboxylated acryl-amido-2-methyl-1-propanesulfonic acid in medium temperature proton exchange membrane fuel cell application

ABSTRACT Initially, the carboxylated-acryl amido propane sulfonic acid (C-AMPSA) was synthesized through the thiol-ene reaction using 2-acrylamido-2-methylpropane sulfonic acid and 3-mercapto propane sulfonic acid monomers. The C-AMPSA was cross-linked with polyvinyl alcohol to create a non-perfluorinated membranes were of these acid group-containing monomers. Using a cross-linking technique, a poly vinyl alcohol cross-linked C-AMPSA (PVA-C-AMPSA) polymer was prepared. Following that, the MoS2 nanosheets (NSs) were synthesized through the one-pot hydrothermal method, and their phase purity, functionality, and morphology were evaluated by p-XRD, FT-IR, and FE-SEM analyses. These nanosheets were then incorporated into PVA-C-AMPSA polymer nanocomposite membranes at various concentrations (0%, 1%, 2%, 3%, and 5% by weight). In addition, the physicochemical properties of bare and MoS2 nanosheets incorporated PVA-C-AMPSA polymer nanocomposite membranes were assessed, including water uptake, swelling ratio, and ion-exchange capacity. Remarkably, the membrane with 5% of MoS2 NSs in PVA-C-AMPSA displayed an ion-exchange capacity of 1.13 mmol g−1 and a proton conduction of 1.8 × 10−3 S cm−1 at 110°C. The Arrhenius plot indicated that the proton transport was involved in both Grotthuss and vehicular mechanisms. In the fuel cell testing, the PVA-C-AMPSA polymer nanocomposite membrane containing MoS2 NSs demonstrated superior performance, achieving a peak power density (PD) exceeding 0.7 W cm−2 and an open-circuit voltage (OCV) surpassing 0.93 V at 110°C. In contrast, the pure PVA-C-AMPSA membrane exhibited a peak PD of over 0.4 W cm−2 and an OCV of around 0.6 V at the same temperature. Additionally, the 5% of MoS2 NSs incorporated PVA-C-AMPSA polymer nanocomposite membrane exhibited outstanding oxidative stability with 87.7% of degradation when exhibited to a Fenton reagent at 80°C for 8 h.

Design of a bifunctional prepolymer for simultaneously facile preparation and highly efficient electrodialysis of anion exchange membranes

A facile fabrication process for separation membranes is crucial to decrease the production cost, while the photo-polymerization approach can be conducted at ambient conditions with short processing time and low energy consumption. Herein, this work designs a bifunctional prepolymer for simultaneously facile preparation and highly efficient electrodialysis of poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange membranes. PPO is selected as the main skeleton of prepolymer because of the excellent mechanical and thermal stability. The dimethylaminoethyl methacrylate (DMAEMA) is grafted with brominated PPO by quaternization, where it contains cationic groups, i.e. quaternary ammonium, and photopolymerized groups, i.e. methacrylate C = C. This resulting prepolymer can be fast polymerized under UV irradiation via C = C from DMAEMA. This structure is synergistically regulated by the amounts of crosslinker DMAEMA and modifier N-bromosuccinimide. The optimized membrane exhibits an excellent ion exchange capacity of 2.19 mmol g−1, a water uptake of 38.17 %, and a tensile strength of 4.8 MPa. Meanwhile, its electrolyzer cell performance achieves a density of 580 mA cm−2 at an adjusted voltage of 2.1 V, and the desalination rate of seawater during electrodialysis reaches 98.34 %. This work provides a universal and facile fabrication route for high-performance AEMs.

Morphology and methanol permeability of sulfosuccinic acid cross‐linked polyvinyl alcohol and polyvinyl alcohol/Nafion nanofibrous membranes

AbstractCross‐linking of polyvinyl alcohol (PVA) and polyvinyl alcohol/Nafion (PVA/Nafion) electrospun nanofibers with sulfosuccinic acid (SSA) was investigated to assess their characterization and the effects of cross‐linking on the methanol permeability performance of the nanofibrous membranes. SSA was directly incorporated into the electrospinning polymer solution. The morphology, chemical functional groups, thermal stability, water stability and water swelling of the resulting nanofibers were examined. The effects of SSA concentration on ion exchange capacity (IEC) and methanol permeability of the nanofibrous membranes were discussed. Bead‐free and smooth nanofibers were produced for all SSA concentrations with a mean nanofiber diameter of 240–270 nm. It was shown that 15% SSA concentration was suitable for preserving the morphology of PVA nanofibers against water, while the morphology of PVA/Nafion nanofibers was preserved even without cross‐linking. The increase in SSA concentration led to increase in swelling in water. SSA cross‐linking was also shown to increase the thermal stability of the produced nanofibers. IEC increased by the increase in SSA concentration, while increase in SSA concentration led to a decrease in methanol permeability.

Effective removal of Calcium and Magnesium Ions from boiler feed Water using Polyacrylonitrile supported titanium tungstovanadate composite ion exchange nanofiber

<p><em><strong>​​​​​​</strong></em><span style="font-family:"Times New Roman","serif";font-size:12.0pt;line-height:150%;">The challenge posed by the presence of calcium ions (Ca<sup>2+</sup>) in process streams is attributed to its adverse effects on the heat transfer efficiency of process equipment. In this study, a novel electrospun nanofibrous composite was synthesized by combining polyacrylonitrile (PAN) with well-dispersed Titanium tungestovanadate (TWV) cation exchanger. Homogeneous precipitation technique was employed to synthesize nano-titanium (IV) tungstovanadate (TWV) cation exchanger. Various synthesis parameters, including reactant volume ratio, amount of precipitating agent and reaction temperature, were optimized to achieve the highest ion exchange capacity (IEC). The prepared ion exchange material exhibited an ion exchange capacity (IEC) of 2.39 meq.g<sup>-1</sup> for Na<sup>+</sup> ions. The incorporation of the prepared nanoparticles into nanofibers conferred the sorption capabilities of the composite. The nanofibers' morphologies and structures were analyzed using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Batch sorption experiments were carried out to investigate the sorption properties. Controlled experiments were conducted to investigate the impact of various factors, including solution pH, temperature, dosage, contact time, and the initial concentration of the hard water. The results indicated that the optimum adsorption conditions that gave the highest percentage of removal 99%, 98% for Ca<sup>2+</sup> and Mg<sup>2+</sup>  ions respectively were 50 mg of adsorbent dosage, 500 ppm of Ca<sup>2+</sup> and Mg<sup>2+</sup>  solution =7, and a contact time of 30 min at room temperature .The  kinetic data were fitted to pseudo second order model. Furthermore, the thermodynamic study suggested that the adsorption on PAN/TWV NF was endothermic and spontaneous.</span></p>

Zn-Al layered double hydroxide supported on waste cow dung-derived biochar as a highly efficient adsorbent for anionic dye removal from contaminated water.

In this study, Zn-Al-SO42- LDH-functionalized biochar was fabricated using the co-precipitation method. The biochar was synthesized from waste cow dung using a low-temperature pyrolysis process (300 °C). The materials were fully characterized by TGA, FTIR, EDS, SEM, and XRD analysis. Then, a comparative study was performed to investigate the adsorption capacity of the materials against an anionic dye (i.e., methyl orange (MO)). The LDH-functionalized biochar demonstrated high adsorption capacity (400 mg/g in 120 min, at pH 5) compared to the raw biochar (212 mg/g in 120 min, at pH 5). The effect of various adsorption parameters (e.g., pH of the dye solution, temperature, initial concentration, adsorbent dosage, and contact time) was investigated. The adsorption of MO on LDH-functionalized biochar followed the Freundlich isotherm and pseudo-second-order kinetics, while the raw biochar followed the Langmuir isotherm and pseudo-second-order kinetics. The thermodynamic data indicated the endothermic nature of adsorption and an increase in the degree of randomness during adsorption. The enhanced adsorption capacity of the Zn-Al LDH-functionalized char was attributed to the synergistic effect of the surface adsorption into the porous biochar matrix, interlayer adsorption, and ion exchange capacity of the LDHs. Therefore, modification of waste cow dung-derived biochar with Zn-Al LDH can be a promising approach to fabricate a highly efficient adsorbent for toxic dyes from wastewater.

Improved Electrode Performance Using Fine‐Tuned Poly(arylene piperidinium) Ionomers In Anion Exchange Membrane Fuel Cells

AbstractIonomers based on poly(arylene piperidinium)s with varying ion exchange capacities are evaluated in different combinations of anode and cathode electrodes in anion exchange membrane fuel cells. The operational conditions are chosen with an asymmetrical regime including a dry anode with 50% relative humidity at the inlet, and full humidification at the cathode. Polarization and impedance measurements are carried out in potentiostatic steps within 0.3–0.9 V and distribution of relaxation times analysis is utilized to deconvolute resistance contributions. The results show that the best cell performance is achieved with both electrodes utilizing an ionomer with the highest ion exchange capacity (IEC) of 2.79 meq g−1. Cells built exclusively from this ionomer achieved a peak power density of 1.01 W cm−2. Deconvolution of the resistance contributions revealed the impact of water content on the effective charge transfer resistance in both electrodes and a diffusion resistance associated with the movement of water from anode to cathode side. The higher conductivity and water uptake of the high IEC ionomer resulted in a reduction of both resistance contributions, leading to the highest performance under the conditions evaluated. These findings provide important insights into how to tailor the electrode layers for optimum fuel cell output.

Sulfonamide-Sulfonimide Copolymers as Novel, Fluorine-Lean Type of Proton Exchange Membranes for Fuel Cell Application.

In this work, a novel type of fluorine-lean proton exchange membranes is presented, using sulfonamide-sulfonimide functional groups for ion conduction. These groups are constructed on a polystyrene backbone for simple and cost-efficient usage as well as rapid scalability. The polymer is further tailored by adjusting the sulfonamide functionality with various end-groups, namely pentafluorophenyl, 4-fluorophenyl, butyl and octyl groups. These groups affect the pKa, leading to pKa values of 5.7 for the pentafluorophenyl substitution and pKa 10.5 for the alkyl chain. The glass transition temperature of the sulfonamide homopolymers can be reduced from Tg=151 °C (Pentafluorophenyl) to 49 °C (Octyl), making the ionomer more flexible at room temperature. The combination of the non-swelling sulfonamide further mitigates the high water uptake of the sulfonimide while maintaining the nominal ion exchange capacity. This combination leads to extremely high proton conductivities with up to σ=283 mS cm-1 at room temperature, which is clearly outperforming Nafion and approaches values for acid doped systems. This approach can pave the way to a novel type of ion conducting class in proton exchange membrane fuel cells.

Eco-friendly non-fluorinated membranes for renewable energy storage

The European Union is studying the possibility of prohibiting the use of fluorinated-based materials which could limit the use of the most studied and used Nafion and Nafion-like membranes for any applications. Therefore, this study focuses on the preparation and performance evaluation of green, non-fluorinated proton exchange membranes in a chlor-alkali-based reversible electrochemical cell system for renewable energy storage applications. The membranes were prepared by casting and cross-linking of polyvinyl alcohol (PVA) with varying chitosan (CS) concentrations (5–20 wt%), followed by sulfonation using diluted sulfuric acid at room temperature. CS concentrations significantly influenced membrane's physicochemical properties, including ion exchange capacity, ionic conductivity, mechanical strength, and water uptake. Positron annihilation lifetime spectroscopy revealed a correlation between free volume properties and other membrane characteristics. A custom-designed 3D-printed electrochemical cell was developed, capable of operating in reversible mode (both electrolysis and fuel cell modes) with a zero-gap configuration. The PVA/CS (20 wt%) membrane outperformed Nafion, exhibiting a lower voltage (4 V vs. 6 V) in electrolysis mode at 50 mA cm⁻2 and a higher specific power density (2.7 vs. 1.9 mW cm⁻2 mgPt) in fuel cell mode. The obtained results demonstrate that crosslinked PVA/CS non-fluorinated based membranes can be sulfonated using diluted sulfuric acid and work effectively in reversible chlor-alkali electrochemical cells.

Sulphonated-graphene oxide nanocomposite membranes with PVA-ZnO nanostructures and mechanized agitation-enhanced pt coating for soft robotics bending actuator

Ionic Polymer-Metal Composite (IPMC) actuators have garnered significant scientific attention in robotics and artificial muscles for their ability to operate at low voltage, high strain capacity, and lightweight construction. The lack of uniform bending in IPMC actuators undermines their control precision and restricts their range of potential applications. This study utilized the unique properties of nanoscale materials and Polyvinyl alcohol (PVA) to develop a membrane for soft robotic bending actuation. Subsequently, a platinum coating was applied to the membrane to mitigate the limitations of IPMCs in soft robotics applications. Herein, mechanized agitation was employed during the solution-casting process to enhance platinum metal (Pt-metal) coating on zinc oxide (ZnO) nanostructures within a PVA- sulphonated graphene oxide nanocomposite, achieving enhanced soft robotics bending actuation capabilities. The resultant membrane composed of sulphonated-graphene oxide and polyvinyl-zinc oxide coated with pt (PsGZ-Pt) was examined by exploring advanced analytical techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction spectroscopy (XRD). Furthermore, the ionic exchange capacity (IEC), proton conductivity (PC), water uptake and water loss characteristics were evaluated to be 2.1 meq. g−1, 1.95 × 10−3 Scm−1, 59.62% at 45 °C and water loss at 9 min immersion found 38%, respectively. Electromechanical studies of the PsGZ-Pt membrane (size 30 mm length, 10 mm width, 0.07 mm thickness) showed an actuation force of 0.3253 mN and a displacement of roughly 22.8 mm at ± 3 VDC. These findings highlighted the PsGZ-Pt membrane’s potential as a low-cost alternative to expensive commercial IPMC actuators based on polymers. These results presented a straightforward, low-cost approach for synthesizing PsGZ-Pt utilizing conventional technologies. The PsGZ-Pt membrane shows promise for generating low-cost, high-performance actuation materials with a wide range of industrial applications.

Cross-Linking of Bromo-Pillar[5]arenes and Sulfonated Poly(Aryl Ether Ketone Sulfone) Enhances Proton Conductivity of Membranes at Low Ion Exchange Capacity

Cross-Linking of Bromo-Pillar[5]arenes and Sulfonated Poly(Aryl Ether Ketone Sulfone) Enhances Proton Conductivity of Membranes at Low Ion Exchange Capacity

Synthesis of ion exchange film based on chemical grafting of styrene onto polyethylene/EPDM rubber blend for thorium removal.

Chemical grafting of low-density polyethylene film blended with ethylene propylene diene monomer rubber (PE/EPDM) using styrene monomer followed by a sulfonation process was investigated. Different factors affecting the grafting process, such as monomer and initiator concentrations, time of reaction, and grafting temperature, were studied. Sulfonation of the grafted films was carried out using chlorosulfonic acid in dichloromethane. Characterization of the grafted and sulfonated films was performed using ATR-FTIR, SEM, TGA, and XRD instruments. The grafting was successfully performed in aqueous media using sodium bisulfite as initiator, reaching a grafting yield of 130% and an ion exchange capacity of 1.2 meq/g. The removal of thorium ions from aqueous solution was studied using the obtained ion exchange films. The results showed that the maximum adsorption capacity of Th(IV) was 177.5 mg. g-1 (pH = 3, 298 K and 60 min). Removal isotherm and Kinetics were investigated, and the results revealed that the adsorption process was chemisorption homogeneous monolayer adsorption, exothermic, and spontaneous.

Dissociative electrochemical analysis of materials degradation of an anion exchange membrane electrolyser

For anion exchange membrane (AEM) electrolysers, degradation studies provide valuable insights into how individual components degrade. Often, this presents a formidable challenge as each component significantly contributes to overall degradation. Here, we propose a methodology to individually compare the degradation of key components in AEM electrolysers: hydrogen evolution reaction (HER) catalyst, oxygen evolution reaction (OER) catalyst, and the AEM itself. First, to measure the degradation of catalyst-coated substrates (CCS) commonly used in AEM electrolysers, the AEM was replaced with a diaphragm (Zirfon Agfa UTP 500) permeable to OH− ions and stable in alkaline media. Subsequently, a cell with a stable catalytic layer (Nafion-coated Ni-felt substrates) was assembled to focus on membrane degradation with an AEM Sustainion X37-50 Grade 60. Chronopotentiometry and electrochemical impedance spectroscopy (EIS) revealed that the cell with the AEM experienced a threefold increase in ohmic resistance, attributed to the loss of functional groups. Additionally, an ion exchange capacity (IEC) analysis indicated that Sustainion lost approximately 20% of its ion exchange capacity. In contrast, the cell composed of CCS and Zirfon showed lower degradation. EIS data fitting demonstrated increased kinetic-related resistances while the ohmic resistance remained unchanged. This work presents a practical approach for comparing component degradation in AEM electrolysers.

Facile construction of polyacrylate membranes with pendent zwitterionic side-chains for high proton conduction

Designing high-performance proton exchange membranes for fuel cells has received tremendous interests and acquired plentiful fruits. However, the complicated preparation process and consequently high cost limit their practical application. This study endeavored to facilely construct a novel type of proton exchange membrane based on polyacrylates which decorated with pendant zwitterionic groups. Chemical structure and micro-morphology of these newly prepared membranes, namely SBPA-x (x = 0, 20, 30,40), were characterized by 1HNMR, FT-IR, XPS, SEM and AFM. Swelling ratio, water uptake and ion exchange capacity were found to be positively correlated with the contents of zwitterionic groups. The hydrophilic zwitterionic groups in the membrane formed a continuous water pathway, which contributed to the proton conductivity. Particularly, SBPA-40 membrane showed the highest proton conductivity of 78.6 mS/cm and the smallest activation energy Ea as 16 kJ/mol at 80 °C and 90 % relative humidity. On the other hand, the other application properties, such as thermal stability, mechanical property and oxidation stability, were also evaluated. Results demonstrated that all the membranes possessed good thermal stability within 300 °C and presented satisfactory mechanical performance by bending and twisting. Besides, the observed power density and open circuit voltage of SBPA-40 membrane were 58.3 mW/cm2 and 0.77 V at 30 °C. In conclusion, the zwitterionic polyacrylate membranes could have prospective application in proton exchange membrane fuel cells.

Functionalization of High-Density Polyethylene Capillaries for Open Tubular Ion Chromatography.

Ion chromatography is the anion analysis benchmark. A miniature form, Open Tubular Ion Chromatography (OTIC), has attractive attributes for efficient ion separations. Here, we fabricate and characterize high-density polyethylene (HDPE) open tubular anion exchange columns (OTCs). We attach positively charged latex particles onto negatively charged capillary surfaces. For efficient OTIC, column diameters need to be < ∼20µm; functionalizing the bore is challenging. Methods to introduce acid groups to an HDPE capillary bore, e.g., sulfonation using chlorosulfonic or sulfuric acid solutions, with or without grafting of an aromatic ring through photo- or chemical grafting first, are explored. Following quaternary ammonium latex attachment, the ion exchange capacity and separating abilities of each OTC were measured as an index of OTC performance. Gradual loss of capacity was observed for many of these; high-resolution mass spectrometry confirmed the leaching of detached oxidized/sulfonated oligomeric fragments and consequent poisoning of the latex sites. Ways to ameliorate this and/or to rejuvenate the columns are also described.