High Performance Anion Exchange Research Articles

Oxophilic gallium single atoms bridged ruthenium clusters for practical anion-exchange membrane electrolyzer

The development of highly efficient and durable alkaline hydrogen evolution reaction (HER) catalysts is crucial for achieving high-performance practical anion exchange membrane water electrolyzer (AEMWE) at ampere-level current density. Herein, we report a design concept by employing Ga single atoms as an electronic bridge to stabilize the Ru clusters for boosting alkaline HER performance in practical AEMWE. Experimental and theoretical results collectively reveal that the bridged Ga sites trigger strong metal-support interaction for the homogeneous distribution of Ru clusters with high density, as well as optimize the Ru–H bond strength due to the electron transfer between Ru and Ga for enhanced intrinsic HER activity. Moreover, the oxophilic Ga sites near the Ru clusters tend to adsorb the hydroxyl species and accelerate the water dissociation for sufficient proton supplement in an alkaline medium. The Ru–GaSA/N–C catalyst exhibits a low overpotential of 4 ± 1 mV (10 mA cm−2) and high mass activity of 9.3 ± 0.5 A mg−1Ru at −0.05 V vs RHE. In particular, the Ru–GaSA/N–C-based AEMWE in 1 M KOH delivers a voltage of only 1.74 V to reach an industrial current density of 1 A cm−2, and can steadily operate at 1 A cm−2 for more than 170 h.

Characterization of Histophilus somni sialic acid uptake mutant (ΔnanP-ΔnanU) using a mouse septicemia and mortality model

Histophilus somni is an important pathogen of the bovine respiratory disease complex, yet the mechanisms underlying its virulence remain poorly understood. It is known that H. somni can incorporate sialic acid into lipooligosaccharide (LOS), and sialylated H. somni is more resistant to phagocytosis and complement-mediated killing by serum compared to non-sialylated bacteria in vitro. However, the virulence of non-sialylated H. somni has not been evaluated in vivo using an animal model. In this study, we investigated the contribution of sialic acid to virulence by constructing an H. somni sialic acid uptake mutant (ΔnanP-ΔnanU) and comparing the parent and mutant strains in a mouse septicemia and mortality model. Intraperitoneal challenge of mice with wildtype H. somni (1 × 108 colony forming units/mouse, CFU) was lethal to all animals. Mice challenged with three different doses (1, 2, or 5 × 108 CFU/mouse) of an H. somni ΔnanP-ΔnanU sialic acid uptake mutant exhibited survival rates of 90 %, 60 %, and 0 % respectively. High-performance anion exchange chromatography analyses revealed that LOS prepared from both parent and the ΔnanP-ΔnanU mutant strains of H. somni were sialylated. These findings suggest the presence of de novo sialic acid synthesis pathway, although the genes associated with de novo sialic acid synthesis (neuB and neuC) were not identified by genomic analysis. The lower attenuation in mice is most likely attributed to the sialylated LOS of H. somni nanPU mutant.

High-Performance Anion Exchange Membrane Water Electrolyzers Enabled by Highly Gas Permeable and Dimensionally Stable Anion Exchange Ionomers.

Designing suitable anion exchange ionomers is critical to improving the performance and in situ durability of anion exchange membrane water electrolyzers (AEMWEs) as one of the promising devices for producing green hydrogen. Herein, highly gas-permeable and dimensionally stable anion exchange ionomers (QC6xBA and QC6xPA) are developed, in which bulky cyclohexyl (C6) groups are introduced into the polymer backbones. QC650BA-2.1 containing 50mol% C6 composition shows 16.6 times higher H2 permeability and 22.3 times higher O2 permeability than that of QC60BA-2.1 without C6 groups. Through-plane swelling of QC650BA-2.1 decreases to 12.5% from 31.1% (QC60BA-2.1)while OH- conductivity slightly decreases (64.9 and 56.2mScm-1 for QC60BA-2.1 and QC650BA-2.1, respectively, at 30 °C). The water electrolysis cell using the highly gas permeable QC650BA-2.1 ionomer and Ni0.8Co0.2O in the anode catalyst layer achieves two times higher performance (2.0Acm-2 at 1.69V, IR-included) than those of the previous cell using in-house ionomer (QPAF-4-2.0) (1.0Acm-2 at 1.69V, IR-included). During 1000h operation at 1.0Acm-2, the QC650BA-2.1 cell exhibits nearly constant cell voltage with a decay rate of 1.1µVh-1 after the initial increase of the cell voltage, proving the effectiveness of the highly gas permeable and dimensionally stable ionomer in AEMWEs.

Quaternized chitosan/polyvinyl alcohol anion exchange membrane enhanced by functionalized attapulgite clay with an ionic “chain-ball” surface structure

Biomass chitosan has garnered considerable interest for alkaline anion exchange membranes (AEMs) due to its eco-friendly and sustainable characteristics, low reactant permeability and easily modifiable nature, but it still faces the trade-off between high hydroxide conductivity and sufficient mechanical properties. Herein, a novel functionalized attapulgite clay (f-ATP) with a unique ionic “chain-ball” surface structure was prepared and incorporated with quaternized chitosan (QCS)/polyvinyl alcohol (PVA) matrix to fabricate high-performance composite AEMs. Due to the strengthened interfacial bonding between f-ATP nanofillers and the QCS/PVA matrix, composite membranes are synergistically reinforced and toughened, achieving peak tensile strength and elongation at break of 24.62 MPa and 33.8 %. Meanwhile, abundant ion pairs on f-ATP surface facilitate ion transport in the composite AEMs, with the maximum OH− conductivity of 46 mS cm−1 at 80 °C and the highest residual IEC of 83 % after alkaline treatment for 120 h. Moreover, the assembled alkaline direct methanol fuel cell exhibits a remarkable power density of 49.3 mW cm−2 at 80 °C. This work provides a new strategy for fabricating high-performance anion exchange membranes.

Surface-Displayed Mannanolytic and Chitinolytic Enzymes Using Peptidoglycan Binding LysM Domains.

Using Lactiplantibacillus plantarum as a food-grade carrier to create non-GMO whole-cell biocatalysts is gaining popularity. This work evaluates the immobilization yield of a chitosanase (CsnA, 30 kDa) from Bacillus subtilis and a mannanase (ManB, 40 kDa) from B. licheniformis on the surface of L. plantarum WCFS1 using either a single LysM domain derived from the extracellular transglycosylase Lp_3014 or a double LysM domain derived from the muropeptidase Lp_2162. ManB and CsnA were fused with the LysM domains of Lp_3014 or Lp_2162, produced in Escherichia coli and anchored to the cell surface of L. plantarum. The localization of the recombinant proteins on the bacterial cell surface was successfully confirmed by Western blot and flow cytometry analysis. The highest immobilization yields (44-48%) and activities of mannanase and chitosanase on the displaying cell surface (812 and 508 U/g of dry cell weight, respectively) were obtained when using the double LysM domain of Lp_2162 as an anchor. The presence of manno-oligosaccharides or chito-oligosaccharides in the reaction mixtures containing appropriate substrates and ManB or CsnA-displaying cells was determined by high-performance anion exchange chromatography. This study indicated that non-GMO Lactiplantibacillus chitosanase- and mannanase-displaying cells could be used to produce potentially prebiotic oligosaccharides.

Relationship between dietary fiber content and prebiotic potential of polysaccharides from the seaweeds of the North west coast of India

The macroalgae are a sustainable bioresource that can be harnessed for their functional food and nutraceutical applications. This study characterized the biochemical composition and bioactive potential of natural biological macromolecules, such as macroalgal polysaccharides extracted using a green, aqueous extraction process. The in-vitro antioxidant and antiglycemic activity of these polysaccharides were evaluated using model, free radical and antiglycemic compounds. The prebiotic potential of macroalgal polysaccharides were analysed based on their ability to promote the growth of two potential probiotic bacteria Lactobacillus acidophilus and L. bulgaricus and suppress the growth of enteric bacteria, Escherichia coli. Among the polysaccharides studied, the brown algal polysaccharide MPS8 MPS9 and MPS10 exhibited good antioxidant, antiglycemic and prebiotic activity. Based on infrared spectroscopy, the functional groups sulfation and carboxylation were identified in potential polysaccharides. The monosaccharide composition in the bioactive polysaccharides was determined using High Performance Anion Exchange Chromatography Pulse Amperometric detector (HPAEC-PAD). These bioactive polysaccharides were fractionated using ion exchange chromatography to purify it and further characterized using gel permeation chromatography and NMR spectroscopy. The results these polysaccharides are mainly composed of fucose and glucose which is due to the fucoidan and laminarin, respectively. Such macromolecules with high dietary fiber content and bioactivity are in global demand as functional food, nutraceutical and pharmaceutical formulations.

Non-precious high entropy alloys and highly alkali-resistant composite membranes based high performance anion exchange membrane water electrolyzers

Cost-effective highly efficient and stable catalysts and alkali-resistant anion exchange membranes (AEMs) are critical for practical applications of anion exchange membrane water electrolyzers (AEMWEs). Here, bifunctional non-precious FeCoNiCuMo high entropy alloys (HEAs), electrochemically deposited on nickel mesh as an anode (FeCoNiCuMo/NM) and on carbon paper as a cathode (FeCoNiCuMo/CP), together with a NiFe layered double hydroxide (LDH) loaded AEM (AEM/LDH), were developed for high performance AEMWEs. The AEMWE thus fabricated delivered an ultrahigh current density of 1777 mA cm−2 at 2 V and exhibited remarkable stability with a less than 0.1% cell voltage increase after a 100-hour operation at 100 mA cm−2 at 50 °C, largely outperforming those of the precious metal based AEMWE, composed of IrO2/NM as the anode and Pt/C/CP as the cathode, 1231 mA cm−2@2 V and 4.57% increase in cell voltages. Composition of the alkali-resistant, hydrophilic, and water electrolysis active NiFe LDH into the AEM improved not only the electrolyte uptake and operational stability, but also the efficiency of the AEMWE, with a 10% boost in current density achieved at 2 V and a reduction in cell voltage increases from 2.94% to 0.0951%. The present development demonstrates the practicality of AEMWEs toward green hydrogen production.

Analysis of unsaturated alginate oligosaccharides using high-performance anion exchange chromatography coupled with mass spectrometry.

Alginate is a commercially important polysaccharide composed of mannuronic acid and its C5 differential isomer guluronic acid. Comprehensive research on alginate and alginate lyases requires efficient and precise analytical methods for alginate oligosaccharides. In this research, high-performance anion exchange chromatography (HPAEC) in parallel with pulsed amperometric detection (PAD) and mass spectrometry (MS) was applied to the analysis of oligosaccharides obtained by alginate lyase. By optimizing the chromatographic conditions including mobile phase concentration, flow rate, and elution gradient, the analysis of a single sample could be completed in 30 min. Seven unsaturated alginate oligosaccharides were separated and identified through their analysis time observed with PAD, including all structurally different unsaturated disaccharides and trisaccharides. The quantitative analysis of seven oligosaccharides was performed based on the quantitative capability of PAD. The method exhibited adequate linearity and precision parameters. All the calibration curves showed good linearity at least in the concentration range of 0.002 to 0.1 mg/mL. The HPAEC-PAD/MS method provides a general and efficient online method to analyze alginate oligosaccharides.

High-Performance Asymmetric Porous Anion Exchange Membrane with Controllable Morphology via Solvent Evaporation and Water Etching

High-Performance Asymmetric Porous Anion Exchange Membrane with Controllable Morphology via Solvent Evaporation and Water Etching

A novel approach to the dual sugar test for the assessment of intestinal epithelium permeability in response to exertional heat stress and nutritional intervention

An acute increase in intestinal epithelium permeability is induced by prolonged exertion in the heat, resulting in the translocation of pathogenic bacteria and endotoxins from the lumen into the circulation, causing a systemic inflammatory response and debilitating symptoms(1). Acute exercise-induced gastrointestinal syndrome mimics chronic health conditions with which an impaired intestinal barrier function is associated, including coeliac disease, inflammatory bowel disease, diabetes, Alzheimer’s and liver diseases(2). Intestinal epithelium permeability is typically assessed using a dual sugar absorption test, by administering a drink containing non-metabolisable sugars (e.g. lactulose [L] and L-rhamnose [R]) that can enter the circulation by paracellular translocation when the epithelium is compromised, and are subsequently excreted and measured cumulatively in the urine(3). We aimed to demonstrate that our recently developed ion chromatography protocol(4) can be used to accurately quantify L/R ratio in the plasma of participants exercising in hot ambient conditions and to determine the impact of nutritional intervention on intestinal epithelium permeability. Further, we hypothesised that measuring L/R in plasma collected at intervals during the post-exercise recovery period would reveal more information about intestinal permeability compared to previously published cumulative urine L/R data(3). Endurance-trained participants completed a set of randomised crossover studies, consisting of 2 h running at 60% V˙O2max in temperate, warm and hot ambient conditions (n = 8) and/or in the heat while consuming water, carbohydrate or protein (n = 9). The dual sugar solution was ingested at 90 min of exercise and blood was sampled at 0, 1, 2 and 4 h post-exercise. Plasma sugars were quantified by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and L/R ratios were compared by two-way repeated measures ANOVA with Tukey’s multiple comparisons. Plasma L/R increased immediately post-exercise in the heat (0.15 ± 0.11) compared with temperate (0.06 ± 0.04, p<0.001) and warm (0.09 ± 0.08, p<0.01) conditions, while consuming glucose before and during exercise alleviated this (0.02 ± 0.02, p<0.001), and this novel information was otherwise missed when measuring urine L/R. Consuming glucose or whey protein hydrolysate during exercise attenuated intestinal permeability from exertional heat stress throughout recovery, with the mean plasma L/R over 4 h reduced from 0.11 ± 0.05 to 0.04 ± 0.03 (p<0.001) and 0.06 ± 0.04 (p<0.01) with glucose and protein, respectively. We recommend using the dual sugar test with quantification of plasma sugars at intervals by HPAEC-PAD to maximise intestinal permeability data collection in exercise gastroenterology research and beyond, as this gives additional acute response information compared to urinary measurements. Our approach can be employed to investigate and develop personalised nutrition strategies that prevent intestinal hyperpermeability during exertional heat stress. This has implications for athlete performance and safety, and can also build upon occupational health and safety practices and inform chronic disease management.

Investigating the effect of polyphenols from nuts on human carbohydrate digestion in vitro

Recent studies have documented the importance of postprandial hyperglycaemia in the incidence of chronic diseases, including type 2 diabetes. Inhibition of digestive enzymes, including membrane-bound brush-border α-glucosidases, leads to slowed carbohydrate digestion and absorption, and reduced postprandial glycemia. Nuts are widely eaten around the world and have the potential to inhibit α-glucosidases through their content of polyphenols and other bioactive compounds. According to our recent systematic review(1), no study has investigated the inhibitory effects of nut extracts on human α-glucosidase activities. Almost all studies in this area have been conducted on yeast α-glucosidase, with only a few using rat α-glucosidase. While there is no sequence homology between yeast and human α-glucosidase, there is 74% to 78% sequence homology between rat and human α-glucosidases(1). The lack of studies on the effect of bioactive compounds from nuts on human α-glucosidases, along with the growing attention to nuts as an important component of a healthy diet with the potential to reduce the risk of chronic diseases(2), highlights the need for research to evaluate the inhibitory effect of nut extracts on human α-glucosidases. The aim of the current study is to explore the inhibitory effect of extracts from nuts on human carbohydrate digestive enzymes. Walnuts and almonds were ground and defatted with hexane, extracted in 80% (v/v) acetone, and further purified using solid-phase extraction to obtain phenolic-rich extracts. The Folin–Ciocalteu assay was used to approximate the polyphenol content of the samples. Following our recently published detailed protocol(3), cell-free extracts from human intestinal Caco-2/TC7 cells were used as a source of α-glucosidase in enzyme inhibition assays, with sucrose, maltose and isomaltose as substrates and appropriate controls. The assay products were quantified using high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Glucose production in the presence of various concentrations of phenol-rich nut extracts was compared using a one-way ANOVA and half-maximal inhibitory concentration (IC50) values were calculated. The Folin–Ciocalteu data demonstrate that walnut extracts comprise a relatively high polyphenol content, with 18.1 ± 0.23 mg (epigallocatechin gallate [EGCG] equivalent) per gram of fresh weight, while almond extracts contain 0.87 ± 0.03 mg EGCG equivalent/g of fresh weight. The walnut phenolic-rich extract dose-dependently inhibited human intestinal sucrase and maltase activities (both p<0.01), with IC50 values of 1.67 mg/mL and 2.84 mg/mL, respectively. We demonstrate that phenolic-rich walnut extracts can inhibit human α-glucosidases in vitro and therefore walnuts may contribute to slowing carbohydrate digestion in humans. As such, we plan to assess the effects of walnuts on postprandial glycaemia in vivo.

Pt single atoms coupled with Ru nanoclusters enable robust hydrogen oxidation for high-performance anion exchange membrane fuel cells

Pt single atoms coupled with Ru nanoclusters enable robust hydrogen oxidation for high-performance anion exchange membrane fuel cells

Intrinsic microporous poly(phenyl-alkane)s with pendent piperazinium for high performance anion exchange membrane fuel cells

Exploring anion exchange membranes (AEMs) with high conductivity and satisfactory stability is very meaningful for the advancement of alkaline fuel cells. Herein, a novel class of intrinsic microporous AEMs with pendent piperazinium are systematically fabricated for alkaline fuel cell performance testing. Contorted and rigid spirobisindane backbone structure expands the free volume of AEMs, inducing broad and interconnected ion transport channels. This unique feature endows membranes a leading advantage for the efficient transmission of hydroxide ions. Consequently, the prepared membrane displays excellent normalized hydroxide conductivity of 78.99 mS g cm−1 mmol−1 at 80 °C. Meanwhile, the hydroxide conductivity degrades by only 8.3 % after treatment in 1 M NaOH for 1000 h at 80 °C. Moreover, the peak power density of H2/O2 single cell employing this membrane exhibits 1.06 W cm−2 at 80 °C and the cell can preserve 93.0 % of its initial voltage after operating for 18 h.

Revealing the structural changes of lignin in Chinese quince (Chaenomeles sinensis) fruit as it matures

Chinese quince fruits (Chaenomeles sinensis) contain substantial amounts of lignin; however, the exact structure of lignin remains to be investigated. In this study, milled wood lignins (Milled wood lignin (MWL)-1, MWL-2, MWL-3, MWL-4, MWL-5, and MWL-6) were extracted from fruits harvested once a month from May to October 2019 to investigate their structural evolution during fruit growth. The samples were characterized via High-performance anion exchange chromatography (HPAEC), Fourier transform–infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), thermogravimetric (TGA), pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) and NMR (2D-heteronuclear single quantum coherence (HSQC) and 31P). The MWL samples in all fruit growth stages were GS-type lignin and lignin core undergoing minimal alterations during fruit development. The predominant linkage in the lignin structure was β-O-4′, followed by β-β' and β-5′. Galactose and glucose were the main monosaccharides associated with MWL. In MWL-6, the lignin exhibited the highest homogeneity and thermal stability. As the fruit matured, a gradual increase in the β-O-4′ proportion and the ratio of S/G was observed. The results provide comprehensive characterization of the cell wall lignin of quince fruit as it matures. This study could inspire innovative applications of quince fruit lignin and provide the optimal harvest time for lignin utilization.

Quantification of Enzymatic Biofilm Removal Using the Sauerbrey Equation: Application to the Case of Pseudomonas protegens.

A methodology for the quantitative analysis of enzymatic removal of biofilms (BF) was developed, based on a quartz crystal microbalance (QCM) under stationary conditions. This was applied to the case of Pseudomonas protegens (PP) BFs, through a series of five enzymes, whose removal activity was screened using the presented methodology. The procedure is based on the following: when BFs can be modeled as rigid materials, QCM can be used as a balance under stationary conditions for determining the BFs mass reduction by enzymatic removal. For considering a BF as a rigid model, energy dissipation effects, associated with viscoelastic properties of the BF, must be negligible. Hence, a QCM system with detection of dissipation (referred to as QCM with dissipation) was used for evaluating the energy losses, which, in fact, resulted in negligible energy losses in the case of dehydrated PP BFs, validating the application of the Sauerbrey equation for the change of mass calculations. The stationary methodology reduces operating times and simplifies data analysis in comparison to dynamic approaches based on flow setups, which requires the incorporation of dissipation effects due to the liquid media. By carrying out QCM, glycosidase-type enzymes showed BF removal higher than 80% at enzyme concentration 50 ppm, reaching removal over 90% in the cases of amylase and cellulase/xylanase enzymes. The highest removal percentage produced a reduction from about 15 to 1 μg in the BF mass. Amylase enzyme was tested from below 50 to 1 ppm, reaching around 60% of removal at 1 ppm. The obtained results were supported by other instrumental techniques such as Raman spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, high performance anion exchange chromatography, thermogravimetric analysis, and differential scanning calorimetry. The removal quantifications obtained with QCM were compared with those obtained by well-established screening techniques (UV-vis spectrophotometry using crystal violet and agar diffusion test). The proposed methodology expands the possibility of using a quartz microbalance to perform enzymatic activity screening.

Label-Free Liquid Chromatography-Mass Spectrometry Quantitation of Relative N- and O-Glycan Concentrations in Human Milk in Japan.

Human milk is abundant in carbohydrates and includes human milk oligosaccharides (HMOs) and N/O-glycans conjugated to proteins. HMO compositions and concentrations vary in individuals according to the maternal secretor status based on the fucosyltransferase 2 genotype; however, the profile of N/O-glycans remains uninvestigated because of the analytical complexity. Herein, we applied a label-free chromatography-mass spectrometry (LC-MS) technique to elucidate the variation in the composition and concentration of N/O-glycans in human milk. We used label-free LC-MS to relatively quantify 16 N-glycans and 12 O-glycans in 200 samples of Japanese human milk (1-2 months postpartum) and applied high performance anion exchange chromatography with pulsed amperometric detection to absolutely quantify the concentrations of 11 representative HMOs. Cluster analysis of the quantitative data revealed that O-glycans and several HMOs were classified according to the presence or absence of fucose linked to galactose while N-glycans were classified into a different group from O-glycans and HMOs. O-glycans and HMOs with fucose linked to galactose were more abundant in human milk from secretor mothers than from nonsecretor mothers. Thus, secretor status influenced the composition and concentration of HMOs and O-glycans but not those of N-glycans in human milk.

Hollow Cuboidal Metal Oxide-Based Asymmetric Electrode Configuration for High-Performance Anion Exchange through Quaternized Pyridine-Poly(vinyl alcohol) @ Metal Hydroxide Nanosheets for Water Dissociation

Hollow Cuboidal Metal Oxide-Based Asymmetric Electrode Configuration for High-Performance Anion Exchange through Quaternized Pyridine-Poly(vinyl alcohol) @ Metal Hydroxide Nanosheets for Water Dissociation

Solvent Effects on the Catalyst Ink and Layer Microstructure for Anion Exchange Membrane Fuel Cells.

Understanding the complex solvent effects on the microstructures of ink and catalyst layer (CL) is crucial for the development of high-performance anion exchange membrane fuel cells (AEMFCs). Herein, we study the solvent effects within the binary solvent ink system composed of water, isopropyl alcohol (IPA), commercial anion exchange ionomer, and Pt/C catalyst. The results show that the Pt/C particles and ionomer tend to form large aggregates wrapped with a thick ionomer layer in IPA-rich ink and promote the formation of large mesopores within the CL. With the increase of the water content in the ink, Pt/C particles are more likely to bridge to each other through wrapped FAA to form a well-connected three-dimensional network. The CL fabricated using water-rich ink shows smaller pores, higher porosity, and a more homogeneous ionomer network without the formation of large aggregates. Based on these results, we propose that the properties of the solvent mixture, including dielectric constant (ε) and solubility parameter (δ), affect the coulomb interaction of charged particles and surface tension at interfaces, which in turn affects the microstructure of ink and CL. By leveraging the solvent effects, we optimize the CL microstructures and improve the performance of AEMFC. These results may guide the rational design and fabrication of AEMFCs.

Poly(fluorenyl alkylene)-based anion exchange membranes for high-performance water electrolysis

Durable and high-performance anion exchange membranes (AEMs) are a pivotal issue for the industrial application of AEM water electrolysis (AEMWE). In this study, a series of poly(fluorenyl alkylene) copolymers with different contents of biphenyls and p-terphenyls are synthesized for the high-performance AEMWE. The resulting AEM with an appropriate content of p-terphenyl well facilitates the microphase separation to get a well-defined microstructure that effectively improves the ionic conductivity and reduces the swelling ratio. The AEM with 20% p-terphenyl possesses an OH– conductivity of 155.7 mS cm−1, a water uptake of 128.7%, and a swelling ratio of 33.8% at 80 °C. Moreover, it also shows durable alkaline stability and retains 83.5% of cationic groups after immersing in 5 M NaOH at 80 °C for 1440 h. The assembled AEMWE cell achieves an excellent current density of 4.9 A cm−2 at 2 V in 1 M KOH (80 °C) and 2200 h of long-term constant current (1 A cm−2) operation with a low voltage rising rate of 77 μV h−1. After this long-term operation, only 13.7% of cationic groups are degraded in the AEM, showing excellent in-situ durability. Therefore, the developed AEMs should have great potential for applications in the AEMWE.

(Poster Award - Honorable Mention) Durable Polybenzimidazole Anion Exchange Membranes for Alkaline Water Electrolyzers

Water electrolysis under alkaline conditions allows the use of inexpensive non-platinum-group catalysts such as nickel.1, 2 Conventional alkaline electrolyzers usually employ a highly concentrated aq. KOH solution as electrolyte (5-7 M) with a porous diaphragm as separator. Alternatively, protolysable polymers such as polybenzimidazole (PBI) may be swollen with electrolyte and used as ion-solvating membranes.2, 3 However, the chemical stability of the polymers can become a serious issue under these harsh conditions. Operation under more dilute conditions, e.g., up to 2 M KOH, may bring the benefits of the alkaline conditions combined with a longer cell lifetime. Under these conditions, aliphatic cyclic quaternary ammonium (QA) cations, such as piperidinium, have shown excellent stability.In the present work, performed as part of the EU project “NEXTAEC”, we have designed and synthesized m-PBI grafted with mono- and bis-piperidinium functionalized side chains, respectively (Figure 1a-b). AEMs were prepared from polymers with varying ion exchange capacities and studied at 80 °C containing KOH solutions in the concentration range 0.5-2 M KOH. The membranes were characterized with respect to, e.g., electrolyte solution uptake, alkaline stability, and electrolyser performance (Figure 1c). The uptake showed a strong inverse correlation with KOH concentration, which also affected the electrochemical performance. The stability as evaluated by 1HNMR spectroscopy was excellent showing, in the worst case, less than 8 % ionic loss after 6 months storage in 2 M KOH at 80 °C. Li, D.; Park, E. J.; Zhu, W.; Shi, Q.; Zhou, Y.; Tian, H.; Lin, Y.; Serov, A.; Zulevi, B.; Baca, E. D.; Fujimoto, C.; Chung, H. T.; Kim, Y. S., Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers. Nature Energy 2020, 5 (5), 378-385.Aili, D.; Kraglund, M. R.; Rajappan, S. C.; Serhiichuk, D.; Xia, Y.; Deimede, V.; Kallitsis, J.; Bae, C.; Jannasch, P.; Henkensmeier, D.; Jensen, J. O., Electrode Separators for the Next-Generation Alkaline Water Electrolyzers. ACS Energy Letters 2023, 8 (4),1900-1910.Aili, D.; Yang, J.; Jankova, K.; Henkensmeier, D.; Li, Q., From polybenzimidazoles to polybenzimidazoliums and polybenzimidazolides. Journal of Materials Chemistry A 2020, 8 (26), 12854-12886.Marino, M. G.; Kreuer, K. D., Alkaline stability of quaternary ammonium cations for alkaline fuel cell membranes and ionic liquids. ChemSusChem 2015, 8 (3), 513-23. Figure 1