Ion Exchange Research Articles

Preparation and Characterization of Nanocellulose/Sulfonated Poly(Ether Imide) Composite Membrane and Its Application as Proton Exchange Membrane

ABSTRACTThe TEMPO‐oxidized cellulose nanofibril (CNF) membrane is combined with sulfonated poly(ether imide) (SPEI) using the solution impregnation method to enhance its proton exchange membrane properties. SPEI solutions with different sulfonation levels, SPEI1, SPEI2, SPEI4, and SPEI5, are prepared by adjusting the acetyl sulfate to PEI mole ratios from 1:1 to 2:1, 3:1, 4:1, and 5:1, respectively. The CNF membranes are immersed in each SPEI solution for 24 h and hot‐pressed at 100°C for 1 h to form composite membranes. The chemical structure, morphology, wettability, and membrane characteristics are analyzed. The wettability of SPEI on the CNF surface varies with sulfonation degree, and it affects the morphology of each CNF‐SPEI membrane. Consequently, proton conductivity and ion exchange capacity (IEC) increase, while methanol permeability decreases with increasing sulfonation levels. The CNF‐SPEI5 membrane exhibits the highest proton conductivity of 4.23 mS.cm−1 and the lowest methanol permeability at 6.67 × 10−7 cm2.s−1. Additionally, the CNF‐SPEI4 membrane achieves maximum tensile strength and flexibility at 4.91 ± 0.09 MPa and 15.05% ± 0.24%, respectively. While its proton conductivity still faces challenges, the CNF/SPEI membrane demonstrates better methanol permeability suppression than Nafion 117 (1.31 × 10−6 cm2.s−1) and superior dimensional stability compared with the pristine CNF membrane.

Promoting CO2 Electroreduction over ion-exchange resin-derived Ni-N-C catalyst with sulfur doping.

The utilization of renewable energy for electrocatalytic carbon dioxide reduction reaction (CO2RR) represents a pivotal technology in sustainable carbon conversion. Single-atom catalysts (SACs) featuring transition metal-nitrogen-carbon (M-N-C) structures have demonstrated exceptional electrocatalytic efficacy in CO2RR by maximizing atom efficiency. Nevertheless, further investigation is warranted to optimize the catalytic performance of SACs through the selection of suitable carbon sources and supports, as well as the modulation of the microenvironment surrounding individual metal atoms. In this study, a sulfur-doped Ni-N-C catalyst was prepared using a two-step strategy involving metal ion adsorption and thermal decomposition, with porous ion exchange resin serving as the carbon source. Due to the uniform distribution of single atom active centers on the resin-based carbon support and sulfur doping, this catalyst efficiently converts CO2 into CO with a Faradaic efficiency exceeding 90% within the range of -0.79 ~ -1.29 V (vs. RHE), reaching a maximum value of 97.7% (-0.79 V vs. RHE). Theoretical calculations indicate that second-shell sulfur doping effectively promotes coupled transfer of protons and electrons, leading to a significant reduction in Gibbs free energy barriers for CO2RR intermediate products.

Removal of Pb(II), Cr(III), Co(II), Cu(II) cations from aqueous solutions using tetraethylenepentamine-functionalized HY cubic zeolite: optimization, characterization, and mechanistic insights.

This research utilized tetraethylenepentamine-functionalized HY cubic zeolite as an adsorbent to effectively remove heavy metals from aqueous solutions. The adsorbent was characterized using FT-IR, XRD, TGA, FE-SEM, and EDS-MAP techniques. The synthesis aimed to optimize and evaluate the removal efficiency of Pb(II), Cr(III), Co(II), and Cu(II) from aqueous solutions by investigating key parameters, including initial pH, concentration, adsorbent dosage, and contact time. The results indicate that the highest adsorption capacities for each metal follow the order: Pb(II) > Cr(III) > Co(II) > Cu(II), with respective percentages of 99.7%, 98.2%, 95.1%, and 92.4%. Analysis of the batch systems reveals that the equilibrium data for Pb(II), Cr(III), Co(II), and Cu(II) align well with the Langmuir and Freundlich isotherms also show a good fit, with correlation coefficients (R2) higher than 0.9335 and 0.9478, respectively. The maximum adsorption capacities (181.82, 175.44, 169.49, and 158.73mg/g) reflect the nature of the adsorption process. Kinetic studies for Pb(II), Cr(III), Cu(II), and Cu(II) yielded correlation coefficients (R2) higher than 0.9971. These high R2 values suggest that the experimental data closely fit a pseudo-second-order model, indicating a two-step adsorption mechanism. Heavy metal removal is attributed to ion exchange and chemisorption within the zeolite pores, involving interactions with nitrogen lone pairs.

Detecting and repairing micro defects in perfluorinated ion exchange membranes for redox flow batteries

Ion exchange membranes play a vital role in redox flow batteries. However, polymer membranes with a microscopic thickness of approximately 20–50 μm are susceptible to micro defects, which substantially reduces the battery's energy efficiency and cycling stability. Hence, there is a need for an effective strategy to identify and resolve membrane imperfections, which is currently missing in the literature. In this work, a pressure-retention setup and hot-pressing method are proposed and show that defective membranes can be effectively identified and resolved. For instance, a membrane with around 100-μm pinholes exhibits a low coulombic efficiency of 77.5 % at the current density of 100 mA cm−2. However, the coulombic efficiency can be raised to 96.3 % by removing the defects, thus attaining the level of the undamaged pristine membrane (96.4 %). The capacity retention rate of the vanadium redox flow batteries with the repaired membrane is 71.1 % over 100 cycles at the current density of 200 mA cm−2, close to that of the pristine membrane (72.2 %). In addition, the repaired membrane exhibits quite similar physicochemical properties to the pristine membrane from various characterizations. The proposed method represents a convenient, economical, and non-destructive membrane detecting and repairing strategy, demonstrating great potential for redox flow batteries.

Emerging roles of mechanosensitive ion channels in ventilator induced lung injury: a systematic review

BackgroundThe pathogenetic mechanisms of ventilator-induced lung injury (VILI) still need to be elucidated. The mechanical forces during mechanical ventilation are continually sensed and transmitted by mechanosensitive ion channels (MSICs) in pulmonary endothelial, epithelial, and immune cells. In recent years, MSICs have been shown to be involved in VILI.MethodsA systematic search across PubMed, the Cochrane Library, Web of Science, and ScienceDirect was performed from inception to March 2024, and the review was conducted in accordance with PRISMA guidelines. The potential eligible studies were evaluated by two authors independently. Study characteristics, quality assessment, and potential mechanisms were analyzed.ResultsWe included 23 eligible studies, most of which were performed with murine animals in vivo. At the in vitro level, 52% and 48% of the experiments were conducted with human or animal cells, respectively. No clinical studies were found. The most reported MSICs include Piezo channels, transient receptor potential channels, potassium channels, and stretch-activated sodium channels. Piezo1 has been the most concerned channel in the recent five years. This study found that signal pathways, such as RhoA/ROCK1, could be enhanced by cyclic stretch-activated MSICs, which contribute to VILI through dysregulated inflammation and immune responses mediated by ion transport. The review indicates the emerging role of MSICs in the pathogenesis of VILI, especially as a signal-transmitting link between mechanical stretch and pathogenesis such as inflammation, disruption of cell junctions, and edema formation.ConclusionsMechanical stretch stimulates MSICs to increase transcellular ion exchange and subsequently generates VILI through inflammation and other pathogeneses mediated by MSICs signal-transmitting pathways. These findings make it possible to identify potential therapeutic targets for the prevention of lung injury through further exploration and more studies.Systematic review registrationhttps://inplasy.com/inplasy-2024-10-0115/, identifier INPLASY2024100115.

Cd adsorption prediction of Fe mono/composite modified biochar based on machine learning: Application for controllable preparation

In this study, artificial neural network (ANN) and random forest (RF) were constructed to predict the Cd adsorption capacity of Fe-modified biochar. The RF model outperformed ANN model in accuracy and predictive performance (R2 = 0.98). Through the contribution factors analysis of SHAP, structural characteristics (55.44%) were most important of Fe composite-modified biochar (CBC). And CBC have the best adsorption performance when C, Fe, O, H, N, and pH content were <50%, 10–20%, 10–20%, 0.5–1%, 0–2%, and >10, respectively. The Fe-Ca modified biochar (FeCa-BC) of different raw materials (wheat straw, corn straw and walnut shell) were successfully prepared according to the ML results, and the experimental data of FeCa-BC verified the accurate predictive ability of RF model (R2 = 0.89). The developed GUI toolbox results showed that the error between predicted and actual values was less than 5% based on the training set, testing set, and experimental validation set. The analysis of FTIR, XRD and XPS indicated that surface complexation, precipitation, and ion exchange were the main Cd adsorption mechanisms of FeCa-BC. This work presents new insights for the targeted preparation of functional biochar and its application in contaminated water through ML.

All-in-one dual-function porous materials derived from polyacrylonitrile for high-performance supercapacitor

Polyacrylonitrile (PAN)-based multifunctional energy storage materials have garnered significant interest in the research community. However, developing multifunctional PAN porous materials for integrated supercapacitors has encountered challenges such as low energy density, insufficient separator wettability, and limited ion conductivity. Herein, two types of versatile PAN-based dual-function porous membranes with varying pore sizes were fabricated using straightforward techniques involving solvent exchange and a directed freezing freeze-drying process. Subsequently, a high-performance-separator (POS) was developed by modifying pristine porous PAN with tetraethoxysilane (TEOS). Energy storage materials (CPAN-MnO2) were fabricated by depositing MnO2 onto the porous carbonised PAN (CPAN) surface through electrodeposition. The resulting structure, with CPAN-MnO2 as the energy storage unit and POS as the separator, achieved an impressive ion conductivity of 32.2 mS cm−1, super hydrophilicity, and high electrolyte uptake (456 %) and retention (302 %). A symmetric supercapacitor (SC) using CPAN-MnO2 and POS demonstrated a maximum energy density of 163 μWh cm−2 and exceptional cyclic stability, with 93.6 % capacitance retention after 10,000 cycles. This superior energy storage performance can be attributed to the TEOS-modified PAN porous channels, which enhance wettability with the electrolyte, improving electrolyte uptake and retention within the porous framework for ion exchange, thereby enhancing the electrochemical performance.

Dynamic simulation-driven analysis of cadmium, nickel, cobalt, and iron adsorption mechanisms in zeolite LTA synthesized from Bentonite

A practical and cost-effective method was successfully developed for synthesizing high-performance zeolite LTA from bentonite clay by fine-tuning activation steps and crystallization parameters. The optimal synthesis conditions and crystallization mechanism were investigated. The synthesized zeolites were characterized using XRD, FTIR, and SEM-EDS techniques. The results highlight the significant influence of factors such as crystallization temperature, duration, and the effect of sodium hydroxide concentration on the formation of zeolites. Optimal conditions set at a crystallization temperature of 97°C, duration of 24 hours, and NaOH concentration of 4M yielded pure zeolite LTA, boasting high crystallinity levels. Achieving a peak crystallinity of 82%. The obtained zeolite LTA showed an exceptional Cd (II) ion exchange capacity. A mechanism involving adsorption of Cd2⁺, Ni2⁺, Co2⁺, and Fe2⁺ ions in zeolite LTA at the α and β-cages has been proposed using dynamic simulation. This mechanism supports all experimental results, in particular for LTA- Cd2⁺, Cd2⁺ ions are predominantly distributed in both α and β-cages, with a denser distribution in the α-cages, indicating a strong preference for these sites due to their geometric and electronic environment. The resulted zeolite LTA demonstrated ability for successful Cd (II) removal, affirming its utility as an efficient material in environmental remediation industries.

Enhanced Cr(vi) removal by Co and PPy co-modified Ca-Al-layered double hydroxides due to adsorption and reduction mechanisms.

Co and polypyrrole co-modified hierarchical CaAl-LDH microspheres (CCALP) were synthesized via hydrothermal and in situ polymerization methods. The synergistic effect of PPy and Co endowed CCALP with higher surface area and more reduction sites than CaAl-LDHs modified by Co or PPy alone, maintaining good recyclability for Cr(vi) removal efficiency over four cycles without any treatment. Compared to Co, PPy doping was the dominant reason for Cr(vi) reduction on CCALP. Under optimized conditions, the theoretical maximum adsorption capacity reached 845.25 mg g-1, and the removal efficiency of Cr(vi) achieved 98.83%. The Langmuir model fitted well with the Cr(vi) adsorption on CCALP, supporting the monolayer adsorption hypothesis. The adsorption process followed the Avrami fractional kinetics (AFO) model, suggesting complex and multiple kinetic stages. Thermodynamic experiments confirmed that the adsorption was a spontaneous exothermic process. The density functional theory (DFT) and electrostatic potential (ESP) calculations confirmed that the oxygen-containing parts of Cr2O7 2- and HCrO4 - were the affinity sites, and the co-doping of Co and PPy significantly improved the Cr(vi) adsorption energy on CCALP. Therefore, the Cr(vi) removal mechanism on CCALP was proposed with electrostatic interaction, ion exchange, complexation and reduction.

Catalytic Transformation of Biomass-Derived Hemicellulose Sugars by the One-Pot Method into Carboxylic Acids Using Heterogeneous Catalysts

This article presents the conditions for the transformation of pulp containing mixtures that occur in the hemicellulose fraction derived from lignocellulosic biomass. Selected materials with strong acid centers were used as catalytic materials: ion exchange resins, including AMBERLYST 15(H) and DOWEX DR-G8(H), and selected zeolite in the hydrogen form of the Beta type (H-BEA). The group was marked with the abbreviations M1, M2 and M3, where it differs in the content of xylose, mannose, galactose, glucose, rhamnose and uronic acids. The catalytic process was carried out in the reactor as a one-pot technique at temperatures of 180–250 °C for 1–5 h. Based on the collected results, the transformation products of hemicellulose pulp were determined and the catalytic abilities of selected materials were determined. The proposed conditions led to the production of organic acids. Levulinic acid was obtained with a selectivity of 25.95% after 1 h of the process at a temperature of 250 °C with the participation of H-BEA, and lactic acid was obtained with a selectivity of 73.28% after 5 h of the process at a temperature of 250 °C using DOWEX DRG8(H). The presence of oxalic, propionic and acetic acids was also observed.

Effect of inorganic component of biochar on lead adsorption performance and the enhancement by MgO modification.

Biomass-derived biochar has enormous potential for sustainable and low-cost treatment of lead-contained wastewater. In this study, corncob and cow dung-derived biochar were prepared. The increase in pyrolysis temperature could improve the porous structures, surface area, functional groups and alkalinity, and further provide a higher Pb2+ capacity in both biochars. Cow dung biochar performed better than corncob for its higher inorganic mineral content and more alkaline surface. Among them, CDB-600 performed the Langmuir maximum capacity of 357.1 mg/g, with a high surface area of 144.3 m2/g; ion exchange and precipitate were the main adsorption mechanisms. After further MgO modification, the M-CDB displayed a high surface area of 166 m2/g, and ion exchangeability and precipitate-promoting effects were improved. M-CDB performed a Langmuir maximum capacity of 833.3 mg/g. The pHpzc was found to be 10 and the adsorbents portray a very good Pb2+ adsorption selectivity among coexisting ions in the solution. The adsorption process was found to be endothermic, feasible, spontaneous and chemisorption. The fixed lead on CDB-600 was stable in water. The immobilized lead could be desorbed by acid wash. CDB-600 performed better in terms of sustainability in use, which could support its continuous application ability.

Efficient in situ synthetic routes of the polymeric composite containing clinoptilolite using ultrasonic assistance for sorption of some lanthanides

The ultrasound assistance synthesis strategy of the polymeric composite is based on free radical polymerization of polyallylamine hydrochloride (PAH) cationic polyelectrolyte, with vinyl sulfonic acid (VSA) anionic monomer with microporous crystalline alumino silicate clinoptilolite clay. The P(AH-co-VSA)/clinoptilolite polymeric composite was fully characterized by fourier transform infrared spectroscopy, energy dispersive X-ray, thermogravimetric analysis, and scanning electron microscope. FTIR demonstrated the presence of PAH and VSA, confirming the composition of the prepared composite. It was also used to map the energy-dispersive X-ray to affirm the interdependence of the clinoptilolite into the polymeric matrix. Consequently, the physicochemical characteristics of this copolymer may be adjusted using VSA and PAH suitable combinations. Batch experiments were applied and maximal sorption capacities for studied ions Nd3+, Ce3+, Y3+, Gd3+, and Eu3+ were 36.6, 50.2, 55.9, 57.2, and 57.7 mg/g, respectively. Sorption kinetics and equilibrium isotherm were conducted. Experimental isotherms of studied ions were successfully fit to pseudo-second-order model, langmuir isotherm model. The Dubinin–Radushkevich (D–R) isotherm was found to be applicable and suggesting that, the sorption occurs via a ion exchange reaction. The breakthrough data were measured in a fixed bed column, and variable process factors were examined, including bed depth, flow velocity, and initial metal ion concentration. The experimental work was then focused, for continuous investigations, on Ce3+, Eu3+, and Y3+ to represent light, intermediate, and heavy lanthanides respectively. The overall bed capacity and total metal ion adsorption increased when the flow rate increased. They reduced with rising initial metal ion concentration and bed depth, and reached 22.8, 31.4, and 28.5 mg/g for Ce3+, Eu3+, and Y3+ metal ions, respectively.

Application of Natural and Modified Zeolite Sediments for the Stabilization of Cadmium and Lead in Contaminated Mining Soil

Soil contamination by many kinds of anthropogenic operations, such as industrial and mining activities, results in the accumulation of various heavy metal contaminants in the environment. Cadmium (Cd) and lead (Pb) are commonly found heavy metals in the Mahad Adahab mining area in Saudi Arabia. In this study, natural and modified zeolite sediments were fractioned by size to nano- and macrosizes and were applied to stabilize Cd and Pb from contaminated mining soil. Among the tested adsorbents, zeolite sediment in the nanosize that was modified by layered double hydroxides (LDH-N) showed the highest sorption and removal efficiency (&gt;98%) for Cd and Pb, followed by nanosized natural zeolite (NZ-N) and HCl-modified nanosized natural zeolite sediment (HCl-N), which removed &gt;90% Cd and Pb from contaminated soil. A pH of 7 was found to be optimal for Cd and Pb sorption, and the kinetics study revealed that first-order and pseudo-second-order kinetic models best fitted the experimental data (R2 = 0.94–0.98) for Cd and Pb sorption by the tested sediments. An incubation period of 16 weeks revealed that LDH-N, HCl-N, and NZ-N reduced the ammonium acetate extractable fraction of Cd by 89.26, 83.70, and 80.54% and Pb by 86.19, 81.42, and 77.98%, respectively. Electrostatic interaction and ion exchange were found to be the principal mechanisms for Cd and Pb sorption. The findings of this study indicate that the utilization of modified zeolite sediment in the nanosize fraction (LDH-N, HCl-N, and NZ-N) could be an effective and feasible strategy in stabilizing heavy metals and mitigating their toxicity in contaminated mining soil.

In vitro analysis of a competitive inhibition model for T7 RNA polymerase biosensors

T7 RNA polymerase (T7 RNAP) biosensors, in which T7 RNAP transcribes some reporter gene or signal in response to external stimuli, have wide applications in synthetic biology and metabolic engineering. We adapted a biochemical reaction network model and used an in vitro transcription assay to determine network parameters for different T7 RNAP constructs. Under conditions where template DNA is limiting, the EC50 values of native and engineered T7 RNAPs ranged from 33 nM (29–37 95 % c.i.) to 570 nM (258–714 95 % c.i.) (wild-type T7 RNAP). The measured EC50 values were largely insensitive to free magnesium, pH, or other buffer conditions. Many biosensor configurations use a split RNAP construct, where the C-terminal (CT7) and N-terminal T7 (NT7) are fused to proximity induced dimerization modules. We used proteolysis and ion exchange chromatography to prepare a CT7 (80 kDa) product. The impact of free CT7 on T7 RNAP transcriptional activity was well described by a competitive inhibition model, with an inhibitory constant KI = 23 nM (18–28 95 % c.i.) of the sensor. These model parameters will be useful for forward modeling and design of T7 RNAP-based genetic circuits.

Adsorption efficiency and photocatalytic activity of silver sulphide-activated carbon (Ag2S-AC) composites

BackgroundThis study investigates the adsorption efficiency and photocatalytic activity of silver sulphide-activated carbon (Ag2S-AC) composites derived from ground coffee waste (GCW). MethodsIn this work, GCW was preceding to carbonized at 500 ± 2°C for hours and formed biochar. Then, GCW was subjected to activation using hydrochloric acid (HCl), phosphoric acid (H3PO4) and potassium hydroxide (KOH). The mixture was left to soak for 24 h at room temperature, followed by carbonization at 350 and 500˚C. In the meantime, the silver sulphide (Ag2S) was synthesized by using an ion exchange method. Sodium sulphide (Na2S) was used as sulphur source and mixed with silver nitrate (AgNO3) and sodium citrate (NaCit) for two hours, then dried in oven at 50 ± 2°C for 10 h. Next, the carbonized AC was subsequently combined with synthesized silver sulphide, resulting in the creation of Ag2S-activated carbon composites that functioned both as adsorbent and photocatalyst. Their capabilities as adsorbents and photocatalyst were studied by using copper ions (Cu2+) and methylene blue (MB) solution. Significance findingsBased on results, GCW and all the prepared activated carbons are in the amorphous phase, except for the Ag2S-AC composites, where the Ag2S peak reflection can be observed from the X-ray diffraction (XRD) pattern. GCW shows rough and dense surface morphology. The AC shows different pore sizes and structures depending on the chemical activators used, where AC-KOH shows the largest pore size (165.31 μm). The existence of micropores can be observed in all the activated carbon samples. For the adsorption of Cu2+, all samples show more than 99 % of the removal efficiency. While for photocatalytic testing, the Ag2S-H3PO4 sample shows the highest degradation rate (97.7 %) of MB solutions.

Cloning of the Thermus thermophilus methionine aminopeptidase gene and confirmation of the enzyme functional activity

Background. Methionine aminopeptidases (MAPs) are a class of enzymes that catalyze the removal of the N-terminal initiator methionine from a polypeptide chain. Bacterial MAPs are considered as targets for the development of broad-spectrum antibacterial drugs, and using MAPs in biotechnology necessitates the search for new MAPs and the study of their functioning and inhibition mechanisms.The aim of the study. To identify methionine aminopeptidase in the Thermus thermophilus genome (Tt-MAP) and to confirm its functional activity.Materials and methods. To identify Tt-MAP, we analyzed the Thermus thermophilus genome in the GeneBank database. Modern genetic engineering techniques (polymerase chain reaction, restriction, transformation, heterologous expression) were used to clone the putative open reading frame (ORF) encoding Tt-MAP in the pHUE vector. Various chromatography techniques (affinity, ion exchange, and size-exclusion) were used to obtain a purified enzyme preparation. The fluorogenic substrate L-methionine 7-amino-4-methylcoumarin (Met-AMC) was used to confirm the specific functional aminopeptidase activity of the enzyme.Results. An ORF encoding MAP was identified in the Thermus thermophilus bacterium genome. Oligonucleotide primers were designed based on the nucleotide sequence. The ORF was cloned in the vector, and the recombinant enzyme was produced in E. coli cells. A method for purifying the enzyme to a homogeneous state was developed using a series of sequential chromatographies, allowing up to 30 mg to be obtained from 1 liter of culture. Using the fluorogenic substrate Met-AMC, the specific functional activity of the enzyme was demonstrated (the enzyme cleaves methionine from the substrate).Conclusion. We have identified the Thermus thermophilus MAP and tested its functional activity. It has been shown that the ORF product TTHA1670 encodes a methionine-specific aminopeptidase, i. e. methionine aminopeptidase. The enzyme can be used in various fields of biotechnology and scientific research.

Functional Assessment of Rat Sciatic Nerve Regeneration Using a Nerve Conduit Based on Ion Exchange Membrane.

The problem with modern nerve conduits is inability to transmit nerve impulses to the distal part of the damaged nerve. Cationic conductivity is a necessary characteristic of the nerve conduit ensuring effective regeneration of the peripheral nerves. We performed a functional assessment of the regeneration of rat sciatic nerve using a nerve conduit based on an ion-exchange membrane. A sciatic nerve defect was experimentally simulated in Wistar rats with further implantation of the LF-4SK membrane. On days 60 and 90 after surgery, the sciatic functional index and the ratio of the shin girth of the operated limb to the intact limb were calculated; on day 90, an electrophysiological assessment of nerve recovery was carried out. The results of the study showed that the conduit based on the LF-4SK membrane optimizes the functional recovery of the sciatic nerve defect.

Structural Disorder of a Layered Lithium Manganese Oxide Cathode Paving a Reversible Phase Transition Route toward Its Theoretical Capacity.

Layered lithium manganese oxides suffer from irreversible phase transitions induced by Mn migration and/or dissolution associated with the Jahn-Teller effect (JTE) of Mn3+, leading to inevitable capacity fading during cycling. The popular doping strategy of oxidizing Mn3+ to Mn4+ to relieve the JTE cannot completely eliminate the detrimental structural collapse from the cooperative JTE. Therefore, they are considered to be impractical for commercial use as cathode materials. Here, we demonstrate a layered lithium manganese oxide that can be charged and discharged without any serious structural collapse using metastable Li-birnessite with controlled structural disorder. Although Li-birnessite is thermodynamically unstable under ambient conditions, Li ion exchange into Na-birnessite followed by an optimal dehydration resulted in a disordered Li-birnessite. The control over crystal water in the interlayer provides intriguing short-range order therein, which can help to suppress parasitic Mn migration and dissolution, thereby ensuring a reversible electrochemical cycling. The Mn redox behavior and local structure change of the Li-birnessite were investigated by ex situ soft X-ray absorption spectroscopy (sXAS) and X-ray pair distribution function (PDF) analysis. The combined sXAS and PDF with electrochemical analyses disclosed that the reversible Mn redox and suppressed phase transitions in Dh Li-birnessite contribute to dramatically improving its electrochemical reversiblity during cycling. Our findings underscore the substantial effects of controlled static disorder on the structural stability and electrochemical reversibility of a layered lithium manganese oxide, Li-birnessite, which extends the practical capacity of layered oxides close to their theoretical limit.

Dual chalcogenide coordination engineering on a self-supported alloy electrode for enhanced hydrogen evolution reaction.

The electrochemical hydrogen evolution reaction (HER) holds substantial promise for large-scale green hydrogen production due to its cost-effectiveness, high performance, and scalability for repeated implementation. A promising strategy that involves a novel transition-metal chalcogenide with a self-supported framework can improve the reaction kinetics in the HER. We synthesize a nano three-dimensional self-supported HER catalyst via a straightforward one-step chemical vapor deposition process. This method incorporates a dual co-reaction with sulfur (S) and selenium (Se) onto a commercially available Monel alloy (CNSSe). The dynamics ion exchange redox reactions promote the formation of heterogeneous catalyst structures. Density functional theory (DFT) calculations indicate that the CNSSe catalyst exhibits low hydrogen coverage, as evidenced by a thermoneutral free energy of adsorbed hydrogen (ΔGH*) of 0.105 eV, which can be attributed to the dual introduction of S and Se. Consequently, the optimized CNSSe electrocatalyst achieves an enhancement in HER performance exceeding 100% compared to catalysts introduced exclusively with either S or Se. These results underscore the substantial potential of the optimized CNSSe electrocatalyst to improve both the performance and economic feasibility of HER technologies in alkaline water electrolysis.

Synthesis of some anion exchange resins for selective separation of 99Mo and 131I: A comparative study

ABSTRACT Amination of styrene-divinylbenzene (SDVB) copolymers is a traditional process for preparing strong anion exchange resins that can greatly improve their performance and applications. In the present investigation, poly(styrene-co-divinyl benzene) copolymers functionalized by various amino groups were synthesized by the amination route. The performance of synthesized exchange resins for the separation and recovery of active Mo(VI) and I(I) isotopes from their aqueous solutions was compared to that of three commercial ion exchange resins, used in the actual production of these radioisotopes in the Radioisotopes Production Facility. The morphology and structural properties of the synthesized copolymers as well as the commercial reference resins were characterized using FT−IR, SEM, TG, and XPS. The results demonstrate that the copolymer was successfully functionalized with amino groups, where trimethylamine produced amination greater than triethylamine. Furthermore, the thermal stability of synthesized anion exchanges was significantly higher than that of commercial beads. The synthesized polymer networks presented excellent radiation stability under applied experimental conditions. Compared to the reference resins, the synthesized co-polymeric beads showed enhanced adsorption capability for MoO4 2− and I− ions from an aqueous solution. Further, the uptake affinity of the networks aminated with trimethylamine for both radioisotopes, in optimal conditions, was greater than that of triethylamine aminated beads. The sorption mechanism was inferred through FT−IR and XPS analysis, and the results clarified that the separation of both radioisotopes was substantially related to the amine functional groups on the resin framework. The spectroscopic analysis illustrated that one molybdenum ion (in the form of MoO4 2−) was subjected to an ion-exchange interaction and two Cl− ions in the amine resin. A similar exchange mechanism was predicted for I− with Cl− ions. Further, the enhanced sorption of Mo(VI) could be additionally attained through coordination interactions with N atoms in the amine groups that have good chelating capability toward metal ions. The reusability performance of the synthesized exchange resins is better than that of the commercial reference resins, where they could be effectively regenerated for up to five cycles. Finally, this study presents a new technique for the separation and recovery of Mo(VI) and I(I) from irradiated low-enriched U-targets by employing highly promising amino-modified polystyrene-divinyl benzene microspheres.