Oxygen Permeable Membrane Research Articles

Oxygen as obturation biomaterial in endodontic treatment: development of novel membranous dental restoration system

Complexities in obturation and difficulties in disinfection are the major problems that make endodontic treatment very time-consuming. A new perspective is needed to reduce the working time as well as to answer these two problems. Until now, none of the established obturation techniques for root canal filling can guarantee a perfect seal. Solid substances cannot be manipulated easily to fill the tiny branches of the root canal system hermetically. At the same time, anaerobes and facultative anaerobes, especially Enterococcus faecalis, are very dominant in endodontic infections discussion. As shown in many studies, it is extremely difficult to perfectly disinfect Enterococcus faecalis even by using some irrigating solutions with strong antibacterial properties. Under anaerobic conditions, the invasion efficiency of facultative anaerobes is increased. In case irrigation and disinfection cannot totally eliminate anaerobes and facultative anaerobes, a new strategy is also needed to deal with the bacteria that still survive in the root canal. Oxygen can fill the root canal system with ease, eliminate anaerobes, and prevent facultative anaerobes from being pathogenic. Therefore, using oxygen as obturation biomaterial after proper cleaning and shaping procedures is expected to solve the two major endodontic problems. The aim of this article was to discuss a new possible concept of dental restoration system that uses an oxygen-permeable membrane to decrease the time required in endodontic treatment. The membrane is placed at the orifice of a duct created to connect the entire root canal system with free air outside the restoration. The function of the membrane is more or less similar to the mask used during the COVID-19 pandemic, as it enables the oxygen to circulate while preventing any fluid, debris, and microorganisms from passing. We hypothesize that the oxygen circulating in the root canal system will also act as an antimicrobial agent that is constantly renewed.

Structural, optical and magnetic characteristics of Mg2+- doped (Ba0.94Sr0.06)(Fe0.80Al0.20-xMgx)O3-ẟ (x = 0–0.20) oxides

Perovskite-type ABO3 oxides have attracted immense attention in recent technologies e.g., gas sensors, solar cells, fuel cells, oxygen-permeable membranes, etc. An attempt has been made here to synthesize (Ba0.94Sr0.06)(Fe0.80Al0.20-xMgx)O3-ẟ (x = 0–0.20) oxides using sol-gel method and characterized with regards to phase, Raman and magnetic properties. X-ray diffraction-cum-Rietveld refinement shows the structural transformation from cubic (Pm3m) to hexagonal (P63/mmc) via cubic (Pm3m) + rhombohedral (R3c) and increase of cubic lattice parameter ac = 4.0369–4.1296 Å with magnesium. FT-IR spectra exhibit different vibrational bands at 548, 555, 638, 667, and 692 cm−1, representing the metal-oxygen (M-O-M) bond vibrations (M - Fe, Mg, Al), deformation of MO6 octahedral, and internal changes in bond lengths. No Raman band was appeared for cubic phase with x=0–0.10. Bands between ∼ 250–450 cm−1 assign the tilting, rotation, and asymmetric bending vibrations of Fe – O, Mg – O and Al – O bonds and asymmetric bending mode of (Fe/Mg/Al)O6 octahedra. Oxygen bending vibration, anti-stretching mode and presence of oxygen vacancies lie in the bands of range ∼498–656 cm−1. Maximum coercivity (Hc ∼ 1081 Oe) and remanent magnetization (Mr ∼ 0.033 emu/g) have been observed for x = 0 and found similar variation with ‘x’. The saturation magnetization (Ms) and anisotropic constant (K1) values lie as Ms = ∼ 0.678 – 0.754 emu/g and K1 = ∼ 1.38× 104 – 1.53× 104 erg/cm3, respectively with magnesium (x). Presence of anion vacancies and high coercivity make the materials suitable for industrial applications.

Effects of copper doping on microstructural evolution and oxygen permeability of Ce0.8Sm0.2O2-δ-Sm0.6Sr0.4Fe1-xCuxO3-δ dual-phase oxygen permeable membranes

Ce0.8Sm0.2O2-δ(wt.70 %)-Sm0.6Sr0.4Fe1-xCuxO3-δ(wt.30 %) (SDC-SSFC) dual-phase oxygen permeable membranes were prepared by one-pot EDTA-citric acid combined complexing method. Effects of copper doping content on crystallographic phase, microstructure and oxygen permeability were deeply investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDXS). Systematic studies reveal that SDC as oxygen ion conductors and SSFC as electron conductor display an excellent synergistic effect only if a suitable doping content of copper was adopted. It can be found that Ce0.8Sm0.2O2-δ-Sm0.6Sr0.4Fe0.9Cu0.1O3-δ exhibits the highest oxygen permeation flux of up to about 0.61 ml cm−2 at 950 °C and lower oxygen permeation activation energy, which displays nearly a two-fold increase in oxygen permeability compared with the sample without any copper doping. If the copper doping content in B-site of SSFC perovskite exceeds about 30 %, a third phase, i.e., CuO, would appear in the bulk of SDC-SSFC dual-phase membrane and the grain size of CuO tend to gradually increase which would degrade the oxygen permeability of SDC-SSFC dual-phase membrane. Kinetical analysis showed that the critical membrane thickness (Lc) of Ce0.8Sm0.2O2-δ-Sm0.6Sr0.4Fe0.9Cu0.1O3-δ membrane is close to approximately 0.6 mm, i.e., if the membrane thickness is larger than 0.6 mm, its rate-determining step would transform into the bulk-diffusion exchange from surface exchange. Meanwhile, Ce0.8Sm0.2O2-δ-Sm0.6Sr0.4Fe0.9Cu0.1O3-δ membrane exhibits a stable oxygen permeation flux of up to 0.32 ml cm−2·min−1 in pure CO2 atmosphere for more than 120 h without any degradation.

From Li–O2 to Li–Air Batteries: Challenges and Progress on Oxygen-Permeable Membranes

From Li–O₂ to Li–Air Batteries: Challenges and Progress on Oxygen-Permeable Membranes

Research on the Influence of Core Sensing Components on the Performance of Galvanic Dissolved Oxygen Sensors.

The galvanic dissolved oxygen sensor finds widespread applications in multiple critical fields due to its high precision and excellent stability. As its core sensing components, the oxygen-permeable membrane, electrode, and electrolyte significantly impact the sensor's performance. To systematically investigate the comprehensive effects of these core sensing components on the performance of galvanic dissolved oxygen sensors, this study selected six types of oxygen-permeable membranes made from two materials (Perfluoroalkoxy Polymer (PFA) and Fluorinated Ethylene Propylene Copolymer (FEP)) with three thicknesses (0.015 mm, 0.03 mm, and 0.05 mm). Additionally, five concentrations of KCl electrolyte were configured, and four different proportions of lead-tin alloy electrodes were chosen. Single-factor and crossover experiments were conducted using the OxyGuard dissolved oxygen sensor as the experimental platform. The experimental results indicate that under the same membrane thickness conditions, PFA membranes provide a higher output voltage compared to FEP membranes. Moreover, the oxygen permeability of FEP membranes is more significantly affected by temperature. Furthermore, the oxygen permeability of the membrane is inversely proportional to its thickness; the thinner the membrane, the better the oxygen permeability, resulting in a corresponding increase in sensor output voltage. When the membrane thickness is reduced from 0.05 mm to 0.015 mm, the sensor output voltage for PFA and FEP membranes increases by 86% and 74.91%, respectively. However, this study also observed that excessively thin membranes might compromise measurement accuracy. In a saturated, dissolved oxygen environment, the sensor output voltage corresponding to the six oxygen-permeable membranes used in the experiment exhibits a highly linear inverse relationship with temperature (correlation coefficient ≥ 98%). Meanwhile, the lead-tin ratio of the electrode and electrolyte concentration have a relatively minor impact on the sensor output voltage, demonstrating good stability at different temperatures (coefficient of variation ≤ 0.78%). In terms of response time, it is directly proportional to the thickness of the oxygen-permeable membrane, especially for PFA membranes. When the thickness increases from 0.015 mm to 0.05 mm, the response time extends by up to 2033.33%. In contrast, the electrode material and electrolyte concentration have a less significant effect on response time. To further validate the practical value of the experimental results, the best-performing combination of core sensing components from the experiments was selected to construct a new dissolved oxygen sensor. A performance comparison test was conducted between this new sensor and the OxyGuard dissolved oxygen sensor. The results showed that both sensors had the same response time (49 s). However, in an anaerobic environment, the OxyGuard sensor demonstrated slightly higher accuracy by 2.44%. This study not only provides a deep analysis of the combined effects of oxygen-permeable membranes, electrodes, and electrolytes on the performance of galvanic dissolved oxygen sensors but also offers scientific evidence and practical guidance for optimizing sensor design.

Mo-doped La0.4Sr0.6FeO3-δ hollow fiber membrane for air separation and methane conversion

Ceramic oxygen transport hollow fiber La0.4Sr0.6Fe0.95Mo0.05O3-δ (LSFM5) membranes were fabricated via combined phase inversion and sintering technique. High-temperature X-ray diffraction experiments indicated that LSFM5 oxide undergoes second order phase transition at temperature above 300 °C from rhombohedral to cubic structure. The inner and outer surfaces of LSFM5 membranes were modified by acid etching and by depositing a surface decoration layer. For both kinds of membranes with modified surfaces, the enhancement of oxygen fluxes was observed at operating temperature range 860–980 °C, which indicates that the surface oxygen exchange reactions play a decisive role in the control of the oxygen transport. Catalytic experiments of methane partial oxidation (POM) by Ni/LSFM5 based oxygen-permeable membrane reactor exhibited good performance both in the mode with synthetic air on the supply side, and in the mode of POM coupled with CO2 splitting on the supply side.

Recycling the spent cobalt-based perovskites for the high-active oxygen catalysts in zinc-air batteries

Cobalt (Co) is widely used in energy storage and conversion devices, although its content on our planet is not adequate. Therefore, recycling Co from the spent Co-enriched materials is indispensable. Co-based perovskites, which contain abundant Co, are extensively utilized in solid oxide fuel cells, three-way catalysts, and oxygen-permeable membranes, and the recovery of Co from the spent Co-based perovskites is necessary to meet the long-term requirement of Co. In this work, a facile and universal thermal reduction method (750 °C and N2 atmosphere) is employed to convert the spent cobalt-based perovskites into high-performance bifunctional oxygen catalysts for zinc-air batteries (ZABs), achieving high-efficient Co recovery and re-utilization. At high temperatures, melamine and dopamine hydrochloride are transformed into carbon nanotubes, C3N4 and reducing gases (such as NH3 and H2). Simultaneously, the metal elements in the spent Co-based perovskites (SrNb0.1Co0.7Fe0.2O3,SNCF) are converted into nano-scale alloy particles and metal nitrides. Then, the phase structures, micromorphology, and element valences of the obtained multiphase oxygen catalyst (SNCF–Ni-PM) are characterized by X-ray diffraction, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties, including oxygen catalytic activities and stability, of SNCF-Ni-PM are measured by linear sweep voltammetry, chronopotentiometry, chronoamperometry, and cyclic voltammetry methods. Considering the practical applications, the aqueous and solid-state ZABs are assembled and measured. The results demonstrate that the multiphase SNCF-Ni-PM mainly includes carbon nanotubes, C3N4 nanosheets, and FeNiN or CoFe nanoparticles. Moreover, SNCF-Ni-PM exhibits excellent bifunctional oxygen catalytic activity, with an oxygen evolution reaction (OER) potential at 10 mA cm−2 of 1.51 V and an oxygen reduction reaction (ORR) half-wave potential of 0.77 V, outperforming most of the reported oxygen catalysts. Using SNCF-Ni-PM, the aqueous and solid-state ZABs can achieve high power densities of 295.9 and 228.4 mW cm−2, respectively, being superior to most ZABs. In addition, the aqueous ZAB with SNCF-Ni-PM can operate stably for 300 h with a slight degradation. This work provides a feasible method for effectively recycling Co from the spent Co-based perovskites.

Sulfonylureas Compromise Microvascular Flow in Mouse Skeletal Muscle

Sulfonylureas are among the most prescribed oral anti-hyperglycaemics, particularly in low- and middle-income countries. Sulfonylureas are insulin secretagogues through blocking ATP-sensitive potassium channels (KATP) in β-cells of the pancreas. Despite wide usage, sulfonylureas are associated with increased cardiovascular disease morbidity and all-cause mortality, with ill-defined mechanisms. We tested the hypothesis that glyburide could block KATP channels in the microvasculature, thereby disrupting tissue oxygen demand-supply balance. We further investigated the contribution of other potassium channels to capillary-to-arteriole signalling. Experiments were conducted using an in-vivo anesthetized mouse skeletal muscle preparation (extensor digitorum longus, EDL); exteriorized and situated at in-situ length, overtop an oxygen-permeable membrane covering a gas chamber, and bathed in PlasmaLyte. C57BL/6 mice were employed (n=6-8). Brightfield images were captured at two wavelengths: oxygen-dependent and oxygen-independent, enabling the simultaneous determination of capillary hemodynamics and RBC oxygen content. Low oxygen challenges were achieved by dropping oxygen levels in the gas chamber from 7% to 2% for 3 minutes. Challenges were conducted before (control) and after drugs were added to bathing solution. Parameters were obtained before the challenge (baseline), during the challenge (2 regions) and after the challenge (recovery). Statistical significance was determined using a paired Student’s t-test. Target channels localization was investigated using immunofluorescence in formalin-fixed EDL. Oxygen challenges augmented EDL surface capillary hematocrit and RBC velocity and supply rate, while reducing RBC oxygen saturation. Incubation of the EDL with 10 μM glyburide decreased the baseline RBC supply rate (p<0.05 vs control) and blunted the magnitude of capillary responses to the oxygen challenge (p<0.05 vs control). Immunofluorescence confirmed the localization of KATP channels in EDL capillaries. Normal capillary responses were obtained when small and intermediate conductance or inward rectifier potassium channels were neutralized. This implies minimal or no contribution of these channels in oxygen signaling in the microvasculature. This data begins to elucidate the acute and direct effects of systemic KATP blockers on capillary-to-arteriole conducted signaling, which is likely key to optimal tissue oxygen regulation. Further experiments are warranted to confirm this conclusion. This work was supported by the Natural Science and Engineering Research Council of Canada (NSERC, RGPIN/04659-2017), an Ontario Graduate Scholarship (M.A.E) and a CIHR doctoral award (M.A.E). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Exploring the potential of decade-air exposed perovskite membranes through sustainable recycling approaches

The stability of perovskite-based oxygen permeable membranes under long-term storage conditions, especially in the presence of water and carbon dioxide, presents a significant challenge. In this study, we examined the impact of extended storage (more than 10 years) on Nb2O5-doped SrCo0.8Fe0.2O3-δ (10Yr-SCFN) membranes. To unlock their industrial application potential, various approaches involving a combination of physical and chemical treatments to restore membrane properties in aged membranes are proposed and validated, while systematically investigating the evolution in chemical composition, microstructure, mechanical strength, and oxygen permeability. The 10Yr-SCFN membranes can be effectively restored through the secondary sintering method, wherein the membrane is first powdered and then calcinated in static air to maximize the removal of impurities. The mechanical strength and oxygen permeability reach levels of 30 MPa and 1.2 ml cm−2 min−1 (900 °C), respectively, comparable to the performance of freshly prepared membranes. These findings shed some light on the potentiality of sustainable recycling of perovskite membranes and provide theoretical and technical support for the practical application and industrialization of oxygen permeable membranes.

Integrated syngas and nitrogen production in La0.6Ca0.4Co0.2Fe0.8O3−δ hollow fiber membrane reactor through oxidative CO2 reforming of methane

Utilizing mixed ion-electronic conducting (MIEC) oxygen permeable ceramic membrane to introduce oxygen from air into the oxidative CO2 reforming of methane (OCRM), which integrates exothermic partial oxidation of methane (POM) with endothermic dry reforming of methane (DRM), not only reduces the energy consumption but also effectively mitigates carbon accumulation. In this study, La0.6Ca0.4Co0.2Fe0.8O3−δ (LCCF) hollow fiber (HF) membrane was fabricated via a phase inversion and sintering technique using LCCF oxide powder. A 10 wt% Ni/LCCF catalyst was prepared by mechanical mixing and high temperature reduction of NiO and LCCF powder. The catalyst and LCCF HF membrane were integrated into an OCRM membrane reactor. The findings indicate that moderate temperature increment was beneficial to the combined OCRM reaction in the membrane reactor. However, the increase in air flow rates, CH4/CO2 ratio, and feed flow rates were found to deteriorate the OCRM performance. At 825 °C, the CO selectivity and carbon balance were maintained at about 99 %. The stabilized oxygen permeation rate at about 2.08 mL min−1 signifies that the permeated oxygen significantly inhibits carbon accumulation in the catalyst. Notably, N2 with purity of 99.47 vol% was obtained at the air feed side of the setup, underlining the potential for efficient carbon management and high-purity N2 production within this OCRM membrane reactor.

Ba-doped Pr2NiO4+δ electrodes for proton-conducting electrochemical cells. Part 3: Electrochemical applications

Layered nickelates, Ln2NiO4+δ, are promising electrode materials for many electrochemical applications, including solid oxide fuel cells and electrolysis cells. Although Ln2NiO4+δ has been extensively modified by various doping strategies to tune its functional properties, the partial substitution of Ln3+ with Ba2+ remains among the least studied routes. At the same time, such substitution is found to be favorable when Ln2NiO4+δ materials are used for protonic ceramic electrochemical cells based on Ba-containing proton-conducting electrolytes (i.e., BaCeO3, BaZrO3, Ba(Ce,Zr)O3). In this work, which is the third part of a systematic study, Pr2–xBaxNiO4+δ materials are used as electrodes for a proton ceramic fuel cell and as oxygen permeable membranes. The oxygen permeation experiments confirm that the compositions with x = 0.2 and 0.3 prevail over x = 0 and 0.1 in terms of their oxygen-ionic conductivity, while the electrochemical cell characterizations confirm the high electrochemical activity of the Pr1.8Ba0.2NiO4+δ electrode in both fuel-cell- and electrolysis-cell modes. Our research thus confirms that a Ba-doping strategy is highly promising for designing new Ln2NiO4+δ-based phases, simultaneously offering good chemical and thermal compatibility with state-of-the-art proton-conducting electrolytes and high electrochemical performance.

Bipolar Clark-Type Oxygen Electrode Arrays for Imaging and Multiplexed Measurements of the Respiratory Activity of Cells.

Various miniature Clark-type oxygen electrodes (COEs), which are typically used to measure dissolved oxygen (DO) concentration in cellular respiration, have been developed since the 1980s. Arrays with individually addressable electrodes that constitute the sensor were used for various applications. However, the large number of leads and contact pads required for connecting the electrodes and the external instrument complicate the electrode layout and make the operation of integrated COE arrays challenging. Here, we fabricated closed bipolar electrochemical systems comprising 6 × 8 and 4 × 4 arrays of COEs for imaging and multiplexed detection. The cathodic compartment was sealed with a hydrophobic oxygen-permeable membrane to separate the internal electrolyte solution from the sample solutions. Using the bipolar Clark-type oxygen electrode (BCOE) arrays and electrochemiluminescence (ECL), we measured the DO concentration at each cathode. The results revealed that the ECL intensity changed linearly with the DO concentration. In addition, we used ECL imaging to investigate the respiratory activity of Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) in suspensions with different cell densities. The ECL images showed that the ECL intensity changed noticeably with the bacterial density. The bacterial respiratory activity was then qualitatively analyzed based on the ECL images acquired successively over a time duration. Further, we measured the antibiotic efficacy of piperacillin, oxacillin, gentamicin, and cefmetazole against E. coli and P. aeruginosa using the BCOE. We found that the ECL intensity increased with the antibiotic concentration, thus indicating the suppression of the bacterial respiratory activity.

A revolutionary design concept: full-sealed lithium-oxygen batteries

At this moment, non-aqueous rechargeable lithium-oxygen batteries (LOBs) with extremely high energy density are regarded as the most viable energy storage devices to potentially replace petroleum. One of the most crucial impediments to their implementation has been ensuring facile oxygen availability. Moreover, as semi-sealed systems, LOBs have confronted challenges including oxygen impurities, product degradation, anode corrosion, frequent side reactions, and mediocre cycling performance. In this work, utilizing the physical adsorption of porous (micro-, meso- and macro-porous) solid carbon materials, we incorporate an oxygen storage layer (OSL) with reversible oxygen ad/desorption capabilities into a LOB to develop novel fully-sealed lithium-oxygen batteries (F-S-LOBs). The results demonstrate mesoporous carbons exhibit optimal oxygen adsorption/desorption kinetics, rendering them highly suitable for F-S-LOBs without developing complex oxygen-permeable membranes or carrying oxygen tanks. The OSL fabricated with mesoporous carbon can sustain battery charge/discharge at various current densities with exceptional cycling performance. Additionally, we provide approximate pore size guidelines for oxygen storage materials to aid future research. This study is anticipated to offer a new robust research direction for metal-air batteries and to forge a new path toward promoting the commercialization and development of this technology.

Quantification of oxygen consumption in head and neck cancer using fluorescent sensor foil technology.

Head and neck squamous cell carcinoma (HNSCC) patients suffer from frequent local recurrences that negatively impact on prognosis. Hence, distinguishing tumor and normal tissue is of clinical importance as it may improve the detection of residual tumor tissue in surgical resection margins and during imaging-based surgery planning. Differences in O2 consumption (OC) can be used to this aim, as they provide options for improved surgical, image-guided approaches. In the present study, the potential of a fluorescent sensor foil-based technology to quantify OC in HNSCC was evaluated in an in vitro 3D model and in situ in patients. In vitro measurements of OC using hypopharyngeal and esophageal cell lines allowed a specific detection of tumor cell spheroids embedded together with cancer-associated fibroblasts in type I collagen extracellular matrix down to a diameter of 440 µm. Pre-surgery in situ measurements were conducted with a handheld recording device and sensor foils with an oxygen permeable membrane and immobilized O2-reactive fluorescent dyes. Lateral tongue carcinoma and carcinoma of the floor of the mouth were chosen for analysis owing to their facilitated accessibility. OC was evaluated over a time span of 60 seconds and was significantly higher in tumor tissue compared to healthy mucosa in the vicinity of the tumor. Hence, OC quantification using fluorescent sensor foil-based technology is a relevant parameter for the differentiation of tumor tissue of the head and neck region and may support surgery planning.

Cold sintering of perovskite‐based mixed conducting membrane for oxygen separation

AbstractCold sintering has attracted significant attention as its remarkably rapid densification process at low sintering temperatures leads to considerable energy savings. However, the sintering behaviors of cold‐sintered perovskite ceramics remain poorly understood and lack precise control over material microstructure. Here, we fabricated dense SrCo0.8Fe0.2O3−δ (SCF) ceramic oxygen permeation membranes by cold sintering. Adding an appropriate ratio of sub‐micron SCF particles can better bridge the sintering interspaces between micron particles, generate amorphous phase through “dissolution‐precipitation,” and aid in the initial densification. The average relative density of SCF membranes undergoes a significant increase to 95.9% after cold sintering and post‐annealing at 900°C, which is much lower than the temperature required for conventional high‐temperature solid‐state sintering (>1200°C). The oxygen permeation flux of the prepared SCF perovskite membrane reaches 2.8 mL min−1 cm−2, which proves that this method has the potential to be an excellent sintering technique for dense perovskite ceramic membranes.

Dual-phase Ce0.8Sm0.2O2−δ–La0.8Ca0.2Al0.3Fe0.7O3−δ oxygen permeation hollow fiber membrane for oxy-CO2 reforming of methane

The SDC–LCAF dual phase oxygen permeable hollow fiber membrane reactor exhibited stable OCRM performance and stability with pure N2 produced in the air side and syngas produced in the methane and CO2 side.

Multiplying Oxygen Permeability of a Ruddlesden-Popper Oxide by Orientation Control via Magnets.

Ruddlesden-Popper-type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade-off by leveraging the anisotropic properties of Nd2 NiO4+δ . Its (a,b)-plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c-axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min-1 cm-2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2 . These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2 NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions.

Multiplying Oxygen Permeability of a Ruddlesden‐Popper Oxide by Orientation Control via Magnets

AbstractRuddlesden‐Popper‐type oxides exhibit remarkable chemical stability in comparison to perovskite oxides. However, they display lower oxygen permeability. We present an approach to overcome this trade‐off by leveraging the anisotropic properties of Nd2NiO4+δ. Its (a,b)‐plane, having oxygen diffusion coefficient and surface exchange coefficient several orders of magnitude higher than its c‐axis, can be aligned perpendicular to the gradient of oxygen partial pressure by a magnetic field (0.81 T). A stable and high oxygen flux of 1.40 mL min−1 cm−2 was achieved for at least 120 h at 1223 K by a textured asymmetric disk membrane with 1.0 mm thickness under the pure CO2 sweeping. Its excellent operational stability was also verified even at 1023 K in pure CO2. These findings highlight the significant enhancement in oxygen permeation membrane performance achievable by adjusting the grain orientation. Consequently, Nd2NiO4+δ emerges as a promising candidate for industrial applications in air separation, syngas production, and CO2 capture under harsh conditions.

Chemical stability aspects of BaCe0.7–xFexZr0.2Y0.1O3–δ mixed ionic-electronic conductors as promising electrodes for protonic ceramic fuel cells

Mixed ion-electron conductors (MIECs) are promising materials for air electrodes for protonic ceramic fuel cells (PCFCs) or oxygen permeation membranes. In this work, various aspects of the chemical stability of Co-free MIEC materials, BaCe0.7–xFexZr0.2Y0.1O3–δ, were studied, including their interaction with another functional material (BaCe0.5Zr0.3Y0.1Yb0.1O3–δ-based proton-conducting electrolyte) and gas components (H2O, CO2, and H2). Chemical compatibility studies indicate no visible chemical interaction between the electrode and electrolyte materials even at 1200 °C, which is significantly higher than the operating temperatures (600–800 °C) of PCFCs. The treatments of BaCe0.7–xFexZr0.2Y0.1O3–δ in different atmospheres at 1100 °C, according to the XRD, SEM, IR and Raman spectroscopy data, resulted in the formation of impurity phases. However, their extremely small amounts suggest that they may not form at the operating temperatures. Thus, it can be assumed that the studied materials can be good candidates for various electrochemical applications.

Optical, magnetic, and electrochemical properties of a fluorite-perovskite Ce0.9Gd0.1O2-∂ - La0.6Sr0.4FeO3-∂ nanocomposite synthesized by one pot sol-gel auto-combustion route

Gadolinium-doped cerium oxide (Ce0.9Gd0.1O2-∂; CGO) and strontium-doped lanthanum ferrite (La0.6Sr0.4FeO3; LSF) are well-known compounds for their application in solid oxide fuel cells, dense oxygen permeable membrane, and high-temperature ceramic reactor. The superior electro-catalytic performance of these two individual oxides or their composites is well established as it originates from multivalent cations (Ce3+/4+ and Fe2+/3+/4+) and doping-induced defects like electrons, holes, and oxygen vacancies. This work focuses on synthesizing and characterizing composite taking CGO and LSF in different weight ratios, i.e., 10:90, 30:70, 50:50, 70:30, and 90:10 by sol-gel auto-combustion process. End members CGO and LSF were also synthesized for comparison purposes. All synthesized nanopowders (single phases and their composites) were characterized with X-ray diffraction (XRD) for phase identification and Scanning electron microscopy (SEM) for elemental composition analysis. XRD and SEM results established the formation of the required phase and targeted composition. The optical properties of the materials were evaluated with the help of ultraviolet–visible Diffuse Reflectance Spectroscopy (UV–Vis DRS). Tauc's approximation measured band gap energies, and all the composites showed a very high band gap in the 4.85–5 eV range. Magnetic properties such as saturation magnetization (Ms), remanence (Mr), and coercive force (Hc) were calculated from a magnetic hysteresis loop obtained from the Vibrating-sample magnetometer (VSM) experiment at room temperature. Furthermore, the law of approach to saturation (LAS) model was applied to more precisely calculate Ms and other essential parameters. In magnetic characterization, the LSF phase fraction controls the overall magnetic property of the composites. Electrochemical behavior, such as the composites' charge storage ability and stability were tested by cyclic voltammetry and chronopotentiometry method. All the samples exhibited good stability, and the highest specific capacitance of 26 F/gm was obtained for the composite sample (CL91) when only 10 % LSF phase was incorporated in the nanocomposite.