Oxygen Migration Research Articles

Improving Copper Active Site Speciation on Cu-Ce/SSZ-13 for Ammonia Oxidation via Si/Al Ratio Modulation.

Catalytic oxidation is a promising purification technique for ammonia (NH3) emission. However, high ignition temperatures and NOx peroxide generation limit its effectiveness due to a lack of active sites. Herein, the effects of Si/Al ratio (SAR) modulation on the speciation of copper active sites and the reaction mechanism at different acidic sites were investigated by loading CuO-CeO2 onto SSZ-13 with different SARs (Cu-Ce/SAR15, 20, and 30). Among them, Cu-Ce/SAR20 exhibits the lowest induction temperature (T20 = 180 °C) and the highest nitrogen selectivity (above 95%), attributing to a higher number of Cu2+ exchange sites. In situ IR spectroscopy and isotopic (18O2) transient response experiments indicate that more active Cu2+ in Cu-Ce/SAR20 provides sufficient Lewis acidic sites for NH3 adsorption and favors the stability of Si-OH-Al structures (Brønsted acid sites). NH3 adsorbed at Lewis acidic sites tends to form peroxide byproducts (NOx), while the NH4+ adsorbed at Brønsted acidic sites generates the key intermediate NH4NO2, which decomposes to N2 at high temperatures, thus enhancing nitrogen selectivity. The whole process mainly follows the Mars-van Krevelen (M-K) mechanism, with the Langmuir-Hinshelwood (L-H) mechanism playing a supporting role. Z2Cu2+ coordinates with adjacent Al atoms within the six-membered ring (6MR) and undergoes a slight deformation at high temperatures, facilitating the migration of the lattice oxygen. SAR plays a crucial role in local environmental speciation of reactive Cu2+, where the sufficient isolated Al provided in SAR20 pulls Cu2+ into the eight-membered ring (8MR), allowing it to come into contact with NH3 more readily.

Theoretical insights into the formation of oxygen activation sites with the affection of protein microenvironment in Flavin-Dependent monooxygenases MsuD

Flavin-dependent monooxygenases are very famous for their capability to catalyze the oxidation of various substrates using oxygen and reduced flavin mononucleotide (FMNH-) or reduced flavin adenine dinucleotide (FADH-). When investigating the catalytic mechanism of flavin-dependent monooxygenase systems, a fundamental problem remains unsolved is that the O2 binding scheme within the reaction cavity is unclear. By applying molecular dynamics simulations, MDpocket simulations, residue mutation molecular dynamics simulation and energy decomposition analyses, this work identified the O2 binding pockets and discovered a possible oxygen migration channel within MsuD enzyme. Molecular dynamics simulations after residue mutation proved that residues Asn104 plays an important role in maintaining the O2 position within the reaction cavity. By analyzing the interaction between O2 and the surrounding protein microenvironment, we demonstrated that N5 is a more favored reaction site and speculated a reasonable O2 activation process. This work recovers the formation of oxygen activation sites in MsuD enzyme, which is of great significance to further investigations of the catalytic reaction mechanism. This work provides a feasible method to study the O2 binding in proteins and the role of the protein microenvironment around the reaction cavity.

Migration roles of different oxygen species over Cu/CeO2 for propane and soot combustion

Determining the migration rules of oxygen species in catalytic combustion, especially for catalysts composed of transition metal oxides, is essential yet challenging. This study hydrothermally synthesized nanosphere-structured cerium dioxide (CeO2) and its copper-loaded catalysts (Cu/CeO2) to identify the distinct functions of superficial oxygen species (O) and lattice oxygen (O2–). The presence of Cu-Ce solid solution at the Cu/CeO2 interface lowered the apparent activation energy for the catalytic combustion of propane and soot. The catalytic combustion of propane followed the Mars-van Krevelen mechanism, with O2– serving as the dominant reactive phase while O played a subordinate role. The solid–solid reaction between soot and superficial oxygen of the catalyst was responsible for catalyzed soot combustion. The O species produced by surface defective sites exhibited higher activity than O2–, which drained easily at the beginning of the reactions. The isotopic oxygen exchange tests revealed the mechanism of metal oxide (CuO/CeO2) interactions for active oxygen species migration, with the results demonstrating the solid solution at the phase interface as portholes for oxygen migration, thus increasing oxygen mobility between the gaseous phase and the surface by lowering the migration activation energy. In situ, infrared results showed that the reaction path of soot catalytic combustion was single, without any intermediate production formation, compared to multiple paths in the propane oxidation process. This study provided an easily implemented and widely applicable method, which deepens our understanding of the characterization of the function and migration of predominant oxygen species in diverse combustion reactions involving oxide-based catalysts. Additionally, this study clarified differences and similarities between the reaction mechanisms of solid–solid and solid–gas catalysis.

Catalytic performance of Pd catalyst supported on CeO2 or ZrO2 modified beta zeolite for methane oxidation

Two kinds of oxide-zeolite composite support, Ce-beta and Zr-beta were prepared by a simple wet impregnation method and adopted for the preparation of palladium-based catalysts for catalytic oxidation of methane. The Pd/6.8Zr-beta catalyst showed superior methane oxidation performance, achieving T50 and T90 of 417 °C and 451 °C, respectively, together with robust hydrothermal stability. Kinetic analysis has shown that incorporating Zr into the catalyst significantly enhanced its efficiency, nearly tripling the turnover frequency (TOF) for methane combustion compared to the Pd/beta catalyst. This enhanced performance was attributed to the dispersion of Zr on the zeolite surface, which not only promoted the formation of active PdO sites but also helped maintain the high Pd2+ content via facilitating the oxygen migration during the reaction, thus improving both the catalyst's activity and stability. In the Pd/8.6Ce-beta catalyst, doped CeO2 tended to aggregate in the zeolite's pores, adversely affecting the catalyst's efficiency. This aggregation promoted the formation of inactive Pd4+ species, a result of the enhanced metal-support interaction. This finding is critical for understanding the implications of dopant selection in the design of high-activity methane oxidation catalysts.

Deep understanding the formation of MnCoOx in-situ grown on foam nickel towards efficient lean methane catalytic oxidation

Methane is the second largest greenhouse gas in the world, with a stronger greenhouse effect than carbon dioxide. The efficient elimination of methane in the atmosphere has important engineering significance in slowing down global temperature rise, energy resource utilization, collaborative control of pollutants, and promoting technological innovation. In this work, a general hydrothermal synthesis method was introduced to in-situ construct four different morphologies of MnCoOx (including rod-, spherical-, filamentous- and bulk-shape) on foam nickel (NF). The synthesis of MnCoOx/NF with different morphologies was due to changes in NF pretreatment conditions and precipitants, which affected the nucleation and growth rates of MnCoOx, ultimately resulting in different morphologies. When the four different morphologies of MnCoOx/NF were used as catalysts for lean methane catalytic oxidation, MnCoOx/NF-r exhibited the best excellent catalytic activity, and the T90 occurred at 428 °C in space velocity of 48,000 mL g−1 h−1. Such an outstanding performance was attributed to the unique properties of the MnCoOx/NF-r including the larger surface area and more oxygen vacancies for providing more active sites and a higher oxygen migration rate, which was very beneficial for improving the catalytic oxidation performance of methane.

Boosting catalytic combustion of diesel soot particles over potassium-promoted CoMn-Co3O4 dual spinel structure catalyst

Catalytic oxidation is an effective method to remove soot particles from diesel exhaust, and the key aspect of this technology is to develop highly effective catalysts. In this work, a potassium-promoted dual spinel structure was prepared for soot elimination with the self-sacrificing template strategy. The highest activity was presented by the CoMn-0.2 H-10%K catalyst under a loose contact mode, with the temperature of soot conversion reaching 90% and turnover frequency value of 365 °C and 3.76×10−3 s−1, respectively. The catalyst was found to have a high content of oxygen vacancy and a superior ability for lattice oxygen migration, which led to elevated performance for soot combustion. The formation of K-OMS-2 at the interface between the CoMn spinel and the Co3O4 spinel was one of the reasons for the elevated lattice oxygen migration at low temperatures. This work provides an effective way to prepare transition metal catalysts for soot combustion.

Hydroxyl-assisted globally spontaneous dynamic oxygen migration on biphenylene

Dynamic covalent interfaces (DCIs) can autonomously adjust their internal structures and dynamically respond to changes in the external environment, thus holding broad application prospects in drug delivery, molecular detection, and interface catalysis. However, the dynamic properties of such DCIs greatly rely on the localized exchanges or formations of chemical bonds, seriously constraining the adaptive response efficiency. To transcend the limitations of the dynamic two-dimensional (2D) scales, employing the experimentally synthesized biphenylene monolayer as a prototype, we systematically study the hydroxyl-assisted globally spontaneous dynamic oxygen migration on biphenylene interface based on the first-principles calculations and machine-learning-based molecular dynamics (MLMD) simulations. The calculated results indicate that the stable dangling oxygen atoms on the biphenylene monolayer can attract the proton in the interfacial water, which in turn undergoes a water dissociation process and produces hydroxyl groups on the biphenylene interface. Assisted by the hydroxyl groups, the dangling oxygen atoms can achieve long-range migration, exhibiting notably low energy barriers (0.09 eV, 0.04 eV) due to the reversible proton transfer reactions. Therefore, the local dynamic covalent behaviors of oxygen atoms on the biphenylene interface are broken with the oxygen atoms migrating between the adjacent C4 rings. More importantly, the charge density difference and Bader charge analysis demonstrate that the presence of hydroxyl groups significantly enhance the stability of the dangling oxygen, effectively reducing energy barriers of oxygen migration compared to epoxy on the biphenylene interface. Furthermore, the MLMD trajectories visually show the process of realizing large-area DCIs on the biphenylene monolayer. Our work not only clarifies the oxygen-related dynamic behavior of the biphenylene interface, but also provides new ideas for the realization of large-area dynamic covalent materials (DCMs) on other carbon-based or 2D materials.

Influence of Li Content on the Topological Inhibition of Oxygen Loss in Li-Rich Cathode Materials.

Lithium-rich layer oxide cathodes are promising energy storage materials due to their high energy densities. However, the oxygen loss during cycling limits their practical applications. Here, the essential role of Li content on the topological inhibition of oxygen loss in lithium-rich cathode materials and the relationship between the migration network of oxygen ions and the transition metal (TM) component are revealed. Utilizing first-principles calculations in combination with percolation theory and Monte Carlo simulations, it is found that TM ions can effectively encage the oxidized oxygen species when the TM concentration in TM layer exceeds 5/6, which hinders the formation of a percolating oxygen migration network. This study demonstrates the significance of rational compositional design in lithium-rich cathodes for effectively suppressing irreversible oxygen release and enhancing cathode cycling performance.

Ce-based three-dimensional mesoporous microspheres with Mn homogeneous incorporation for toluene oxidation

Ce-based three-dimensional (3D) mesoporous microspheres with Mn homogeneous incorporation were synthesized. The CeMn-0.4, characterized by a Ce/Mn molar ratio of 6:4, demonstrated exceptional catalytic activity and stability. The formation of CeMn solid solution strengthened the Ce-Mn interaction, yielding higher concentrations of Ce3+ and Mn4+. Mn4+ initiated toluene preliminary activation owing to its robust oxidative properties, while Ce3+ contributed to oxygen vacancy generation, enhancing the activation of gaseous oxygen and lattice oxygen mobility. Integrating experiments and Density Functional Theory (DFT) calculations elucidated the oxygen reaction mechanisms. A portion of oxygen was converted into surface reactive oxygen species (Oads) that directly oxidized toluene. Additionally, the presence of oxygen vacancies promoted the participation of oxygen in toluene oxidation by converting it into lattice oxygen, which was crucial for the deep oxidation of toluene. Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) indicated the accumulation of benzene-ring intermediates on the catalyst surface hindered continuous toluene oxidation. Thus, the abundant oxygen vacancies in CeMn-0.4 played a pivotal role in sustaining the oxidation process by bolstering the activation of gaseous oxygen and the mobility of lattice oxygen.

Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions.

A skeletal rearrangement of a series of 6,8-dioxabicyclo[3.2.1]octan-4-ols has been developed using SOCl2 in the presence of pyridine. An oxygen migration from C5 to C4 was observed when the C4 alcohols were treated with SOCl2/pyridine, giving a 2-chloro-3,8-dioxabicyclo[3.2.1]octane ring-system via the chlorosulfite intermediate. Analogous allylic alcohols with endocyclic and exocyclic unsaturations underwent chlorination without rearrangement due to formation of allylic cations. The rearrangement was also demonstrated using Appel conditions, which gave similar results via the alkoxytriphenylphosphonium intermediate. Several reactions of the products were investigated to show the utility of the rearrangement.

Oxygen permeability and electrochemical performance of Ca-doped NdBaCo2O5+δ in IT-SOFC

The layered perovskites NdBa1−xCaxCo2O5+δ (NBCax, where x = 0.0, 0.1, 0.2, 0.3, and 0.4) have been synthesized through a conventional solid-state reaction and examined as potential cathode candidates for intermediate-temperature solid oxide fuel cells (IT-SOFC; 600°C–800°C). The Ca-substituted oxides exhibit a P4/mmm tetragonal structure and a phase transition to simple perovskite at x ≥ 0.3. The electrical conductivity in air at 300°C–800°C and oxygen permeation flux of NBCax oxides are influenced by Ca doping content. The activation energy for the oxygen migration process indicates that bulk diffusion is predominant at temperatures below 800°C. X-ray photoelectron spectroscopy indicates the coexistence of Co3+ and Co4+ and oxygen-active sites on the surface of the NBCax oxides. Variations in Co4+ and adsorbed oxygen contents are related to the number of oxygen vacancies and are influenced by Ca content. Among the oxides examined, NdBa0.9Ca0.1Co2O5+δ exhibits good electrical conductivity, high amounts of Co4+ and adsorbed oxygen, high maximum power density of 1286 mW·cm−2 at 800°C in H2 fuel in the La0.9Sr0.1Ga0.8Mg0.2O3 electrolyte–supported cell, and low polarization resistance of the cell, as determined using AC impedance spectroscopy. These findings suggest that Ca incorporation can improve the electrochemical performance of NdBaCo2O5+δ, rendering it a promising candidate for use as a cathode material in IT-SOFCs.

Pressureless sintering behavior of ZrC ceramic particles encapsulated by nano-sized carbon layer

The typical high-density zirconium carbide (ZrC) ceramic requires high temperature and high pressure, leading to high manufacturing cost for complex shapes. Herein, nano-sized carbon layer encapsulated ZrC particles were pressureless sintered to achieve near-net preparation of high-density and complex-shape ZrC ceramic. The results indicate that reaction between carbon layer and the ZrCxOy phase in ZrC was improved because the carbon layer shortened the oxygen diffusion pathway. The oxygen content decreased from 3.52 wt% to 0.82 wt% while the thickness of carbon layer decreased from 4.0 nm to 0.75 nm after sintering at 1950 °C for 1 h. Furthermore, the migration of oxygen from ZrCxOy phase to the carbon layer effectively facilitate the formation and growth of the sintering neck. The resulting ZrC ceramic exhibited a high relative density of 92.3 % and excellent mechanical properties. The Vickers hardness, indentation fracture toughness, micro hardness, elastic modulus, and flexural strength were 17.3 ± 0.7 GPa, 4.0 ± 0.5 MPa m1/2, 22.2 ± 2.4 GPa, 429.9 ± 20.7 GPa, and 324 ± 8 MPa, respectively. This work provides a novel perspective to fabricate near-net, high-density and complex-shape ZrC ceramic at lower temperature without pressure.

Oxygen bond cleavage and its migration mechanisms during pyrolysis of naomaohu sub-bituminous coal

Investigating the oxygen bond cleavage and its migration mechanisms during the pyrolysis process of sub-bituminous coals is essential for their classification utilization. The present study employed a fixed-bed pyrolysis technique (temperature range: 350–600 °C) to explore the cleavage of oxygen-containing bonds and subsequent behavior of oxygen migration and transformation during the pyrolysis process of Naomaohu sub-bituminous coal (NSBC). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results reveal that the organic oxygen in NSBC predominantly exists as the form of C–O bonds, accounting for 22.81 wt% of the total composition, mainly encompassing hydroxyl, carbonyl, ester, and ether groups. The organic oxygen in the light tar is mainly in the form of phenols, reaching 1.71 wt%, of which methyl substituted phenols is predominant at a final pyrolysis temperature of 600 °C. This can be attributed to the presence of more aryl ether bonds and hydroxyl groups in NSBC, which are prone to cleavage at higher temperatures, resulting in the formation of phenoxyl radicals. Additionally, the higher temperature facilitates the weakening of hydrogen bonds between phenolic hydroxyl groups, thereby enhancing the yield of phenolic compounds. The ester compounds present a decreasing trend with increasing temperature, primarily associated with the cleavage temperature of ester linkers being 350 °C, suggesting that an increase in temperature favors the cleavage of ester bonds. In addition, the cleavage of C–O bonds begins to accelerate significantly during the pyrolysis temperature range of 450–500 °C, subsequently accounting for the pronounced proliferation of phenols within this specific thermal interval. The oxygen content in semi-coke decreased with the increase of temperature, from 85.27 wt% at 350 °C to 37.17 wt% at 600 °C, while the oxygen content in the pyrolysis gas increases from 11.63 wt% at 350 °C to 47.53 wt% at 600 °C, indicating that a significant migration of organic oxygen to the pyrolysis gas during the pyrolysis of NSBC. This study can deepen the understanding of the transformation mechanism of oxygen-containing structure in NSBC pyrolysis process, and provide a theoretical basis for high-grade utilization of low-rank coals.

Enhanced co-production of high-quality syngas and highly-concentrated hydrogen via chemical looping steam methane reforming over Ni-substituted La0.6Ce0.4MnO3 oxygen carriers

Chemical looping steam methane reforming (CLSMR) is increasingly attracting more and more attention as a promising technology for co-production of syngas and hydrogen. However, low reactivity, poor selectivity and weak resistance to carbon deposition of oxygen carriers (OCs) probably discourage further commercial application of CLSMR. With this background, a novel strategy of incorporating Ce and Ni into LaMnO3 is advised to promote lattice oxygen migration rate and improve syngas selectivity. The redox activity and cycle stability of La0.6Ce0.4Mn1−xNixO3 for CLSMR are explored in a fixed-bed reactor coupling with various characterization methods. The characterization results show that La0.6Ce0.4Mn1−xNixO3 OCs still maintain the standard perovskite structures and well-ordered skeleton. The introduction of Ce3+ induces large amounts of oxygen vacancies on the surface of OCs and improve the syngas selectivity of methane reforming, leading to higher oxygen mobility and lower carbon deposition. Meanwhile, the experimental results also confirm that the doping of Ni into La0.6Ce0.4MnO3 can greatly improve the oxygen-donation ability and effectively provide more active sites for reaction with methane. While excessive Ni in perovskite will enhance the methane dissociation, which is the main reason of carbon deposits. The proper amount of Ni doping can well match the methane activation rate to migration rate of bulk lattice oxygen that is feasible to realize the balance between productivity and efficiency. In addition, the reduced metal elements along with great amounts of oxygen vacancies together contribute to more active sites for the following steam splitting which avails to produce high-purity H2. La0.6Ce0.4Mn0.7Ni0.3O3 oxygen carrier eventually achieve syngas yield of 2.8 mmol/g H2 and 1.4 mmol/g CO that is closed to the ideal value without obvious carbon deposition, and pure H2 yield of 3.8 mmol/g, exhibiting the best redox performance and good regenerability. Meanwhile, La0.6Ce0.4Mn0.7Ni0.3O3 can still maintain high redox activity and basic perovskite structure after 15 cyclic redox tests, illustrating a desirable stability and reliability. In summary, this study offers a valuable and effective strategy to tackle with the bottleneck of CLSMR, paving the way of doping transition metal as a pathway of modulating reaction performance and stability of OCs in chemical looping processes.

Application of lattice expansion effect in SrCoO3 based cathodes by Ba doping with elevated electrochemical performances for low-temperature solid oxide fuel cells

Developing excellent-performance cathode materials is an inevitable and challenging obstacle in the process of developing practical solid oxide fuel cells, especially in low temperature range. In this paper, we introduce barium into the premium SrCoO3-based cathodes and research its consequent effect in the oxygen reduction reaction process. It is observed that the barium dopant could expand the lattice, produce more oxygen vacancies and at some extent reduce the thermal expansion coefficient of parent perovskite, which results from the expanded free space for oxygen migration and weakened Co–O bond by Ba doping. The polarization resistances of single cells with Sr1-xBaxCo0.8Sc0.1Nb0.05Ti0.05O3-δ cathodes (x = 0, 0.2 and 0.5, defined as SCSNTi, SB0.2CSNTi and SB0.5CSNTi, correspondingly) are 0.038, 0.025 and 0.016 Ω cm2 at 600 °C, respectively, and corresponding peak power density of 0.852, 1.054 and 1.217 W cm−2. The SB0.5CSNTi cathode is selected and it stably operates for 200 h at 550 °C. And it also exhibits excellent performance when CH4 is used as fuel and good stability for 100 h at 600 °C. First principle calculations prove that the Ba doping effectively reduces the oxygen vacancy formation energy and oxygen migration barrier. This work proves that the lattice expansion effect is an effective strategy for accelerating the oxygen exchange rate and designing high-performance cathode materials.

Medium-entropy perovskite Pr0.4Ba0.2Ca0.2La0.2Co0.2Fe0.8O3 as a promising bifunctional electrocatalyst for electrochemical energy conversion device

Reversible solid oxide cells (R-SOCs) are considered to be a promising energy conversion device that can achieve efficient conversion between fuel and electrical energy. However, there are still significant challenges in developing a promising bifunctional electrocatalyst as an electrode material for R-SOC devices. Here, a medium-entropy perovskite Pr0.4Ba0.2Ca0.2La0.2Co0.2Fe0.8O3 (PBCLCF) is designed to enhance the electrochemical oxidation and reduction activity. Under hydrogen atmosphere, cobalt metals are in situ exsolved from the perovskite structure, accompanied by partial phase transformation (denoted as R-PBCLCF). Characterizations show that PBCLCF and R-PBCLCF can increase the concentration of oxygen vacancies, thereby enhancing oxygen migration ability. Combined with electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis, the medium-entropy PBCLCF exhibits better oxygen reduction reaction (ORR) activity and R-PBCLCF shows better hydrogen oxidation reaction (HOR) activity. Furthermore, the oxygen dissociation is identified as the rate-determining step (RDS) in the ORR process, whereas the HOR process is dominated by the hydrogen adsorption and dissociation. The single cell with (R-)PBCLCF showcases remarkable reversible performance. When O2 is employed as the oxidant and H2 as the fuel, this cell achieves a maximum power density of 468.1 mW cm−2 in solid oxide fuel cell (SOFC) mode at 700 °C. Moreover, when O2 is employed as the oxidant and humidified H2 (30 %H2O) as the fuel, the current density of the cell in solid oxide electrolysis cell (SOEC) mode is −647.3 mA cm−2 at 1.3 V and 700 °C.

Effect of metal insertion on the magnetic properties and anomalous Hall effect in MgO/CoFeB/Ta/MgO films

CoFeB-based nano-magnetic multilayers can be applied in magnetic sensors, magnetic random access memory and other logic devices, which have attracted wide attention. The magnetic properties and interface structure of the magnetic multilayers still need further research for future applications. The effects of Pt insertion on the perpendicular magnetic anisotropy (PMA) and the anomalous Hall effect (AHE) of MgO/CoFeB/Pt/Ta/MgO multilayers were studied. It is found that the sample with 0.2 nm Pt insertion at the CoFeB/Ta interface and annealed at 250 °C can transform the films from in-plane magnetic anisotropy to PMA. The effective magnetic anisotropy K eff can reach 1.82 × 106 erg cm−3. The Pt insertion and annealing heat treatment can promote the migration of oxygen from MgO at the top layer to CoFeB/Ta interface and combine with Fe to generate iron oxide, and improve the orbital hybridization of Fe 3d and O 2p, thus successfully inducing the PMA of the film samples. In addition, Pt insertion and annealing treatment can improve the side-jump mechanism and the skew scattering mechanism which contribute to the AHE. This work provides guidance for the application of PMA materials in magnetic sensor and memory devices.

Antagonism effect of residual S triggers the dual-path mechanism for water oxidation

Transition metal chalcogenides (TMCs) are recognized as pre-catalysts, and their (oxy)hydroxides derived from electrochemical reconstruction are the active species in the water oxidation. However, understanding the role of the residual chalcogen in the reconstructed layer is lacking in detail, and the corresponding catalytic mechanism remains controversial. Here, taking Cu1−xCoxS as a platform, we explore the regulating effect and existence form of the residual S doped into the reconstructive layer for oxygen evolution reaction (OER), where a dual-path OER mechanism is proposed. First-principles calculations and operando 18O isotopic labeling experiments jointly reveal that the residual S in the reconstructive layer of Cu1−xCoxS can wisely balance the adsorbate evolution mechanism (AEM) and lattice oxygen oxidation mechanism (LOM) by activating lattice oxygen and optimizing the adsorption/desorption behaviors at metal active sites, rather than change the reaction mechanism from AEM to LOM. Following such a dual-path OER mechanism, Cu0.4Co0.6S-derived Cu0.4Co0.6OSH not only overcomes the restriction of linear scaling relationship in AEM, but also avoids the structural collapse caused by lattice oxygen migration in LOM, so as to greatly reduce the OER potential and improved stability.

Novel Metal–Organic Framework Nanoparticle for Letrozole Delivery: A New Advancement in Breast Cancer Treatment

Water-stable metal-organic frameworks based on UIO-66@NH2 were synthesized to transport Letrozole into breast cancer cells. The UIO-66@NH2 nanoparticles had a spherical shape and triangular base pyramid morphology, with a size range of 100-200 nm. Fourier transform infrared spectroscopy confirmed the efficient adsorption of Letrozole on UIO-66@NH2. The drug release profile showed a gradual, pH-dependent release of Letrozole from the nanoparticles, with a significant increase in acidic environments, indicating the adaptable release potential of UIO-66@NH2@Let in the breast cancer microenvironment. The size and entrapment efficiency were more stable at 4 °C than at 25 °C. To evaluate the cytotoxic effects of UIO-66@NH2@Let, MTT assay, gene expression analysis, flow cytometry, reactive oxygen species generation, migration assay, and DAPI staining were performed. Moreover, according to IC50 results, the incorporation of Letrozole into UIO-66@NH2 significantly improved its anticancer activity. The results also showed that the developed formulations induced apoptosis through both intrinsic and extrinsic pathways and inhibited cancer progression. The efficacy of the formulations in inducing apoptosis was validated by DAPI staining microscopy and flow cytometry analysis. Therefore, the Letrozole-loaded UIO-66@NH2 MOFs developed in this study can be considered as a unique and sophisticated anticancer delivery nanosystem with promising in vitro anticancer properties.

Modification of structural, morphological, and dielectric properties of barium calcium titanate ceramics with yttrium addition

Barium calcium titanate (BCT) ceramics with varying yttrium doping concentrations were fabricated using the solid-state compaction process to explore the attributes of dopants. (Ba0.75Ca0.25) TiO3 and (Ba0.75Ca0.25) (YyTi(1-y)) O3 where, y = 0.00, 0.10, 0.15, and 0.20 ceramics were synthesized by pressing isostatically in pellet press apparatus, then sintered at 1250 °C with consequent cooling in furnace ambient. The structural, morphological, and dielectric properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and impedance spectroscopy interpretations, respectively. The XRD analysis revealed that the cubic BCT lattice was transformed into a tetragonal structure with Yttrium doping. Scanning electron microscopy (SEM) disclosed that yttrium doping countered the liquid phase formation of BCT as well as influenced grain development and microstructure, leading to the formation of distinct grain boundaries and improved densification. The average grain size (18–29 nm) of the Y-BCT increases as the doping level rises. At 60 Hz, it was reported that the dielectric constant obtained a maximum value of 70000 with a resistivity of 5 × 108 Ώ-cm for y = 0.15. The manifestation of the secondary phase confirmed from XRD, allocating an easy path for oxygen migration, might be responsible for the rise in oxygen vacancy, higher leakage current, and dielectric loss for y = 0.01. Co-doping of calcium and yttrium in BCT ceramics has modified the basic structure and ameliorated composites' structural stability and dielectric characteristics. The optimized sample, upon demonstrating outstanding efficiency, ought to be employed for specific uses such as energy storage devices and capacitors.