Rare Earth Metal Oxides Research Articles

Catalyst development for O2-assisted oxidative dehydrogenation of propane to propylene.

O2-Assisted oxidative dehydrogenation of propane (O2-ODHP) could convert abundant shale gas into propylene as an important chemical raw material, meaning O2-ODHP has practical significance. Thermodynamically, high temperature is beneficial for O2-ODHP; however, high reaction temperature always causes the overoxidation of propylene, leading to a decline in its selectivity. In this regard, it is crucial to achieve low temperatures while maintaining high efficiency and selectivity during O2-ODHP. The use of catalytic technology provides more opportunities for achieving high-efficiency O2-ODHP under mild conditions. Up to now, many kinds of catalytic systems have been elaborately designed, including transition metal oxide catalysts (such as vanadium-based catalysts, molybdenum-based catalysts, etc.), transition metal-based catalysts (such as Pt nanoclusters), rare earth metal oxide catalysts (especially CeO2 related catalysts), and non-metallic catalysts (BN, other B-containing catalysts, and C-based catalysts). In this review, we have summarized the development progress of mainstream catalysts in O2-ODHP, aiming at providing a clear picture to the catalysis community and advancing this research field further.

Advanced Machine Learning Algorithms for Accurate Prediction of Band Gaps in Rare Earth Metal Oxides Nanoparticles

Advanced Machine Learning Algorithms for Accurate Prediction of Band Gaps in Rare Earth Metal Oxides Nanoparticles

First-principles investigation of the catalytic mechanism of CeO2/KB composite separator in Li-S batteries

The CeO2/Ketjen Black (KB) composite separator has been shown to effectively reduce the shuttle effect and improve the reaction kinetics of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. A thorough investigation has been conducted using the Perdew-Burke-Ernzehof plus Hubbard U (PBE + U) calculations implemented within the Vienna ab initio simulation package (VASP). The focus has been on the catalytic mechanism of the separator, particularly the migration behavior of LiPSs and the conversion mechanism of Li2S2 → Li2S on CeO2 and KB surfaces. The study revealed that LiPSs have a strong preference for the CeO2 surface due to more potent adsorption energies. Moreover, it has been discovered that the subsequent migration and conversion processes of LiPSs are governed by the synergistic catalytic effect between CeO2 and KB. The rate-determining step in the overall catalytic process is the migration of Li2S2 on CeO2. These findings provide a deeper understanding of the catalytic mechanism and migration behavior of LiPSs, potentially guiding the development of advanced composite materials for Li-S batteries and facilitating the use of rare earth metal oxides for high energy storage and extended battery life.

A new magnetic heterogeneous catalyst for fast degradation of rhodamine B by peroxymonosulfate oxidation: Monodisperse-porous and Fe3O4 incorporated manganese oxide microspheres

A new synthetic method, “staged shape templating decomposition” suitable for transition or rare-earth metal oxide microspheres was developed for obtaining magnetic, uniform and porous manganese oxide (MagMnOx) microspheres. The microspheres 4.7 μm in size were obtained with a specific surface area of 45.5 m2 g−1. Fe3O4, Mn5O8, MnO2 and Mn2O3 phases were shown by X-ray diffraction spectroscopy. Mn2+, Mn3+ and Mn4+ states were observed on the surface by X-ray photoelectron spectroscopy. Catalase-like and oxidase-like activities of MagMnOx microspheres were explained by coexistence of Mn and Fe crystallites in a mesoporous structure with a sufficiently large surface area and a particle interior with large mesopores facilitating substrate diffusion. The maximum substate consumption rates for catalase-like and peroxidase-like activities were determined as 15.6 mM/min and 20.3 μM/min, respectively. By considering their ROS generation ability, MagMnOx microspheres were evaluated as a heterogeneous catalyst for rhodamine B (Rh B) removal via peroxymonosulfate (PMS) activation. Rh B was removed in the periods shorter than 15 min via chemical degradation with a limited physical adsorption. Superoxide anion (O2−●) and singlet oxygen (1O2●) radicals generated by MagMnOx-PMS system were responsible for degradation of Rh B. The highest apparent first order rate constant for Rh B degradation was calculated as 0.5771 min−1. The apparent first order rate constant increased with increasing MagMnOx and PMS concentrations and decreasing initial Rh B concentration. Rh B was almost completely removed in each of five recycling runs and only lower than 1.5 % w/w of Fe and Mn contents of MagMnOx microspheres were leached over five recycling runs. The catalyst with large particle size, resistant to agglomeration exhibited high removal rate, low dye adsorption, high magnetization, and high reusability for Rh B removal via peroxymonosulfate activation.

Photocatalytic degradation of aqueous Congo red dye pollutants by rare-earth metal oxide (CeO2) nanorods

Existing nano powder-based photocatalysts face challenges in degradation performance, particularly for the degradation of complex dyes like Congo red (CR). In this work, cerium dioxide (CeO2) nanorods are successfully fabricated combining hydrothermal synthesis with calcination for the photocatalytic degradation of CR dyes. The synthesized CeO2 nanorods possess a diameter of ∼ 100 nm based on field emission scanning electron microscopy (FE-SEM) investigation. The atomic percentages of Ce and O elements are measured to be 44.2 at% and 39.2 at%, respectively, by the energy dispersive X-ray spectroscopy (EDS). By means of X-Ray diffraction (XRD) analysis, all the prepared samples show cubic CeO2 with a small amount of Ce2O3. To validate their photocatalytic function, the CeO2 nanorods are tested towards CR dyes, where the degradation of CR solution under UV irradiation is faster than that in dark condition. A high CR degradation efficiency of up to 97.7% is revealed within 130 min photocatalytic activity. From the scavenger test, superoxide radical (•O2–) and hole (h+) are discovered to be the most reactive oxygen species generated during photodegradation process. This finding provides a simple yet effective method to fabricate highly effective photocatalytic materials for dye pollutant degradation in wastewater treatment. Future work will focus on optimizing the material properties and degradation mechanisms further, opening avenues for the scaled application of these materials.

Urea-Assisted Synthesis of Microspherical Hollow CeO2 Nanostructures for Supercapacitor Applications

In the present work, cerium oxide (CeO2), the most abundant and least expensive rare earth metal oxide with the capability of rapid conversion between the oxidation states of Ce+3 and Ce+4, is synthesized via a urea-assisted solvothermal method in methanol. Along with its role as a precipitating agent, urea reacted with methanol and thus initiated a series of organic reactions which are responsible for the formation of spherical layered assembly of cerium oxide leading to a multi-layered structure with high porosity. The morphology and chemical structure of the material are investigated using SEM, TEM, XRD, and FTIR spectroscopy. The porous and spherical architecture achieved here enhanced the surface area, active sites, and electrical conductivity and also introduced more diffusion pathways at the electrode/electrolyte interface, which collectively improved the performance of CeO2 as a supercapacitor electrode material. The outstanding redox characteristics of CeO2 are explored in supercapacitor applications, and the electrode exhibited a specific capacitance of 319.68 F/g at a current density of 0.5 A/g in a three-electrode configuration which proved the excellence of the present CeO2 microspheres in the field of energy storage applications.

Yttrium Oxide nanoparticles induce cytotoxicity, genotoxicity, apoptosis, and ferroptosis in the human triple-negative breast cancer MDA-MB-231 cells

BackgroundTriple-negative breast cancer (TNBC) is a lethal mammary carcinoma subtype that affects females and is associated with a worse prognosis. Chemotherapy is the only conventional therapy available for patients with TNBC due to the lack of therapeutic targets. Yttrium oxide (Y2O3) is a rare earth metal oxide, whose nanoparticle (NPs) formulations are used in various applications, including biological imaging, the material sciences, and the chemical synthesis of inorganic chemicals. However, the biological activity of Y2O3-NPs against TNBC cells has not been fully explored. The current study was conducted to assess Y2O3-NPs’ anticancer activity against the human TNBC MDA-MB-231 cell line.MethodsTransmission electron microscopy (TEM), X-ray diffraction, Zeta potential, and dynamic light scattering (DLS) were used to characterize the Y2O3-NPs. SRB cell viability, reactive oxygen species (ROS) measurement, single-cell gel electrophoresis (comet assay), qPCR, flow cytometry, and Western blot were employed to assess the anticancer activity of the Y2O3-NPs.ResultsOur results indicate favorable physiochemical properties of Y2O3-NPs (with approximately average size 14 nm, Zeta Potential about − 53.2 mV, and polydispersity index = 0.630). Y2O3-NPs showed a potent cytotoxic effect against MDA-MB-231 cells, with IC50 values of 74.4 µg/mL, without cytotoxic effect on the normal retina REP1 and human dermal fibroblast HDF cell lines. Further, treatment of MDA-MB-231 cells with IC50 Y2O3-NPs resulted in increased oxidative stress, accumulation of intracellular ROS levels, and induced DNA damage assessed by Comet assay. Upon Y2O3-NPs treatment, a significant increase in the early and late phases of apoptosis was revealed in MDA-MB-231 cells. qPCR results showed that Y2O3-NPs significantly upregulated the pro-apoptotic genes CASP3 and CASP8 as well as ferroptosis-related gene heme oxygenase-1 (HO-1), whereas the anti-apoptotic gene BCL2 was significantly downregulated.ConclusionThis study suggests that Y2O3-NPs are safe on normal REP1 and HDF cells and exhibited a potent selective cytotoxic effect against the TNBC MDA-MB-231 cells through increasing levels of ROS generation with subsequent DNA damage, and induction of apoptosis and ferroptosis.

Dry Reforming of Methane over Rare-Earth Metal Oxide Ni–M–Al (M = Ce, La) Catalysts

Dry Reforming of Methane over Rare-Earth Metal Oxide Ni–M–Al (M = Ce, La) Catalysts

Superexchange antiferromagnetism and cryogenic magnetocaloric effect in scheelite-type GdTi0.5Mo0.5O4 compound

Scheelite-type LnLiF4 compounds have become promising cryogenic magnetic refrigerants due to their giant low-field magnetocaloric effect (MCE). This work presents an example of a scheelite-type rare-earth transition metal oxide GdTi0.5Mo0.5O4. The magnetic interactions, magnetic phase transition (MPT) and MCE of GdTi0.5Mo0.5O4 compound were investigated through magnetization measurements and a mean-field approach. A mean-field model was used to elucidate the role of primarily superexchange antiferromagnetic (AFM) coupling on the magnetocaloric performance in this compound. From the analysis of the magnetization dependence, an isotropic AFM exchange coupling with energy scale εex = JnnS2 ≈ 1.7 K was estimated. The magnetic susceptibility reveals the occurrence of MPT from paramagnetic (PM) to AFM at the Néel temperature (TN ≈ 1.3 K). GdTi0.5Mo0.5O4 exhibits a large magnetic entropy change up to 43.3 J/(kg·K) at 1.3 K for μ0ΔH = 0−7 T, which makes it a cryogenic magnetic refrigerant with potential applications. Furthermore, a mean-field model with superexchange AFM above 3 K can well predict the MCE observed in GdTi0.5Mo0.5O4.

Broadband Amplification in the 2.6–2.9 μm Wavelength Range in High-Purity Er3+-Doped Zinc-Tellurite Fibers Pumped by Diode Lasers

In recent years, great progress has been made in the technology of high-purity and ultra-dry tellurite glasses, which has enabled the creation of high-purity single-mode tellurite fibers doped with rare-earth ions. This technology has made it possible to demonstrate laser generation in the range of about 2.7 μm in erbium-doped tungsten tellurite fibers. In this paper, we present an experimental study of broadband amplification in erbium-doped zinc-tellurite fibers. Zinc-tellurite glasses containing modifying components, such as Na2O, La2O3, Bi2O3, or rare-earth metal oxides, are known to have noticeably lower phonon energy than heavy metal-tellurite systems, namely, tungsten tellurite glasses, which leads to better lasing output. The on-off gain of 30- and 60-cm long zinc-tellurite fibers has been measured in a wide range of diode pump powers. It has been shown for the first time that the amplification band is essentially extended, with pump power reaching over 250 nm (2600–2850 nm) at a peak power of about 40 W for a 30-cm long fiber.

Advances in Oxidative Coupling of Methane

C2+ hydrocarbons, especially C2+ olefins, as important basic chemical raw materials, mainly come from petroleum cracking. With the increasing scarcity of petroleum resources, the search for new olefins production routes has become the focus of research, and the production of olefins by the oxidative coupling of methane (OCM) process has attracted extensive attention. The OCM route is an important alternative to the production of olefins from petroleum resources and is also an important direction for the development of efficient and clean utilization of natural gas. In this paper, the mechanism, catalysts, and other key factors for the production of olefins by methane oxidative coupling are reviewed. The mechanism of OCM, including the reaction pathway and the formation of intermediate products, is introduced. Then, commonly used catalysts, such as alkali metal/alkaline earth metal oxides, rare earth metal oxides, composite metal oxides with special structures, and classical catalysts Mn/Na2WO4/SiO2, and their mechanisms of action in the reaction are discussed. In addition, the application of chemical looping oxidative coupling of methane (CLOCM) in olefin production is also investigated, which is a promising alternative way due to the high selectivity of olefins and the low cost of catalysts owing to the excellent performance of the catalyst recycling. These studies will help to further understand the mechanism of OCM for olefin production and provide guidance and support for applications in related fields.

Recovery of rare earth metal oxides from NdFeB magnet leachate by hydrophobic deep eutectic solvent extraction, oxalate stripping and calcination

With the scarcity of resources and the growing consumer demand for rare earth elements (RE), it is imperative to develop clean and sustainable methods to recover these valuable elements. This research proposes a novel green process for the selective recovery of RE from spent NdFeB permanent magnet using hydrophobic deep eutectic solvent (HDES). A total of 13 HDES systems composed of trioctylphosphine oxide (TOPO) as hydrogen bond acceptor (HBA) and alcohols as hydrogen bond donor (HBD) were prepared and characterized. Through a simple screening process, it was determined that ternary HDES (DA:MA:TOPO = 5:5:4) exhibited the best extraction and separation performance for REs and Fe. The extraction conditions such as aqueous phase acidity, organic/aqueous phase ratio, the concentration of Fe3+ and equilibration time were further studied and optimized. Under the most suitable conditions, HDES (DA:MA:TOPO = 5:5:4) was used for batch countercurrent extraction, where the concentration of REs in the raffinate was lowered from 4390 mg/L to 34 mg/L, and the recovery reached 99%. The HDES could be stripped by 0.2 mol/L Na2C2O4, which could further separate a small amount of loaded Fe (133 mg/L) and RE, so that the purity of the final product reached >99%. The stripped HDES could be recovered after washing with deionized water. Even after five cycles, HDES still maintained good stability. This innovative process does not require the use of salting-out agents or toxic volatile solvents, providing new possibilities for efficient and clean separation.

Novel 2D CeO2 nanoflakes as a high-performance asymmetric supercapacitor electrode material

Enhancing the performance and durability of benchmarked metal catalysts using nanostructured non-metallic materials is an active area of research that is exciting from both a fundamental and an application perspective. The 2D CeO2 nanoflakes are characterized using structural and electrochemical techniques. Galvanostatic charge-discharge (GCD) revealed that the material delivers a specific capacitance of 1801 F/g at 1 A/g, among the best-reported values for transition and rare earth metal oxide electrode material. Due to its nanoflake-like structure, the sample has a modest surface area (12.6 m2/g). Asymmetric supercapacitor device (CeO2//AC) fabricated delivered an energy density of 57.6 Wh/kg and a power density of 771 W/kg with 83 % capacitance retention after 1000 cycles in 3 M KOH. This study reveals that CeO2 is a promising electrode material for energy storage applications.

Interface Modification via Rare Earth Material to Assist Hole Migration for Efficiency and Stability Promotion of Perovskite Solar Cells

Interface defect is a limiting factor of the charge dynamics and stability of perovskite solar cells (PSCs). Herein, a rare earth metal oxide cerium oxide is introduced into the interface between perovskite and spiro‐OMeTAD [2,2,7,7‐tetrakis (N,N ‐di‐p‐methoxyphenyl‐amine) 9,9‐spirobifluorene] to passivate interfacial defects. Due to the nearest‐neighbor interaction of CeO2 with spiro‐OMeTAD, it can accelerate the oxidization process of spiro‐OMeTAD to form a donor–acceptor complex at this interface, which can overcome the interface barrier for the high hole collecting ability. The bonding formation between lead and oxygen makes this heterojunction show metal conduction behavior at this interface. The insertion of CeO2 between perovskite and spiro‐OMeTAD, can improve hole transferring to balance the extraction of electron and hole by their respective electrodes, for the decreased device hysteresis with the higher efficiency and improved stability. The results show that the CeO2‐based PSC device achieve a power conversion efficiency (PCE) of over 24%, retaining more than 87% of the initial PCE after 2570 h of storage at 20 ≈ 30% humidity.

A porous Eu-PTA/Tb-SSA/ZrO2/ZnZrO3 light color adjustable phosphor: Luminescent property and application of warm white LED

Light emitting diode (LED) is the fourth generation lighting source, but it has some shortcomings such as complex chip packaging process and the unbalanced light color of phosphor in long-time application. In this study, a kind of Eu-terephthalic acid/Tb-sulfosalicylate/ZrO2/ZnZrO3 (Eu-PTA/Tb-SSA/ZrO2/ZnZrO3) phosphor with warm white light emission properties was prepared, and the warm white light LED (w-WLEDs) was successfully prepared by encapsulating Eu-PTA/Tb-SSA/ZrO2/ZnZrO3 phosphors together with 270 nm UV-chip. The ZrO2/ZnZrO3, Tb-SSA/ZrO2/ZnZrO3 and Eu-PTA/ZrO2/ZnZrO3 samples show blue emission, green emission and red emission under deep ultraviolet (UV, 270 nm) excitation, respectively. The Tb-SSA and Eu-PTA are co-doped into ZrO2/ZnZrO3 matrix with blue emission to achieve the warm white light emission, and the light color can be adjusted by controlling the doping amount of Eu3+ and Tb3+. Through the excitation method of single-component phosphor by the single chip, the complex chip packaging process of w-LED can be solved. By doping rare earth organic complexes into porous ZrO2/ZnZrO3 matrix, the problems of the light color unbalanced of phosphor and the low luminescence intensity of rare earth doped metal oxides composites can be solved.

A Review on Photocatalysis Used For Wastewater Treatment: Dye Degradation.

Water pollution is a global issue as a consequence of rapid industrialization and urbanization. Organic compounds which are generated from various industries produce problematic pollutants in water. Recently, metal oxide (TiO2, SnO2, CeO2, ZrO2, WO3, and ZnO)-based semiconductors have been explored as excellent photocatalysts in order to degrade organic pollutants in wastewater. However, their photocatalytic performance is limited due to their high band gap (UV range) and recombination time of photogenerated electron-hole pairs. Strategies for improving the performance of these metal oxides in the fields of photocatalysis are discussed. To improve their photocatalytic activity, researchers have investigated the concept of doping, formation ofnanocomposites and core-shell nanostructures of metal oxides. Rare-earth doped metal oxides have the advantage of interacting with functional groups quickly because of the 4f empty orbitals. More precisely, in this review, in-depth procedures for synthesizing rare earth doped metal oxides and nonocomposites, their efficiency towards organic pollutants degradation and sources have been discussed. The major goal of this review article is to propose high-performing, cost-effective combined tactics with prospective benefits for future industrial applications solutions.

Preparation and stability of the hexagonal phase of samarium oxide on Ru(0001)

We have used low-energy electron microscopy (LEEM), micro-illumination low-energy electron diffraction (µLEED) supported by ab initio calculations, and X-ray absorption spectroscopy (XAS) to investigate in-situ and in real-time the structural properties of Sm2O3 deposits grown on Ru(0001), a rare-earth metal oxide model catalyst. Our results show that samarium oxide grows in a hexagonal A-Sm2O3 phase on Ru(0001), exhibiting a (0001) oriented-top facet and (113) side facets. Upon annealing, a structural transition from the hexagonal to cubic phase occurs, in which the Sm cations exhibit the +3 oxidation state. The unexpected initial growth in the A-Sm2O3 hexagonal phase and its gradual transition to a mixture with cubic C-Sm2O3 showcases the complexity of the system and the critical role of the substrate in the stabilization of the hexagonal phase, which was previously reported only at high pressures and temperatures for bulk samaria. Besides, these results highlight the potential interactions that Sm could have with other catalytic compounds with respect to the here gathered insights on the preparation conditions and the specific compounds with which it interacts.

MODIFICATION OF LANTHANUM OXIDE La<sub>2</sub>O<sub>3</sub> ON THE STRUCTURE OF SUPRASTRUCTURAL UNITS IN ALKALI BORATS

It shows a significant change in structurally sensitive properties in the experiment of modifying a melt (or glass) of the B2O3–Na2O system with lanthanum oxide La2O3 with the destruction of superstructural units when lanthanum atoms hit, since small additions of rare earth metal oxides lead to a significant change in the properties of alkali borate melts. Molecular models of some of the superstructural units, the structure and properties of which were calculated by semi-empirical quantum chemical methods with MNDO and PM7 parameters: as a result of the optimization procedure, both methods lead to models that are qualitatively close, but differ in bond lengths, and practically the same value of heat of formation. The superstructural unit of the considered type is preserved, while its characteristics change: the volume occupied by it increases, the newly formed bond is less strong and its ionic degree is greater.

Preparation and Mechanical Characteristics of Multicomponent Ceramic Solid Solutions of Rare Earth Metal Oxides Synthesized by the SCS Method

A study into the use of the Solution Combustion Synthesis (SCS) method with glycine and citric acid to synthesize fine powders of multicomponent solid solutions of oxides of rare earth (RE) metals (Nd, Sm, Eu, Gd, Dy, and Ho) for the preparation of ceramic materials is presented. Synthesis parameters of 4-, 5-, and 6-component entropy-stabilized rare earth oxides (REOs) with a C-type cubic structure are determined. The stability of entropy-stabilized oxides (ESOs) with a C-type structure is shown to depend not only on heavy RE metal quantity, but also on the rate of heating/cooling of the samples. The temperature of the polymorphic transformation of C-type REO structures into B-type (monoclinic) or H-type (hexagonal) structural variants can be described by the equation T (°C) = 0.0214Vcr2 − 62.737Vcr + 46390, where Vcr is the unit cell volume of an oxide with a C-type structure regardless of the number of cations in the solid solution. High-temperature thermal analysis up to 1250 °C revealed that dispersed powders, which contain impurities of basic carbonates along with hydroxocarbonates of RE metals and X-ray amorphous carbon formed during SCS reactions, also react with air moisture during storage. The influence of the ESO phase and cationic composition on the morphology, porosity and microhardness of ceramics was studied. Higher-entropy oxides form samples with higher density, microhardness and a smaller size of particle agglomerates.

High-Performance Organic Field-Effect Transistors Using Rare Earth Metal Oxides as Dielectrics

Rare earth metal oxides (REOs) represent promising gate dielectric materials for field-effect transistors due to their high dielectric constants required for suppressing leakage currents in devices. In this paper, we present an approach to deposition of uniform REO gate dielectric coatings by oxidation of thin rare earth metal films in air at relatively low temperatures (100–250 °C). The proposed methodology was extensively explored in organic field-effect transistors (OFETs) using five benchmark organic semiconductors and six REOs as gate dielectrics. It was shown that OFETs with the REO gate dielectrics deliver on average considerably better characteristics compared to the reference devices using electrochemically grown aluminum oxide dielectric (AlOx). OFETs on a flexible plastic substrate were demonstrated, which makes this approach very attractive for developing flexible and wearable electronic devices with improved performance.