Rare Earth Metals Research Articles

Recent Progress in Non-Noble Metal Catalysts for Oxygen Evolution Reaction: A Focus on Transition and Rare-Earth Elements.

The demand for renewable energy sources has become more urgent due to climate change and environmental pollution. The oxygen evolution reaction (OER) plays a crucial role in green energy sources. This article primarily explores the potential of using non-noble metals, such as transition and rare earth metals, to enhance the efficiency of the OER process. Due to their cost-effectiveness and unique electronic structure, these non-noble metals could be a game-changer in the field. 'Doping,' which is the process of adding a small amount of impurity to a material to alter its properties, and 'synergistic effects,' which refer to the combined effect of two or more elements that is greater than the sum of their individual effects, are two key concepts in this field. Transition and rare earth metals can reduce the overpotential, a measure of the excess potential required to drive a reaction, thus enhancing the OER process by engineering the electronic and surface molecular structure. This article summarizes the roles of various non-noble metals in the OER process and highlights opportunities for researchers to propose innovative ways to optimize the OER process.

Cold Molecular Ions via Autoionization below the Dissociation Limit.

Several diatomic transition metal oxides, rare-earth metal oxides, and fluorides have the unusual property that their bond dissociation energy is larger than their ionization energy. In these molecules, bound levels above the ionization energy can be populated via strong, resonant transitions from the ground state. The only relevant decay channel of these levels is autoionization; predissociation is energetically not possible and radiative decay is many orders of magnitude slower. Starting from translationally cold neutral molecules, translationally cold molecular ions can thus be produced with very high efficiency. By populating bound levels just above the ionization energy, internally cold molecular ions, exclusively occupying the lowest rotational level, are produced. This is experimentally shown here for the dysprosium monoxide molecule DyO, for which the lowest bond dissociation energy is determined to be 0.0831(6)eV above the ionization energy.

Breaking Symmetry for SHG Response: Lanthanide Acetate Crystals via Water Molecule Regulation Strategy.

In the field of nonlinear optical (NLO) materials research, the design and synthesis of novel materials are crucial for advancing modern scientific and technological development. This study employs an innovative coordination strategy, building upon the existing structure of [Ln2(CH3COO)6(H2O)4]·4H2O (Ln = Tb, Sm), to successfully synthesize a series of acetate rare-earth metal compounds [Ln2(CH3COO)6(H2O)]n [Ln = Tb(1), Er(2), Y(3)] by regulating the number of water molecules. This approach achieved a structural transition from centrosymmetric (CS) to noncentrosymmetric (NCS), endowing these compounds with significant nonlinear optical responses. We discovered that reducing the coordinated water molecules and introducing acetate as a bidentate ligand is an effective method for modulating crystal structure and realizing NLO performance. This finding not only deepens the understanding of the structure of acetate salts but also provides important theoretical and experimental support for the development of materials with potential NLO propeties.

Application of Y-MOF-CNT-Derived Y2O3-C@CNT Composites in Lithium-Sulfur Battery Separators.

In order to mitigate the shuttle effect of lithium polysulfides in lithium-sulfur batteries, we propose a yttrium-metal-organic framework-carbon nanotube (Y-MOF-CNT)-derived Y2O3-C@CNT composite for modifying the separator in this study. The Y-MOFs, comprising yttrium (Y) rare earth metal and terephthalic acid, exemplify a prototypical category of metal-organic framework (MOF) materials. They manifest the advantageous attributes associated with MOFs while concurrently possessing distinctive catalytic traits ascribed to rare earth elements. In this study, Y-MOF nanoparticles were synthesized on carbon nanotube (CNT) substrates via a facile aqueous solution method, succeeded by high-temperature carbonization to yield Y2O3-C@CNT composite materials. These composites were subsequently employed as coatings on one side of polyethylene (PE) separators. The resultant Y2O3-C@CNT composite inherits the particle-like morphology and porosity from its precursor Y-MOF, alongside the inherent conductivity in carbon-based materials. This amalgamation is conducive to polysulfide capture and catalytic conversion processes within lithium-sulfur batteries. The application of the Y2O3-C@CNT-coated PE separator effectively mitigated polysulfide shuttle effects and significantly enhanced the battery electrochemical performance. At a sulfur loading level of 3 mg cm-2 under a 0.5 C rate, an initial discharge specific capacity of 900 mAh g-1 was achieved. After 400 cycles, the discharge specific capacity remained at 483.85 mAh g-1 with a capacity retention rate of 53.7%. Upon increasing sulfur loading to 5 mg cm-2, the discharge specific capacity at a lower rate (0.1 C) reached 817.8 mAh g-1; even after 100 cycles, it maintained a value of 700 mAh g-1 with a capacity retention rate of 85.6%. Notably, our modified Y2O3-C@CNT separator demonstrated exceptional cycling stability, even under conditions involving high sulfur loading.

Rational Design of Novel Polar Nonlinear Optical Materials in Alkali Metal Rare Earth Iodates.

Four new potassium rare earth iodates, namely, acentric K2Lu(IO3)5 and KM(IO3)4(HIO3)0.33 (M = Ce/Pr) and centric KLa(IO3)4, were successfully grown by mild hydrothermal reactions. Three of them exhibit polar structures; K2Lu(IO3)5, KCe(IO3)4(HIO3)0.33, and KPr(IO3)4(HIO3)0.33 show second-harmonic generation (SHG) responses of 3.0, 1.0, and 0.8 × KDP, respectively. These three iodates are phase-matchable for second-harmonic generation. The influence of changes in the radius and coordination mode of rare earth ions on the crystal structure and SHG response has been discussed in detail. Our findings suggest that in the alkali metal rare earth iodate, modulating the arrangement of iodate groups by changing the coordination geometry of rare earth ions is an effective strategy for designing polar NLO materials.

Construction of heterojunction based on Nd2S3 and tin dioxide for rapid detection of ethanol

The gas-sensing properties of Nd2S3 have not been previously explored. In this study, a novel composite material comprising rare-earth metal sulfide (Nd2S3) and metal oxide (SnO2) was successfully prepared using a two-step hydrothermal method for the rapid detection of ethanol. Characterization results revealed that the morphology and specific surface area of Nd2S3-SnO2 remained largely unchanged after composite formation. However, the built-in electric field established between Nd2S3 and SnO2 significantly enhanced carrier transport and separation. Additionally, the introduction of extra oxygen vacancies increased the content of chemisorbed oxygen, providing more active sites for ethanol molecules, thereby improving the gas-sensing performance. The Nd2S3-SnO2 sensor demonstrated extremely high detection accuracy (R2=0.9965) over the 20–300 ppm ethanol concentration range, with response/recovery time of 8/274 s at 100 ppm ethanol concentration and response value of 93. It also possesses excellent selectivity to ethanol, long-term stability and reversibility. This work represents a preliminary exploration of the gas-sensing properties of Nd2S3 and its underlying mechanisms through the construction of a heterojunction structure between metal sulfide and metal oxide.

Rare-earth elements in dictyonema shales of the Baltic sedimentary paleobasin

The results of a study of rare-earth metals in dictyonema shales of the Paleozoic Baltic sedimentary basin, have been given. On the territory of the studied Kaibolovo-Gostilitsy prospecting area, high up to potentially industrial contents of rare-earth elements were confirmed on a large factual and analytical material. The average REE concentration is 289 g/t with maximum up to 724 g/t. REE are found in dictyonema shales in various forms (mineral, organic, ionic, molecular, colloidal). Apparently, the occurrence of REE in the mineral part of dictyonema shales prevails. The proportion of heavy (and most valuable) lanthanides (15.6% in the relative total amount) in the studied dictyonema shales is twice the ore deposits range. This, and the presence of large geological resources of the REE in the dictyonema shales of the Baltic region of Russia, determine the need for their integrated development with other associated components.

Effect of Addition of Rare Earth Metal (Ce) on the Microstructure, Mechanical Properties and Corrosion Behavior of NiTi Alloys

Effect of Addition of Rare Earth Metal (Ce) on the Microstructure, Mechanical Properties and Corrosion Behavior of NiTi Alloys

Lanthanide conjugate Pr-MPO elicits anti-cancer activity by targeting lysosomal machinery and inducing zinc-dependent cataplerosis.

Acquired drug resistance is a major challenge in the management of cancer, which underscores the need for discovery and development of novel therapeutic strategies. We report here the mechanism of the anti-cancer activity of a small coordinate complex composed of the rare earth metal praseodymium (Pr) and mercaptopyridine oxide (MPO; pyrithione). Exposure of cancer cells to relatively low concentrations of the conjugate Pr-MPO (5 µM) significantly impairs cell survival in a p53-independent manner and irrespective of the drug resistant phenotype. Mechanistically, Pr-MPO-induced cell death is caspase-independent, not inhibitable by necrostatin, but associated with the appearance of autophagy markers. However, further analysis revealed incomplete autophagic flux, thus suggesting altered integrity of lysosomal machinery. Supporting the lysosomal targeting activity are data demonstrating increased lysosomal Ca2+ accumulation and alkalinization, which coincides with cytosolic acidification (drop in pHc from 7.75 to 7.00). In parallel, an increase in lysosomal activity of glycosidase alpha acid (GAA), involved in passive glycogen breakdown, correlates with rapid depletion of glucose stores upon Pr-MPO treatment. This is associated with swift cataplerosis of TCA cycle intermediates, loss of NAD+/NADH and increase in pyruvate dehydrogenase (PDH) activity to compensate for pyruvate loss. Addition of exogenous pyruvate rescued cell survival. Notably, lysosomal impairment and metabolic catastrophe triggered by Pr-MPO are suggestive of Zn2+-mediated cytotoxicity, which is confirmed by the ability of Zn2+ chelator TPEN to block Pr-MPO-mediated anti-tumor activity. Together, these results highlight the ability of the small molecule lanthanide conjugate to target the cells' waste clearing machinery as well as mitochondrial metabolism for Zn2+-mediated execution of cancer cells, which could have therapeutic potential against cancers with high metabolic activity.

Rare-Earth Metal-Based Materials for Hydrogen Storage: Progress, Challenges, and Future Perspectives.

Rare-earth-metal-based materials have emerged as frontrunners in the quest for high-performance hydrogen storage solutions, offering a paradigm shift in clean energy technologies. This comprehensive review delves into the cutting-edge advancements, challenges, and future prospects of these materials, providing a roadmap for their development and implementation. By elucidating the fundamental principles, synthesis methods, characterization techniques, and performance enhancement strategies, we unveil the immense potential of rare-earth metals in revolutionizing hydrogen storage. The unique electronic structure and hydrogen affinity of these elements enable diverse storage mechanisms, including chemisorption, physisorption, and hydride formation. Through rational design, nanostructuring, surface modification, and catalytic doping, the hydrogen storage capacity, kinetics, and thermodynamics of rare-earth-metal-based materials can be significantly enhanced. However, challenges such as cost, scalability, and long-term stability need to be addressed for their widespread adoption. This review not only presents a critical analysis of the state-of-the-art but also highlights the opportunities for multidisciplinary research and innovation. By harnessing the synergies between materials science, nanotechnology, and computational modeling, rare-earth-metal-based hydrogen storage materials are poised to accelerate the transition towards a sustainable hydrogen economy, ushering in a new era of clean energy solutions.

Unraveling Oxygen Vacancies Effect on Chemical Composition, Electronic Structure and Optical Properties of Eu Doped SnO2.

The influence of Eu doping (0.5, 1 and 2 mol.%) and annealing in an oxygen-deficient atmosphere on the structure and optical properties of SnO2 nanoparticles were investigated in relation to electronic structure. The X-ray diffraction (XRD) patterns revealed single-phase tetragonal rutile structure for both synthesized and annealed Eu-doped SnO2 samples, except for the annealed sample with 2 mol.% Eu. The results of X-ray photoelectron spectroscopy (XPS) emphasized that europium incorporated into the SnO2 host lattice with an oxidation state of 3+, which was accompanied by the formation of oxygen vacancies under cation substitution of tetravalent Sn. Moreover, XPS spectra showed the O/Sn ratio, which has been reduced under annealing for creating additional oxygen vacancies. The pulse cathodoluminescence (PCL) demonstrated the concentration dependence of Eu site symmetry. Combination of XRD, XPS and PCL revealed that Eu doping and following annealing induce strongly disordering of the SnO2 crystal lattice. Our findings provide new insight into the interaction of rare-earth metals (Eu) with host SnO2 matrix and new evidence for the importance of oxygen vacancies for optical and electronic structure formation.

Synthesis of Pt-Rare Earth Metal Alloys and Their Applications.

The alloying of platinum (Pt) with rare earth (RE) metals has emerged as a highly promising strategy for enhancing both the activity and stability of catalysts. Consequently, the development of methods for the controlled synthesis of Pt-RE alloys has received growing attention. This review comprehensively explores diverse synthesis methodologies for Pt-RE alloys, including physical metallurgy method, chemical reduction method, electrodeposition method, and dealloying method. Additionally, this review summaries the applications of Pt-RE alloys in various fields. By providing a critical analysis of existing literature and highlighting key challenges and future directions, this review aims to offer valuable insights and serve as a springboard for further advancements in the controlled synthesis and diverse applications of Pt-RE alloys.

Terahertz Crystal-Field Transitions and Quasi Ferromagnetic Magnon Excitations in a Noncollinear Magnet for Hybrid Spin-Wave Computation.

The complexity of interactions between the crystal-field and unusual noncollinear spin arrangement in nontrivial magnets demands novel tools to unravel the mystery underneath. In this work, we study such interaction dynamics of crystal-field excitations (CFE) and low-energy magnetic excitations in orthochromite TmCrO3 with controls of temperature and magnetic field using high-resolution magneto-terahertz (THz) time-domain spectroscopy. The THz energy spectrum spanning 0.5-10 meV possesses a low-frequency spin-excitation (magnon) mode and a multitude of CFE modes at 10 K, all of which uniquely embody a range of phenomena. For the magnon mode, a temperature dependence of peak frequency is induced by magnetic interactions between Tm and Cr subsystems. While a change from blue to red shift of peak frequency of this mode marks the magnetization reversal transition, the spin-reorientation temperature and change of magnetic anisotropy are depicted by different features of field and temperature dependent peak frequency dynamics. The modes corresponding to CFE are robust and laden with a multitude of submodes, which are attributes of nontrivial interactions across different transitions. These modes are suppressed only upon substitution of Tb3+ at the Tm3+ site, which suggests a dominant role of single-ion anisotropy in controlling entire THz excitation spectra. Overall, this remarkable range of phenomena seen through the unique lens of all-optical THz tools provides deeper insights into the origin of magnetic phases in systems with complex interactions between rare-earth and transition metal ions and provides a multitude of novel combinations of closely spaced modes for emerging hybrid spin-wave computation.

Stabilization of the Compressed Planar Benzene Dianion in Inverse-Sandwich Rare Earth Metal Complexes.

For the first time, the capture of a planar antiaromatic benzene dianion in between two trivalent rare earth (RE) metal cations, each stabilized by two guanidinate ligands, is reported. The synthesized inverse-sandwich complexes [{(Me3Si)2NC(NiPr)2}2RE]2(µ-ƞ6:ƞ6-C6H6), (RE = Y (1), Dy (2), and Er (3)) feature a remarkably planar benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The -2 charge localization at the benzene ligand was deduced from the results obtained by single-crystal X-ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations. In the 1H NMR spectrum of the diamagnetic Y complex 1, the equivalent proton resonance of the bridging benzene dianion ligand is drastically shifted to higher field in comparison to free benzene. This and the calculated highly positive Nucleus-Independent Chemical Shift (NICS) values are attributed to the antiaromatic character of the benzene dianion ligand. The crucial role of the ancillary guanidinate ligand scaffold in stabilizing the planar benzene dianion conformation was also elucidated by DFT calculations. Remarkably, the planarity of the benzene dianion originates from the stabilization of the π-type orbitals of the d-manifold and compression through its strong electrostatic interaction with the two REIII sites.

Stabilization of the Compressed Planar Benzene Dianion in Inverse‐Sandwich Rare Earth Metal Complexes

For the first time, the capture of a planar antiaromatic benzene dianion in between two trivalent rare earth (RE) metal cations, each stabilized by two guanidinate ligands, is reported. The synthesized inverse‐sandwich complexes [{(Me3Si)2NC(NiPr)2}2RE]2(µ–ƞ6:ƞ6–C6H6), (RE = Y (1), Dy (2), and Er (3)) feature a remarkably planar benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The ‐2 charge localization at the benzene ligand was deduced from the results obtained by single‐crystal X‐ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations. In the 1H NMR spectrum of the diamagnetic Y complex 1, the equivalent proton resonance of the bridging benzene dianion ligand is drastically shifted to higher field in comparison to free benzene. This and the calculated highly positive Nucleus‐Independent Chemical Shift (NICS) values are attributed to the antiaromatic character of the benzene dianion ligand. The crucial role of the ancillary guanidinate ligand scaffold in stabilizing the planar benzene dianion conformation was also elucidated by DFT calculations. Remarkably, the planarity of the benzene dianion originates from the stabilization of the π‐type orbitals of the d‐manifold and compression through its strong electrostatic interaction with the two REIII sites.

Designing a series of RE based carbon composites (RE=Tb, Gd, Ho, Lu, Nd, Sm, Yb, Eu, and Ce)-especially Tb-N-Cs for oxygen reduction enhancement

Iron and nitrogen co-doped carbon materials (Fe–N–Cs) have enormous application prospects in cathodic oxygen reduction reaction (ORR) as efficient electrode materials. However, their stability is of great importance, but is still limited by severe Fenton reaction due to the preferential reaction between Fe2+ and H2O2. This paper intends to rationally design a series of rare earth (RE) metals based carbon matrix anchoring RE centers directly converted from RE oxides and small nitrogen-containing carbon molecules by employing the molten-salts-assisted pyrolysis. A class of prepared RE based carbon (RE-N-Cs) catalysts surprisingly exhibits ORR activities comparable to that of Pt/C. The Tb–N–Cs sample with the best catalytic activity among them was characterized by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-Ray Diffraction (XRD). The characterization results show the presence of Tb single-sites in carbon substrate, with Eonset of 1.06 V and Jd of 6.37 mA cm−2, exceeding those of the commercial Pt/C (Eonset = 0.96 V vs. RHE; Jd = 5.64 mA cm−2).

Modification of microstructural, mechanical and optical properties with carbon ion irradiation in Y2SiO5 crystals

Yttrium orthosilicate Y2SiO5 crystals, a member of the silicate family, are versatile and multifunctional materials when doped with rare earth or transition metal ions. However, there have been limited investigations into the impact of ion irradiation on the crystal structure of Y2SiO5 crystals to date. In this paper, the effect of microstructure, mechanical and optical properties of Y2SiO5 crystal before and after different fluences of carbon ions irradiation was investigated utilizing complementary characterization techniques. The results indicate that carbon ion irradiation caused lattice disorder and damage, which resulted in structural deterioration and changes in optical properties, such as decrease in the optical band gap energy (from5.77 eV to 5.44 eV), changes in the effective refractive index (neff) which resulted in the formation of “well + barrier” type and “barrier” type waveguides. In addition, elastic modulus increased after carbon ion irradiation. The results will be helpful for understanding the damage study of the Y2SiO5 crystal with carbon ion irradiation and proving that ion beam techniques can be used for material modification.

Investigation of rare earth metal ions (Sm and Er) doped CoMoO4 polymorphs for photocatalytic dye degradation

Cobalt molybdate (CoMoO4) and its rare earth doped variants have emerged as promising photocatalysts for degrading dye pollutants in wastewater. The photocatalysts were prepared using a modified sol-gel method, employing ammonium heptamolybdate tetrahydrate and cobalt (II) nitrate hexahydrate as precursors. The incorporation of samarium and erbium as a dopant was hypothesized to improve the photocatalytic activity of CoMoO4 by altering its band structure and creating defect sites for improved dye adsorption and degradation. The structural and optical properties of the synthesized photocatalysts were characterized using various techniques. The photocatalytic performance of CoMoO4, Sm:CoMoO4 and Er:CoMoO4 was evaluated by monitoring the degradation of MB dye under light irradiation. The results reveal that Sm:CoMoO4 and Er:CoMoO4 catalysts achieve a degradation efficiencies of 99 % and 97 %, respectively, highlighting the potential of rare earth-doped CoMoO4 as an efficient photocatalyst for the remediation of dye contaminated wastewater.

Implementation of 2,2'-azobispyridine radical mono- and dianions in dinuclear rare earth metal complexes.

The seminal isolation of a dinuclear rare earth metal complex comprising a bridging 2,2'-azobispyridyl radical anion, [(Cptet2Y)2(μ-abpy˙)](BPh4), is presented, which was obtained from a one-electron chemical oxidation of [(Cptet2Y)2(μ-abpy)]. The unprecedented compounds were characterized by crystallography, spectroscopy and DFT computations. The radical character was proven by EPR spectroscopy.

Research progress of Mn-based low-temperature SCR denitrification catalysts.

Selective catalytic reduction (SCR) is a efficiently nitrogen oxides removal technology from stationary source flue gases. Catalysts are key component in the technology, but currently face problems including poor low-temperature activity, narrow temperature windows, low selectivity, and susceptibility to water passivation and sulphur dioxide poisoning. To develop high-efficiency low-temperature denitrification activity catalyst, manganese-based catalysts have become a focal point of research globally for low-temperature SCR denitrification catalysts. This article investigates the denitrification efficiency of unsupported manganese-based catalysts, exploring the influence of oxidation valence, preparation method, crystallinity, crystal form, and morphology structure. It examines the catalytic performance of binary and multicomponent unsupported manganese-based catalysts, focusing on the use of transition metals and rare earth metals to modify manganese oxide. Furthermore, the synergistic effect of supported manganese-based catalysts is studied, considering metal oxides, molecular sieves, carbon materials, and other materials (composite carriers and inorganic non-metallic minerals) as supports. The reaction mechanism of low-temperature denitrification by manganese-based catalysts and the mechanism of sulphur dioxide/water poisoning are analysed in detail, and the development of practical and efficient manganese-based catalysts is considered.