Rare Earth Oxides Research Articles

Drying-wetting cycles affect soil structure by impacting soil aggregate transformations and soil organic carbon fractions

Drying-wetting (DW) cycles influence the formation and breakdown of soil aggregates and consequently impact the physical protection of soil organic carbon (SOC). However, the interaction between soil structural dynamics and SOC fraction changes driven by DW cycles is still unclear. Herein, aggregation pathways were tracked by using rare earth oxides (REOs) as tracers. The recombined soil columns were subjected to different DW frequencies (0, 1, 2, 4 and 8 cycles) and two DW intensities (low intensity, Q1; high intensity, Q2). During a 56-day incubation, aggregate distributions, mean water diameter (MWD), REO concentrations, the contents of SOC and its fractions (particulate organic carbon, POC; mineral-associated organic carbon, MOC) were measured. The results showed that MWD markedly increased with DW frequencies regardless of DW intensities and was significantly related to the relative changes of 2–0.25 mm aggregates (P < 0.05). Based on transformation paths, DW cycles stimulated the breakdown of > 0.25 mm aggregates and the aggregation of < 0.053 mm aggregates, thus leading to the increasing formation of 0.25–0.053 mm aggregates. Soil aggregate turnover time was affected by DW intensities and extended with DW frequencies (P < 0.05). Soil aggregate turnover time was displayed in the order of < 0.25 mm aggregates < 2–0.25 mm aggregates < 5–2 mm aggregates. MOC concentration exhibited an increasing trend with DW frequencies. A higher loss of SOC under high DW intensity resulted from more exposure of POC through soil aggregate breakdown. POC concentration was sensitive most to the 2–0.25 mm aggregates turnover time. The structural equation model (SEM) revealed that DW cycles exerted remarkable effects on MWD by impacting SOC fractions and soil aggregate transformations. Overall, our findings suggested that soil aggregate breakdown and formation processes, rather than aggregate size distributions, were more of a concern when evaluating the effects of DW cycles on soil structural stability.

Characterization of a novel TORT cable wound of stabilized striated REBCO tapes for reduced magnetization AC losses

REBCO (rare-earth barium copper oxide) high-temperature superconducting tapes, have a high potential for winding of large magnet coils. Tapes on round tube (TORT) cables represent a promising option for achieving a conductor suitable for the winding of magnet coils. However, certain applications, such as accelerator magnets, require the use of superconducting cables with low magnetization alternative current (AC) losses. There are several methods to reduce AC losses in TORT cables. Our first approach was to get rid of eddy currents by replacing the copper former with dielectric materials based on polymers and composites, i.e. polyethylene terephthalate glycol-modified reinforced with carbon fibers. Additional reduction of hysteretic loss was achieved by striating of copper coated REBCO tapes. We employed chemo-mechanical striating, for these objectives. However, the superconductor is exposed during the striating process, which may lead to later moisture-related degradation. Hence multilayers based on Ti/AlN were deposited using magnetron sputtering in order to protect the superconductor immediately after the striating process from water and atmospheric moisture corrosion. Subsequently, striated tapes as well as the non-striated tapes were then wound onto formers with diameters of 10 mm, 7 mm and 5.5 mm, and then on the short TORT cables bending tests were performed. After each technological step, direct current measurements were performed on the samples and finally the AC losses were measured.

Breakthrough in High-Efficiency Photocatalytic Degradation of Acebutolol by Advanced Binary CeO2-MnO2 Oxide System.

The sustainable catalytic efficacy of transition metal oxides (TMO) and rare earth element-based oxides positions them as pivotal materials for effectively treating contaminated wastewater. This study successfully synthesized a series of Ce@MnO2 photocatalysts using a straightforward hydrothermal method. These photocatalysts were thoroughly characterized for their optical properties, structural morphology, and phase purity. Among the synthesized materials, the Ce@MnO2 (40:60) exhibited the highest photocatalytic activity for the degradation of Acebutolol (ACB), achieving a remarkable degradation efficiency of 92.71% within 90 min under visible light irradiation. This superior performance is attributed to the increased presence of active species and the efficient separation of photogenerated carriers. Additionally, the photocatalytic reaction mechanism was elucidated, highlighting the catalyst's surface charge properties which significantly enhanced performance in a solution with pH 8. The outstanding photo-response in the visible spectrum renders this method not only cost-effective but also environmentally benign, presenting a promising approach for large-scale water purification.

Improvements in recovery of rare earth elements (REEs) from coal via fluidized-bed combustion: Thermal alteration of REE mineralogy and its impact on element extractability

The extraction of rare earth elements (REE) from coal ash has attracted significant attention, but satisfactory solutions have not yet been achieved. Indeed, the REE extractability is largely determined by the transformation behavior of REE during coal combustion. This study found that the controlled combustion conditions of circulated fluidized-bed boiler (CFB) can both utilize the heating value and enhance the recovery of REE from coal. Tests were conducted using a bituminous coal with REE concentration of approximately 149 ppm in an industrial 35 t/h CFB boiler with controlled boiler loads and coal sources. Advanced automated image analysis by scanning electron microscopy (AIA-SEM) and sequential leaching procedure were employed to clarify the speciation transformation behavior of REE in boilers and investigate the effects of these transformations on the leachability of REE. Approximately 75 % of REE partitioned into fly ash and enriched in particles < 45 μm (∼710 ppm) after combustion. Acid leaching tests under mild conditions (1 M HCl at 60 ℃ and S/L = 1:25) performed on coal, bulk ashes, and sieved ashes revealed an improvement in REE leaching ratio from coal (21.34 %) to fly ash (71.07 %). Particle size played a crucial role in acid extractability, particularly for middle and heavy REE in cyclone ash but had no influence on those in fly ash. The dominant forms of REE in coal including Ca-REE fluorocarbonates (36.7 %), aluminophosphates (12.0 %), and organic-bound REE (approximately 20 %) significantly decreased, contributing to the formation of leachable rare earth oxides (∼65 %) in ash. Furthermore, the small size of REE mineral grains in coal (over 50 % below 5 μm) and extensive mineral fragmentation occurring in boiler resulted in the enrichment and enhanced REY leachability in fine ash.

Effects of rare-earth oxides on grain boundary strength of silicon nitride ceramics

This study investigates the grain boundary (GB) strengths for Si3N4 ceramics doped with 3 wt% RE2O3 (RE = Y, La, or Lu) and 7 wt% MgO, using microcantilever beam specimens having different misorientation angles of the two adjacent grains. The measured strengths are so high that they are comparable to the theoretical strength of the intergranular glassy film (IGF). They are also widely scattered with a Weibull modulus of 3.0. The strength depends on the type of RE2O3 and increases in order of Y<La<Lu. It is suggested that the fracture occurs from the IGF/Si3N4 interfaces rather than within the IGF, and that O anions, which reside within the IGF and do not dissolve into the β-Si3N4 crystal lattice because of the high cationic field strength, reduce the IGF/grain interface strength. The GB strength also little depends on the misorientation angles, which is discussed in relation with the IGF accommodation ability of mismatch.

Improving the reliability of using rare earth elements as soil erosion tracers

Rare earth elements (REEs) have been successfully used as tracers in field-scale erosion experiments to provide spatially distributed erosion data for process-based soil erosion models. This study aimed to demonstrate how differences in the erodibility of individual REEs naturally present in the soil affect the evaluation of data from such experiments.A four-year field experiment was carried out at an experimental site used for arable farming to investigate soil erosion. The concentrations of tracer REEs (Pr, Sm, Gd, Ho, Er, and Yb) and reference REEs (all other REEs) were evaluated and compared both in the soil and eroded sediment.The tracer REE concentrations in the eroded sediments were consistently significantly higher than the average background soil concentrations. Even when compared with the maximum values of background soil concentrations, enrichment of Er, Sm, and Ho in the sediment was still evident. However, in some cases, the reference REE concentrations in the sediment were often higher than the maximum soil background concentrations by more than 10%. These enrichment differences indicate the varying erodibility of individual REEs during erosion. The elements chosen as tracers could also be enriched in the sediment from their natural background sources, thus influencing the measured concentration values in the sediment after tagging.This study demonstrated that different REEs naturally present in soil exhibit varying degrees of erodibility, which affects data evaluation in soil erosion tracing experiments using REE oxides as tracers. Therefore, the reliable application of the REE tracer method can only be suggested under certain requirements defined in this study.

Preparation and investigation of TbCrO3/montmorillonite-K10 nanocomposite electrode for electrochemical hydrogen storage application

The limited resources of fossil fuels and the increase in human’s demand for energy have made the use of alternative green energies like hydrogen very important. In this regard, achieving superior specific capacity and high-performance electrochemical hydrogen storage requires the structural design and development of highly active electrode material with cooperative influence of “spillover”, “redox”, and “physisorption” mechanisms. The aim of this report is to fabricate a binary TbCrO3/montmorillonite-K10 (TC/MMT) nanocomposite and to skillfully ensure its electrochemical ability for hydrogen storage in 2.0 M KOH electrolyte, for the first time. A facile sonochemical strategy was presented to successfully form uniform orthorhombic TC nanoparticles with varying tetradentate Schiff base ligands derived from salicylaldehyde and relative diamines as well as the molar ratio of H2Salbn to Tb3+. Characterization analyses displayed that the nucleation and growth process of TC samples can be well controlled by a molar ratio of H2Salbn:Tb3+ = 1:1 within the range of 17–72 nm. Furthermore, implementation of a well-organized MMT-based nanocomposite with various amounts of nano-TC perovskites was evaluated on the structural and electrochemical features. The greatly enhanced hydrogen storage capacity of TC/MMT nanocomposites was acquired as 734.3 mAh/g after 15 cycles, when 10.0 % of perovskite oxide is induced by MMT layers. Moreover, architecture of pristine TC and MMT electrodes possessed a 936.87 and 341.52 mAh/g discharge capacities at the same situation. These merits allow a promising potential application of the nanocomposite electrodes containing rare-earth chromite oxide and clay substrates in electrochemical energy-storage devices.

Enhancing high‐temperature mechanics and degradation for phthalonitrile resin via constructing rare earth oxide supported low melt‐point molten oxide

AbstractIn order to improve the comprehensive performance of thermosetting phthalonitrile resin (PN) composites, a novel molten hybrid (Nd2O3@DM35) was successfully prepared by loading Neodymium Oxide (Nd2O3) on the surface of low melt‐point molten oxide (DM35). In thermal gravimetric analysis, the addition of 30 wt% Nd2O3@DM35 postponed the temperature of 5% mass loss (T5%) of PN hybrid (PN‐NdD30) from 485 to 521°C. A series of thermal aging experiments were designed to prove the thermal stability of modified PN. The surface morphology of PN‐NdD30 was mostly maintained after thermal aging. Compared with pure PN, the flexural strength (FS) and interlaminar shear strength (ILSS) of PN‐NdD30 composites at room temperature increased by 31.4% and 32.8%, respectively. After aging at 400°C for 20 min, the FS and ILSS retention rates of PN‐NdD30 composites were 78.4% and 91.5%, respectively. In this work, the introduction of novel hybrid improved the thermal stability of PN composites, while enhancing their mechanical properties at different temperatures. Based on all the results, the heat resistance and mechanical mechanism of PN‐NdD30 composites were carefully analyzed.Highlights A molten hybrid was prepared by Nd2O3 and low melt‐point molten oxide. The novel hybrid can form a continuous protective layer at high temperatures. In the aging test, the mass loss of PN‐NdD30 was significantly reduced. Mechanical properties of PN composites at different temperatures were improved. A novel molten concept was introduced in the heat resistance modification of PN.

Advancements in Aluminum Matrix Composites: A Comprehensive Review on the Mechanical and Microstructural Attributes of Rare Earth Elements (REEs) and Rare Earth Oxides (REOs) Doped Materials

Advancements in Aluminum Matrix Composites: A Comprehensive Review on the Mechanical and Microstructural Attributes of Rare Earth Elements (REEs) and Rare Earth Oxides (REOs) Doped Materials

Enhanced Spin-Orbit Torque Efficiency in Platinum-Gadolinium Oxide Nanocomposite Films.

Spin-orbit torque (SOT) has emerged as an effective means of manipulating magnetization. However, the current energy efficiency of SOT operation is inefficient due to low damping-like SOT efficiency per unit current bias. In this work, we dope conventional rare earth oxides, GdOy, into highly conductive platinum by magnetron sputtering to form a new group of spin Hall materials. A large damping-like spin-orbit torque (DL-SOT) efficiency of about 0.35 ± 0.013 is obtained in Pt0.70(GdOy)0.30 measured by the spin-torque ferromagnetic resonance (ST-FMR) technique, which is about five times that of pure Pt under the same conditions. The substantial enhancement of the spin Hall effect is revealed by theoretical analysis to be attributed to the strong side jump induced by the rare earth oxide GdOy impurities. Moreover, this large DL-SOT efficiency contributes to a low critical switching current density (8.0 × 106 A·cm-2 in the Pt0.70(GdOy)0.30 layer) in current-induced magnetization switching measurements. This systematic study on SOT switching properties suggests that Pt1-x(GdOy)x is an attractive spin current source with large DL-SOT efficiency for future SOT applications and provides another idea to regulate the spin Hall angle.

Charge ordering as the driving mechanism for superconductivity in rare-earth nickel oxides

Charge ordering as the driving mechanism for superconductivity in rare-earth nickel oxides

Silica nanoparticle-reinforced polyurethane plastic immobilized with strontium aluminate nanofiller: Ultraviolet protection, superhydrophobicity and photoluminescence

A simple strategy was reported toward a possible industrial preparation of smart plastic materials with persistent afterglow, ultraviolet protection, superhydrophobic properties and photochromism. Nanoparticles of rare-earth doped aluminate (NREA) were embedded into a polyurethane plastic composite. A combination of polyurethane (bulk material), silica nanoparticles (nanofiller), and NREA (luminous agent) was prepared. Achieving a uniform distribution of NREA in a polyurethane fluid allows for the manufactured plastic to be colorless. NREA showed diameters between 12 nm and 26 nm. When excited at 365 nm, the produced photoluminescent polyurethane composite demonstrated an emission band at 519 nm. NREA contents more than 1 % were found to exhibit persistent photoluminescence, whereas pigment concentrations less than 1 % were found to exhibit fluorescence emission. The created plastic concrete exhibited photochromism, as shown by the coloration parameters and photoluminescence spectra, which proved a change in color between transparent during daylight, green under ultraviolet rays, and greenish-yellow in darkness. The static contact angle tests demonstrated effective superhydrophobic properties. Significant improvements were detected ultraviolet protection and photostability. The hardness properties, structural compositions, and morphology of the developed polyurethane plastics were also explored.

A facility for cryogenic ion irradiation and in situ characterization of rare-earth barium copper oxide superconducting tapes.

Superconducting magnets based on Rare Earth Barium Copper Oxides (REBCO) offer transformative capabilities in the fields of fusion energy, high energy physics, and space exploration. A challenge shared by these applications is the limited lifetime of REBCO due to radiation damage sustained during operation. Here we present a new ion-beam facility that enables simultaneous cryogenic irradiation and in situ characterization of commercial REBCO tapes. The ion source provides spatially uniform fluxes up to 1018protons/m2s with kinetic energies up to 3.4MeV, in addition to helium and higher-Z species. Using this facility, we can induce uniform damage profiles in the first 10-20 µm of REBCO tapes with less than 0.25 appm of hydrogen implanted in REBCO after a dose of 1020protons/m2. The tape can be held between 20 and 300K with an accuracy of ±0.1K and is connected to a four-point probe measuring the critical current, Ic, and critical temperature, Tc, before, during, and after irradiation with transport current ranging from 100 nA to 100A, and a typical voltage noise less than 0.1 μV. These capabilities are presently used to study the effect of irradiation temperature on REBCO performance change during and after proton bombardment, to assess the possibility of Ic and Tc recovery after irradiation through thermal annealing, and to explore the instantaneous and recoverable suppression of Ic and Tc observed during irradiation.

Model-based catalyst screening and optimal experimental design for the oxidative coupling of methane

The oxidative coupling of methane (OCM) to produce ethane and ethylene (C2 compounds) as platform chemicals involves complex chemistry with reactions both in the gas phase and on the catalyst surface, resulting in a distribution of products at the expense of C2 selectivity. This work uses experimental data from a variety of mixed metal oxides on supports at different reaction conditions (temperature, contact time, and reactant flow rates) to train a random forest regressor that predicts methane conversion and C2 selectivity (key performance indicators (KPIs)). The kinetically validated random forest models are deployed to locate optimal conditions that maximize C2 yield for each of the catalysts. Investigating the regressor interpretability via feature importance reveals that the choice of metals and support are crucial to C2 selectivity predictions in addition to the reaction conditions, while the predictions of methane conversion are largely governed by the reaction conditions. The machine learning (ML) regressor is used as a kinetic surrogate to find a locus of optimal reaction conditions that maximize both selectivity-conversion for each of the catalysts via a multi-objective optimization routine. The maximum C2 yields for catalysts are projected to be improved by 15% on average. Analyzing the catalysts with respect to a popular OCM catalyst, Mn-Na2WO4/SiO2, using the optimal locus eliminates variability in the process conditions to reveal distinct patterns based on intrinsic properties of metals and supports. Further, the decision space with catalyst descriptors and reaction conditions is optimized for high C2 yields using the ML surrogate, in a static multi-objective optimization routine, and an adaptive Bayesian routine, where the latter was found to have a wider field focus in proposing catalyst formulations and reaction conditions. Transition metal oxides on a variety of supports were proposed but not their lanthanide oxide counterparts. The framework has the potential to lend itself to materials acceleration platforms where it is crucial to consider multi-scale phenomena that impact downstream KPIs.

Sustainable recovery of rare earth elements from Ni-MH batteries: Flux-free thermal isolation and Subsequent hydrometallurgical refinement

This study details a sustainable approach for efficient recovery of highly pure rare earth elements oxides (REOs) from Ni-MH batteries. REOs (i.e., La, Ce, Sm, Nd, and Pr oxides) were thermally isolated from spent Ni-MH batteries into an oxide phase with the REO concentration of 67.4 wt%. Subsequently, separate leaching processes were conducted using sulfuric acid and hydrochloric acid solutions, and the results were compared in terms of efficiency and feasibility. Sodium REEs sulfate hydrate (NaRE(SO4)2.xH2O) was precipitated from the sulfuric acid leachate by adjusting the pH to 1.5 using sodium hydroxide, while the addition of oxalic acid to the hydrochloric acid leachate enabled the recovery of REEs as oxalate hydrate (RE2(C2O4)3.xH2O). The resulting sulfate salt was mixed with a sodium hydroxide solution, leading to the formation of REEs hydroxide. The REEs hydroxide and oxalate were calcined at 1000 °C, resulting in the production of REOs with a purity exceeding 99.7%. This research demonstrates the feasibility of developing an efficient, environmentally friendly, and sustainable approach for the recovery of highly pure REOs from Ni-MH batteries which potentially can minimize the environmental impact associated with the extraction of REOs from virgin sources, while addressing the challenge of effective recycling of end-of-life Ni-MH batteries.

Wide Temperature Stability of BaTiO3-NaNbO3-Gd2O3 Dielectric Ceramics with Grain Core–Shell Structure

As consumer electronics and industrial control systems continue to evolve, the operating temperature range of capacitors is gradually increasing. Barium titanate-based ceramic capacitors are widely used in the field of high dielectrics, so temperature-stable barium titanate-based dielectric materials have been a hot research topic in the field of dielectric ceramics. The construction of a core–shell structure by unequal doping is an effective way to obtain temperature-stable dielectric materials. At the same time, this structure retains part of the highly dielectric tetragonal phase, and materials with overall high dielectric constants can be obtained. In this work, we prepared BaTiO3-xNaNbO3-0.002Gd2O3 (x = 1.0–6.0 mol%) as well as BaTiO3-0.05NaNbO3-yGd2O3 (y = 0–0.30 mol%) dielectric ceramics. On the basis of high-electronic-bandgap NaNbO3-modified BaTiO3 dielectric ceramics, a core–shell structure with a larger proportion of core phase was obtained by further doping the amphiphilic rare-earth oxide Gd2O3. By designing this core–shell structure, the temperature stability range of capacitors can be expanded. At a doping level of 5.0 mol% NaNbO3 and 0.20 mol% Gd2O3, the room temperature dielectric constant εr = 4266 and dielectric loss tan δ = 0.95% conforms to the X8R standard (from −55 °C to 150 °C, TCC &lt; ±15%); volume resistivity ρv = 10,200 GΩ·cm and breakdown strength Eb = 13.5 kV/mm is attained in BaTiO3-based ceramics. The system has excellent dielectric and insulating properties; it provides a new solution for temperature-stable dielectric ceramics.

Enhanced performance of electrospun PVDF membranes modified with rare-earth metal oxides for membrane distillation: A systematic study

In the presented studies, the novel type of separation materials dedicated to membrane distillation was generated and systematically analyzed. Utilizing poly(vinylidene fluoride) (PVDF) electrospun membranes as a base, hybrid organic-inorganic materials were developed to enhance performance. These materials exhibited high hydrophobicity, featuring superhydrophobicity on a micro-scale due to fractal-like structures on the inorganic domain surface. Rare-earth metal oxides (REMO) were implemented for the first time as smart modifiers, covalently attached to the functionalized membrane surface. Three REMO types were selected to investigate their impact on membrane performance in air-gap membrane distillation (AGMD) for the desalination process. Chemical attachment via long enough linkers formed a flexible active surface structure, facilitating transport and separation. Dynamic goniometric studies evaluated membrane wetting stability. Particularly noteworthy was the membrane enhanced with Ho2O3 particles, with high flux and salt rejection rates of 14.41 ± 1.35 kg m−2 h−1 and >99.5 %, respectively. The membrane stability and affinity were further examined using Hansen Solubility Parameters and Pearson's hard–soft acid–base (HSAB) theory. The potential of the hybrid membranes is seen not only in desalination. With the ability to control surface properties by using different silane linkers, oleophobicity/oleophilicity can be achieved, and practical use in wastewater treatment or oil/water separation is possible.

High-Grade REE accumulation in regolith: Insights from supergene alteration of an apatite-rich vein at the Kapunda Cu mine, South Australia

AbstractThe stratiform and vein-hosted Kapunda Cu deposit in South Australia contains a saprolitized hydrothermal vein with 12.37 wt.% total rare earth oxide (TREO). The vein was analyzed by X-ray diffraction, scanning electron microscopy, synchrotron-based X-ray fluorescence microscopy and electron backscatter diffraction to understand the controls that govern high-grade REE accumulation during periods of intense weathering. Petrological assessments indicate the transformation of an apatite-calcite-aluminosilicate-bearing protolith to a supergene assemblage of Fe-oxides, kaolinite and REE-phosphate minerals that include rhabdophane-(Ce), monazite-(Ce) and florencite-(Ce). This transformation was facilitated by progressive acidification of the weathering fluid, which is indicated by: 1) the increasing crystallinity of authigenic Fe-oxides and kaolinite, which led to REE desorption; 2) the textural evolution and increase in grain size of authigenic REE-phosphates from nanoscopic crystallites, to acicular needles, to micro-scale hexagonal prisms; 3) the late dissolution of REE-phosphates; and 4) the replacement of goethite by jarosite, whose sulfate component originated from the oxidation and weathering of proximal sulfide minerals. Alongside the depletion of pH-buffering carbonate minerals that are indicated by the preservation of calcite menisci, this sulfide dissolution also facilitated acid generation. Results illustrate how highly acidic weathering fluids might facilitate either REE mobilization or REE accumulation in regolith. High-grade REE accumulation under acidic supergene conditions is prioritized when the host-rock contains a significant source of depositional ligands (i.e., phosphate in the form of apatite) that can be readily leached during intense weathering. Exploration companies should therefore assay routinely for REEs in any heavily weathered phosphatic rock, due to the observed efficiency of phosphate minerals as geochemical traps for REE accumulation.

Regular study of lanthanide oxides for boosting photocatalytic hydrogen production on ZnIn2S4 photocatalysts

Lanthanide oxides have potential advantages for photocatalytic hydrogen production. To systematically investigate the photocatalytic performance of lanthanide oxides on metal sulfides, a series of LnxOy/ZnIn2S4 (LnxOy/ZIS) were synthesized by hydrothermal method. Comprehensive characterization demonstrated that LnxOy synergistically improved the performance of ZnIn2S4 by extending light absorption, reducing contact interface resistance and enhancing carrier separation. The photocatalytic hydrogen evolution (PHE) rates of the LnxOy/ZIS photocatalysts were improved, which were 1.6–4.2 times higher than those of pure ZnIn2S4 (198.0 μmol g−1 h−1). The PHE rates of LnxOy/ZIS decreased with increasing lanthanide atomic number, and when the lanthanides contained variable valence ions, the PHE rates of LnxOy/ZIS were superior to those of neighbouring lanthanides. The heterojunction formed by LnxOy and ZnIn2S4 effectively promoted carrier separation. Lanthanide ions with unoccupied 4 f orbital were more likely to accept electrons and served as a hydrogen adsorption site for further hydrogen reduction. Multivalent ions could also promote the migration of electrons and generate oxygen vacancies to inhibit the recombination of carriers. In conclusion, for ZnIn2S4, lanthanide oxides are promising candidates to improve the performance of PHE. This study provides guidance on the selection of appropriate lanthanide oxides for the construction of efficient sulphur-based heterojunction photocatalysts.

Novel routes for synthesis of rare earth oxychlorides

Rare earth oxychlorides (REOCl) have received significant interest for their potential applications in chloride ion conductors, catalysts, luminescent materials due to their unique and special properties. Many synthesis methods were reported for their production including solid-state, flux-assisted, and sol-gel techniques. The present study introduces two straightforward solid state synthesis routes for synthesizing desired oxychlorides. In the first route, REOCl is prepared by roasting of a mixture of hydrous rare earth chloride (RECl3.xH2O) and rare earth oxide (RE2O3) powder. The second route involves, initial curing followed by roasting a portion of RE2O3 with hydrochloric acid (HCl) for production of the oxychlorides. For both routes, the optimal process conditions were first defined for LaOCl synthesis. Subsequently, the refined conditions of second method were successfully applied to the synthesis of NdOCl and SmOCl. The thorough mineralogical and morphological analysis of the obtained products under these conditions provides valuable insights into their characteristics and potential applications.