Search Results (362)

This study integrates conventional sediment geochemistry with explainable machine learning to investigate the provenance of surface sediments from Wular Lake, Kashmir Valley, NW Himalaya. Twenty-two samples were analysed for 49 geochemical variables (10 major oxides, 25 trace elements and 14 rare earth elements), complemented by XRD mineralogy, which reveals an assemblage dominated by quartz, muscovite/illite, chlorite and feldspar. The Chemical Index of Alteration (CIA = 68.5–75.1, mean 72.1), corroborated by CIW, PIA and the A–CN–K trend, indicates moderate weathering under a cold temperate climate, and the Index of Compositional Variability (ICV > 1), together with uniformly low Zr/Sc ratios (3.4–6.0), which preclude significant zircon addition through recycling, records compositionally immature, first-cycle detrital input. Conventional discrimination ratios and the Herron system classify the sediments as geochemically equivalent to shale, and elevated Fe₂O₃/K₂O (2.6–4.0), Al₂O₃/TiO₂ (12.6–16.0), Cr/Th and Co/Th ratios record a substantial mafic imprint. Chondrite-normalised REE patterns show pronounced LREE enrichment ((La/Yb)_N = 8.0–19.4), moderate negative Eu anomalies (Eu/Eu* = 0.56–0.73) and negligible Ce anomalies (Ce/Ce* = 0.98–1.03), with Eu/Eu* discriminating felsic crystalline from mafic volcanic contributions. A three-stage pipeline (principal component analysis (PCA) → random forest → SHapley Additive exPlanations (SHAP)) achieved a median leave-one-out cross-validation (LOO-CV) accuracy of 95.5% (n = 22; Wilson 95% CI 78%–99%), and unsupervised k-means clustering reproduced the same three geochemically distinct provenance end-members: siliceous-mature, detrital-mafic and carbonate-bearing, without reference to the assigned labels (Adjusted Rand Index = 1.0). Because the training labels derive from the same geochemical dataset, the classification quantifies the internal consistency of the provenance model, but does not provide independent validation. SHAP analysis reveals that trace elements (Cr, Co, Sc, Ni, Zn) carry greater discriminating power than do conventional major-oxide ratios, demonstrating that explainable machine learning robustly supplements and extends traditional provenance approaches. Full article

Supported Pt catalysts are highly active for the selective catalytic oxidation of ammonia (NH₃-SCO), but their practical use is limited by poor N₂ selectivity and insufficient hydrothermal durability under high-temperature exhaust conditions. Herein, we report a composition-regulated high-entropy oxide interface strategy to stabilize Pt–Cu dual sites and steer NH₃ oxidation toward selective N₂ formation. A series of fluorite-type Ce-based high-entropy oxides, including CeZrLaPrYO_x, CeSmLaPrYO_x, and CeSnLaPrYO_x, were constructed as thermally robust supports for Pt and Cu loading. Among them, PtCu/HEO-Zr calcined at 1000 °C exhibits the best NH₃-SCO performance, achieving 90% NH₃ conversion at 260 °C while maintaining N₂ selectivity above 80% over a broad temperature window of 100–300 °C under a high weight hourly space velocity of 100,000 mL·g⁻¹·h⁻¹. More importantly, after harsh hydrothermal aging at 800 °C with 10 vol% H₂O for 12 h, the catalyst shows negligible activity loss and nearly unchanged N₂ selectivity, demonstrating exceptional structural and catalytic robustness. Structural and surface analyses reveal that Zr incorporation optimizes the fluorite high-entropy lattice, increases oxygen vacancy concentration, promotes lattice oxygen mobility, strengthens surface acidity, and enriches active Cu²⁺ species, thereby enhancing the interfacial cooperation between NH₃ activation and oxygen-assisted intermediate conversion. In situ DRIFTS further reveals that PtCu/HEO-Zr favors an O_lat-assisted internal selective catalytic reduction pathway, in which adsorbed NH₃ is activated to -NH₂ species and subsequently reacts with lattice oxygen-derived intermediates to form N₂O₂²⁻-like species that decompose into N₂ and H₂O. Meanwhile, the formation of nonselective NO_x and N₂O products is suppressed. This work highlights high-entropy oxide-supported Pt–Cu interfaces as a promising platform for designing hydrothermally durable and N₂-selective NH₃-SCO catalysts. Full article

The sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air cathodes severely restrict the practical application of rechargeable zinc–air batteries (ZABs). Herein, equimolar lanthanide-doped spinel Co₃O₄ bifunctional electrocatalysts were synthesized via a citric acid-assisted sol–gel method. Among Ce-, Pr-, La-, and Sm-doped catalysts, Sm-Co₃O₄ exhibits the optimal electrocatalytic performance with a high ORR half-wave potential of 0.72 V and superior OER activity with an overpotential of 1.65 V at 10 mA cm⁻², achieving a minimal potential gap ΔE of 0.93 V. Rotating ring-disk electrode (RRDE) measurements and Koutecky–Levich (K–L) analyses confirm the exclusive 4e⁻ ORR pathway. Characterizations reveal that Sm doping modulates the electronic structure and lattice distortion of Co₃O₄, raises the Co²⁺/Co³⁺ ratio (0.59) and creates abundant oxygen vacancies, thereby significantly lowering the overpotentials for both ORR and OER. This study provides new insights for designing high-performance spinel-based bifunctional electrocatalysts for ZABs. Full article

Rock-forming minerals, olivine and pyroxene, from three ore-bearing intrusions in the Norilsk districts were studied. They are the Norilsk 1 and the Northern and Southern Maslovsky massifs with PGE-Cu-Ni ores, located in the Norilsk syncline. Trace elements such as Al, Ti, Co, Cu, Nd, Sm, Ce, Cr, V, Dy, Y, Yb, Er, Sr, and Eu were determined by LA-ICP-MS. The authors found differences in mineral compositions between picritic gabbro-dolerites from these intrusions. The parental melt of the Southern Maslovsky intrusion corresponded to tholeiitic basalt containing (wt.%) H₂O—0.65, CO₂—0.16, and B—0.004. It was concluded that parental magmas for ore-bearing intrusions had no specific features and were closed to intraplate basalts. Full article

In this study, an electrochemical system for methane conversion was developed, employing Ni- and Ce-doped LaCoO₃ perovskite as the anode catalyst in an Na₂CO₃ electrolyte. Structural characterization revealed that the La_1−yCe_yCo_1−xNi_xO₃ (x = 0–0.5, y = 0–0.12) synthesized by the sol–gel method maintains the perovskite structure, but is rich in oxygen vacancies. Electrochemical studies revealed that the performance of methane activation is related to the presence of Ni(III) in the catalyst, and reactive oxygen species (•OH and HOO⁻) are provided through water oxidation reactions (WOR) in the Na₂CO₃ electrolyte. The electrocatalytic performance of the synthesized La_0.92Ce_0.08Co_0.5Ni_0.5O₃ during methane conversion was verified in an electrolysis cell, and ethanol and acetic acid were identified as the methane conversion oxygenates. Under ambient conditions, the formation rate of ethanol reached 577.0 μmol g_cat⁻¹ h⁻¹ at 0.90 V (vs. Ag/AgCl) in 0.5 mol L⁻¹ Na₂CO₃. The catalyst was found to retain structural integrity and sustain catalytic activity over multiple reaction cycles. Full article

Ammonia decomposition over non-precious metal thermos-catalysts offers a viable and cost-effective pathway for sustainable hydrogen production. In this study, LaCeO₃ perovskite was synthesized using a citric acid complexation method and employed as a support for mono- and bimetallic catalysts prepared by incipient wetness impregnation, maintaining a total metal loading of 10 wt%. Structural and surface properties were systematically investigated using BET, XRD, H₂-TPR, SEM, TEM, and CO₂-TPD. Among the monometallic catalysts (Ni, Co, and Fe), 10%Ni/LaCeO₃ exhibited the highest activity, which is attributed to its enhanced reducibility and optimal surface basicity, facilitating NH₃ activation. Bimetallic systems (Ni-Co, Ni-Fe, and Co-Fe) with equal metal loadings (5 wt% each) showed better activity compared to their monometallic counterparts following the order: 5%Ni–5%Co/LaCeO₃ > 5%Ni–5%Fe/LaCeO₃ > 5%Co–5%Fe/LaCeO₃. The improved performance of the Ni-Co system is due to structural interactions between Ni and Co, which promote hydrogen desorption and accelerate N–H bond cleavage, while suppressing nitrogen recombination as the rate-limiting step. Further systematic optimization of the Ni/Co ratio showed that 8%Ni–2%Co/LaCeO₃ had the highest catalytic activity with consistent performance over 50 h. This optimal composition provides a balanced distribution of active metallic sites and moderate-to-strong basic sites, enhancing NH₃ adsorption and intermediate transformation. These findings show that LaCeO₃-supported Ni-Co catalysts are promising candidates for efficient hydrogen production from ammonia without using noble metals. Full article

Perovskite-type oxides are among the most promising cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to their mixed ionic–electronic conductivity and compositional flexibility. Many high-performance cathodes rely on Sr substitution at the A-site, often associated with surface segregation and long-term degradation. In this work, we explore an alternative strategy based on defect engineering and phase interactions in Sr-free composites. Perovskite-fluorite composites based on LaFe_0.8Co_0.2O₃ were synthesized through a one-pot route designed to promote the formation of a perovskite phase and a limited amount of fluorite-type ceria. This approach allows the introduction of small fractions of Ce into the perovskite lattice, favoring the cooperative coexistence with La-doped CeO₂. Structural, microstructural and spectroscopic characterization indicates that Ce influences the crystallization pathway and composite defect chemistry. Variations in lattice parameters and Raman features suggest modifications of perovskite structure consistent with defect formation and lattice distortion. Reduction properties and electrical conductivity measurements indicate that Ce incorporation in the perovskite and oxide interaction affect charge transport and oxygen mobility. The electrochemical results demonstrate that the optimal trade-off between activation energy (Ea) and polarization resistance (Rp) is achieved for the sample, with a nominal cerium content, Ce/(La + Ce) of 0.16. Moreover, the electrochemical properties are found to correlate with the nominal cerium content, which regulates defect chemistry and the resulting composite composition. Overall, results suggest that the one-pot synthesis promotes beneficial interactions between the perovskite and ceria phases, allowing the development of Sr-free ferrite-based materials with enhanced functional properties, minimizing the amount of ceria in the composite. Full article

In advanced oxide materials, additive selection is increasingly constrained by the simultaneous requirements of functional response, phase stability, morphology control, processing tolerance, scalability, and critical raw material security. This study develops a ZnO-centered framework to compare boron-based strategies (direct B doping, B₄C/ZnO composite formation, and h-BN/ZnO interface engineering) with rare-earth strategies (Ce/CeO₂, La/La₂O₃, and Y/Y₂O₃). Structural, morphological, chemical-state, and vibrational evidence from XRD, FE-SEM/EDX, XPS, Raman, and FT-IR studies is interpreted through an evidence hierarchy that separates lattice incorporation, surface/grain-boundary segregation, and deliberate secondary-phase or heterointerface formation. The synthesis shows that boron-containing routes usually provide broader phase retention, lower agglomeration tendency, more gradual defect modulation, and greater processing robustness, whereas rare-earth routes offer stronger oxygen-vacancy regulation, redox activity, luminescence tuning, and heterojunction-assisted function but require tighter process control and more rigorous verification of incorporation mode. Reanalysis of seven primary experimental pathways indicates that B₄C/ZnO and h-BN/ZnO are mechanistically non-equivalent: B₄C supports rigid composite-interface growth, while h-BN promotes sheet-mediated interface multiplication and Maxwell–Wagner–Sillars polarization. Türkiye is treated as an illustrative boron-rich producer case within a transferable producer/importer decision model. Dopant selection is therefore framed as a multi-criteria decision involving performance thresholds, reproducibility, technology-readiness potential, and supply-security exposure, not peak output alone. Full article

Dry reforming of methane (DRM) converts the greenhouse gases methane (CH₄) and carbon dioxide (CO₂) into syngas (hydrogen (H₂) and carbon monoxide (CO)). Despite its numerous advantages, DRM has not yet been industrialized due to catalyst deactivation and competing side reactions. While Ni-based catalysts have been widely used, they are prone to increased carbon deposition and sintering, and although bimetallic systems and oxygen-based supports have shown promise, their effects on carbon deposition are yet to be fully understood. In this study, carbon nanotube (CNT)-supported Pt-Ni catalysts incorporating mixed oxides of CeZrO₂ and CeZrLaO₂ were investigated to evaluate the impact of support composition and metal–support interactions in DRM. The catalysts were synthesized and subsequently tested in DRM. Catalysts supported on CNTs displayed higher CH₄ and CO₂ conversions compared to conventional ceria–zirconia, highlighting the beneficial role of the carbon nanotube support in improving dispersion and accessibility of the metal active sites. Addition of Pt was found to promote reverse water–gas shift (RWGS) reaction, whereas the addition of La was found to decrease catalytic activity. Despite the formation of a Ni-Pt alloy, the obtained catalysts favored RWGS over DRM. These findings illustrate key limitations and design considerations for optimization of CNT-supported bimetallic catalysts in DRM. Full article

Clay minerals in coal play a key role in controlling mineralogical composition, geochemical signatures, and the industrial behavior of coal and its combustion residues. This study investigates the occurrence, provenance, and potential applications of clay minerals in Carboniferous ash-rich coals from the Bogatyr, Lenin, and Saradyr coal mines in northeastern Kazakhstan. A total of 60 coal samples were analyzed using XRD, SEM–EDS/BSE, XRF, and ICP-OES following acid leaching. Based on ash yield, 52 samples were classified as coal (<50% ash), while 8 samples were classified as carbonaceous shale or mudstone (>50% ash). Mineralogical assemblages show clear variability among the studied mines. Saradyr samples are strongly quartz-dominated with lower clay proportions, Bogatyr samples exhibit highly heterogeneous quartz–clay–mica assemblages, whereas Lenin samples are relatively more clay-rich and dominated by kaolinite and illite-group minerals. Across all samples, kaolinite is the dominant clay mineral (16.6–46 wt.%), occurring mainly as authigenic pore- and cell-filling aggregates. Minor phases include illite–muscovite (7.1–29.9 wt.%), illite–smectite (up to 7.6 wt.% in Bogatyr), and smectite–montmorillonite (0.4–0.7 wt.%). Clay minerals occur as discrete particles, coatings, and pore fillings, contributing to ash formation; however, their correlation with ash yield is weak (R = 0.03–0.05), reflecting heterogeneous mineral inputs and diagenetic overprinting. All geochemical data are reported on a high-temperature coal ash (HTA) basis (815 °C). Geochemical indices (CIA, CIW, CIX) and Al₂O₃/TiO₂ ratios (1.8–17.4) indicate variable provenance and moderate to high weathering intensity, reflecting mixed mafic to intermediate source rocks. A total of 23 trace elements were identified. Au occurs at trace levels (up to 0.02 ppm), while selected rare earth elements (REE: Ce, Dy, Eu, La, Nd, Sm, Y, Yb) average 0.2–0.3 ppm, indicating negligible economic recovery potential. REEs show a strong positive correlation with clay minerals (r = 0.93), indicating adsorption and minor structural incorporation. In contrast, Au correlates with As, V, Zn, Cu, Ni, and Nb, suggesting sulfide association. HTA is enriched in SiO₂–Al₂O₃ phases dominated by kaolinite and quartz, indicating strong potential for cement, geopolymer, ceramic, and zeolite applications. Full article

This study investigates the synergistic promotional effects of CeO₂ and La₂O₂SO₄ as composite catalytic oxygen storage systems for soot oxidation in Gasoline Particulate Filters (GPFs) across a broad operating temperature range. Two 5 wt % CeO₂-promoted Lanthanum oxysulfate compounds were prepared by mechanical mixing of pure phases or by supporting CeO₂ via incipient wetness impregnation with a cerium nitrate precursor. The soot oxidation activity was evaluated using Thermogravimetric Analysis coupled with Mass Spectrometry (TG-MS) under both anaerobic and lean-O₂ (1% vol.) environments, with the performance benchmarked against pure La- or Pr-oxysulfates and CeO₂ reference materials. Comprehensive characterization via XRD, SEM, N₂-physisorption, and H₂-TPR revealed that the observed synergistic effects transcend the simple additive properties of the individual components. Full article

This study presents an experimental investigation of the influence of dopant type and calcination temperature on BaTiO₃-based piezoceramics synthesized by a solid-state calcination process. The effects of Mn, Nb, La, and Ce dopants on the structural, morphological, and piezoelectric characteristics of powders calcined at 1000 °C and 1100 °C were systematically evaluated. In addition, two co-doped BaTiO₃ compositions, namely Mn–Nb and La–Nb, calcined at 1000 °C, were investigated in order to assess the combined effect of acceptor–donor and donor–donor doping strategies on microstructural evolution and structural stability. The synthesized powders were characterized by scanning electron microscopy (SEM), particle size analysis, energy-dispersive X-ray spectroscopy (EDS), elemental mapping, and X-ray diffraction (XRD), in comparison with a commercial BaTiO₃ reference powder. The piezoelectric response was assessed by correlating the structural modifications induced by doping with the estimated piezoelectric coefficient d₃₃, calculated as a function of the tetragonality ratio (c/a) and further correlated with the crystallite size. The results reveal significant variations in grain growth, dopant distribution, and crystallographic stability, highlighting the critical role of dopant chemistry and calcination temperature in tailoring the functional properties of BaTiO₃ for piezoelectric applications. Full article

Owing to the high stability and low cost of nanozymes, they have been extensively investigated and reported. In this work, highly active CeO₂ nanoflowers were first prepared and then different metal elements were doped into the CeO₂ nanoflower matrix via a novel synthesis method to fabricate M-CeO₂ (M = Cu, Fe, Co, Mn, La) nanomaterials. Mn-CeO₂ with the highest peroxidase-like activity was selected via systematic screening, the as-prepared Mn-CeO₂ nanocomposites exhibited enhanced enzyme-like activity due to the strong metal-support interaction. This article explored the effects of doping ratio, pH, temperature, reaction time, and material concentration on its activity. A simple sensitive and selective colorimetric method was established and successfully used to detect hydrogen peroxide and ascorbic acid sensitively. When the hydrogen peroxide (H₂O₂) concentration is within the 2.0–120.0 μM range, the UV-visible absorbance at 652 nm was associated linearly with the H₂O₂ concentration, R² = 0.9959, LOD = 1.7 μM (S/N = 3). The absorbance of the reaction system showed a good linear relationship with the ascorbic acid (AA) concentration (1.0–40.0 μM, R² = 0.992), LOD = 0.98 μM (S/N = 3). This study provides an effective way to construct efficient nanozymes and their potential applications in sensing and detection. Full article

Birefringence, arising from the low-symmetry structure in orthorhombic LaFeO₃, limits the observation and utilization of magneto-optical effects. In this study, the pure-phase perovskite-typed La_1−xCe_xFe_1−xTi_xO₃/SiO₂ thin films were successfully fabricated via radio-frequency magnetron sputtering, where the co-doping of Ce³⁺ and Ti⁴⁺ ions effectively induced a structure transition from orthorhombic to a highly symmetric cubic phase, eliminating birefringence effect and thus reducing optical transmission loss. At the same time, the doped Ce³⁺ ions also effectively enhanced the magnetic and magneto-optical effects of the system due to their strong spin coupling effect and superexchange interaction with Fe³⁺ ions. The results show that the cubic-phase La_0.5Ce_0.5Fe_0.5Ti_0.5O₃/SiO₂ thin film exhibits excellent magnetic and magneto-optical performance. Their saturation magnetization reaches 180 emu/cm³ with an in-plane easy magnetic axis. And their magnetic circular dichroic ellipticity |ψ_F| reaches 3054 degrees/cm. Full article

In recent decades, ion-adsorption-type rare earth element (iREE) deposits have been widely documented in the weathering crusts of granitic and volcanic rocks and their geological characteristics and genetic mechanisms extensively studied. Ion-adsorption-type REE mineralization was documented for the first time in the weathered crust overlying the epimetamorphic rocks in Ningdu County, China. In contrast to well-documented granite-derived weathering profiles, investigations of epimetamorphic rocks as protoliths for such REE deposits remain limited, particularly regarding the mineralogy of REE-bearing phases and the geochronology and geochemistry of their parent rocks. To address this gap, the present study combines comprehensive petrographic and mineralogical analyses of REE-mineralized Shenshan Formation phyllites with the U–Pb dating of zircon and apatite and trace element geochemical investigations. U–Pb zircon and apatite geochronology yields a protolith age of ca. 785 Ma for Shenshan Formation metamorphic rocks, consistent with mid-Neoproterozoic magmatism. REE-bearing minerals in the Shenshan Formation phyllites comprise allanite-(Ce), apatite, cerianite-(Ce), monazite-(Ce), rhabdophane-(La), rutile, Y-bearing thorianite and xenotime-(Y). Among these, apatite is the most abundant and likely the principal source of ionic REEs in the deposit. Ti-in-zircon thermometry indicates crystallization temperatures of 641–749 °C (mean ~704 °C), reflecting a prolonged magmatic–hydrothermal evolution. This extended history chiefly controlled the differentiation and redistribution of rare earth elements (REEs), thus governing their availability for subsequent supergene enrichment. Zircon-based oxygen fugacity (fO₂) estimates a range from −31.4 to −9.9 (mean −17.9), consistent with reduced magmatic conditions. Trace element correlation diagrams for zircon and apatite indicate that the intrusion underwent an extensive fractional crystallization of accessory phases (zircon, monazite, apatite, titanite, rutile) and plagioclase. The distribution patterns of trace elements further suggest that the Shenshan Formation protolith formed in a continental margin arc or arc-related orogenic belt setting, with geochemical signatures characteristic of an S-type granite. The Shenshan Formation phyllites in southern Jiangxi exhibit high REE abundances and host a labile assemblage of weatherable REE-bearing minerals, providing an optimal material framework for ion-adsorption-type REE deposits and indicating substantial mineralization potential. Full article