Search Results (1,660)

Cobalt oxide (Co₃O₄), a transition metal oxide with a cubic spinel structure, shows high potential in peroxymonosulfate (PMS) activation, while its catalytic efficiency is often limited by sluggish interfacial charge transfer. In this study, a chlorine-doped Co₃O₄ (Cl-Co₃O₄) was synthesized via a hydrothermal method for the degradation of bisphenol A (BPA) through PMS activation. Systematic characterizations and electrochemical tests demonstrated that chlorine doping could effectively modulate the surface electronic structure of the catalyst, significantly reducing the interfacial charge transfer resistance. Degradation performance evaluations revealed that, compared to pristine Co₃O₄, Cl-Co₃O₄ exhibited a significantly enhanced BPA degradation, achieving near-complete removal of BPA within 15 min under neutral to weakly alkaline conditions. The optimal operational parameters were determined as catalyst dosage of 0.20 g/L, PMS concentration of 0.10 mM and initial pH of 7.0–9.0, with the pseudo-first-order rate constant reaching 0.37 min⁻¹. High-concentration NO₃⁻ showed weak inhibition, while Cl⁻ showed moderate inhibition; 50 mM HCO₃⁻ drastically reduced the rate constant to 0.05 min⁻¹ and almost completely suppressed the reaction. Sulfate (SO₄•⁻) and superoxide (O₂•⁻) radicals were the primary reactive species in this system, explicitly excluding the role of the non-radical electron transfer pathway. Furthermore, three plausible BPA degradation pathways involving C-C bond cleavage, hydroxylation and C-O bond breakage were proposed with 19 intermediates identified. Ecotoxicological assessments based on ECOSAR verified that both acute and chronic toxicity of the intermediates to fish, daphnid and green algae decreased gradually, and the final small-molecule products exhibited significantly lower toxicity than the parent BPA. This study provides a novel strategy for enhancing the PMS activation performance of cobalt-based catalysts by modulating their electronic structures via halogen doping. Full article

This study explores the potential of utilizing biogenic manganese oxides (BMOs) produced by Mn-oxidizing Pseudomonas putida MnB1 to facilitate metal cation uptake for rare earth element (REE) sequestration and the synthesis of novel materials. Previous studies have shown that P. putida MnB1 efficiently oxidizes environmental Mn(II) to Mn(IV)-oxides, producing BMOs with unique physicochemical properties. Unlike their abiotic counterparts, BMOs exhibit high surface area, reactivity, and amorphous, poorly crystalline structures, making them promising platforms for adsorbing metal cations. This research study, building on the prior work, demonstrates the incorporation of ten different main group, transition, and rare earth metals into the BMO material, with structural characterization conducted via scanning electron microscopy and powder X-ray diffraction. Compositional characterization was determined by inductively coupled plasma optical emission spectroscopy and energy dispersive X-ray spectroscopy via scanning electron microscopy. Following the initial screening of these ten cations, batch adsorption studies were performed for a representative light REE, heavy REE, and transition metal-spiked sample prepared with real wastewater effluent indicating that the BMO material in this study is promising for sequestering REEs from real water streams. These findings advance the understanding of biologically mediated metal adsorption and open pathways for designing new functional materials with potential applications in rare earth sequestration and catalysis. To highlight this later point, the BMO materials with an incorporated main group (Al³⁺, Ca²⁺) or transition metal cation (Fe³⁺, Cu²⁺) were tested electrochemically for their ability to act as water oxidation catalysts, and each of these materials’ activity was comparable to BMO except for the material with incorporated iron, which showed significantly enhanced activity. Full article

The removal of sulfur compounds such as ethyl mercaptan from natural gas remains a critical challenge due to their detrimental effects on downstream processes, catalyst poisoning, and environmental emissions. In this study, a series of halloysite-supported transition metal oxide catalysts was synthesized and evaluated for the removal of sulfur compounds from natural gas at 25 °C, 200 psi, and 36 mL/min, using 0.5 g of the catalyst. The nanotubular structure and dual surface chemistry of halloysite promote enhanced metal dispersion and improved mass transfer. Single-metal (manganese, copper, zinc, and nickel) catalysts were developed and tested, after which a multi-metal oxide (base) catalyst comprising a composite of the single metals (Zn-Cu-Mn-Ni) was developed as a base catalyst to combine adsorption-active and redox-active functionalities, and its performance was further enhanced by the addition of palladium as promoter. A combination of analytical techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), provided evidence that highly dispersed metal oxide phases were formed and the halloysite structure was preserved. XPS data showed the presence of oxidation states of metals that were active (Zn²⁺, Cu²⁺, Ni²⁺, Mn³⁺/Mn⁴⁺ and Pd²⁺), an indication of a redox-active surface for sulfur interaction. Results from the breakthrough experiments showed that the base catalyst significantly improved sulfur removal compared to single-metal catalysts, while the Pd-promoted catalyst exhibited the highest performance, with a breakthrough time of 630 min. Palladium was incorporated at low loading as a promoter, enhancing adsorption performance while maintaining a favorable balance between efficiency and material cost. This enhancement is attributed to synergistic interactions between adsorption-active sites and redox-active species, as well as improved electron transfer facilitated by palladium. The results demonstrate that rational design of multi-metal oxide catalysts supported on naturally occurring halloysite provides an effective and scalable approach for sulfur removal from natural gas, with strong potential for industrial applications. Full article

In this paper we investigate the use of sucrose as a reducing agent for the carbothermal reduction in spent ternary cathode materials. During this process, lithium from the cathode material is converted into water-soluble Li₂CO₃, while the high-valent transition metals are reduced to insoluble metallic elements and oxides. The influence of various pyrolysis temperatures, sucrose dosages, and pyrolysis times on the reduction degree of high-valent metals. Furthermore, the influence of leaching conditions on lithium recovery efficiency is examined. Under the optimal conditions of a pyrolysis temperature of 650 °C, a sucrose dosage of 15 wt.%, a pyrolysis time of 30 min, a leaching solid–liquid ratio of 30 g/L, and a leaching time of 30 min, the lithium leaching rate reaches 97.9%. Characterization via XRD, XPS and SEM reveals that sucrose serves as an effective carbothermal reducing agent. It facilitates the reduction of high-valent transition metals to insoluble metallic elements and oxides while simultaneously enabling the recovery of lithium as Li₂CO₃. Consequently, this method achieves an efficient separation of lithium from other metallic elements. Compared to traditional recycling processes, it avoids the low lithium recovery rates often associated with subsequent separation steps. Full article

High-frequency immersed plasma discharge represents an efficient method for the generation of reactive oxygen and nitrogen species (RONS) in liquid media, leading to complex redox and oxidative processes in biologically relevant systems. Although plasma-generated reactive species in liquids have been widely investigated, it remains insufficiently understood how working-gas-dependent plasma chemistry translates into oxidative outcomes in iron-containing model systems, where plasma-derived species may interact with transition-metal redox cycling. The novelty of this study lies in the combined assessment of gas-dependent RONS accumulation, deoxyribose oxidative degradation, and plasma-induced changes in Fe(II) availability using a high-frequency immersed plasma discharge. Herein, we examined whether treatment with high-frequency immersed discharge influences the redox state of iron in a working gas-dependent manner, thereby affecting oxidative degradation in the deoxyribose model. Plasma treatment was performed under air and argon working gas conditions, and oxidative degradation was evaluated using the thiobarbituric acid reactive substances (TBA-RS) assay. In parallel, the concentrations of long-lived reactive species, including hydrogen peroxide, nitrites, and nitrates, were determined spectrophotometrically. The results demonstrated a treatment-time-dependent increase in oxidative degradation and reactive species accumulation, with more pronounced oxidative effects observed under argon plasma conditions. In the presence of ferrous ions, plasma treatment resulted in a gas-dependent effect, characterized by a synergistic enhancement of oxidative degradation under argon and a biphasic effect under air. Most notably, in Fe(II)-containing samples, 10 min of argon plasma treatment increased TBA-RS formation to approximately 2.7-fold of the Fe(II) control, whereas air plasma produced a biphasic response, with an initial decrease followed by an approximately 40% increase at the longest exposure time. Additional experiments suggest that plasma may influence the redox state and availability of ferrous ions, thereby affecting their participation in Fenton-type reactions and radical-mediated processes. The findings suggest that the overall oxidative outcome in plasma-treated systems is governed not only by the concentration of plasma-generated reactive species but also by plasma-induced modifications of transition metal redox chemistry. These preliminary results on the combined roles of plasma-generated reactive species and transition-metal chemistry contribute to understanding plasma–liquid interactions in such systems. Full article

The quest for sustainable hydrogen production via water electrolysis requires the development of efficient, non-precious-metal electrocatalysts. This work presents the sonochemical-assisted synthesis of cobalt ferrite (CoFe₂O₄) nanoparticles as a sustainable alternative to noble metal catalysts. Nanoparticles were synthesized by varying the ultrasonic tip power (40%, 50%, and 60%) to investigate the this effect on their structural and electrochemical properties. Comprehensive characterization using X-ray diffraction, Mössbauer spectroscopy, and transmission electron microscopy confirmed the formation of phase-pure nanoscale spinel structures, with crystallite size increasing from 11.28 to 21.79 nm as the sonication power increased. Electrochemical analysis revealed that the sample synthesized at 60% power (CoFe₂O₄-60) exhibited the highest electrocatalytic performance among the synthesized samples for both the hydrogen and oxygen evolution reactions (HER and OER) in alkaline media. This superior performance is attributed to its largest electrochemically active surface area (ECSA = 6.95 cm²) and lowest overpotentials (${\eta }_{10}=-360$ mV for HER and 410 mV for OER). Despite the larger crystallite size, high-power sonication induced higher density of surface defects and roughness, as evidenced by Mössbauer spectroscopy and electrochemical capacitance measurements. Furthermore, all samples exhibited excellent operational stability during 120 h of chronopotentiometric testing. Moreover, the efficiency of the electrolizer for water splitting was calculated to be 64.7%. These findings demonstrate that ultrasonic power tuning can influence the structural and electrochemical properties of CoFe₂O₄ nanoparticles, contributing to improving durability and bifunctional efficient electrocatalytic activity for alkaline water electrolysis. Full article

This study presents the production of isoamyl, n-butyl and cyclohexyl esters of levulinic acid with an excellent yield under solvent-free conditions. The catalysts used were MgAlO and M²⁺MgAlO-mixed oxides containing the transition metals (M²⁺ = Co²⁺, Ni²⁺, Zn²⁺), obtained from calcined layered double hydroxides (LDH). They are easily accessible, low-cost, and environmentally friendly and possess the requisite acid–base properties for esterification reactions. The effect of reaction time and the molar ratio of levulinic acid to the alcohols used on the esterification reaction was investigated. The catalysts were characterized by X-ray diffraction (XRD), XRF, SEM and temperature-programmed desorption of CO₂ (TPD-CO₂). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. Mixed oxides containing transition metals exhibited significantly higher activity than MgAlO. Under the selected reaction conditions, the conversion of levulinic acid and the yield of isoamyl ester reached 100% at a reagent ratio of 1:1. As a by-product of esterification, only dicyclohexyl ether was found at a reactant ratio of 1:1.5. Full article

The transition metal copper (Cu) is an essential trace element for humans and serves as a cofactor for numerous enzymes. Therefore, intracellular Cu homeostasis must be tightly regulated. Meanwhile, Cu is increasingly used in industrial and biomedical applications, particularly in nanoparticle (NP) form. However, studies have demonstrated that Cu(II) oxide (CuO) NPs are highly toxic. Therefore, understanding the underlying toxic effects of such compounds is of the utmost importance. In this context, transcriptomic profiling is regarded as a valuable tool. Nevertheless, comparative studies addressing organ-relevant models, such as the liver and lungs, are scarce. Furthermore, no transcriptomic studies have been conducted on human bronchial lung epithelial cells exposed to CuO NPs and Cu²⁺. In this study, we compared the cellular effects of human bronchial lung epithelial cells exposed to both CuO NPs and Cu²⁺ to the effects in human liver cells exposed to Cu²⁺ by applying RNA sequencing. Although cytotoxicity was comparable, we showed that Cu uptake was highly dependent on both the cell type and the form of Cu. The most pronounced concentration-dependent transcriptional changes were observed with CuO NP exposure in BEAS-2B cells. The only differentially expressed genes (DEGs) found by all exposures and treatments were metallothioneins (MTs). The most sensitive targets of Cu-induced toxicity were related to nuclear factor erythroid 2-related factor 2 (NRF2), nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB), and mitogen-activated protein kinase (MAPK) signaling. Furthermore, the effects observed at the transcriptome level were studied at the functional level, such as cell cycle regulation and cytokine release. Thus, we demonstrated that the two cell types differ in susceptibility, and that complementing transcriptome profiling with functional studies provides important mechanistic insights. Full article

This study investigates the integration of nanofiltration (NF) and membrane distillation (MD) for the selective separation and recovery of critical metals from effluents generated by supercritical water oxidation (SCWO) of lithium-ion batteries. Beyond resource recovery, the proposed hybrid system addresses the urgent environmental challenge associated with highly contaminated battery recycling effluents, which pose severe risks to aquatic ecosystems if improperly managed. NF90 and NF270 membranes exhibited complementary behavior: NF90 achieved high rejection of Co, Ni, and Mn (>70%) with a minimum lithium rejection of 30%, whereas NF270 showed lower rejection of divalent metals (40%) and lower lithium rejection (<20% at pH = 7), along with a higher permeability. Subsequent MD enabled water recovery while concentrating lithium in the MD concentrate (brine), maintaining near-complete rejection of transition metals (>90%) and reducing the effluent conductivity by more than 85%. Surface characterization (SEM–EDS, AFM, BET, and contact angle) revealed fouling mechanisms and wettability loss, highlighting operational stability limitations. In this hybrid approach, nanofiltration enables the selective separation of lithium from transition metals, while membrane distillation promotes water recovery and concentrates lithium into a recoverable brine, with fouling and wetting defining the operational boundaries of the process. Overall, the results demonstrate that coupling SCWO with NF–MD represents a viable and scalable pathway for simultaneous effluent detoxification and lithium recovery, contributing to circular economy strategies and the sustainable management of battery-recycling wastewater. Full article

Understanding the atomic-scale ionic motion and transport in layered transition-metal oxides is essential for elucidating structural stability and electronic behaviour in complex systems. Here, we investigate nanoscale Na dynamics in Na₁RuO₃ and Na_1.5RuO₃ using room-temperature ab initiomolecular dynamics at the r²SCAN + U level. While Na mobility plays a key role in local coordination, its nanoscale mechanism remains nuanced and unexplored. Our simulations show that Na ions undergo pervasive rattling, with Na_1.5RuO₃ enabling exploration of larger volumes and exhibiting incipient migration compared to the more confined behaviour in Na₁RuO₃. In addition, oxygen’s contribution to redox capacity decreases from $43\%$ to $24\%$ with increasing Na content. These nanoscale insights demonstrate that tuning the local ionic environment governs charge compensation and dynamical response in ruthenate frameworks, with direct implications for the design of Na-ion battery cathodes. Full article

High-entropy oxide (HEO) thin films hold significant potential for applications in spintronics and catalysis; however, their widespread utilization is hindered by weak room-temperature ferromagnetism (RTFM). Herein, we demonstrate a facile vacuum annealing strategy to enhance the RTFM of HEO thin films. (FeNiAlCrMn)O films exhibit a saturation magnetization (M_S) of 5.9 emu/cm³ and a Curie temperature (T_C) of 350 K after vacuum annealing at 1173 K. Mechanistic investigations reveal that the enhanced RTFM originates from an annealing-induced phase transition from rocksalt-to-spinel. Structurally, annealing facilitates cation diffusion from octahedral to tetrahedral sites, forming a highly crystalline, long-range magnetic lattice of spinel ferrite. Electronically, tetrahedral occupation shortens M–O bonds, drives electron transfer toward metal cations, and enhances orbital hybridization, thereby strengthening magnetic exchange coupling. This study provides a simple and effective strategy for tailoring the RTFM of HEO thin films. Full article

O3-type layered transition-metal oxides are widely regarded as promising cathode materials for sodium-ion batteries due to their intrinsically high sodium content and favorable energy density. Nevertheless, their practical rate capability is hindered by sluggish Na⁺ transport and relatively high diffusion barriers. To address this issue, elemental substitution has emerged as an effective modification strategy. In this work, fluorine (F), characterized by strong electronegativity and a small ionic radius, is introduced to partially substitute oxygen in the bulk lattice of O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ (NNFM). First-principles calculations demonstrate that F incorporation leads to an expansion of the interlayer spacing along the c-axis and a weakening of Na–O interactions, both of which facilitate Na⁺ migration. Among the considered configurations, Mn-adjacent substitution exhibits the lowest formation energy, indicating enhanced thermodynamic stability. Furthermore, electronic structure analysis reveals a reduced band gap (from 0.515 eV to 0.342–0.356 eV) and strengthened O-2p/Mn-3d orbital hybridization, contributing to improved electronic conductivity. These findings provide atomistic insights into F-induced modulation mechanisms and suggest an effective pathway for optimizing Na⁺ transport in O3-type cathodes. Full article

Oxygen stoichiometry critically governs the phase stability and physical properties of transition-metal oxides, yet a unified understanding of how oxygen-stoichiometry-driven phase reconstruction underlies the cooperative evolution of multiple physical properties in SrCoO_x remains lacking. Here, high-quality epitaxial brown millerite SrCoO_2.5 and perovskite SrCoO_3−δ thin films were grown by pulsed laser deposition under controlled oxygen conditions. Their structural, magnetic, electrical, optical, and photocatalytic properties were systematically compared. SrCoO_2.5 exhibits antiferromagnetic insulating behavior, infrared-dominant transmittance, and higher photocatalytic activity, whereas SrCoO_3−δ shows ferromagnetism, much lower resistivity, and strong optical opacity. First-principles calculations reveal that oxygen-stoichiometry-driven phase reconstruction strongly modifies the electronic structure, accounting for the distinct magnetic, transport, and optical responses. These results establish a direct correlation between oxygen stoichiometry, structural transformation, and multifunctional properties in SrCoO_x, highlighting oxygen-vacancy ordering as an effective route to tailoring correlated oxide functionalities. Full article

High-nickel layered oxide cathodes, exemplified by LiNi_0.9Co_0.05Mn_0.05O₂ (NCM90), exhibit high specific capacity but suffer from severe interfacial degradation and structural instability during electrochemical cycling. Herein, we present a phosphate-based in situ modification approach that forms a durable, self-established cathode–electrolyte interphase (CEI), thereby resolving these key challenges from the root. We employ a controlled (NH₄)₂HPO₄ coating and optimized thermal treatment to fabricate a thin, dense layer of crystalline lithium phosphate on the NCM90 surface. This coherent layer serves as an artificial CEI precursor, which electrochemically evolves into a highly stable and ionically conductive interfacial shield during operation. It effectively suppresses parasitic reactions, mitigates transition metal dissolution, and alleviates mechanical strain induced by phase transitions. Comprehensive optimization of calcination temperature and coating content identifies 760 °C and 1 wt% as the optimal conditions, yielding a well-preserved layered structure and effectively suppressed Li⁺/Ni²⁺ mixing compared with the pristine NCM90. When tested at 0.1 C in the potential range of 2.75–4.3 V, the coated electrode delivers a high initial discharge specific capacity of 204.08 mAh g⁻¹. After 100 charge–discharge cycles at 1 C, it retains 89.24% of its capacity, and its rate capability is also significantly improved. Collectively, these findings verify that forming a customized CEI via precursor coating successfully suppresses interfacial degradation and improves structural integrity, thus representing a viable, scalable pathway toward advanced lithium-ion batteries with exceptionally stable cathodes. Full article

The demand for high-performance energy storage systems with enhanced energy and power density is growing alongside the renewable energy, mobile devices, and electric vehicle sectors. MXenes, a class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, have emerged as promising electrode materials for next-generation energy storage systems owing to their high electrical conductivity, hydrophilicity, and tunable surface chemistry. This review provides a comprehensive analysis of recent progress in MXene-based energy storage systems, focusing on MXene synthesis routes, their performance in energy storage applications, associated challenges, and future research directions. It discusses the advantages and disadvantages of various MXene synthesis routes and MXene-based composites, defect engineering, and MXene oxidation, which are crucial for energy storage applications, including rechargeable batteries and supercapacitors. The review also explores the challenges and prospects of scaling up MXenes and their composites for energy storage applications and the existing obstacles to integrating these materials into energy storage systems, with the aim of developing next-generation energy storage systems. Full article