Oxide Research Articles

Progress in 2D MoS2-Based Advanced Materials for Hydrogen Evolution and Energy Storage Applications

The increasing energy demand for and fast depletion of fossil fuels have driven the need to explore renewable and clean energy sources. Hydrogen production via water electrocatalysis is considered a promising green fuel technology for addressing global energy and environmental challenges while supporting sustainable development. Molybdenum disulfide (MoS2) has emerged as a potential electrocatalyst for hydrogen evolution reactions (HERs) and super-capacitor (SC) applications due to its high electrochemical activity, low cost, and abundance. However, compared to noble metals like platinum (Pt), MoS2 exhibit lower HER activity in water electrocatalysis. Therefore, further modification is needed to enhance its catalytic performance. To address this, MoS2 has been effectively modified with materials such as reduced graphene oxide (rGO), carbon nanotubes (CNTs), polymers, metal oxides, and MXenes. These modifications significantly improve the electrochemical properties of MoS2, enhancing its performance in HER and SC applications. In this review article, we have compiled recent reports on the fabrication of MoS2-based hybrid materials for HER and SC applications. The challenges, advantages, and future perspectives of MoS2-based materials for HERs and SCs have been discussed. It is believed that readers may benefit from the recent updates on the fabrication of MoS2-based hybrid materials for HER and SC applications.

Sustainable Approach to Catalytic Cracking of Heavy Crude Oil: Asphaltene Sand Composite as Hybrid Metal Oxides from Oil-Contaminated Sand

Sustainable Approach to Catalytic Cracking of Heavy Crude Oil: Asphaltene Sand Composite as Hybrid Metal Oxides from Oil-Contaminated Sand

Evaluation of Antibacterial Properties of Zinc Oxide Nanoparticles Against Bacteria Isolated from Animal Wounds

Background/Objectives: This research aimed to determine the efficacy of metallic oxide nanoparticles, especially zinc oxide nanoparticles (ZnO-NPs), in inhibiting a wide range of bacteria isolated from animal wounds, indicating their potential as alternative antimicrobial therapies in veterinary medicine. Method: The disc diffusion technique, broth microdilution technique, and time-kill kinetic assay were performed to determine the antibacterial activity of the ZnO-NPs. Results: Transmission electron microscopy (TEM) and scanning electron microscopy (SEM showed that the ZnO-NPs were spherical and polygonal with sizes ranging from 50 to 100 nm, while DLS (NanoSizer) measured an average size of 512.3 to 535.7 nm with a polydispersity index (PDI) of 0.50 to 0.63 due to particle size agglomeration. The ZnO-NPs exhibited antibacterial activity against several bacterial strains isolated from animal wounds, including Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, with inhibition zones ranging from 10.0 to 24.5 mm, average MIC values ranging from 1.87 ± 0.36 to 3.12 ± 0.62 mg/mL, and an optimum inhibitory effect against Staphylococcus spp. The time-kill kinetic assay revealed that the Zn-ONPs eradicated Staphylococcus spp. and Klebsiella pneumoniae, as well as Escherichia coli and Pseudomonas aeruginosa (99.9% or 3-log10 reduction), within 30 min of treatment. They also demonstrated a varying degree of antibiofilm formation activity, as indicated by the percentage reduction in biofilm formation compared to the untreated biofilm-forming bacterial strains. Conclusion: ZnO-NPs effectively inhibit bacterial growth and biofilm formation in animal wound isolates.

Inorganic Nanoparticles in Reproduction Biology: Opportunities and Challenges

The development of inorganic metal and metal oxide nanoparticles (MNPs) has attracted significant attention in biomedical and biotechnological fields. An emerging field in this context is the use of MNPs in reproduction biology. Here, we review the development of MNPs in the field of reproduction by focusing on their interactions with highly delicate and specialized germ cells like spermatozoa and oocytes as well as developing embryos. By their unique physicochemical properties, MNPs are good candidates for targeted imaging and delivery of biofunctional molecules to the specific sites of the gametes and reproductive cells. Furthermore, functionalized MNPs can serve as transfection vectors for the generation of transgenic animals by sperm‐mediated gene transfer (SMGT) in artificial insemination or in vitro fertilization. In addition, MNPs have shown great promise in application fields such as semen collection, nano‐purification, cryopreservation, and sex sorting of sperm in the livestock industry. The article includes an in‐depth discussion on the uptake, translocation mechanism, and bioresponse of the MNPs to reproduction‐relevant sites on the clinical, cellular, and molecular levels. Based on these promising achievements, the current challenges and prospects of the development of these functionalized MNPs for clinical research in conjunction with the reproductive system will be discussed.

Band-Gap Engineering of High-Entropy Fluorite Metal Oxide Nanoparticles Facilitated by Pr3+ Incorporation by Gel Combustion Synthesis

Tailoring the bandgap of a material is necessary for improving its optical properties. Here, the optical bandgap of high-entropy oxide Ce0.2Gd0.2Sm0.2Y0.2Zr0.2O2-δ (HEO) nanoparticles was modified using Pr3+. Various concentrations of Pr3+ (x = 0, 0.01, 0.02, 0.05, 0.075, 0.1, 0.15) were incorporated into the host high-entropy oxide using a gel combustion synthesis. After the gel combustion step, the powders were heat-treated at various temperatures (650 °C, 800 °C, 950 °C) for 2 h. The obtained Pr3+-incorporated HEO powders were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV–visible spectroscopy. The results indicate that, when the samples are calcined at 950 °C, a single-phase cubic fluorite structure is obtained without any phase separation or impurity. The optical absorbance red-shifts to higher wavelengths when the concentration of Pr3+ is increased. This reduces the bandgap of the material from 3.15 eV to 1.87 eV for Pr3+ concentrations of x = 0 (HEO-0) and x = 0.15 (HEO-6), respectively. The obtained HEOs can be suitable candidates for photocatalytic applications due to their absorbance in the visible region.

High-Throughput Discovery of Kagome Materials in Transition Metal Oxide Monolayers

Abstract Kagome materials are known for hosting exotic quantum states, including quantum spin liquids, charge density waves, and unconventional superconductivity. The search for kagome monolayers is driven by their ability to exhibit neat and well-defined kagome bands near the Fermi level, which are more easily realized in the absence of interlayer interactions. However, this absence also destabilizes the monolayer forms of many bulk kagome materials, posing significant challenges to their discovery. In this work, we propose a strategy to address this challenge by utilizing oxygen vacancies in transition metal oxides within a "1+3" design framework. Through high-throughput computational screening of 349 candidate materials, we identified 12 thermodynamically stable kagome monolayers with diverse electronic and magnetic properties. These materials were classified into three categories based on their lattice geometry, symmetry, band gaps, and magnetic configurations. Detailed analysis of three representative monolayers revealed kagome band features near their Fermi levels, with orbital contributions varying between oxygen 2p and transition metal d states. This study demonstrates the feasibility of the "1+3" strategy, offering a promising approach to uncovering low-dimensional kagome materials and advancing the exploration of their quantum phenomena.

Battery-Type Transition Metal Oxides in Hybrid Supercapacitors: Synthesis and Applications

Hybrid supercapacitors (HSCs) have garnered growing interest for their ability to combine the high energy storage capability of batteries with the rapid charge–discharge characteristics of supercapacitors. This review examines the evolution of HSCs, emphasizing the synergistic mechanisms that integrate both Faradaic and non-Faradaic charge storage processes. Transition metal oxides (TMOs) are highlighted as promising battery-type electrodes owing to their notable energy storage potential and compatibility with various synthesis routes, including hydro/solvothermal methods, electrospinning, electrodeposition, and sol–gel processes. Particular attention is directed toward Ti-, Co-, and V-based TMOs, with a focus on tailoring their properties through morphology control, composite formation, and doping to enhance electrochemical performance. Overall, the discussion underscores the potential of HSCs to meet the growing demand for next-generation energy storage systems by bridging the gap between high energy and high power requirements.

Ultrafast and Universal Synthetic Route for Nanostructured Transition Metal Oxides Directly Grown on Substrates.

Nanostructured transition metal oxides (NTMOs) have consistently piqued scientific interest for several decades due to their remarkable versatility across various fields. More recently, they have gained significant attention as materials employed for energy storage/harvesting devices as well as electronic devices. However, mass production of high-quality NTMOs in a well-controlled manner still remains challenging. Here, a universal, ultrafast, and solvent-free method is presented for producing highly crystalline NTMOs directly onto target substrates. The findings reveal that the growth mechanism involves the solidification of condensed liquid-phase TMO microdroplets onto the substrate under an oxygen-rich ambient condition. This enables a continuous process under ambient air conditions, allowing for processing within just a few tens of seconds per sample. Finally, it is confirmed that the method can be extended to the synthesis of various NTMOs and their related compounds.

Tailoring P2/P3‐Intergrowth in Manganese‐Based Layered Transition Metal Oxide Positive Electrodes via Sodium Content for Na‐Ion Batteries

AbstractHigh‐manganese content sodium‐ion positive electrodes have received heightened interest as an alternative to contemporary Li‐ion chemistries due to their high abundance, low toxicity, and even geographical distribution. However, these materials typically suffer from poor capacity, unstable cycling performance, and sluggish Na+ kinetics. Herein, we explore a manganese‐based layered transition metal oxide (NaxN0.25Mn0.75O2) and show by X‐ray diffraction (XRD) and high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) that careful variation of the sodium content can instigate the formation of a biphasic intergrowth. This intergrown P2/P3 material offered a higher capacity than its monophasic P2 counterpart due to the P3 structure having greater low‐voltage Mn3+/4+ redox. Further, the intergrowth material offers greatly enhanced kinetics and cycling stability when compared to single‐phase P3 material, due to the stabilizing nature of the P2 structure, elucidated by galvanostatic intermittent titration technique (GITT) and operando synchrotron X‐ray diffraction. These results highlight the beneficial effect that the intergrowth structure has on the electrochemical performance of high‐manganese content positive electrode for future sodium‐ion batteries.

Self-optimizing Cobalt Tungsten Oxide Electrocatalysts toward Enhanced Oxygen Evolution in Alkaline Media.

Self-optimizing mixed metal oxides represent a novel class of electrocatalysts for the advanced oxygen evolution reaction (OER). Here, we report self-assembled cobalt tungsten oxide nanostructures on a lab-synthesized copper oxide substrate through a single-step deposition approach. The resulting composite exhibits remarkable self-optimization behavior, shown by significantly reduced overpotentials and enhanced current densities, accompanied with substantial increase in OER kinetics, electrocatalytically active surface area, surface wettability, and electrical conductivity. Under operating conditions, interfacial restructuring of the electrocatalyst reveals the in situ formation of oxidized cobalt species as the true active site. Complementary density functional theory (DFT) calculations further demonstrate the formation of *OOH intermediate as the rate-determining step of OER, and highlight the adaptive binding of oxygen intermediates, which transitions from tungsten to cobalt sites during OER process. Our study provides a fundamental understanding of the self-optimization mechanism and advances the knowledge-driven design of efficient water-splitting electrocatalysts.

An atomically economical and environmentally benign approach for the scalable synthesis of rare‐earth metal‐organic framework catalysts

AbstractMetal–organic frameworks (MOFs), as an emerging class of porous materials, demonstrated substantial potential for applications in chemical engineering processes. However, their production often generates significant waste including ionic residues and organic solvents, posing considerable environmental concerns. Herein, we report the environmentally benign MOF synthesis with metal oxides precursors, yielding water as the exclusive by‐product. This approach not only enhances atom economy but also promotes solvent recycling by preventing anion accumulation, significantly reducing waste generation. The synthesis can be easily scaled up in a 10‐L reactor with an impressive space–time yield of 608 kg·m−3·day−1. Furthermore, MOF‐76(Y) was implemented in a reactor for catalytic cycloaddition reaction at kg‐scale. Through optimization of the interfacial contact between CO2 and the reaction liquid phase, a yield of 96.7% was achieved under mild conditions. This work demonstrates a rare example of scalable and sustainable synthesis of MOF materials coupled with catalysis implementation at kilogram scale.

High-Performance CsPbBr3 Quantum Dot/ZTO Heterojunction Phototransistor with Enhanced Stability and Responsivity.

Although all inorganic metal halide perovskite quantum dots (QDs) have shown great potential in photodetectors, many reported devices still suffer from low responsivity due to poor mobility and high defect densities. To overcome these challenges, heterojunction structures that separate electron and hole pathways have emerged as a promising approach to improve the responsivity by reducing radiative recombination. Two-dimensional materials such as graphene and MoS2 have been integrated with perovskites to enhance performance; however, these materials often lead to high dark-state currents, which hinder the on/off ratios in photodetectors. Hence, identifying alternative functional materials that can complement perovskite QDs while minimizing these drawbacks is critical. Amorphous metal oxide semiconductors, such as zinc tin oxide (ZTO), have attracted attention as high-performance channel materials in thin-film transistors (TFTs) due to their high field-effect mobility, thermal stability, and ability to be processed at low temperatures over large areas. However, ZTO suffers from persistent photoconductivity (PPC) caused by oxygen vacancies, which leads to slow response times and prolonged conductivity after light exposure, thereby limiting its effectiveness in optoelectronic devices. In this work, we demonstrate a high-performance phototransistor using a planar heterojunction structure composed of CsPbBr3 quantum dots and ZTO via a simple solution-processing method. This device exhibits a responsivity of over 103 A/W, a specific detectivity of 7.0 × 1014 Jones, and an on/off ratio of 5 × 104 under 390 nm light illumination with an intensity of 0.03 mW/cm2. The combination of ZTO and CsPbBr3 QDs offers significant improvements over devices that lack either layer, showcasing superior performance compared to that of most perovskite photodetectors.

Sintering Behaviour, Physical Properties and Environmental Assessment of Glass Foam from Waste Glass

Abstract Glass foam, a porous material, is developed by sintering waste glass with foaming agents at high temperature, yielding chemically robust structures. However, the decomposition of foaming agents and chemical changes during sintering raises concerns about emissions during sintering and leaching from the final product. Despite various sintering methods and materials studied, their environmental impacts are not well explored. A recently introduced modified curing-sintering method was developed without the use of stabilizing chemicals, which could potentially reduce emissions and environmental impacts. However, the extent of its impact is unknown. This research studies potential emissions from materials during sintering and the heavy metal leaching from glass foams made by the newly modified sintering technique. Waste glass obtained from vehicle windshields is used as the primary raw material for glass foam preparation, supplemented by commercial fly ashes and slag as additives. Emissions from raw materials during the sintering process and the changes in chemical composition after sintering have been studied. Lastly, the heavy metals leaching possibilities from the final glass foam products have been assessed. Results reveal that the decomposition of foaming agents and organic content in raw materials leads to CO2 emission during the sintering. Due to low-temperature sintering (800℃) and no reduction agents, alkali and metallic oxide levels remain constant post-sintering. Heavy metal concentrations are extremely low, and their immobilization during the curing-sintering process ensures that leaching stays below safe limits. Therefore, this research provides insight into the potential environmental impacts of glass foam made of waste glass. Graphical Abstract

Ferroelectric properties of functionalized metal and metal oxide nanoparticles embedded on bacterial cellulose films

Ferroelectric properties of functionalized metal and metal oxide nanoparticles embedded on bacterial cellulose films

Self‐optimizing Cobalt Tungsten Oxide Electrocatalysts toward Enhanced Oxygen Evolution in Alkaline Media

Self‐optimizing mixed metal oxides represent a novel class of electrocatalysts for the advanced oxygen evolution reaction (OER). Here, we report self‐assembled cobalt tungsten oxide nanostructures on a lab‐synthesized copper oxide substrate through a single‐step deposition approach. The resulting composite exhibits remarkable self‐optimization behavior, shown by significantly reduced overpotentials and enhanced current densities, accompanied with substantial increase in OER kinetics, electrocatalytically active surface area, surface wettability, and electrical conductivity. Under operating conditions, interfacial restructuring of the electrocatalyst reveals the in situ formation of oxidized cobalt species as the true active site. Complementary density functional theory (DFT) calculations further demonstrate the formation of *OOH intermediate as the rate‐determining step of OER, and highlight the adaptive binding of oxygen intermediates, which transitions from tungsten to cobalt sites during OER process. Our study provides a fundamental understanding of the self‐optimization mechanism and advances the knowledge‐driven design of efficient water‐splitting electrocatalysts.

Cyanide Functionalization and Oxygen Vacancy Creation in Ni-Fe Nano Petals Sprinkled with MIL-88A Derived Metal Oxide Nano Droplets for Bifunctional Alkaline Seawater Electrolysis.

This work investigates novel improvements in FeNi-layered double hydroxide (LDH)/MIL-88A heterocomposite for sustainable seawater electrolysis through a single-step dual functionalization process. The Fe/Ni precursor weight ratio is optimized, resulting in the formation of smaller LDH petals and nano-sized MIL-88A metal-organic framework, which transforms into clusters of Fe2O3 nanospheres within a nitrogen-functionalized carbon matrix over NiFe2O4 nano petals upon calcination. Furthermore, oxygen vacancies, and nitrogen functionalization are attained in a single step by employing thermal ammonia reduction, significantly improving the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities. Particularly the oxygen vacancy and nitrogen functionalization are found to accelerate the O─O coupling step in OER by lowering the activation barrier. Likewise, the dual functionalization promotes destabilizing the hydride intermediates in HER potentially facilitating faster proton-coupled electron transfer. Hence, the optimized electrode achieves current densities of 200mAcm-2 at overpotentials of 350 and 240mV for OER and HER respectively. The chronopotentiometry stability tests confirms the electrode's durability over 200h at 20mAcm-2 in alkaline seawater electrolyte. The optimized electrode, composed of cost-effective and environmentally friendly materials, demonstrates robustness in alkaline seawater electrolytes, positioning it as a strong candidate for practical and sustainable water electrolysis applications.

Enhanced Removal of Acid Orange 7 onto Layered Interleaved Symmetrical 3D Flower-like CeO2 with Y(III) Doping

CeO2 has a potential application in the purification of organic dye wastewater because of the abundant oxygen vacancy (VO) defects in its crystals. In this study, a cubic CeO2 microsphere with layered interleaved symmetrical 3D flower-like morphology was synthesized, and its adsorption capacity for acid orange 7 (AO7) was further enhanced by Y doping. The impact of varying amounts of Y ions on the phase composition, lattice parameters, and morphology of the product was investigated, revealing that 4 mol.% was determined as the doping level limit of Y ions in CeO2 crystals. XPS, Raman, and H2−TPR techniques were employed to compare surface species changes before and after 4 mol.% Y doping in the CeO2 crystals, including O−Ce(III), O−Ce(IV), O−Y(III), and VO correlation, yielding a rough quantitative assessment of these species. The 4 mol.% Y-doped CeO2 (2.0 g/L) demonstrated the highest removal rate for 20 mg/L of AO7 dye within just 20 min to reach adsorption–desorption equilibrium, half the time required by undoped CeO2, achieving an impressive adsorption rate of 94.6%, compared to only 69.5% for undoped CeO2 at 20 min. The adsorption capacity of undoped CeO2 was enhanced by 19.05% through the doping of 4 mol.% Y, achieving a value of 16.56 mg/L. The feasibility of enhancing the adsorption capacity of CeO2 by Y doping provides a reference for the application of CeO2 and other metal oxides.

Laser-Micro-Annealing of Microcrystalline Ni-Rich NCM Oxide: Towards Micro-Cathodes Integrated on Polyethylene Terephthalate Flexible Substrates

Here in this work, we report on micro-Raman spectroscopy investigations performed on freestanding Ni-rich NCM (LixNi0.83Co0.11Mn0.06O2) microcrystals transferred to flexible polyethylene terephthalate (PET) host substrates. This technological procedure introduces a first building block for future on-chip-integrated micro-accumulators for applications in flexible optoelectronics, sensors, microbiology, and human medicine. An after-synthesis thermal treatment was used to help improve the material homogeneity and perfection of the cathode material. To this end, a local laser micro-annealing process was applied to the freestanding Ni-rich NCM microcrystals. The thermally initialized structural processes in the singular micro-cathode units were characterized and determined by micro-Raman spectroscopy. Micro-Raman mapping images revealed the evolution of a recrystallization process after the local annealing procedure. Furthermore, laser micro-annealing led to the suppression of the pristine “polycrystalline morphology” of the investigated micro-cathode regions. Besides the dominant characteristic Raman mode at ~1085 cm−1, most likely ascribed to lithium carbonate, metal oxides with Raman modes around ~550 cm−1 were identified. This highly efficient transfer and integration technology represents a basic building block towards micrometer-sized accumulators for a large range of emerging applications.

Z-scheme heterojunction BiOBr/MIL-100(Fe) visible photocatalytic-permonosulfate degradation of AO7

ABSTRACT Metal–organic frameworks (MOFs) have garnered significant interest in the field of photocatalysis. In this study, Z-scheme heterojunction BM-x composites consisting of bismuth bromide oxide (BiOBr) and iron-based metal–organic backbone (MIL-100(Fe)) were successfully synthesized using ethylene glycol as a solvent. The composites were characterized using various techniques. BM-x exhibit abundant functional groups, large specific surface areas, and narrow band gap energy, thus provide numerous active sites for catalytic reactions and respond well to visible light. Notably, BM-7 displays remarkable catalytic activity in a visible light-activated permonosulfate (PMS) system and achieves a degradation rate of 99.02% over 100 mg/L gold orange II (AO7) within 60 min. The effects of BM-7 and PMS addition, initial AO7 concentration, initial pH, inorganic anions, and humic acid on the degradation system were investigated. The proposed mechanism of the Z-scheme heterojunction in the BM-7 photocatalyst demonstrates effective photoelectron transfer from the BiOBr conduction band to the MIL-100(Fe) valence band, resulting in excellent catalytic activity. Radical burst experiments identified 1O2, h+, and ·O2− as the main active substances. BM-7 has high stability and reusability, with a degradation rate reduction of only 14.48% after three recycles. These findings provide valuable insights into using persulfate combined with visible light.

Nanofluids in Thermal Energy Storage Systems: A Comprehensive Review

Nanofluids, which consist of nanosized particles dispersed in a base fluid, represent a promising solution to improve the performance of thermal energy storage systems. This review offers a comprehensive overview of nanofluids and their applications in thermal energy storage systems, discussing their thermal properties, heat transfer mechanisms, synthesis techniques, and application in latent heat storage systems. Various types of nanofluids are examined, including metal oxide, carbon-based, and metallic nanofluids, highlighting their effects on thermal conductivity, latent heat and the phase change temperature. A review of experimental and numerical studies showcases the performance of thermal energy storage systems incorporating nanofluids and the factors influencing their thermophysical characteristics and energy storage capacity. Finally, the key findings of current research are summarized, as well as the challenges and the potential future directions in nanofluid-based thermal energy storage systems research, emphasizing the need to optimize nanoparticle concentration and long-term durability.