Structure Of Oxide Research Articles

How Can 4D-STEM Inform Atom Probe Experiments? Relating Structure and Composition of Multiferroic Oxides at the Atomic Scale

How Can 4D-STEM Inform Atom Probe Experiments? Relating Structure and Composition of Multiferroic Oxides at the Atomic Scale

Structure engineering with sodium doping for cobalt-free Li-rich layered oxide toward improving electrochemical stability

Structure engineering of the Li-rich layered cathodes to overcome insufficient structural stability and the rapid decay of capacity and voltage is crucial for commercializing of the materials for the lithium-ion batteries. Alkali metal element doping at the lithium sites has proven to be a feasible approach to boost the performance of the Li-rich layered oxides. Herein, the Na+-doping strategy in the lithium slabs is introduced to modify the structure of the cobalt-free layered Li-rich oxide, Li1.2Ni0.2Mn0.6O2. It is revealed that the doped Na+ ions can promote the activation of the Li2MnO3 phase, endowing the materials with high initial discharge capacity of 284.2 mAh g−1 at 0.1C. Due to the pillaring effect of the doped Na+ ions in the lithium slabs and the induced formation of oxygen vacancies, the electrochemical stability of the material is significantly improved, providing a capacity retention of 94.0 % after 100 cycles at 0.5C. The voltage decay per cycle is only 2.0 mV, less than 3.2 mV of the Li1.2Ni0.2Mn0.6O2. The results suggest that the facile strategy of introducing Na+ ions into the lithium slabs is an efficient approach for optimizing structure design of the Li-rich layered oxides for the lithium-ion batteries.

Regulation of oxygen vacancies in MnCO3-based catalysts by thermally inducing for efficiently catalytic benzene combustion

Tuning oxygen vacancies through carbon pyrolysis is an effective strategy for fabricating high-performance catalysts to oxidize volatile organic compounds (VOCs). Herein, a series of MnCO3-based catalysts were synthesized by pyrolyzing MnCO3 precursors with different morphologies including dumbbell-like (D), bayberry-like (B) and cubic (C) structures for the benzene oxidation. The catalyst (D-300) derived from dumbbell-like MnCO3 exhibited superior catalytic performance for the benzene oxidation with a T90 of 176 °C and remarkable stability in long-term, cycling and water-resistance tests. Abundant oxygen vacancies in D-300 improved lattice oxygen mobility and redox ability, resulting in superior oxygen uptake and release capabilities. Moreover, oxygen vacancies greatly facilitated the activation and replenishment of gaseous oxygens to generate active oxygen species, thereby dramatically accelerating the cleavage of benzene rings and deep mineralization. In situ DRIFTS analysis demonstrated that benzene preferentially adsorbed onto D-300 due to its abundant acidic sites, and the oxidation of phenolate species was a rate-determining step. H2O may hinder the activation of gaseous oxygen, suppressing the activity of the catalyst.

Tungsten, copper and cobalt-single metal atom oxides embedded CeO2-MnO2-rGO nanorods as electrocatalysts for efficient oxygen evolution reaction

BackgroundAn important aspect of energy conversion and storage technology is primarily based on the electrocatalytic oxygen evolution process (OER). MethodHere, we present the newly designed synthesis of an improved variety of WCuCo-CeO2-MnO2-R-3 nanocomposites, to enhance OER by incorporating the reduced graphene oxide (rGO), and SMAO of W, Cu, and Co with the nanorods of CeO2-MnO2 materials. Interestingly, the higher density of SMAO (W, Cu, and Co), atomic utilization and electron transfer layer of rGO influenced the CeO2-MnO2 nanorods with remarkably superior electrocatalytic OER activity. Significant findingsThis makes WCuCo-CeO2-MnO2-R-3 achieve 10 mA cm-2 with an overpotential of 275 mV and a lower Tafel slop of 64.46 mV dec‑1. The higher number of SMAO (W, Cu, and Co) species close to the catalyst surface served as potential active sites assembly to enhance the OER activity by improving the chemical and electrochemical steps during the OER process. The chronoamperometry test revealed that the WCuCo-CeO2-MnO2-R-3 nanocomposite is not degrade in a 1 M KOH solution for 24 h, and it is stable up to 2000 CV cycles. In order to create very effective catalysts for OER, the DFT theoretical results shed light on the connection between the catalytic characteristics of metal oxide structures and their inherent electronic configuration.

Structure and Formation Mechanisms in Tantalum and Niobium Oxides in Superconducting Quantum Circuits.

Improving the qubit's lifetime (T1) is crucial for fault-tolerant quantum computing. Recent advancements have shown that replacing niobium (Nb) with tantalum (Ta) as the base metal significantly increases T1, likely due to a less lossy native surface oxide. However, understanding the formation mechanism and nature of both surface oxides is still limited. Using aberration-corrected transmission electron microscopy and electron energy loss spectroscopy, we found that Ta surface oxide has fewer suboxides than Nb oxide. We observed an abrupt oxidation state transition from Ta2O5 to Ta, as opposed to the gradual shift from Nb2O5, NbO2, and NbO to Nb, consistent with thermodynamic modeling. Additionally, amorphous Ta2O5 exhibits a closer-to-crystalline bonding nature than Nb2O5, potentially hindering H atomic diffusion toward the oxide/metal interface. Finally, we propose a loss mechanism arising from the transition between two states within the distorted octahedron in an amorphous structure, potentially causing two-level system loss. Our findings offer a deeper understanding of the differences between native amorphous Ta and Nb oxides, providing valuable insights for advancing superconducting qubits through surface oxide engineering.

Photocatalytic Degradation of Organic Dyes by Magnetite Nanoparticles Prepared by Co-Precipitation.

Iron oxide nanoparticles were synthesized by co-precipitation using three different iron salt stoichiometric mole ratios. Powder X-ray diffraction patterns revealed the inverse cubic spinel structure of magnetite iron oxide. Transmission electron microscopic images showed Fe3O4 nanoparticles with different shapes and average particle sizes of 5.48 nm for Fe3O4-1:2, 6.02 nm for Fe3O4-1.5:2, and 6.98 nm for Fe3O4-2:3 with an energy bandgap of 3.27 to 3.53 eV. The as-prepared Fe3O4 nanoparticles were used as photocatalysts to degrade brilliant green (BG), rhodamine B (RhB), indigo carmine (IC), and methyl red (MR) under visible light irradiation. The photocatalytic degradation efficiency of 80.4% was obtained from Fe3O4-1:2 for brilliant green, 61.5% from Fe3O4-1.5:2 for rhodamine B, and 77.9% and 73.9% from Fe3O4-2:3 for both indigo carmine and methyl red. This indicates that Fe3O4-2:3 is more efficient in the degradation of more than one dye. This study shows that brilliant green degrades most effectively at pH 9, rhodamine B degrades best at pH 6.5, and indigo carmine and methyl red degrade most efficiently at pH 3. Recyclability experiments showed that the Fe3O4 photocatalysts can be recycled four times and are photostable.

Structure and molecular-level transformation for oxidation of effluent organic matters by manganese oxides

As important organic components in water environments, effluent organic matters (EfOMs) from wastewater treatment plants are widely present in Mn-rich environments or engineered treatment systems. The redox interaction between manganese oxides (MnOx) and EfOMs can lead to their structural changes, which are crucial for ensuring the safety of water environments. Herein, the reactivities of MnOx with EfOMs were evaluated, and it was found that MnOx with high specific surface area, active high-valent manganese content and lattice oxygen content (i.e., amorphous MnO2) possessed stronger oxidizing ability towards EfOMs. Accompanying by EfOMs oxidation, Mn(IV) and Mn(III) were reduced into Mn(II), with Mn(III) as the significant active species. Through molecular-level transformation analysis by ultrahigh mass spectrometry (FT-ICR MS), the highly reactive compounds in EfOMs were clearly determined to be that with more aromatic and unsaturated structures, especially lignin-like compounds (the highest content in EfOMs (over 60 %)). EfOMs were oxidized by amorphous MnO2 into products with lower humification index (0.60 vs. 0.46), smaller apparent molecular weight (386.94 Da vs. 368.68 Da), and higher biodegradability (BOD5/COD: 0.12 vs. 0.78). This finding suggested that redox reactions between MnOx and EfOMs might alter their abiotic and biotic behaviors in receiving water environments.

Recovery of valuable metal elements from spent lithium-ion battery via a low temperature ammonium persulfate roasting approach

A low-cost and eco-friendly recycling method is crucial for recovering valuable elements from end-of-life lithium-ion batteries (LIBs), which plays a vital role in addressing resource scarcity and reducing the environmental impact. This study aims to develop a low-temperature pyro-metallurgical combined process to recycle spent LiNi0.5Co0.2Mn0.3O2 (NCM523). Unlike traditional pyrometallurgy methods that generate liquid alloys and slags at temperatures exceeding 1000 °C, the (NH4)2S2O8 roasting approach operates at 350 °C and converts NCM523 to water-soluble sulfates, exhibiting remarkable leaching efficiencies of Li, Ni, Co, and Mn, with values of 99.43 %, 99.87 %, 98.88 %, and 99.19 %, respectively. Systematic studies were conducted to investigate the influence of roasting temperature, (NH4)2S2O8-to-NCM mass ratio, and roasting time on the sulfation process. Furthermore, the mechanism of sulfation reaction was identified by combining experiments with thermodynamic calculation. At temperatures above 160 °C, (NH4)2S2O8 decomposes into (NH4)2S2O7, which reacts with NCM. Lithium in a layered structure forms Li2SO4, while transition elements form MnSO4, Li2Co (SO4)2, and NiSO4. At around 350 °C, (NH4)2S2O8 further decomposes into NH4HSO4, releasing SO2 and NH3. SO2 reacts with remaining NCM or unsulfated transition metal oxides, converting them into MnSO4, Li2Co (SO4)2, and NiSO4. Above 800 °C, the metal sulfates decompose into stable oxides. This study presents a low-temperature sulfation method that effectively disintegrates the crystal structure of lithium metal oxides without the need for acids or reducing agents.

Initial oxidation of low index Mg surfaces investigated by SCLS and DFT

Magnesium (Mg) is a metal having a high structural efficiency and a very high chemical reactivity at the same time. Its potential areas of applications include the automotive industry, biomedicine, and energy storage and generation. Further developments in these very diverse application areas require a more detailed investigation of the behavior of Mg surfaces under oxidative conditions. The basic mechanisms of magnesium reactivity are not yet fully understood and therefore need to be further investigated by a combination of theoretical and experimental studies on representative surfaces with different crystallographic orientations.For this, we measured in situ high-resolution Mg 2p core level spectra at critical low-index Mg(0001), Mg(101¯0), and Mg(112¯0) surfaces to obtain surface core level shifts (SCLSs) at the early stages of Mg oxidation. We also used density functional theory (DFT) to obtain theoretical estimates of the SCLSs for respective surfaces and associated possible reconstructions to guide the analysis of the experimental spectra and to rule out un-reconstructed Mg(112¯0). DFT simulations were also used to reveal the energies of O atom adsorption, and the formation of evolving oxide structures in the Mg surfaces.

Supersonic hot jet ablative testing and analysis of boron nitride nanotube hybrid composites

Boron nitride nanotubes (BNNTs) are high-strength, high-modulus nanotubes with high thermal and oxidative stabilities. Two hybrid composites were prepared with satin weave carbon fiber (CF) and resole-type phenolic resin: one with surface layers of BNNTs and one with alternating interlayers of BNNTs. The samples were subjected to hot jet tests that simulate realistic high-pressure-temperature conditions to understand the behavior of BNNTs under high-pressure erosion. Adding BNNTs to CF/phenolic laminates enhanced the ablation resistance by reinforcing the char material and mitigated localized thermal damage. Hybrid laminates exhibited up to 14 % lower weight loss, 55 % increase in flexural modulus, higher thermal diffusivity, and improved char yield and microstructure compared to CF/phenolic samples. The surface layer hybrid had many surviving nanotubes reinforcing the char and crystalline oxide structures that could mitigate further oxygen diffusion. Various characterization methods were used to deduce possible mechanisms and their products, indicating that BNNTs could serve as growth templates for direct crystalline boron oxide formation. Overall, hybrid BNNT/CF/phenolic laminates displayed better ablation resistance and favorable microstructure evolution under high-pressure conditions.

New mixed ligand oxido-vanadium(V) complexes with O,O-donor and diimine ligands: Synthesis, crystal structure and catalytic activity in eco-friendly oxidation of olefins and phenol

The facile synthesis and structural characterization of a set of three new oxidovanadium(V) complexes of general formula [VO2(L)(diimine)], where L is ethyl-maltol(emal) (1), deferiprone(def) (2) or, maltol(mal) (3), and diimine is 5,6-dimethyl-1,10-phenanthroline(5,6-DMP) are described. The neutral complexes 1–3 have been comprehensively characterized by employing various analytical and spectroscopic techniques including single crystal X-ray diffraction analysis. The coordination geometry around the V(V) in each of the complexes was indicated by XRD-analysis to be distorted octahedral with equatorial plane being occupied by the deprotonated O,O-donor ligands. The complexes 1–3 could be successfully implemented in organic oxidations viz., hydroxylation of phenol (PH) and olefin epoxidation under environmentally clean organic-solvent-free conditions with aqueous H2O2 as oxidant. Phenol was selectively converted into dihydroxybenzene (DHB) products, catechol (CT) and hydroquinone (HQ) (HQ/CT=1.3:1) with aqueous H2O2 as oxidant at room temperature, with a TON value of 266. Moreover, the catalysts showed impressive activity in epoxidation of styrene and a range of cyclic olefins such as cyclohexene, cyclooctene, and norbornene in absence of organic solvent, to provide high conversion (up to 100 %) with excellent epoxide selectivity and good TON values. The catalysts are stable and afford recyclability for multiple cycles of epoxidation with virtually unaltered catalytic activity.

Efficiency enhancement of novel ITO/ZnSe/CNTs thin film solar cell

This study presents a novel photovoltaic cell design utilizing a layered structure of Indium Tin Oxide (ITO), Zinc Selenide (ZnSe), and Carbon Nanotubes (CNTs) for enhanced solar energy conversion. We employed the Solar Cell Capacity Simulator (SCAPS-1D) to model and optimize the device under AM 1.5 spectrum conditions. Our simulations systematically investigated the influence of key parameters including layer thicknesses, doping concentrations, temperature, back contact work function, and parasitic resistances on cell performance. The optimized structure demonstrated a theoretical power conversion efficiency of 29.91%, with an open-circuit voltage (Voc) of 799 mV, a short-circuit current density (Jsc) of 43.49 mA/cm², and a fill factor (FF) of 86.02%. These promising results are attributed to the synergistic combination of CNTs' broad spectral absorption, ZnSe's effective charge separation, and optimized layer properties. We found that the CNT absorber layer's doping concentration significantly impacted cell performance, with an optimal value of 10¹⁷ cm⁻³. The ZnSe buffer layer thickness showed minimal effect on efficiency within the studied range. Temperature increases from 300 K to 400 K led to a significant efficiency drop from 33.97% to 24.65%, primarily due to Voc reduction. While these results represent idealized conditions and upper theoretical limits, they provide valuable insights for the potential of CNT-based solar cells. This study offers a roadmap for future experimental work in high-efficiency thin-film photovoltaics, highlighting the promise of novel material combinations and the importance of device architecture optimization.

Elucidating the interaction mechanisms between polyacrylic acid and Alloy 800 oxide films under pressurized water reactor steam generator conditions

The interaction mechanisms between polyacrylic acid (PAA) and Alloy 800 were investigated. Alloy 800 formed a bilayer oxide structure in all conditions, with an outer layer of Fe-rich spinel and α-Ni(OH)2 and a Cr-rich inner layer. The chelating effect of PAA on Fe ions reduced the presence of Fe-rich spinel in the outer layer and increased the Cr content in the inner layer. However, thermal degradation of PAA (≥ 500 ppb) promoted dissolution of Cr in the initial inner layer, increasing the initial corrosion rate. The optimal PAA dosage in steam generators is determined to be approximately 250 ppb.

Synergism of carbonaceous additives in engineering of the supercapacitive performance of α-and λ-phases of manganese oxide

Owing to the presence of valence shells for charge transfer, a high theoretical specific capacitance, and variable redox properties, MnO2 appears as a promising agent in the realm of energy storage. Crystallographic structures of manganese oxide (MnO2), a transition metal oxide, play a crucial role in determining its capacitive behavior by controlling the ion intercalation and double-layer formation. In this work, two different phases of MnO2 were synthesized using the facile chemical reduction method and biological method, say α-MnO2 and λ-MnO2. The phases were incorporated with different carbonaceous additives including GO and CNT while maintaining a constant weight ratio of 8:1:1 between active materials (MnO2), additive, and PVDF binder. Among different composites formed, the best electrode performance is demonstrated by λ-MnO2/CNT/PVDF composite with an excellent specific capacitance of 356 F/g at a scan rate of 1 A/g. Moreover, the best-performing electrodes are investigated with a symmetrical two-electrode system yielding a wide potential window of 1.8V with an outstanding power density of 13.5 KW/Kg at 5 A/g and an energy density of 53.78 Wh/Kg at 1A/g having a specific capacitance of 190 F/g.

Ni–Cr dental alloys - porcelain firing impact on corrosion properties and surface characteristics

Biocompatibility is a critical aspect of the use of materials in the human body. The use of base metal alloys in dentistry is primarily regulated by health and safety standards set by regulatory authorities in various countries. The porcelain-fused-to-metal (PFM) process applied to Ni-Cr dental alloys can alter their properties, particularly in terms of corrosion and surface characteristics. This study aimed to assess the effect of the heat processing used for dental porcelain firing on these properties. The two casted alloys: Ceramic N and Ivoclar Vivadent 4all, used in the study were characterized by analyzing the microstructure by scanning electron microscopy (SEM), composition with energy dispersive x-ray spectroscopy (EDS), hardness, surface profile and electrochemical corrosion resistance (Ecorr, jcorr, polarization curve, Ebr and electrochemical impedance spectroscopy (EIS) results), as well as ions release before and after the simulated porcelain firing. Based on the conducted research the following conclusions can be drawn: Analyzes of the material characteristics before and after the simulation showed that the discussed process, although it does not cause the formation of chemical impurities on the surface of the alloys, results in changes in the chemical composition and structure of surface oxides, increases roughness and reduces hardness. The results of the corrosion examinations showed a deterioration in anti-corrosion properties after the simulation. The statistically significant decrease in corrosion resistance may result from the increased heterogeneity of the surface oxide layers and partial changes in their composition.

Development of a Novel Structured Mesh-Type Pd/γ-Al2O3/Al Catalyst on Nitrobenzene Liquid-Phase Catalytic Hydrogenation Reactions

Nitrobenzene liquid-phase catalytic hydrogenation is commonly regarded as one of the most effective technologies for aniline production. The traditional granular catalysts have the disadvantages that the reactor bed pressure drop is large and the mass transfer efficiency between gas and liquid phases is low. In this study, a novel structured mesh-type Pd/γ-Al2O3/Al catalyst was prepared by anodic oxidation and pore structures of γ-Al2O3/Al supports were constructed by acid pore-widening treatments. The results showed that acid pore-widening treatments can improve the pore size of γ-Al2O3/Al supports; the support with HNO3 pore-widening treatment exhibited the largest pore size, being enlarged from 3.7 nm to 4.6 nm. The Pd/γ-Al2O3/Al catalysts prepared with different acid pore-widening treatment supports contribute to the increased active metal Pd loading, more Pd0 content, and better dispersion of the Pd particles. The catalyst prepared with HNO3 pore-widening treatment support exhibited the largest active metal Pd loading, enlarging from 1.82% to 1.95%, the largest Pd0 content being enlarged from 52.1% to 58.5% and the smallest Pd particle size being reduced from 103 nm to 41 nm, resulting in the highest nitrobenzene conversion, increasing from 67.2% to 74.3%. Eventually, we calculated that the pressure drop of structured catalysts was 1/72 of that of granular catalysts, resulting in a better diffusion of the H2 through nitrobenzene solution to active sites on the catalyst surface and a significant increase in the catalytic activity.

Dependence of the incorporated boron concentration near SiO2/4H–SiC interface on trap passivation reduction

By systematically varying the boron concentration near the oxide/4H–SiC interface within a specifically designed boron-diffusion layer oxide structure, this paper explores the influence of boron concentration on interface state density and near-interface trap density in 4H–SiC MOS capacitors. Additionally, the effect of boron near the oxide/4H–SiC interface on device stability under elevated temperature conditions was examined. The boron species were introduced into the SiO2/4H–SiC interface by spin coating followed by annealing, whose temperature controls the amount of boron present in the near interface region. It is suggested that a higher concentration of boron leads to a better trap passivation effect while preserving the stability of flat band voltage.

Refining catalytic oxidation of volatile organic compounds over Gd-Sr-Co perovskite-based oxides fabricated via viscous mixture induction: Unveiling the crucial factors influencing catalytic activity

A series of Gd-Sr-Co perovskite-based oxides have been successfully synthesized by thermally driving viscous mixture, wherein only very trace amounts of water need and the metal salts powders do not need to be thoroughly mixed. By the characterization of XRD, XPS, EPR, and Raman, the levels of oxygen vacancies, lattice oxygen, and adsorbed oxygen in the catalyst are controlled by varying the amount of Sr doping. Unlike traditional conclusions, we found that the catalytic activities of the catalysts did not enhance with the increase in the contents of adsorbed oxygen and oxygen vacancies. H2-TPR and O2-TPD confirmed that the migration of lattice oxygen in catalysts determined their activities. Comparative activity of individual catalysts was evaluated by catalytic oxidation of toluene. The best active catalyst also showed superior catalytic activity for the oxidation of acetone, ethyl acetate, and chlorobenzene. The effects of humidity and weight hourly space velocity on the stability of the catalyst were also evaluated. Catalyst’s surface structural changes in toluene oxidation were also analyzed by in-situ DRIFTS. This study provides a simple approach to tailor perovskite-based oxide structures, crucial for effective catalytic oxidation of VOCs.

The Role of Water on the Oxidation Process of Graphene Oxide Structures

The Role of Water on the Oxidation Process of Graphene Oxide Structures

Overcoming metals redox rate limitations in spinel oxide-driven Fenton-like reactions via synergistic heteroatom doping and carbon anchoring for efficient micropollutant removal

The transition metals redox rate limitations of spinel oxides during Fenton-like reactions hinder its efficient and sustainable treatment of actual wastewater. Herein, we propose to optimize the electronic structure of Co-Mn spinel oxide (CM) via sulfur doping and carbon matrix anchoring synergistically, enhancing the radicals-nonradicals Fenton-like processes for efficient water decontamination. Activating peroxymonosulfate (PMS) with optimised spinel oxide (CMSAC) achieved near-complete removal of ofloxacin (10 mg/L) within 6 min, showing 8.4 times higher efficiency than CM group. Significantly higher yields of SO4·− and high-valent metal species in CMSAC/PMS system provided exceptional resistance to co-existing anions, enabling efficient removal of various emerging contaminants in high salinity leachate. Specifically, sulfur coordination and carbon anchoring-induced oxygen vacancy synergistically improved the electronic structure and electron transfer efficiency of CMSAC, thus forming highly reactive Co sites and significantly reducing the energy barrier for Co(IV)=O generation. The reductive sulfur species facilitated the conversion of Co(III) to Co(II), thereby maintaining the stability of the catalytic activity of CMSAC. This work developed a synergistic optimization strategy to overcome the metals redox rate limitations of spinel oxides in Fenton-like reactions, providing deep mechanistic insights for designing Fenton-like catalysts suitable for practical applications.