Oxygen Vacancies In Lattice Research Articles

Technological solutions for NOx, SOx, and VOC abatement: recent breakthroughs and future directions.

NOx, SOx, and carbonaceous volatile organic compounds (VOCs) are extremely harmful to the environment, and their concentrations must be within the limits prescribed by the region-specific pollution control boards. Thus, NOx, SOx, and VOC abatement is essential to safeguard the environment. Considering the importance of NOx, SOx, and VOC abatement, the discussion on selective catalytic reduction, oxidation, redox methods, and adsorption using noble metal and non-noble metal-based catalytic approaches were elaborated. This article covers different thermal treatment techniques, category of materials as catalysts, and its structure-property insights along with the advanced oxidation processes and adsorption. The defect engineered catalysts with lattice oxygen vacancies, bi- and tri-metallic noble metal catalysts and non-noble metal catalysts, modified metal organic frameworks, mixed-metal oxide supports, and their mechanisms have been thoroughly reviewed. The main hurdles and potential achievements in developing novel simultaneous NOx, SOx, and VOC removal technologies are critically discussed to envisage the future directions. This review highlights the removal of NOx, SOx, and VOC through material selection, properties, and mechanisms to further improve the existing abatement methods in an efficient way.

Magnesium doping to improve the light to heat conversion of OMS-2 for formaldehyde oxidation under visible light irradiation

Mg-doped manganese oxide octahedral molecular sieve (Mg-OMS-2) catalysts were prepared by hydrothermal method. The photothermal degradation performance of these catalysts for formaldehyde (HCHO) in batch system and continuous system was investigated. The light absorption of OMS-2 was increased by Mg-doped, especially for near infrared light, which promoted surface temperature reach a maximum of 214.8 °C under xenon irradiation. At this temperature, the reinforced surface lattice oxygen and oxygen vacancy that formed by lattice distortion via Mg-doped were activated. The best HCHO elimination efficiency was achieved over Mg0.2/OMS-2 catalyst with Mg2+/Mn2+ = 1/5, which could reduce HCHO from 250 ppm to 10 ppm within 20 min. The in situ DRIFTS was also carried out to monitor the changes in the content of reaction intermediates and analyze the degradation paths of HCHO. It was found the HCHO was attacked by formed •OH and •O2− to generate formate species and carbonate species, and finally transformed to CO2 and H2O. This photothermal catalytic oxidation process exhibited a high efficiency purification of HCHO without the help of extra energy consumption.

Evidence of oxygen evolution over sputtered zinc ferrite (ZnFe2O4) thin film by enhanced lattice oxygen participation

We report evidence of oxygen evolution over zinc ferrite (ZnFe2O4) thin films grown on indium tin oxide and quartz substrates using the RF sputtering. The thin films are deposited at ambient temperature with different argon/oxygen gas ratios, specifically 1:0 (Z–Ar), 1:1 (Z–Ar:O), and 0:1 (Z–O). Structural characterization using grazing incidence x-ray diffraction at a 0.400° grazing angle confirmed the polycrystalline nature of the films. X-ray photoelectron spectroscopy scans of Zn 2p, Fe 2p, and O1s were conducted to investigate the lattice oxygen vacancies. The lattice oxygen vacancies in the Z–Ar film resulted in a lower bandgap of 2.05 eV than the Z–O film of 2.36 eV. The oxygen evolution reaction (OER) performances of the thin films are investigated to understand the effect of oxygen vacancies on electrochemical activity and observed that the Z–Ar film, with oxygen vacancies, exhibits a decrease in overpotential by ∼12.5% at 10 mA cm−2, eightfold increase in current density at 520 mV overpotential deduced from linear sweep voltammetry, and a 71.9% increase in donor density inferred from the Mott–Schottky plot, as compared to the Z–O film. The findings suggest that the Z–Ar film follows a “lattice oxygen participation mechanism” for the OER, instead of an “adsorbate evolution mechanism” observed in the Z–O film. The results highlight the significant impact of argon/oxygen gas ratios on the structural, optical, and electrochemical properties of zinc ferrite thin films and provide insight into the role of oxygen vacancies in modulating the OER performance for potential applications.

Oxygen uncoupling chemical looping gasification of biomass over heterogeneously doped La-Fe-O perovskite-type oxygen carriers

Biomass chemical looping gasification (BCLG) is a promising technology utilizes lattice oxygen for partial oxidation to produce high-value fuels. But in the field of BCLG, oxygen uncoupling chemical looping gasification (OU-CLG) is a novel concept that introduces molecular oxygen to optimize traditional gas-solid reactions. In this work, based on the most representative oxygen uncoupling elements successfully doped into La-Fe-O oxygen carriers, the results showed that the reaction performance not be positively correlated with the degree of oxygen uncoupling, only Co doping exhibited a better gasification performance than LaFeO3 did. Further, Co-LF differs from conventional LF in that it performs better in ex-situ gasification than in-situ gasification, with a total gas yield and carbon conversion efficiency of 1078.70 ml/g and 75.15% respectively. Further characterizations revealed that Co doping led to changes in the physical structure and reducibility. More importantly, enriched lattice oxygen and oxygen vacancies induced the formation of disordered reactive oxygen species in perovskite lattice, which promote the further oxygen uncoupling and the formation of oxygen uncoupling vacancies in ex-situ gasification. Moreover, doped but failure to promote the CLG might due to oxygen scarcity, impurity and elemental catalytic properties. Finally, a clear reaction mechanism regarding OU-CLG was proposed.

Inhibiting oxygen vacancies and twisting NbO6 octahedron in erbium modified KNN-based multifunctional ceramics

It is a challenge to obtain highly tunable multifunctional performances in one ferroelectric system by a simple approach to meet the miniaturization, integration, and functionalization requirements of advanced electronic components. Herein, rare earth erbium (Er) modulated 0.9K0.5Na0.5NbO3-0.1Sr(1-x)ErxTi(1-x/4)O3, (0.9KNN-0.1ST: xEr) transparent-photoluminescent-ferroelectric energy storage multifunctional ceramics are prepared to solve this problem. The effect of lattice distortion and oxygen vacancies by Er doping on the optical and electrical properties is systematically investigated. The Er3+ ions can introduce a large distortion of the NbO6 octahedron by replacing the A-site in KNN-based ceramics. Thanks to the higher c/a ratio and lower oxygen vacancy content are simultaneously obtained in 0.9KNN-0.1ST: 0.1Er ceramics. The effective energy storage density (Wrec) of 0.86 J/cm3, excellent near-infrared transmittance of 51.7% (1 100 nm) and strong green upconversion photoluminescence are achieved in this multifunctional ceramic. This study provides a solid basis for rare earth ions doped ferroelectric ceramics with tunable multifunctional properties and has significant potential for applications in optoelectronic devices.

Effective Atomic N Doping on CeO2 Nanoparticles by Environmentally Benign Urea Thermolysis and Its Significant Effects on the Scavenging of Reactive Oxygen Radicals.

Atomic nitrogen doping on CeO2 nanoparticles (NPs) by an efficient and environmentally benign urea thermolysis approach is first studied, and its effects on the intrinsic scavenging activity of the CeO2 NPs for reactive oxygen radicals are investigated. The N-doped CeO2 (N-CeO2) NPs, characterized by X-ray photoelectron and Raman spectroscopy analyses, showed considerably high levels of N atomic doping (2.3-11.6%), accompanying with an order of magnitude increase of the lattice oxygen vacancies on the CeO2 crystal surface. The radical scavenging properties of the N-CeO2 NPs are characterized by applying Fenton's reaction with collective and quantitative kinetic analysis. The results revealed that the significant increase of surface oxygen vacancies is the leading cause for the enhancements of radical scavenging properties by the N doping of CeO2 NPs. Enriched with abundant surface oxygen vacancies, the N-CeO2 NPs prepared by urea thermolysis provided about 1.4-2.5 times greater radical scavenging properties than the pristine CeO2. The collective kinetic analysis revealed that the surface-area-normalized intrinsic radical scavenging activity of the N-CeO2 NPs is about 6- to 8-fold greater than that of the pristine CeO2 NPs. The results suggest the high effectiveness of the N doping of CeO2 by the environmentally benign urea thermolysis approach to enhance the radical scavenging activity of CeO2 NPs for extensive applications such as that in polymer electrolyte membrane fuel cells.

Synergetic effect of lattice distortion and oxygen vacancies on high-rate lithium-ion storage in high-entropy perovskite oxides

Synergetic effect of lattice distortion and oxygen vacancies on high-rate lithium-ion storage in high-entropy perovskite oxides

Triggering High Capacity and Superior Reversibility of Manganese Oxides Cathode via Magnesium Modulation for Zn//MnO2 Batteries.

Aqueous zinc-ion batteries (ZIBs) have attracted extensive attention in recent years because of its high volumetric energy density, the abundance of zinc resources, and safety. However, ZIBs still suffer from poor reversibility and sluggish kinetics derived from the unstable cathodic structure and the strong electrostatic interactions between bivalent Zn2+ and cathodes. Herein, magnesium doping into layered manganese dioxide (Mg-MnO2 ) via a simple hydrothermal method as cathode materials for ZIBs is proposed. The interconnected nanoflakes of Mg-MnO2 possess a larger specific surface area compared to pristine δ-MnO2 , providing more electroactive sites and boosting the capacity of batteries. The ion diffusion coefficients of Mg-MnO2 can be enhanced due to the improved electrical conductivity by doped cations and oxygen vacancies in MnO2 lattices. The assembled Zn//Mg-MnO2 battery delivers a high specific capacity of 370mAhg-1 at a current density of 0.6Ag-1 . Furthermore, the reaction mechanism confirms that Zn2+ insertion occurred after a few cycles of activation reactions. Most important, the reversible redox reaction between Zn2+ and MnOOH is found after several charge-discharge processes, promoting capacity and stability. It believes that this systematic research enlightens the design of high-performance of ZIBs and facilitates the practical application of Zn//MnO2 batteries.

Electrocatalytic removal of persistent organic contaminants at molybdenum doped manganese oxide coated TiO2 nanotube-based anode

Electrooxidation is an attractive technique that can be effectively applied for the treatment of persistent organic contaminants, but its implementation in practice is limited by the lack of efficient and low-cost anode material that would not lead to the generation of chlorinated by products. Herein, we developed a novel anode based on TiO2 nanotube array (NTA) coated with Mo-doped MnxOy, and applied it for electrooxidation of persistent organic contaminants. The Ti/TiO2 NTA–MnxOy-Mo anode outperformed the commercial Ti/IrOx-Pt anode and effectively oxidized organic contaminants, with a significantly reduced electric energy per order, and avoiding chlorine evolution reaction. Mo doping played a key role in the excellent performance of the synthesized anode as it favored the formation of oxygen vacancies in the host lattice and Mn and Mo species redox couples, which increased the oxidizing power of the anode and ensured its complete stability.

Europium induced point defects in SrSnO3-based perovskites employed as antibacterial agents

The antibacterial activity of Eu3+-doped SrSnO3-type materials against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria is described. Two Eu3+-doped SrSnO3 perovskites - (SrEu)SnO3 and Sr(SnEu)O3 - were synthesised by a modified-Pechini method and characterised by XRD, FT-IR, FE-SEM, HR-STEM/EDX, BET, Photoluminescence (PL), UV-Vis, Q-band EPR and XPS to understand the impact of Eu doping on the materials’ properties. Structural characterisations indicated that the desired perovskite phase completely crystallised after calcination at 700 °C. Long and short-range structural changes were observed as a function of the site-doping with Eu and calcination temperature. Small specific surface area, which varied from 8.09 to 13.28 m2/g, was observed for the samples. Nonetheless, the formation of nanoparticles under 10 nm, clusters of nanoparticles> 100 nm, and nanorods with 100–600 nm × 10–50 nm (length × width) was evidenced. Eu3+ doping led to an increase of Sn2+ and oxygen vacancies in SrSnO3 lattice, playing an essential role in the antibacterial activity. Reduced Eu2+ species were also observed. The samples had activity below 5 % against Escherichia coli, whereas (SrEu)SnO3 displayed an efficiency of 100 % after 24 h against Staphylococcus aureus at a concentration of 1 mg/mL. Our results demonstrate that a specific chemical doping with Eu induces the formation of distinct point defect (Sn2+, Eu2+ and VO•) in the materials, which promoted a negative surface charge that seems to have improved the redox ability and, therefore, enhanced the biocide property.

Na+ Lattice Doping Induces Oxygen Vacancies to Achieve High Capacity and Mitigate Voltage Decay of Li-Rich Cathodes.

In this work, we synthesized 1D hollow square rod-shaped MnO2, and then obtained Na+ lattice doped-oxygen vacancy lithium-rich layered oxide by a simple molten salt template strategy. Different from the traditional synthesis method, the hollow square rod-shaped MnO2 in NaCl molten salt provides numerous anchor points for Li, Co, and Ni ions to directly prepare Li1.2Ni0.13Co0.13Mn0.54O2 on the original morphology. Meanwhile, Na+ is also introduced for lattice doping and induces the formation of oxygen vacancy. Therefrom, the modulated sample not only inherits the 1D rod-like morphology but also achieves Na+ lattice doping and oxygen vacancy endowment, which facilitates Li+ diffusion and improves the structural stability of the material. To this end, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and other characterization are used for analysis. In addition, density functional theory is used to further analyze the influence of oxygen vacancy generation on local transition metal ions, and theoretically explain the mechanism of the electrochemical performance of the samples. Therefore, the modulated sample has a high discharge capacity of 282 mAh g-1 and a high capacity retention of 90.02% after 150 cycles. At the same time, the voltage decay per cycle is only 0.0028 V, which is much lower than that of the material (0.0038 V per cycle) prepared without this strategy. In summary, a simple synthesis strategy is proposed, which can realize the morphology control of Li1.2Ni0.13Co0.13Mn0.54O2, doping of Na+ lattice, and inducing the formation of oxygen vacancy, providing a feasible idea for related exploration.

Molecular structure-dependent contribution of reactive species to organic pollutant degradation using nanosheet Bi2Fe4O9 activated peroxymonosulfate

Iron-based catalysts have attracted increasing attention in heterogeneous activation of peroxymonosulfate (PMS). However, the activity of most iron-based heterogenous catalysts is not satisfactory for practical application and the proposed activation mechanisms of PMS by iron-based heterogenous catalyst vary case by case. This study prepared Bi2Fe4O9 (BFO) nanosheet with super high activity toward PMS, which was comparable to its homogeneous counterpart at pH 3.0 and superior to its homogeneous counterpart at pH 7.0. Fe sites, lattice oxygen and oxygen vacancies on BFO surface were believed to be involved in the activation of PMS. By using electron paramagnetic resonance (EPR), radical scavenging tests, 57Fe Mössbauer and 18O isotope-labeling technique, the generation of reactive species including sulfate radicals, hydroxyl radicals, superoxide and Fe (IV) were confirmed in BFO/PMS system. However, the contribution of reactive species to the elimination of organic pollutants very much depends on their molecular structure. The effect of water matrices on the elimination of organic pollutants also hinges on their molecular structure. This study implies that the molecular structure of organic pollutants governs their oxidation mechanism and their fate in iron-based heterogeneous Fenton-like system and further broadens our knowledge on the activation mechanism of PMS by iron-based heterogeneous catalyst.

Tunable oxygen vacancies in MoO3 lattice with improved electrochemical performance for Li-ion battery thin film cathode

MoO3 is a kind of promising cathode material for lithium-ion batteries (LIBs), owing to its high specific capacity (279 mA h g−1) and layered structure. However, low electrical conductivity and sluggish reaction kinetics results in poor rate and Li-ions storage capability. The introduction of oxygen vacancies (OVs) can promote Li+ diffusion, and produce great electrical conductivity. Here, we report a strategy to synergize the merits of OVs by pulsed laser deposition (PLD) by adjusting oxygen partial pressures (2～20 Pa). The appropriate OVs concentration not only significantly approves electrochemical performance but also increases pseudocapacitance contribution. The Li-ion diffusion coefficient of MoO3−x is remarkably improved by one or two orders of magnitude compared with that of MoO3. Therefore, this facile and efficient strategy on OVs could afford a reference for other metal oxides for high-performance electrode materials.

The effect of non-equimolar doping on the preparation and electrical conductivity of Sr(Ti,Zr,Zn,Sn,Hf)O3-σ high entropy perovskite oxide

A series of high entropy oxides (HEOSs) with non-isomolar ratios of perovskite structures were prepared by ball milling a mixture of SrO, TiO2, ZrO2, ZnO, SnO2 and HfO2 followed by sintering using a high-temperature solid-phase method. Both XRD and TG-DSC results indicate that single-phase Sr(Ti0.2Zr0.2Zn0.2Sn0.2Hf0.2)O3-σ is formed at 1500 °C. According to the SEM-EDS pictures, the elements in the oxide are uniformly distributed with no significant segregation or accumulation. The TEM results show that the polycrystalline ceramic powders can be classified as orthogonal Pbnm perovskite structure. The electrical conductivity (σ) was measured by the EIS technique and the activation energy (Ea) of HEOSs is calculated. In the temperature range of 300–750 °C, Sr(Ti0.28Zr0.18Zn0.18 Sn0.18 Hf0.18)O3-σ exhibits the highest conductivity (2.41 × 10−3 S/cm) and the lowest activation energy (Ea = 0.57 eV) due to lattice distortion and oxygen vacancy concentration.

Copper Ferrite Nanoparticles Synthesized Using Anion-Exchange Resin: Influence of Synthesis Parameters on the Cubic Phase Stability

Copper ferrite is of great interest to researchers as a material with unique magnetic, optical, catalytic, and structural properties. In particular, the magnetic properties of this material are structurally sensitive and can be tuned by changing the distribution of Cu and Fe cations in octahedral and tetrahedral positions by controlling the synthesis parameters. In this study, we propose a new, simple, and convenient method for the synthesis of copper ferrite nanoparticles using a strongly basic anion-exchange resin in the OH form. The effect and possible mechanism of polysaccharide addition on the elemental composition, yield, and particle size of CuFe2O4 are investigated and discussed. It is shown that anion-exchange resin precipitation leads to a mixture of unstable cubic (c-CuFe2O4) phases at standard temperature and stable tetragonal (t-CuFe2O4) phases. The effect of reaction conditions on the stability of c-CuFe2O4 is studied by temperature-dependent XRD measurements and discussed in terms of cation distribution, cooperative Jahn-Teller distortion, and Cu2+ and oxygen vacancies in the copper ferrite lattice. The observed differences in the values of the saturation magnetization and coercivity of the prepared samples are explained in terms of variations in the particle size and structural properties of copper ferrite.

Impact of lattice properties on the CO2 splitting kinetics of lanthanide-doped cerium oxides for chemical looping syngas production

Cerium oxide (CeO2) is the state-of-the-art material for syngas production from CO2 and H2O splitting via (methane assisted-) solar-driven thermochemical cycles. This technology consists of two separate processes: (1) a partial reduction of the oxide with methane at ∼900 °C that produces syngas and generates oxygen vacancies in the oxide lattice; and (2) oxidation of the reduced oxide by reaction with H2O and/or CO2 to form H2 and/or CO, respectively, which incorporates oxygen into the oxygen vacancy lattice sites. Doping the cerium oxide with other cations enables to increase the oxygen-vacancy concentration or to induce changes in the crystal lattice, aiming at increasing the fuel yield and/or boosting the redox oxygen-exchange kinetics. Traditionally, CeO2 has been doped with lanthanides to improve the redox behavior and enhance ionic conduction. For lanthanide-doped cerium oxides, a correlation between the dopant's ionic radius and the material's ionic conductivity has been established. Here, we examine the impact of the trivalent lanthanide dopants on the methane partial oxidation and CO2 splitting. Our results reveal a correlation between the dopant ionic radius, ionic conductivity, oxygen exchange kinetics, and CO2 splitting kinetics. We could identify the optimum ionic radius for enhanced CO2 splitting kinetics based on our observations. These findings are an essential framework for designing more advanced redox materials for chemical looping syngas production.

Dynamic cooperations between lattice oxygen and oxygen vacancies for photocatalytic ethane dehydrogenation by a self-restoring LaVO4 catalyst

Dynamic cooperations between lattice oxygen and oxygen vacancies for photocatalytic ethane dehydrogenation by a self-restoring LaVO4 catalyst

Regulation and prediction of defect-related properties in ZnO nanosheets: synthesis, morphological and structural parameters, DFT study and QSPR modelling

The work is aimed to consider photocatalytic efficiency and photoluminescence dependence on oxygen vacancies and other crystal lattice defects in ZnO nanosheets in order to provide their regulation and perdictionA synthesis via precipitation method under different conditions followed by hydrothermal treatment under different temperatures to obtain series of nanosheet samples with various amounts of defects was performed. Obtained samples were fully characterized (SEM, XRD, FTIR, XPS, Raman, absorbance spectra). A novel approach has been proposed and applied to determine the amount of oxygen vacancies and defects from XPS and Raman spectroscopy data. Quantum-chemical calculations (DFT) were performed to obtain density of states and band structure and to study the impact of lattice parameters and oxygen vacancies on electronic structure.The photocatalytic properties under UV and visible light irradiation were studied. Relations between morphological, structural parameters and functional properties (photoluminescent and photocatalytic) of ZnO nanosheets using quantitative structure–property relationship (QSPR) method were established. The impact of defects in combinations with other parameters on functional properties was demonstrated. Revealed dependencies and QSPR model provide a possibility to predict functional properties of nanosheets can be used for the development of new materials.

Sputtered terbium iron garnet films with perpendicular magnetic anisotropy for spintronic applications

We report the structural, magnetic, and interfacial spin transport properties of epitaxial terbium iron garnet (TbIG) ultrathin films deposited by magnetron sputtering. High crystallinity was achieved by growing the films on gadolinium gallium garnet substrates either at high temperatures, or at room temperature followed by thermal annealing, above 750 °C in both cases. The films display large perpendicular magnetic anisotropy (PMA) induced by compressive strain, and tunable structural and magnetic properties through growth conditions or the substrate lattice parameter choice. The ferrimagnetic compensation temperature (TM) of selected TbIG films was measured through the temperature-dependent anomalous Hall effect in Pt/TbIG heterostructures. In the studied films, TM was found to be between 190 and 225 K, i.e., approximately 25-60 K lower than the bulk value, which is attributed to the combined action of Tb deficiency and oxygen vacancies in the garnet lattice evidenced by x-ray photoelectron spectroscopy measurements. Sputtered TbIG ultrathin films with large PMA and highly tunable properties reported here can provide a suitable material platform for a wide range of spintronic experiments and device applications.

Oxygen-Related Defect Engineering of Amorphous Vanadium Pentoxide Cathode for Achieving High-Performance Thin-Film Aqueous Zinc-Ion Batteries

Thin-film aqueous zinc-ion batteries are expected to serve as next-generation energy storage devices that are both low-cost and safe. However, to realize practical energy storage devices based on zinc-ion batteries, it is necessary to develop reliable, high-capacity cathode materials. In this study, we prepared a V2O5-based thin-film electrode and investigated the effect of varying the Ar pressure during radio frequency magnetron sputtering of V2O5, a representative cathode material in thin-film zinc-ion batteries, to control the number of oxygen vacancies in the oxide lattice. The optimized V2O5 thin-film electrode exhibited enhanced electrochemical activities, low degree of polarization, improved ion diffusion, and increased electrical conductivities. Specifically, an oxygen-deficient V2O5–x thin-film prepared by sputtering under high pressure exhibited a high rate capability (57.2 mAh g–1 at 20 C) and superior electrochemical performance (105.2 mAh g–1 for up to 1000 cycles at a current density of 5 C). The mechanism for the performance enhancement was revealed by density functional theory calculations, which showed that the oxygen-deficient V2O5–x had a lower Zn2+-ion diffusion energy barrier than that of pristine V2O5. This defect engineering strategy for tuning the oxidation state should aid in designing high-performance cathodes for advanced thin-film aqueous battery chemistry.