Induced Oxygen Vacancies Research Articles

In Situ Induced Lattice-Matched Interfacial Oxygen-Passivation-Layer Endowing Li-Rich and Mn-Based Cathodes with Ultralong Life.

The high capacity of Li-rich and Mn-based (LRM) cathode materials is originally due to the unique hybrid anion- and cation redox, which also induces detrimental oxygen escape. Furthermore, the counter diffusion of released oxygen (into electrolyte) and induced oxygen vacancies (into the interior bulk phase) that occurs at the interface will cause uncontrolled phase collapse and other issues. Therefore, due to its higher working voltage (>4.7V) than the activation voltage of lattice oxygen in LRM (≈4.5V), the anion-redox-free and structurally consistent cobalt-free LiNi0.5 Mn1.5 O4 (LNMO) is selected to in situ construct a robust, crystal-dense and lattice-matched oxygen-passivation-layer (OPL) on the surface of LRM particles by the electrochemical delithiation to protect the core layered components. As expected, the modified sample displays continuously decreasing interfacial impedance and high specific capacity of 135.5 mAh g-1 with a very small voltage decay of 0.67mV per cycle after 1000 cycles at 2 C rate. Moreover, the stress accumulation during cycling is mitigated effectively. This semicoherent OPL strengthens the surface stability and interrupts the counter diffusion of oxygen and oxygen vacancies in LRM cathode materials, which would provide guidance for designing high-energy-density layered cathode materials.

Oxygen Vacancy Induced Boosted Visible-Light Driven Photocatalytic CO2 Reduction and Electrochemical Water Oxidation Over CuCo-ZIF@Fe2 O3 @CC Architecture.

Herein, the obtained Cu0.5 Co0.5 -ZIF@Fe2 O3 @CC-150 heterojunction (termed as Cu1- x Cox -ZFC-150) showed high hydrogen and oxygen evolution reaction (HER and OER) activities with low overpotential small Tafel slope. When employed to be the bifunctional anode and cathode, they only needed a cell voltage of 1.62V. The composite also exhibited excellent photocatalytic performance on CO2 evolution into CO and CH4 . The enhanced OER kinetics and Z-scheme charge transfer model for photocatalytic property have been discussed based on the experiments and density functional theory (DFT) analysis. The optimized phase interfaces, abundant active sites, optional oxygen vacancy, and adjusted Gibbs free energy were beneficial for the fast electron/ion transport enhancing the water splitting performance.

Modulating the Oxidation State of Titanium via Dual Anions Substitution for Efficient N2 Electroreduction.

The electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable ammonia synthesis but remains significantly challenging due to the low yield and poor selectivity. Herein, a facile N and S dual anions substitution strategy is developed to tune the Ti oxidation states of TiO2 nanohybrid catalyst (NS-TiO2 /C), in which anatase TiO2 nanoplates with dense Ti3+ active sites are uniformly dispersed on porous carbon derived from 2D Ti3 C2 Tx nanosheets. The catalyst NS-TiO2 /C exhibits a superior ambient NRR efficiency with an NH3 yield rate of 19.97µg h-1 mg-1cat and Faradaic efficiency of 25.49% and is coupled with a remarkable 50 h long-term stability at -0.25V versus RHE. Both experimental and theoretical results reveal that the N and S dual-substitution effectively regulate the Ti oxidation state and electronical properties of the NS-TiO2 /C via simultaneously forming interstitial and substitutional TiS and TiN bonds in the anatase TiO2 lattice, inducing oxygen vacancies and dense Ti3+ active species as well as better electronic conductivity, which substantially facilitates N2 chemisorption and activation, and reduces the energy barrier of the rate-determining step, thereby essentially boosting NRR efficiency. This work provides a valuable approach to the rational design of advanced materials by modulating oxidation states for efficient electrocatalysis.

Inducing Oxygen Vacancies to Modulate Ignition Threshold of Nanothermites

Inducing Oxygen Vacancies to Modulate Ignition Threshold of Nanothermites

Controlling oxygen vacancies of CoMn2O4 by loading on planar and tubular clay minerals and its application for boosted PMS activation

A representative transition metal oxide (TMO), CoMn2O4 (CMO), is recognized as an effective peroxymonosulfate (PMS) activator with disadvantages like limited reactive sites and metal leakage. Herein, novel catalysts were synthesized by anchoring CMO on kaolinite (Kln) and halloysite (Hal) matrixes, two natural clay minerals with lamellar and tubular structures, for PMS activation in pharmaceutical degradation. Hal and Kln helped to control the crystallinity of CMO spontaneously with induce oxygen vacancies (OVs), which significantly enhanced the working efficiency. The reaction rate constants of Hal/CMO and Kln/CMO towards OFX degradation were nearly triple and twice that of bare CMO, respectively, with a 60% decrease in metal usage. The formation of OVs provided additional active sites for the reaction and accelerated the electron transfer. CMO/Hal and CMO/Kln exhibited better stability and durability than CMO, while CMO/Kln showed higher structural stability with lower metal leaching after 3 rounds of reaction. The higher crystallinity of CMO/Kln resulted in less OVs, but higher structural stability. The universal applicability of CMO/Hal and CMO/Kln were verified by using three other pharmaceuticals as probes. This work shed light on the modification of TMO catalysts by introducing clay mineral substrates for the efficient and ecofriendly remediation of pharmaceuticals in wastewater.

Indium element - induced oxygen vacancies and polycrystalline structure enabled SnO2 nanofibers for highly sensitive detection of NOx

High response and high selectivity of SnO2-based NOX sensors play a major role in industry and biology. However, there are still some disadvantages such as high production cost, low response and high detection limit. Therefore, a simple electrospinning method is reported for the preparation of In-doped SnO2 nanofibers (In-SnO2 NFs) for high response and selectivity to NOX in this paper. The results showed that In doping not only changed the morphology of the nanofibers but also improved the gas response to NOX (Rg/Ra = 737.8 under 100 ppm). The gas-sensing mechanism of In-SnO2 NFs to NOX was researched by XPS, O2-TPD and H2-TPR tests. The results showed that the excellent sensing performance was due to the polycrystalline structure consist of nanoparticles which provided multiple active centers for sensing reactions, and the In dopant increased the carrier concentration, adsorbed oxygen and oxygen vacancy. Therefore, In-SnO2 NFs has a good application value in sensing materials.

Aerogel-structured MnO2 cathode assembled by defect-rich ultrathin nanosheets for zinc-ion batteries

Rechargeable MnO2//Zn zinc-ion batteries (ZIBs) gain increasing attention as prospective candidates for large-scale energy storage applications, but MnO2 cathode materials are afflicted by intrinsic low electrical conductivity, sluggish Zn2+ diffusion kinetics and unstable crystal structure during Zn2+ insertion/extraction. Herein, we report the scalable synthesis of an aerogel-structured MnO2 (A-MnO2) assembled by defect-rich ultrathin nanosheets for ZIBs. For the A-MnO2, V doping and its induced oxygen vacancies manipulate electronic structure to enhance electrical conductivity and decrease Zn2+ diffusion energy barrier, and meanwhile, the ultrathin nanosheets-assembled aerogel structure favors the exposure of more electrochemically active sites and the shortening of ion diffusion distance. As a consequence, the A-MnO2 is endowed with markedly boosted electrochemical kinetics and thus superior electrochemical performance than defect-free MnO2 nanorod counterpart. Furthermore, flexible ZIB devices with both impressive flexibility and outstanding electrochemical properties can be realized using the A-MnO2 cathode material. This work is expected to promote the practical application of MnO2//Zn ZIBs.

Construction of CuO/Cu/WO3−x/WO3/W self-supported electrodes by a dry chemical route for hydrogen evolution reaction

Heterostructrural electrocatalysts are promising for enhancing reaction performance by increasing the carriers mobility and lowering the activation energy. Herein, an environmentally friendly dry chemical route based on ion beam technology is designed to construct the heterostructural CuO/Cu/WO3−x/WO3/W electrocatalysts. Through H+ beam bombardment, the oxygen vacancies in the tungsten oxide are created, and the Cu species are deposited simultaneously on the surface oxidized W mesh. This fabrication leads to a significant elevation of HER performance for WO3 based electrocatalysts. The self-supported CuO/Cu/WO3−x/WO3/W electrode exhibits an overpotential of 127 mV at −10 mA cm−2 in 0.5 M H2SO4 aqueous solution, which is much better than those of the other samples without the WO3−x layer or the deposited Cu species. The H+ bombardment induced oxygen vacancies enhance the conductivity of the tungsten oxide via narrowing its bandgap, as well as provide large amounts of unsaturated W atoms that could serve as active sites. The Cu species play a role of electron mobility promoter for further enhancing the HER activity. This strategy offers a facile route for the construction of transition metal based heterostructural electrocatalysts.

Atomistic and cluster dynamics modeling of fission gas (Xe) diffusivity in TRISO fuel kernels

TRISO fuel particles are candidates for use in next generation reactors including gas reactors, fluoride salt-cooled high temperature reactors, and micro-reactors. The UCO fuel kernel consists of a uranium dioxide (UO2) and uranium carbide mixture. The addition of UC2 helps suppress the formation of carbon monoxide gas, which led to failures during initial TRISO development. The addition of uranium carbide alters the chemistry of the UO2 kernel, which is known to influence performance parameters such as fission gas diffusivity, although the impact has not been quantified and no models exist that take the change in chemistry into account. Therefore, better understanding and more accurate models of the impact of chemistry on fuel performance are of high priority. In this paper, a first-principles density functional theory (DFT) and empirical potential based multi-scale study has been carried out to model the diffusivity of fission gas xenon (Xe) in UCO TRISO fuel kernels. The focus is on the UO2 component in the UCO fuel kernels, as that represents the largest volume fraction of the fuel kernels. The study relies on DFT and empirical potential calculations to determine Xe and point defect properties, which are then used in thermodynamic and kinetic models to predict diffusion for intrinsic conditions. In addition, the information is utilized in cluster dynamics simulations using the Centipede code to estimate the impact of irradiation on defect transport. The presence of UC2 or UC2−x in the UCO fuel kernels is shown to have a substantial impact on the UO2 non-stoichiometry by inducing oxygen vacancies and driving UO2 sub-stoichiometric, which causes much slower Xe diffusion in UCO compared to light water reactor UO2 fuel. The application of this model in fuel performance simulations using the Bison code is also demonstrated.

Indium Element - Induced Oxygen Vacancies and Polycrystalline Structure Enabled Sno2 Nanofibers for Highly Sensitive Detection of Nox

Indium Element - Induced Oxygen Vacancies and Polycrystalline Structure Enabled Sno2 Nanofibers for Highly Sensitive Detection of Nox

Significant enhancement of scintillation performance by inducing oxygen vacancies in alkali metal ion (A+ = Li+, Na+, K+)-incorporated (Lu, Sc)BO3:Ce.

The incorporation of Sc3+ can stabilize calcite-phase LuBO3:Ce3+ to grow large-sized single crystals but leads to the significant degradation of scintillation performance. In the present work, alkali metal ion (A+ = Li+, Na+, K+)-incorporated (Lu, A, Sc)BO3:Ce was rapidly synthesized in batches via a high-throughput sol-gel method. The aliovalent substitution of Lu3+ with A+ is balanced by the generation of oxygen vacancies by forming complexes. Thanks to the increased oxygen vacancies, the luminescence and XEL intensity of (Lu, Li, Sc)BO3:Ce are significantly enhanced by 2.2 times and 1.9 times, respectively. Further, the incorporation of A+ is attributed to the improved transition efficiency of charge carriers. The prepared scintillation screen fabricated with LASBO:Ce and PMMA shows that the spatial resolution can reach 8.6 lp mm-1, indicating its potential application in efficient and low-cost non-destructive X-ray detection. This work is of great significance in improving the luminescence and scintillation performance of (Lu, Sc)BO3:Ce single crystals and thin films and their application in the scintillation field.

Self-doping induced oxygen vacancies and lattice strains for synergetic enhanced upconversion luminescence of Er3+ ions in 2D BiOCl nanosheets.

Rare earth (RE) ions combined with two-dimensional (2D) semiconductors can exhibit unexpected optical properties. However, fluorescence quenching has always been inevitable due to defects associated with the synthesis and doping of 2D materials. In this work, we reported an efficient upconversion (UC) enhancement of Er3+ doped BiOCl nanosheets, utilizing a defect engineering strategy conversely rather than eliminating defects. Experiments and theoretical calculations provide evidence that oxygen vacancies (OVs) and lattice strain are simultaneously formed in the BiOCl:Er3+ nanosheets through self-doping of Cl- ions. Under 980 nm excitation, samples doped with 300 mol% Cl- ions exhibit the best luminescent emission, and the green and red UC emissions are enhanced 3.5 and 15 times, respectively. We showed that the OVs in the 2D semiconductor can act as energy bridges to transfer charges to the Er3+ energy level, enriching the electron population at the excited levels; while, the lattice strain enhances the energy transfer and charge accumulation, which synergistically enhance the UC luminescence. This research provides a new insight into the development of defect engineering for UC PL in 2D nanomaterials.

Cobalt doped titania-carbon nanosheets with induced oxygen vacancies for photocatalytic degradation of uranium complexes in radioactive wastes.

The photocatalytic degradation of uranium complexes is considered among the most efficient techniques for the efficient removal of uranium ions/complexes from radioactive wastewater. Described here is a nanostructured photocatalyst based on a cobalt-doped TiO2 composite with induced oxygen vacancies (Co@TiO2-C) for the photocatalytic removal of uranium complexes from contaminated water. The synergy between oxygen vacancies and Co-doping produced a material with a 1.7 eV bandgap, while the carbon network facilitates electron movement and hinders the e-h recombination. As a result, the new photocatalyst enables the decomposition of uranium-arsenazo iii complexes (U-ARZ3), followed by photocatalytic reduction of hexavalent uranium to insoluble tetravalent uranium. Combined with the nanosheet structure's high surface area, the photocatalytic decomposition, reduction efficiency, and kinetics were significantly enhanced, achieving almost complete U(vi) removal in less than 20 minutes from solution with a concentration as high as 1000 mL g-1. Moreover, the designed photocatalyst exhibits excellent stability and reusability without decreasing the photocatalytic performance after 5 cycles.

Improving the Photocatalytic Performance of Cobalt-Doped Titania Nanosheets by Induced Oxygen Vacancies for Efficient Degradation of Organic Pollutants

Improving the Photocatalytic Performance of Cobalt-Doped Titania Nanosheets by Induced Oxygen Vacancies for Efficient Degradation of Organic Pollutants

Transition Metal and Pr Co-Doping Induced Oxygen Vacancy in Pd/Ceo2 Catalyst Boosts Low-Temperature Co Oxidation

Transition Metal and Pr Co-Doping Induced Oxygen Vacancy in Pd/Ceo2 Catalyst Boosts Low-Temperature Co Oxidation

Advanced catalytic CO2 hydrogenation on Ni/ZrO2 with light induced oxygen vacancy formation in photothermal conditions at medium-low temperatures

Selective CH4 formation from CO2 hydrogenation is an appealing yet challenging sunlight-driven or thermal-driven process due to low solar energy utilization efficiency or high energy input.

Cobalt Doped Titania-Carbon Nanosheets with Induced Oxygen Vacancies for Photocatalytic Degradation of Complex Radioactive Waste

Cobalt Doped Titania-Carbon Nanosheets with Induced Oxygen Vacancies for Photocatalytic Degradation of Complex Radioactive Waste

High mechanical quality factor and piezoelectricity in potassium sodium niobate ceramics

Plenty of works have done to enhance the piezoelectricity of potassium-sodium niobate (KNN), aiming to replace lead-zirconate titanate (PZT) in the consideration of eco-friendly requirement. However so far, KNN ceramics with high piezoelectric performances tend to have a low mechanical quality factor (Qm), which could result in excessive dielectric loss, especially when working in high frequencies. Thus, increasing Qm is a crucial task in KNN-based ceramics. By constructing phase boundaries together with inducing oxygen vacancies, a new KNN ceramic system is built by using conventional solid-state method with high Qm (>250), high piezoelectric performance as well as outstanding temperature stability. Optimum overall properties of KNN-based ceramics can be as large as d33 = 231 pC/N, Qm = 355, TC = 366 °C. This work provides a deeper insight to KNN-based ceramics with high mechanical quality factor and makes a progress on the high frequency application of lead-free ceramics.

Improved photodegradation efficiency in Fe3+-doped Bi3TiNbO9 nanosheets through oxygen vacancies introduction and ferroelectric polarization enhancement simultaneously

Suffering from wide bandgaps and poor charge carrier mobility, most of the ferroelectric photocatalysts are still faced with low efficiency in spite of the advanced intrinsic ferroelectric polarization. Herein we proposed a simple Fe3+-doping strategy to induce oxygen vacancies and enhance ferroelectric polarization in Bi3TiNbO9 nanosheets simultaneously, realizing band structure modulation and charge carrier kinetics steering. Combining DFT calculations and systematic experimental characterizations, it was demonstrated that the introduction of Fe not only reduce the bandgaps but also improve electron-hole separation. The promoted carrier transport and increased carrier density was related to the Fe3+/Fe2+ redox cycle and oxygen vacancies (OVs) arising from the substitution of Ti4+ with Fe3+. More importantly, the enlarged ferroelectric polarization strength after doping verified by hysteresis loop can provide further driving force for charge carrier migration. Benefitting from these optimized properties, under the optimum doping concentration, the photocatalytic degradation rate of antibiotic tetracycline hydrochloride and organic dye rhodamin B under visible light were about 1.6 times and 2.1 times of that in pure Bi3TiNbO9 respectively, outperforming the benchmark P25 and the majority of bismuth layer structured ferroelectrics. This work shed light on the feasibility of defect engineering and ferroelectric polarization modulation for efficient ferroelectric photocatalysts development.

Controlled engineering of tunable 3D-BiOX (X = Cl, Br) hierarchical nanostructures via dopamine-mediated synergetic interactions for efficient visible-light absorption photocatalysis

Integration of surface tunable 3D-BiOX hierarchical nanostructures (HNS) from size and facet controlled ultra thin 2D-nanosheets in aqueous solutions under an environmental benign process is remains a challenge. Because of their visible light response is highly depending on structural characteristics and yet most fabrications are involved hydrothermal methods. Herein, a simple dopamine-mediated bioinspired approach is proposed to integrate surface tunable 3D-BiOCl, 3D-BiOBr and 3D-BiOCl0.875Br0.125 hierarchical microspheres assembled by ultra thin 2D-nanosheets in aqueous solutions under mild conditions. The biomolecule dopamine (DA.HX) here played a multiple role as reactant, template and halogen source for 3D-BiOX materials, and its amount precisely controlled surface textural properties and nanosheets thickness with exposed (001) facets. Interestingly, the interfacial surface chelate interactions of dopamine facilitated the band-edge shift towards visible range along with surface induced oxygen defect impurities, which effectively reduced their forbidden bandwidth for extended visible light absorptions and photoluminescence quenching with an efficient charge separations. The photocatalytic activities of resulting 3D-BiOX HNS have shown excellent Rhodamine B degradation provided by highly oxidative h+ and surface induced oxygen vacancies acted as e- trapping centers to generate highly active O2− radicals for selective benzyl alcohol oxidation with high photostability and recyclability than their bare BiOX materials.