Oxygen Vacancy-Laden Confinement Impact on Degradation of Metal Complexes

Oxygen vacancies (Vo) have been recognized as the superior active site for PS-mediated environmental remediation; however, the formation and activation of Vo associated with the effects of chemical and spatial environments remain ambiguous. Herein, attributing to the low defect-formation energy of Vo in the presence of sulfonate groups, an in situ nucleating Vo-laden CuO nanosheet was deliberately fabricated inside the phase of a sulfonated mesoporous polystyrene substrate (Vo-CuO@SPM). The as-prepared nanocomposite demonstrated an excellent treatment efficiency toward metal complexes [Cu-EDTA as a case] with ignorable Cu(II) leaching, and it can be repeatedly employed for 25 recycles (not limited). Mechanistically, the electron transfer and the mass transport for PDS nonradical activation were proved to be substantially enhanced by the delocalized electrons and with the assistance of the microchannel environment. This work not only establishes insight into the formation of oxygen vacancies but also reveals the PS activation mechanism in the spatially confined sites.

Defect Engineering for SnO2 Improves NO2 Gas Sensitivity by Plasma Spraying

Large emissions of nitrogen dioxide (NO2) pose a significant threat to human health, Monitoring its content and implementing timely measures are crucial. Utilizing oxide semiconductors, such as tin dioxide (SnO2), has proven to be an effective way to detect and analyze NO2. The design and preparation of sensing materials with high sensitivity and excellent selectivity is the key to improve the detection efficiency. SnO2 nanopowders with small and uniform particle size, large specific surface area, adjustable defect content, and no impurities were prepared by a new plasma spraying method. The SnO2 nanopowders exhibit outstanding performance in detecting NO2 at a low temperature of 100 °C, the response to 5 ppm of NO2 reaches 48, and the material demonstrates rapid response and recovery times, coupled with excellent selectivity. The exceptional gas-sensitive properties can be attributed to the superior morphology and structure of SnO2. It provides more reaction sites for gas sensitive reactions, fast electron transport, a large number of charge carriers, and improved adsorption of the material to the target gas. This study provides valuable insights into nanomaterial preparation and the enhancement of gas-sensitive properties for SnO2.

Tunneling Proton Grotthuss Transfer Channels by Hydrophilic-Zincophobic Heterointerface Shielding for High-Performance Zn-MnO2 Batteries

Hollandite-type manganese dioxide (α-MnO2) is recognized as a promising cathode material upon high-performance aqueous zinc-ion batteries (ZIBs) owing to the high theoretical capacities, high working potentials, unique Zn2+/H+ co-insertion chemistry, and environmental friendliness. However, its practical applications limited by Zn2+ accommodation, where the strong coulombic interaction and sluggish kinetics cause significant lattice deformation, fast capacity degradation, insufficient rate capability, and undesired interface degradation. It remains challenging to accurately modulate H+ intercalation while suppressing Zn2+ insertion for better lattice stability and electrochemical kinetics. Herein, proton Grotthuss transfer channels are first tunneled by shielding MnO2 with hydrophilic-zincophobic heterointerface, fulfilling the H+-dominating diffusion with the state-of-the-art ZIBs performance. Local atomic structure and theoretical simulation confirm that surface-engineered α-MnO2 affords to the synergy of Mn electron t2g-eg activation, oxygen vacancy enrichment, selective H+ Grotthuss transfer, and accelerated desolvation kinetics. Consequently, fortified α-MnO2 achieves prominent low current density cycle stability (≈100% capacity retention at 1 C after 400 cycles), remarkable long-lifespan cycling performance (98% capacity retention at 20 C after 12 000 cycles), and ultrafast rate performance (up to 30 C). The study exemplifies a new approach of heterointerface engineering for regulation of H+-dominating Grotthuss transfer and lattice stabilization in α-MnO2 toward reliable ZIBs.

Engineering H2O2 Self-Supplying Platform for Xdynamic Therapies via Ru-Cu Peroxide Nanocarrier: Tumor Microenvironment-Mediated Synergistic Therapy

Of the most common, hypoxia, overexpressed glutathione (GSH), and insufficient H2O2 concentration in the tumor microenvironment (TME) are the main barriers to the advancment of reactive oxygen species (ROS) mediated Xdynamic therapies (X = photo, chemodynamic, chemo). Maximizing Fenton catalytic efficiency is crucial in chemodynamic therapy (CDT), yet endogenous H2O2 levels are not sufficient to attain better anticancer efficacy. Specifically, there is a need to amplify Fenton reactivity within tumors, leveraging the unique attributes of the TME. Herein, for the first time, we design RuxCu1-xO2-Ce6/CPT (RCpCCPT) anticancer nanoagent for TME-mediated synergistic therapy based on heterogeneous Ru-Cu peroxide nanodots (RuxCu1-xO2 NDs) and chlorine e6 (Ce6), loaded with ROS-responsive thioketal (TK) linked-camptothecin (CPT). The Ru-Cu peroxide NDs (RCp NDs, x = 0.50) possess the highest oxygen vacancy (OV) density, which grants them the potential to form massive Lewis's acid sites for peroxide adsorption, while the dispersibility and targetability of the NDs were improved via surface modification using hyaluronic acid (HA). In TME, RCpCCPT degrades, releasing H2O2, Ru2+/3+, and Cu+/2+ ions, which cooperatively facilitate hydroxyl radical (•OH) formation and deactivate antioxidant GSH enzymes through a cocatalytic loop, resulting in excellent tumor therapeutic efficacy. Furthermore, when combined with laser treatment, RCpCCPT produces singlet oxygen (1O2) for PDT, which induces cell apoptosis at tumor sites. Following ROS generation, the TK linkage is disrupted, releasing up to 92% of the CPT within 48 h. In vitro investigations showed that laser-treated RCpCCPT caused 81.5% cell death from PDT/CDT and chemotherapy (CT). RCpCCPT in cancer cells produces red-blue emission in images of cells taking them in, which allows for fluorescence image-guided Xdynamic treatment. The overall results show that RCp NDs and RCpCCPT are more biocompatible and have excellent Xdynamic therapeutic effectiveness in vitro and in vivo.

Tuning Adsorbate-Mediated Strong Metal-Support Interaction by Oxygen Vacancy: A Case Study in Ru/TiO2

The adsorbate-mediated strong metal-support interaction (A-SMSI) offers a reversible means of altering the selectivity of supported metal catalysts, thereby providing a powerful tool for facile modulation of catalytic performance. However, the fundamental understanding of A-SMSI remains inadequate and methods for tuning A-SMSI are still in their nascent stages, impeding its stabilization under reaction conditions. Here, we report that the initial concentration of oxygen vacancy in oxide supports plays a key role in tuning the A-SMSI between Ru nanoparticles and defected titania (TiO2-x). Based on this new understanding, we demonstrate the in-situ formation of A-SMSI under reaction conditions, obviating the typically required CO2-rich pretreatment. The as-formed A-SMSI layer exhibits remarkable stability at various temperatures, enabling excellent activity, selectivity and long-term stability in catalyzing the reverse water gas-shift reaction. This study deepens the understanding of the A-SMSI and the ability to stabilize A-SMSI under reaction conditions represents a key step for practical catalytic applications.

Highly Effective Pyroelectric Catalysis for Simultaneous Tumor-Targeted Dynamic Therapy and Gentle Photothermal Therapy by Oxygen-Vacancy-Rich CeO2-BaTiO3 Nanorods

Pyroelectric nanostructures could effectively generate temperature-mediated reactive oxygen species (ROS) through the pyroelectric effect, providing promise for treating hypoxic tumors, and therefore, the synergistic application of photothermal therapy (PTT) and pyroelectric dynamic therapy (PEDT) presents an intriguing approach for cancer therapy. However, this method still faces challenges in improving pyroelectric catalysis and achieving precise tumor localization. In this study, a nano-heterojunction based on CeO2-BaTiO3 nanorods (IR1061@PCBNR) is reported, which exhibits highly effective pyroelectric catalysis for simultaneous tumor-targeted dynamic therapy and gentle photothermal therapy through the utilization of the rich oxygen vacancies. The oxygen vacancies create active sites that facilitate the migration of pyroelectrically-induced charge carriers, improving charge separation and ROS generation. IR1061@PCBNR also demonstrates high tumor penetration while minimizing damage to normal cells. This precise nanomedicine strategy holds great potential for advancing dynamic cancer therapies by overcoming the limitations of conventional approaches. This article is protected by copyright. All rights reserved.

Self-modification of Defective TiO2 under Controlled H2/Ar Gas Environment and Dynamics of Photoinduced Oxygen Vacancies

In recent years, defective TiO2 has caught considerable research attention because of its potential to overcome the limits of low visible light absorption and fast charge recombination present in pristine TiO2 photocatalysts. Among the different synthesis conditions for defective TiO2, ambient pressure hydrogenation with the addition of Ar as inert gas for safety purposes has been established as an easy to realize process. Whether the Ar gas might still influence the resulting photocatalytic properties and defective surface layer remains an open question. Here, we reveal that the gas flow ratio between H2 and Ar has a crucial impact on the defective structure as well as the photocatalyic activity of TiO2. In particular, transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS) revealed a larger width of the defective surface layer when using a H2/Ar (50%-50%) gas mixture over pure H2. Here, a possible reason could be the increase in dynamic viscosity of the gas mixture when Ar is added. Additionally, photoinduced enhanced Raman spectroscopy (PIERS) is implemented as a complementary approach to investigate the dynamics of the defective structures under ambient conditions which cannot be effortlessly realized by vacuum techniques like TEM.

Engineering Oxygen Vacancies in In2O3 with Enhanced Polysulfides Immobilization and Selective Catalytic Capability

Lithium-sulfur (Li-S) battery is identified as an ideal candidate for next-generation energy storage systems in consideration of its high theoretical energy density and abundant sulfur resources. However, the shuttling behavior of soluble polysulfides (LiPSs) and their sluggish reaction kinetics severely limit the practical application of the current Li-S battery. In this work, a series of In2O3 nanocubes with different oxygen vacancy concentrations are designed and prepared via a facile self-template method. The introduced oxygen vacancy on In2O3 can effectively rearrange the charge distribution and enhance sulfiphilic property. Moreover, the In2O3 with high oxygen vacancy concentration (H-In2O3) can slightly slow down the solid-liquid conversion process and significantly accelerate the liquid-solid conversion process, thus reducing the accumulation of LiPSs in electrolyte and inhibiting the shuttle effect. Contributed by the unique selective catalytic capability, the prepared H-In2O3 exhibits excellent electrochemical performance when used as sulfur host. For instance, a high reversible capacity of 609 mAh g-1 is obtained with only 0.044% capacity decay per cycle over 1000 cycles at 1.0 C. This work presents a typical example for designing advanced sulfur hosts, which is crucial for the commercialization of Li-S battery.

Highly Reactive Peroxide Species Promoted Soot Oxidation over an Ordered Macroporous Ce0.8Zr0.2O2 Integrated Catalyzed Diesel Particulate Filter

Particulate matter, represented by soot particles, poses a significant global environmental threat, necessitating efficient control technology. Here, we innovatively designed and elaborately fabricated ordered hierarchical macroporous catalysts of Ce0.8Zr0.2O2 (OM CZO) integrated on a catalyzed diesel particulate filter (CDPF) using the self-assembly method. An oxygen-vacancy-enriched ordered macroporous Ce0.8Zr0.2O2 catalyst (VO-OM CZO) integrated CDPF was synthesized by subsequent NaBH4 reduction. The VO-OM CZO integrated CDPF exhibited a markedly enhanced soot oxidation activity compared to OM CZO and powder CZO coated CDPFs (T50: 430 vs 490 and 545 °C, respectively). The well-defined OM structure of the VO-OM CZO catalysts effectively improves the contact efficiency between soot and the catalysts. Meanwhile, oxygen vacancies trigger the formation of a large amount of highly reactive peroxide species (O22-) from molecular oxygen (O2) through electron abstraction from the three adjacent Ce3+ (3Ce3+ + Vö + O2 → 3Ce4+ + O22-), contributing to the efficient soot oxidation. This work demonstrates the fabrication of the ordered macroporous CZO integrated CDPF and reveals the importance of structure and surface engineering in soot oxidation, which sheds light on the design of highly efficient PM capture and removal devices.

A Facile Strategy for the Preparation of N-Doped TiO2 with Oxygen Vacancy via the Annealing Treatment with Urea

Although titanium dioxide (TiO2) has a wide range of potential applications, the photocatalytic performance of TiO2 is limited by both its limited photoresponse range and fast recombination of the photogenerated charge carriers. In this work, the preparation of nitrogen (N)-doped TiO2 accompanied by the introduction of oxygen vacancy (Vo) has been achieved via a facile annealing treatment with urea as the N source. During the annealing treatment, the presence of urea not only realizes the N-doping of TiO2 but also creates Vo in N-doped TiO2 (N-TiO2), which is also suitable for commercial TiO2 (P25). Unexpectedly, the annealing treatment-induced decrease in the specific surface area of N-TiO2 is inhibited by the N-doping and, thus, more active sites are maintained. Therefore, both the N-doping and formation of Vo as well as the increased active sites contribute to the excellent photocatalytic performance of N-TiO2 under visible light irradiation. Our work offers a facile strategy for the preparation of N-TiO2 with Vo via the annealing treatment with urea.

Enhanced Light Absorption and Photo-Generated Charge Separation Efficiency for Boosting Photocatalytic H2 Evolution through TiO2 Quantum Dots with N-Doping and Concomitant Oxygen Vacancy

Low-range light absorption and rapid recombination of photo-generated charge carriers have prevented the occurrence of effective and applicable photocatalysis for decades. Quantum dots (QDs) offer a solution due to their size-controlled photon properties and charge separation capabilities. Herein, well-dispersed interstitial nitrogen-doped TiO2 QDs with stable oxygen vacancies (N-TiO2-x-VO) are fabricated by using a low-temperature, annealing-assisted hydrothermal method. Remarkably, electrostatic repulsion prevented aggregation arising from negative charges accumulated in situ on the surface of N-TiO2-x-VO, enabling complete solar spectrum utilization (200-800 nm) with a 2.5 eV bandgap. Enhanced UV-vis photocatalytic H2 evolution rate (HER) reached 2757 µmol g-1 h-1, 41.6 times higher than commercial TiO2 (66 µmol g-1 h-1). Strikingly, under visible light, HER rate was 189 µmol g-1 h-1. Experimental and simulated studies of mechanisms reveal that VO can serve as an electron reservoir of photo-generated charge carriers on N-doped active sites, and consequently, enhance the separation rate of exciton pairs. Moreover, the negative free energy (-0.35 V) indicates more favorable thermodynamics for HER as compared with bulk TiO2 (0.66 V). This research work paves a new way of developing efficient photocatalytic strategies of HER that are applicable in the sustainable carbon-zero energy supply.

Reservoir Computing Based on Oxygen-Vacancy-Mediated X-ray Optical Synaptic Device for Medical CT Bone Diagnosis

Recognition and judgment of X-ray computed tomography (CT) images play a crucial role in medical diagnosis and disease prevention. However, the storage and calculation of the X-ray imaging system applied in the traditional CT diagnosis is separate, and the pathological judgment is based on doctors' experience, which will affect the timeliness and accuracy of decision-making. In this paper, a simple-structured reservoir computing network (RC) is proposed based on Ga2O3 X-ray optical synaptic devices to recognize medical skeletal CT images with high accuracy. Through oxygen vacancy engineering, Ga2O3 X-ray optical synaptic devices with adjustable photocurrent gain and a persistent photoconductivity effect were obtained. By using the Ga2O3 X-ray optical synaptic device as a reservoir, we constructed an RC network for medical skeletal CT diagnosis and verified its image recognition capability using the MNIST data set with an accuracy of 78.08%. In the elbow skeletal CT image recognition task, the recognition rate is as high as 100%. This work constructs a simple-structured RC network for X-ray image recognition, which is of great significance in applications in medical fields.

Fe3+-activated magnetoplumbite persistent luminescence phosphor by modulating the oxygen vacancy

Broadband near-infrared (NIR) spectroscopy has gained significant attention due to its versatile application in various fields. In the realm of NIR phosphors, Fe3+ ion is an excellent activator known for its nontoxic and harmless nature. In this study, we prepared an Fe3+-activated SrGa12O19 (SGO) NIR phosphor and analyzed its phase and luminescence properties. Upon excitation at 326 nm, the SGO:Fe3+ phosphor exhibited a broadband emission in the range 700-1000 nm, peaking at 816 nm. The optical band gap of SGO:Fe3+ was evaluated. To enhance the long-lasting phosphorescence, an oxygen vacancy-rich SGO:Fe3+ (VO-SGO:Fe3+) sample was prepared for activation. Interestingly, the increase in the oxygen-vacancy concentration indeed contributed to the activation of persistent luminescence of Fe3+ ions. The VO-SGO:Fe3+ sample has a long duration and high charge storage capacity, allowing it to perform efficiently in various applications. This work provides the foundation for further design of Cr3+-free PersL phosphors with efficient NIR PersL.

Observation of High-Capacity Monoclinic B-Nb2O5 with Ultrafast Lithium Storage

Apart from Li4Ti5O12, there are few anode substitutes that can be used in commercial high-power lithium-ion batteries. Orthorhombic T-Nb2O5 has recently been proven to be another substitute anode. However, monoclinic B-Nb2O5 of same chemistry is essentially inert for lithium storage, but the underlying reasons are unclear. In order to activate the "inert" B-Nb2O5, herein, nanoporous pseudocrystals to achieve a larger specific capacity of 243 mAh g-1 than Li4Ti5O12 (theoretical capacity: 175 mAh g-1) are proposed. These pseudocrystals are rationally synthesized via a "shape-keep" topological microcorrosion process from LiNbO3 precursor. Compared to pristine B-Nb2O5, experimental investigations reveal that B-Nb2O5- x delivers ≈3000 times higher electronic conductivity and tenfold enhanced Li+ diffusion coefficient. An ≈30% reduction of energy barrier for Li-ion migration is also confirmed by the theoretical calculations. The nanoporous B-Nb2O5- x delivers unique ion/electron transport channels to proliferate the reversible and deeper lithiation, which activate the "inert" B-Nb2O5. The capacitive-like behavior is observed to endow B-Nb2O5- x ultrafast lithium storage ability, harvesting 136 mAh g-1 at 100 C and 72 mAh g-1 even at 250 C, superior to Li4Ti5O12. Pouch-type full cells exhibit the energy density of ≈251 Wh kg-1 and ultrahigh power density up to ≈35 kW kg-1.

Ultrafine Pt Nanoparticles on Defective Tungsten Oxide for Photocatalytic Ethylene Synthesis

The selective conversion of ethane (C2H6) to ethylene (C2H4) under mild conditions is highly wanted, yet very challenging. Herein, it is demonstrated that a Pt/WO3-x catalyst, constructed by supporting ultrafine Pt nanoparticles on the surface of oxygen-deficient tungsten oxide (WO3-x) nanoplates, is efficient and reusable for photocatalytic C2H6 dehydrogenation to produce C2H4 with high selectivity. Specifically, under pure light irradiation, the optimized Pt/WO3-x photocatalyst exhibits C2H4 and H2 yield rates of 291.8 and 373.4 µmol g-1 h-1, respectively, coupled with a small formation of CO (85.2 µmol g-1 h-1) and CH4 (19.0 µmol g-1 h-1), corresponding to a high C2H4 selectivity of 84.9%. Experimental and theoretical studies reveal that the vacancy-rich WO3-x catalyst enables broad optical harvesting to generate charge carriers by light for working the redox reactions. Meanwhile, the Pt cocatalyst reinforces adsorption of C2H6, desorption of key reaction species, and separation and migration of light-induced charges to promote the dehydrogenation reaction with high productivity and selectivity. In situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculation expose the key intermediates formed on the Pt/WO3-x catalyst during the reaction, which permits the construction of the possible C2H6 dehydrogenation mechanism.

α-MnO2 Cathode with Oxygen Vacancies Accelerated Affinity Electrolyte for Dual-Ion Co-Encapsulated Aqueous Aluminum Ion Batteries

Aluminum batteries (ABs) are identified as one of the most promising candidates for the next generation of large-scale energy storage elements because of their efficient three-electron reaction. Compared to ionic electrolytes, aqueous aluminum-ion batteries (AAIBs) are considered safer, less costly, and more environmentally friendly. However, considerable cycling performance is a key issue limiting the development of AAIBs. Stable, efficient, and electrolyte-friendly cathodes are most desirable for AAIBs. Herein, a rod-shaped defect-rich α-MnO2 is designed as a cathode, which is capable to deliver high performance with stable cycling for 180 cycles at 500 mA g-1 and maintains a discharge specific capacity of ≈100 mAh g-1. In addition, the infiltrability simulation is effectively utilized to corroborate the rapid electrochemical reaction brought about by the defective mechanism. With the formation of oxygen vacancies, the dual embedding of protons and metal ions is activated. This work provides a brand-new design for the development and characterization of cathodes for AAIBs.

Mn-doped Sequentially Electrodeposited Co-based Oxygen Evolution Catalyst for Efficient Anion Exchange Membrane Water Electrolysis

Designing high-performance and durable oxygen evolution reaction (OER) catalysts is important for green hydrogen production through anion exchange membrane water electrolysis (AEMWE). Herein, a series of Mn-doped Co-based OER catalysts supported on FeOxHy (FCMx) are presented to enhance the OER activity. Mn doping effectively reduces the size of the Co oxide particles, thereby augmenting the active surface area. Moreover, Mn doping induces the creation of oxygen vacancies, leading to an efficient structural conversion during the OER, which is confirmed via in situ Raman spectroscopy. Under optimal conditions, the catalyst exhibits an overpotential of 234.4 mV at 10 mA cm-2 and a Tafel slope of 37.2 mV dec-1 under half-cell conditions. The AEMWE single-cell system demonstrates a current density of 1560 mA cm-2 at 1.8 V at 60 °C with a degradation rate of 0.4 mV h-1 for 500 h at 500 mA cm-2. Our development of a robust OER catalyst represents notable progress in the field of nonprecious-metal water electrolysis, marking a step toward cost-effective green hydrogen production.

Enhanced oxygen reduction activity ofα-MnO2by NH3plasma treatment

Oxygen vacancies and heteroatom doping play important role in oxygen reduction activity of metal oxides. Developing efficient modification method is one of the key issues in catalysts research. Room temperature plasma treatment, with the advantages of mild working conditions, no emissions and high efficiency, is a new catalyst modification method developed in recent years. In this work, hydrothermal synthesizedα-MnO2nanorods are treated in NH3plasma at room temperature. In the reducing atmosphere, oxygen vacancies and N doping are achieved simultaneously on the surface. The NH3plasma etched MnO2demonstrate a significant enhanced oxygen reduction activity with half-wave potential of 0.84 V, limiting current density of 6.32 mA cm-2and transferred electrons number of 3.9. The Mg-air battery with N-MnO2display a maximum power density of 76.3 mW cm-2as well as stable discharge performance. This work provides new ideas for preparing efficient and cost-effective method to boost the catalysts activity.

Tuning the crystallinity of the MnOx catalysts to promote toluene catalytic oxidation

In this paper, the MnOx catalysts with excellent toluene oxidation performance were prepared by a simple precipitation method. The physicochemical properties of the prepared MnOx catalysts were investigated by XRD, BET, H2-TPR, O2-TPD and XPS. The obtained results revealed that the crystallinity of the prepared MnOx catalysts could be effectively regulated by changing the (NH4)2CO3/Mn(NO3)2 molar ratio, and thus affecting the oxygen vacancy concentration of the prepared MnOx catalysts. The prepared MnOx-4 catalyst with the (NH4)2CO3/Mn(NO3)2 molar ratio of 4.0 had the poor crystallinity and small grain size, which effectively promoted the oxygen defects in the MnOx catalyst to be formed. At the same time, the MnOx-4 catalyst had a large specific surface area, the highest low temperature reducibility and the largest number of oxygen vacancies and surface adsorbed oxygen species, which allowed more surface oxygen species to participate in the redox reaction, and promoted the toluene deep oxidation. Therefore, when the (NH4)2CO3/Mn(NO3)2 molar ratio was 4.0, the prepared MnOx-4 catalyst exhibited an excellent toluene catalytic oxidation performance and robust catalytic stability. What's more, the toluene oxidation conversion on the MnOx-4 catalyst reached 99% at 230°C, and the MnOx-4 catalyst showed excellent resistance to water vapour.

Vacancy-Engineered Nickel Ferrite Forming-Free Low-Voltage Resistive Switches for Neuromorphic Circuits

Innovations in resistive switching devices constitute a core objective for the development of ultralow-power computing devices. Forming-free resistive switching is a type of resistive switching that eliminates the need for an initial high voltage for the formation of conductive filaments and offers promising opportunities to overcome the limitations of traditional resistive switching devices. Here, we demonstrate mixed charge state oxygen vacancy-engineered electroforming-free resistive switching in NiFe2O4 (NFO) thin films, fabricated as asymmetric Ti/NFO/Pt heterostructures, for the first time. Using pulsed laser deposition in a controlled oxygen atmosphere, we tune the oxygen vacancies together with the cationic valence state in the nickel ferrite phase, with the latter directly affecting the charge state of the oxygen vacancies. The structural integrity and chemical composition of the films are confirmed by X-ray diffraction and hard X-ray photoelectron spectroscopy, respectively. Electrical transport studies reveal that resistive switching characteristics in the films can be significantly altered by tuning the amount and charge state of the oxygen vacancy concentration during the deposition of the films. The resistive switching mechanism is seen to depend upon the migration of both singly and doubly charged oxygen vacancies formed as a result of changes in the nickel valence state and the consequent formation/rupture of conducting filaments in the switching layer. This is supported by the existence of an optimum oxygen vacancy concentration for efficient low-voltage resistive switching, below or above which the switching process is inhibited. Along with the filamentary switching mechanism, the Ti top electrode also enhances the resistive switching performance due to interfacial effects. Time-resolved measurements on the devices display both long- and short-term potentiation in the optimized vacancy-engineered NFO resistive switches, ideal for solid-state synapses achieved in a single system. Our work on correlated oxide forming-free resistive switches holds significant potential for CMOS-compatible low-power, nonvolatile resistive memory and neuromorphic circuits.

Effect of Facet on Local Electron Density of Oxygen Vacancy in Catalysts for Nitrogen Electro-Reduction

Oxygen-vacancy (Ov) engineering is an effective strategy to manipulate the electronic configuration of catalysts for electrochemical nitrogen reduction reaction (eNRR). The influence of the stable facet on the electronic configuration of Ov is widely studied, however, the effect of the reactive facet on the local electron density of Ov is unveiled. In this work, an eNRR electrode R(111)-TiO2/HGO is provided with a high proportion exposed reactive facet (111) of rutile-TiO2 (denoted as R(111)-TiO2) nanocrystals with Ov anchored in hierarchically porous graphite oxide (HGO) nanofilms. The R(111)-TiO2/HGO exhibits excellent eNRR performance with an NH3 yield rate of 20.68 µg h-1 cm-2, which is ≈20 times the control electrode with the most stable facet (110) exposed (R(110)-TiO2/HGO). The experimental data and theoretical simulations reveal that the crystal facet (111) has a positive effect on regulating the local electron density around the oxygen vacancy and the two adjacent Ti-sites, promoting the π-back-donation, minimizing the eNRR barrier, and transforming the rate determination step to *NNH→*NNHH. This work illuminates the effect of crystal facet on the performance of eNRR, and offers a novel strategy to design efficient eNRR catalysts.

Molecularly Imprinted Heterostructure-Assisted Laser Desorption Ionization Mass Spectrometry Analysis and Imaging of Quinolones

Quinolone residues resulting from body metabolism and waste discharge pose a significant threat to the ecological environment and to human health. Therefore, it is essential to monitor quinolone residues in the environment. Herein, an efficient and sensitive matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) method was devised by using a novel molecularly imprinted heterojunction (MIP-TNs@GCNs) as the matrix. Molecularly imprinted titanium dioxide nanosheets (MIP-TNs) and graphene-like carbon nitrides (GCNs) were associated at the heterojunction interface, allowing for the specific, rapid, and high-throughput ionization of quinolones. The mechanism of MIP-TNs@GCNs was clarified using their adsorption properties and laser desorption/ionization capability. The prepared oxygen-vacancy-rich MIP-TNs@GCNs heterojunction exhibited higher light absorption and ionization efficiencies than TNs and GCNs. The good linearity (in the quinolone concentration range of 0.5-50 pg/μL, R2 > 0.99), low limit of detection (0.1 pg/μL), good reproducibility (n = 8, relative standard deviation [RSD] < 15%), and high salt and protein resistance for quinolones in groundwater samples were achieved using the established MIP-TNs@GCNs-MALDI/MS method. Moreover, the spatial distributions of endogenous compounds (e.g., amino acids, organic acids, and flavonoids) and xenobiotic quinolones from Rhizoma Phragmitis and Rhizoma Nelumbinis were visualized using the MIP-TNs@GCNs film as the MALDI/MS imaging matrix. Because of its superior advantages, the MIP-TNs@GCNs-MALDI/MS method is promising for the analysis and imaging of quinolones and small molecules.

Strengthening the Synergy between Oxygen Vacancies in Electrocatalysts for Efficient Glycerol Electrooxidation

Defect-engineered bimetallic oxides exhibit high potential for the electrolysis of small organic molecules. However, the ambiguity in the relationship between the defect density and electrocatalytic performance makes it challenging to control the final products of multi-step multi-electron reactions in such electrocatalytic systems. In this study, controllable kinetics reduction is used to maximize the oxygen vacancy density of a Cu─Co oxide nanosheet (CuCo2O4 NS), which is used to catalyze the glycerol electrooxidation reaction (GOR). The CuCo2O4-x NS with the highest oxygen-vacancy density (CuCo2O4-x-2) oxidizes C3 molecules to C1 molecules with selectivity of almost 100% and a Faradaic efficiency of ≈99%, showing the best oxidation performance among all the modified catalysts. Systems with multiple oxygen vacancies in close proximity to each other synergistically facilitate the cleavage of C─C bonds. Density functional theory calculations confirm the ability of closely spaced oxygen vacancies to facilitate charge transfer between the catalyst and several key glycolic-acid (GCA) intermediates of the GOR process, thereby facilitating the decomposition of C2 intermediates to C1 molecules. This study reveals qualitatively in tuning the density of oxygen vacancies for altering the reaction pathway of GOR by the synergistic effects of spatial proximity of high-density oxygen vacancies.

Stabilizing Single-Atom Pt on Fe2O3 Nanosheets by Constructing Oxygen Vacancies for Ultrafast H2 Sensing

Single-atom catalysts (SACs) hold great promise in highly sensitive and selective gas sensors due to their ultrahigh atomic efficiency and excellent catalytic activity. However, due to the extremely high surface energy of SACs, it is still a huge challenge to synthesize a stable single-atom metal on sensitive materials. Here, we report an atomic layer deposition (ALD) strategy for the elaborate synthesis of single-atom Pt on oxygen vacancy-rich Fe2O3 nanosheets (Pt-Fe2O3-Vo), which displayed ultrafast and sensitive detection to H2, achieving the stability of Pt single atoms. Gas-sensing investigation showed that the Pt-Fe2O3-Vo materials enabled a significantly enhanced response of 26.5-50 ppm of H2, which was 17-fold higher than that of pure Fe2O3, as well as ultrafast response time (2 s), extremely low detection limit (86 ppb), and improved stability. The experimental and density functional theory (DFT) studies revealed that the abundant oxygen vacancy sites of Fe2O3 contributed to stabilizing the Pt atoms via electron transfer. In addition, the stabilized Pt atoms also greatly promote the electron transfer of H2 molecules to Fe2O3, thereby achieving an excellent H2 sensing performance. This work provides a potential strategy for the development of highly selective and stable chemical sensors.

Oxygen Vacancy and Heterostructure Modulation of Co2P/Fe2P Electrocatalysts for Improving Total Water Splitting

Designing a stable and highly active catalyst for hydrogen evolution and oxygen evolution reactions (HER/OER) is essential for the industrialization of hydrogen energy but remains a major challenge. This work reports a simple approach to fabricating coupled Co2P/Fe2P nanorod array catalyst for overall water decomposition, demonstrating the source of excellent activity in the catalytic process. Under alkaline conditions, Co2P/Fe2P heterostructures exhibit an overpotential of 96 and 220 mV for HER and OER, respectively, at 10 mA cm-2. For total water splitting, a low voltage of 1.56 V is required to provide a current density of 10 mA cm-2. And the catalyst exhibits long-term durability for 30 h at a high current density of 250 mA cm-2. The analysis of the results revealed that the presence of interfacial oxygen vacancies and the strong interaction between Co2P/Fe2P provided the catalyst with more electrochemically active sites and a faster charge transfer capability, which improved the hydrolysis dissociation process. Electrochemically active metal (oxygen) hydroxide phases were produced after OER stability testing. The results of this study prove its great potential in practical industrial electrolysis and provide a reasonable and feasible strategy for the design of nonprecious metal phosphide electrocatalysts.

Construction of Oxygen Vacancy-Rich TiO2 Nanocrystals for Boosting the Ammonolysis of Caprolactam to 6-Aminocapronitrile

Hexamethylene diamine, an important chemical intermediate for polyamides, can be synthesized through the two-step route of caprolactam (CPL) ammonolysis to 6-aminocapronitrile (ACN), followed by hydrogenation. This method has received increasing attention from academia and industry. However, studies on the catalyst structure-performance correlation in CPL ammonolysis are still sporadic. In this work, a series of anatase TiO2 with different oxygen vacancy concentrations was prepared by chemical reduction using NaBH4. The oxygen vacancy on TiO2 surface, presented as Ti3+ sites, substantially enhances the adsorption and activation of NH3, which are demonstrated as the key steps in ammonolysis. Owing to the synergistic effect of Ti3+ and Ti4+ species, the CPL conversion rate and ACN selectivity of 85 and 97%, respectively, are achieved within 250 h. Density functional theory calculations showed that the intermediates on oxygen vacancy-rich TiO2 had a more favorable adsorption energy compared to those on intact TiO2, which is in good agreement with the experimental results.

Oxygen Vacancy-Rich Manganese Nanoflowers as Ferroptosis Inducers for Tumor Radiotherapy

The combination of ferroptosis and innovative tumor therapy methods offers another promising answer to the problem of tumors. In order to generate effective ferroptosis in tumor cells, iron-based nanomaterials are commonly utilized to introduce foreign iron as a trigger for ferroptosis. However, this usually necessitates the injection of larger doses of iron into the body. These exogenous iron increases are likely to create concealed concerns for symptoms such as liver damage and allergy. Herein, an iron-free radiosensitizer is introduced, oxygen-vacancy-rich MnO2 nanoflowers (ovs-MnO2 ), that promotes ferroptosis and modifies the tumor microenvironment to assist radiotherapy. ovs-MnO2 with enriched oxygen vacancies on the surface induces the release of intracellular free iron (Fe2+ ), which functions as an activator of Fenton reaction and enhances the accumulation of intracellular reactive oxygen species. On the other hand, Fe2+ also triggers the ferroptosis and promotes the accumulation of lipid peroxides. Subsequently, the depletion of glutathione and accumulation of lipid peroxidation in tumor cells leads to the inactivation of glutathione peroxidase 4 (GPX4) and ferroptosis, thereby enhancing the therapeutic efficacy of radiotherapy. The nanoplatform provides a novel strategy for generating novel nanomedicines for ferroptosis-assisted radiotherapy.

Elevating Lithium-Sulfur Battery Durability through Samarium Oxide/Ketjen Black Modified Separator

Lithium-sulfur batteries have garnered significant attention as a promising next-generation battery technology due to their potential for high energy density. However, their practical application is hampered by slow reaction kinetics and the shuttle effect of lithium polysulfide intermediates. In this context, the authors introduce a pioneering solution in the form of a novel porous carbon nanostructure modified with samarium oxide, denoted as Sm2O3/KB. The material has a highly polar surface, allowing lithium polysulfide to be chemisorbed efficiently. The unsaturated sites provided by the oxygen vacancies of Sm2O3 promote Li2S nucleation, lowering the reaction energy barrier and accelerating Li2S dissolution. The porous structure of Ketjen Black provides a highly conductive channel for electron transport and effectively traps polysulfides. Meanwhile, the batteries with Sm2O3/KB/PP spacers exhibited remarkable electrochemical performances, including a low-capacity decay rate of only 0.046 % for 1000 cycles at 2 C and an excellent multiplicative performance of 624 mAh g-1 at 3 C. This work opens up a new avenue for the potential use of rare-earth-based materials in lithium-sulfur batteries.

Enhancing Photocatalytic CO2 Conversion through Oxygen-Vacancy-Mediated Topological Phase Transition

Weak adsorption of gas reactants and strong binding of intermediates present a significant challenge for most transition metal oxides, particularly in the realm of CO2 photoreduction. Herein, we demonstrate that the adsorption can be fine-tuned by phase engineering of oxide catalysts. An oxygen vacancy mediated topological phase transition in Ni-Co oxide nanowires, supported on a hierarchical graphene aerogel (GA), is observed from a spinel phase to a rock-salt phase. Such in situ phase transition empowers the Ni-Co oxide catalyst with a strong internal electric field and the attainment of abundant oxygen vacancies. Among a series of catalysts, the in situ transformed spinel/rock-salt heterojunction supported on GA stands out for an exceptional photocatalytic CO2 reduction activity and selectivity, yielding an impressive CO production rate of 12.5 mmol g-1  h-1 and high selectivity of 96.5 %. This remarkable performance is a result of the robust interfacial coupling between two topological phases that optimizes the electronic structures through directional charge transfer across interfaces. The phase transition process induces more Co2+ in octahedral site, which can effectively enhance the Co-O covalency. This synergistic effect balances the surface activation of CO2 molecules and desorption of reaction intermediates, thereby lowering the energetic barrier of the rate-limiting step.

Realizing Near Infrared Mechanoluminescence Switch in LAGO:Cr Based on Oxygen Vacancy

Mechanoluminescence (ML) materials are featured with the characteristic of "force to light" in response to external stimuli, which have made great progress in artificial intelligence and optical sensing. However, how to effectively enable ML in the material is a daunting challenge. Here, a Lu3 Al2 Ga3 O12 :Cr3+ (LAGO: Cr3+ ) near infrared (NIR) ML material peaked at 706 nm is reported, which successfully realizes the key to unlock ML by the lattice-engineering strategy Ga3+ substitution for Al3+ to "grow" oxygen vacancy (Ov ) defects. Combined with thermoluminescence measurements, the observed ML is due to the formation of defect levels and the ML intensity is proportional to it. It is confirmed by X-ray photoelectron spectroscopy and electron paramagnetic resonance that such a process is dominated by Ov , which plays a crucial role in turning on ML in this compound. In addition, potential ML emissions from 4 T2 and 2 E level transitions are discussed from both experimental and theoretical aspects. This study reveals the mechanism of the change in ML behavior after cation substitution, and it may have important implications for the practical application of Ov defect-regulated turn-on of ML.

Constructing Efficient CuAg Nanoalloys on Ce0.90In0.10Oδ for Methanol Deep Oxidation Catalysis at Low Temperature

So far, it is still extremely challenging to develop an efficient catalyst for deep oxidation of methanol at low temperature. Herein, we report the construction of the highly dispersed CuAg alloy on the surface of Ce0.90In0.10Oδ nanorods support for catalyzing methanol deep oxidation. The composition, structure and properties of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the CuxAg100-x/Ce0.90In0.10Oδ alloy catalysts exhibit superior catalytic activity and stability compared to pure Ag/Ce0.90In0.10Oδ, with the highest activity observed for Cu40Ag60/Ce0.90In0.10Oδ, accompanied by the light-off temperature (T50) and full conversion temperature (T90) of 115 and 145 °C, respectively. This is attributed to the synergistic effect of CuAg alloy, which results in electron transfer, generating more Ag0, and enhanced interaction between CuAg alloy and the support, leading to increased Ce3+ content and higher oxygen vacancy concentration. This work successfully applies CuAg alloy catalysts in thermo-catalytic reaction, offering promising prospects for CuAg alloy catalysts in the methanol deep oxidation.

Oxygen Vacancies on NH4 V4 O10 Accelerate Ion and Charge Transfer in Aqueous Zinc-Ion Batteries

Vanadium-based compounds are identified as promising cathode materials for aqueous zinc ion batteries due to their high specific capacity. However, the low intrinsic conductivity and sluggish Zn2+ diffusion kinetics seriously impede their further practical application. Here, oxygen vacancies on NH4 V4 O10 is reported as a high-performing cathode material for aqueous zinc ion batteries via a facile hydrothermal strategy. The introduction of oxygen vacancy accelerates the ion and charge transfer kinetics, reduces the diffusion barrier of zinc ions, and establishes a stable crystal structure during zinc ion (de-intercalation). As a result, the oxygen vacancy enriched NH4 V4 O10 exhibits a high specific capacity of ≈499 mA h g-1 at 0.2 A g-1 , an excellent rate capability of 296 mA h g-1 at 10 A g-1 and the specific capacity cycling stability with 95.1% retention at 5 A g-1 for 4000 cycles, superior to the NVO sample (186.4 mAh g-1 at 5 A g-1 , 66% capacity retention).

Comment on "Bipolar Resistive Switching in Lanthanum Titanium Oxide and an Increased On/Off Ratio Using an Oxygen-Deficient ZnO Interlayer"

The Mott-based resistive switching random access memory (RRAM) has been considered as a promising candidate for next-generation nonvolatile mass storage. Its performance relies on the oxygen migration process. In ACS Appl. Mater. Interfaces 2022, 14, 17682-17690, Wang et al. demonstrated that inserting a ZnO layer between the top tungsten electrode and the lanthanum titanium oxide (LTO) layer can improve the ON/OFF current ratio of the RRAM. This improvement was attributed to the increased oxygen vacancies in the ZnO layer. We argue their interpretation with the role, significance, and statistics of the oxygen vacancy in the samples. Our experimental evidence contradicts their claim, and we propose that hydroxy groups should be the responsible candidate for their claimed oxygen vacancy peak at around 531-532 eV in the O 1s photoelectron spectroscopy observed in their samples. We thus propose an alternative mechanism for the ON/OFF ratio enhancement with the ZnO interlayer: the ZnO layer prevents the LTO oxygen and hydroxy groups migration and from reacting with the multivalent tungsten electrode.

Lithium-Induced Oxygen Vacancies in MnO2@MXene for High-Performance Zinc-Air Batteries

The traditional methods for creating oxygen vacancies in materials present several challenges and limitations, such as high preparation temperatures, limited oxygen vacancy generation, and morphological destruction, which hinder the application of transition metal oxides in the field of zinc-air batteries (ZABs). In order to address these limitations, we have introduced a pioneering lithium reduction strategy for generating oxygen vacancies in δ-MnO2@MXene composite materials. This strategy stands out for its simplicity of implementation, applicability at room temperature, and preservation of the material's structural integrity. This research demonstrates that aqueous Ov-MnO2@MXene-5, with introduced oxygen vacancies, exhibits an outstanding oxygen reduction reaction (ORR) activity with an ORR half-wave potential reaching 0.787 V. DFT calculations have demonstrated that the enhanced activity could be attributed to adjustments in the electronic structure and alterations in adsorption bond lengths. These adjustments result from the introduction of oxygen vacancies, which in turn promote electron transport and catalytic activity. In the context of zinc-air batteries, cells with Ov-MnO2@MXene-5 as the air cathode exhibit outstanding performance, featuring a significantly improved maximum power density (198.3 mW cm-2) and long-term cycling stability. Through the innovative strategy of introducing oxygen vacancies, this study has successfully enhanced the electrochemical catalytic performance of MnO2, overcoming the limitations associated with traditional methods for creating oxygen vacancies. Consequently, this research opens up new avenues and directions for nonprecious metal catalyst application in ZABs.

Heterostructure of Fe-Doped CoMoOx/CoMoOx as an Efficient Electrocatalyst for Oxygen Evolution Reaction

Oxygen evolution reaction (OER) plays a crucial role as a counter half-reaction for both electrochemical hydrogen production through water splitting and the generation of valuable carbon compounds via CO2 reduction. To overcome the sluggish kinetics of the OER, significant efforts have been devoted to developing cost-effective, sustainable, and efficient electrocatalysts, with transition-metal-based catalysts emerging as promising candidates. Herein, we successfully synthesized a core-shell type nanostructure of Fe-doped CoMoOx/CoMoOx (CMFO), which exhibits excellent electrocatalytic properties for OER. The presence of an amorphous layer of Fe-doped CoMoOx with abundant oxygen vacancies, along with the stability of a key OER intermediate, *O, contributes to the enhanced activity of CMFO catalyst compared to pristine CoMoOx (CMO). The optimized catalyst of CMFO-550 achieved much lower overpotential and Tafel slope and also exhibited better remarkable long-term stability for over 90 h compared to CMO-550. These findings highlight the potential of CMFO-550 as a cost-effective and highly efficient electrocatalyst for the OER. The successful development of this core-shell nanostructure opens up a new opportunity for the design and synthesis of advanced electrocatalysts for the OER, with implications for various applications in energy conversion and storage.

Oxygen Vacancy and Bandgap Simultaneous Modulation to Achieve High Lithiophilicity and Mechanical Strength of Lithium Metal Anodes

Metal oxides with conversion and alloying mechanisms are more competitive in suppressing lithium dendrites. However, it is difficult to simultaneously regulate the conversion and alloying reactions. Herein, conversion and alloying reactions are regulated by modulation of the zinc oxide bandgap and oxygen vacancies. State-of-the-art advanced characterization techniques from a microcosmic to a macrocosmic viewpoint, including neutron diffraction, synchrotron X-ray absorption spectroscopy, synchrotron X-ray microtomography, nanoindentation, and ultrasonic C-scan demonstrated the electrochemical gain benefit from plentiful oxygen vacancies and low bandgaps due to doping strategies. In addition, high mechanical strength 3D morphology and abundant mesopores assist in the uniform distribution of lithium ions. Consequently, the best-performed ZnO-2 offers impressive electrochemical properties, including symmetric Li cells with 2000 h and full cells with 81% capacity retention after 600 cycles. In addition to providing a promising strategy for improving the lithiophilicity and mechanical strength of metal oxide anodes, this work also sheds light on lithium metal batteries for practical applications.

Iron-Based Catalysts with Oxygen Vacancies Obtained by Facile Pyrolysis for Selective Hydrogenation of Nitrobenzene

The development of preparation strategies for iron-based catalysts with prominent catalytic activity, stability, and cost effectiveness is greatly significant for the field of catalytic hydrogenation but still remains challenging. Herein, a method for the preparation of iron-based catalysts by the simple pyrolysis of organometallic coordination polymers is described. The catalyst Fe@C-2 with sufficient oxygen vacancies obtained in specific coordination environment exhibited superior nitro hydrogenation performance, acid resistance, and reaction stability. Through solvent effect experiments, toxicity experiments, TPSR, and DFT calculations, it was determined that the superior activity of the catalyst was derived from the contribution of sufficient oxygen vacancies to hydrogen activation and the good adsorption ability of FeO on substrate molecules.

Geometrical Stabilities and Electronic Structures of Ru3 Clusters on Rutile TiO2 for Green Hydrogen Production

In response to the vital requirement for renewable energy alternatives, this research delves into the complex interactions between ruthenium (Ru3) clusters and rutile titanium dioxide (TiO2) (110) interfaces, with the aim of enhancing photocatalytic water splitting processes to produce environmentally friendly hydrogen. As the world shifts away from traditional fossil fuels, this study utilizes the density functional theory (DFT) and the HSE06 hybrid functional to thoroughly assess the geometric and electronic properties of Ru3 clusters on rutile TiO2 (110) surfaces. Given TiO2's renown role as a photocatalyst and its limitations in visible light absorption, this research investigates the potential of metals like Ru to serve as additional catalysts. The results indicate that the triangular Ru3 cluster exhibits exceptional stability and charge transfer effectiveness when loaded on rutile TiO2 (110). Under ideal adsorption scenarios, the cluster undergoes oxidation, leading to subsequent changes in the electronic configuration of TiO2. Further exploration into TiO2 surfaces with defects shows that Ru3 clusters influence the creation of oxygen vacancies, resulting in a greater stabilization of TiO2 and an increase in the energy required for creating oxygen vacancies. Moreover, the attachment of the Ru3 cluster and the creation of oxygen vacancies lead to the emergence of polaronic and hybrid states centered on specific titanium atoms. These states are vital for enhancing the photocatalytic performance of the material within the visible light spectrum. This DFT study provides essential insights into the role of Ru3 clusters as potential supplementary catalysts in TiO2-based photocatalytic systems, setting the stage for practical experiments and the development of highly efficient photocatalysts for sustainable hydrogen generation. The observed effects on electronic structures and oxygen vacancy generation underscore the intricate relationship between Ru3 clusters and TiO2 interfaces, offering a valuable direction for future research in the pursuit of clean and sustainable energy solutions.

Enhanced Electrocatalytic Oxygen Reduction Reaction of TiO2 Nanotubes by Combining Surface Oxygen Vacancy Engineering and Zr Doping

This work examines the cooperative effect between Zr doping and oxygen vacancy engineering in anodized TiO2 nanotubes (TNTs) for enhanced oxygen reduction reactions (ORRs). Zr dopant and annealing conditions significantly affected the electrocatalytic characteristics of grown TNTs. Zr doping results in Zr4+ substituted for Ti4+ species, which indirectly creates oxygen vacancy donors that enhance charge transfer kinetics and reduce carrier recombination in TNT bulk. Moreover, oxygen vacancies promote the creation of unsaturated Ti3+(Zr3+) sites at the surface, which also boosts the ORR interfacial process. Annealing at reductive atmospheres (e.g., H2, vacuum) resulted in a larger increase in oxygen vacancies, which greatly enhanced the ORR activity. In comparison to bare TNTs, Zr doping and vacuum treatment (Zr:TNT-Vac) significantly improved the conductivity and activity of ORRs in alkaline media. The finding also provides selective hydrogen peroxide production by the electrochemical reduction of oxygen.

Defect Engineering of Bi2 WO6 for Enhanced Photocatalytic Degradation of Antibiotic Pollutants

Infiltration of excessive antibiotics into aquatic ecosystems plays a significant role in antibiotic resistance, a major global health challenge. It is therefore critical to develop effective technologies for their removal. Herein, defect-rich Bi2 WO6 nanoparticles are solvothermally prepared via epitaxial growth on pristine Bi2 WO6 seed nanocrystals, and the efficiency of the photocatalytic degradation of ciprofloxacin, a common antibiotic, is found to increase markedly from 62.51% to 98.27% under visible photoirradiation for 60 min. This is due to the formation of a large number of structural defects, where the synergistic interactions between grain boundaries and adjacent dislocations and oxygen vacancies lead to an improved separation and migration efficiency of photogenerated carriers and facilitate the adsorption and degradation of ciprofloxacin, as confirmed in experimental and theoretical studies. Results from this work demonstrate the unique potential of defect engineering for enhanced photocatalytic performance, a critical step in removing antibiotic contaminants in aquatic ecosystems.

General and Scalable Synthesis of Mesoporous 2D MZrO2 (M = Co, Mn, Ni, Cu, Fe) Nanocatalysts by Amorphous-to-Crystalline Transformation

In modern heterogeneous catalysis, it remains highly challenging to create stable, low-cost, mesoporous 2D photo-/electro-catalysts that carry atomically dispersed active sites. In this work, a general shape-preserving amorphous-to-crystalline transformation (ACT) strategy is developed to dope various transition metal (TM) heteroatoms in ZrO2 , which enabled the scalable synthesis of TMs/oxide with a mesoporous 2D structure and rich defects. During the ACT process, the amorphous MZrO2 nanoparticles (M = Fe, Ni, Cu, Co, Mn) are deposited within a confined space created by the NaCl template, and they transform to crystalline 2D ACT-MZrO2 nanosheets in a shape-preserving manner. The interconnected crystalline ACT-MZrO2 nanoparticles thus inherit the same structure as the original MZrO2 precursor. Owing to its rich active sites on the surface and abundant oxygen vacancies (OVs), ACT-CoZrO2 gives superior performance in catalyzing the CO2 -to-syngas conversion as demonstrated by experiments and theoretical calculations. The ACT chemistry opens a general route for the scalable synthesis of advanced catalysts with precise microstructure by reconciliating the control of crystalline morphologies and the dispersion of heteroatoms.

Regulating the Oxygen Vacancy and Electronic Structure of NiCo Layered Double Hydroxides by Molybdenum Doping for High-Power Hybrid Supercapacitors

Amelioration of nickel-cobalt layered double hydroxides (NiCo-LDH) with a high specific theoretical capacitance is of great desire for high-power supercapacitors. Herein, a molybdenum (Mo) doping strategy is proposed to improve the charge-storage performance of NiCo-LDH nanosheets growing on carbon cloth (CC) via a rapid microwave process. The regulation of the electronic structure and oxygen vacancy of the LDH is consolidated by the density functional theory (DFT) calculation, which demonstrates that Mo doping narrows the band gap, reduces the formation energy of hydroxyl vacancies, and promotes ionic and charge transfer as well as electrolyte adsorption on the electrode surface. The optimal Mo-doped NiCo-LDH electrode (MoNiCo-LDH-0.05/CC) has an amazing specific capacity of 471.1 mA h g-1 at 1 A g-1 , and excellent capacity retention of 84.8% at 32 A g-1 , far superior to NiCo-LDH/CC (258.3 mA h g-1 and 76.4%). The constructed hybrid supercapacitor delivers an energy density of 103.3 W h kg-1 at a power density of 750 W kg-1 and retains the cycle retention of 85.2% after 5000 cycles. Two assembled devices in series can drive thirty LED lamps, revealing a potential application prospect of the rationally synthesized MoNiCo-LDH/CC as an energy-storage electrode material.

Influence of Oxygen Vacancy-Induced Coordination Change on Pd/CeO2 for NO Reduction

The byproduct formation in environmental catalysis is strongly influenced by the chemical state and coordination of catalysts. Herein, two Pd/CeO2 catalysts (PdCe-350 and PdCe-800) with varying oxygen vacancies (Ov) and coordination numbers (CN) of Pd were prepared to investigate the mechanism of N2O and NH3 formation during NO reduction by CO. PdCe-350 exhibits a higher density of Ov and Pd sites with higher CN, leading to an enhanced metal-support interaction by electron transformation from the support to Pd. Consequently, PdCe-350 displayed increased levels of byproduct formation. In situ spectroscopies under dry and wet conditions revealed that at low temperatures, the N2O formation strongly correlated with the Ov density through the decomposition of chelating nitro species on PdCe-350. Conversely, at high temperatures, it was linked to the reactivity of Pd species, primarily facilitated by monodentate nitrates on PdCe-800. In terms of NH3 formation, its occurrence was closely associated with the activation of H2O and C3H6, since a water-gas shift or hydrocarbon reforming could provide hydrogen. Both bridging and monodentate nitrates showed activity in NH3 formation, while hyponitrites were identified as key intermediates for both catalysts. The insights provide a fundamental understanding of the intricate relationship among the local coordination of Pd, surface Ov, and byproduct distribution.

Boosting N2O Catalytic Decomposition by the Synergistic Effect of Multiple Elements in Cobalt-Based High-Entropy Oxides

Nitrous oxide (N2O) has a detrimental impact on the greenhouse effect, and its efficient catalytic decomposition at low temperatures remains challenging. Herein, the cobalt-based high-entropy oxide with a spinel-type structure (Co-HEO) is successfully fabricated via a facile coprecipitation method for N2O catalytic decomposition. The obtained Co-HEO catalyst displays more remarkable catalytic performance and higher thermal stability compared with single and binary Co-based oxides, as the temperature of 90% N2O decomposition (T90) is 356 °C. A series of characterization results reveal that the synergistic effect of multiple elements enhances the reducibility and augments oxygen vacancy in the high-entropy system, thus boosting the activity of the Co-HEO catalyst. Moreover, density functional theory (DFT) calculations and the temperature-programmed surface reaction (TPSR) with isotope labeling demonstrate that N2O decomposition on the Co-HEO catalyst follows the Langmuir-Hinshelwood (L-H) mechanism with the promotion of abundant oxygen vacancies. This work provides a fundamental understanding of the synergistic catalytic effect in N2O decomposition and paves the way for the novel environmental catalytic applications of HEO.

Translating the Optimized Durability of Co-Based Anode Catalyst into Sustainable Anion Exchange Membrane Water Electrolysis

Development of robust electrocatalysts for the oxygen evolution reaction (OER) underpins the efficient production of green hydrogen via anion exchange membrane water electrolysis (AEMWE). This study elucidates the factors contributing to the degradation of cobalt-based (Co-based) OER catalysts synthesized via electrodeposition, thus establishing strategic approaches to enhance their longevity. Systematic variations in the electroplating process and subsequent heat treatment reveal a delicate balance between catalytic activity and durability, substantiated by comprehensive electrochemical assessments and material analyses. Building upon these findings, the Co-based anode is successfully optimized in the AEMWE single-cell configuration, showcasing an average degradation rate of 0.07 mV h-1 over a continuous operation for 1500 h at a current density of 1 A cm-2 .

Three-Dimensional Visualization of Oxygen-Vacancy Migration and Redistribution in Ca-Substituted BiFeO3

Ionic movement has received renewed attention in recent years, particularly in the field of ferroelectric oxides, since it is intrinsically linked to chemical reaction kinetics and ferroelectric phase stability. The associated surface electrochemical processes coupled local ionic transport with an applied electric bias, exhibiting very high ionic mobility at room temperature based on a simple electrostatics scenario. However, few studies have focused on the applied-polarity dependence of ionic migration with directly visualized maps. Here, we use incorporated experiments of conductive scanning probe microscopy and time-of-flight secondary ion mass spectrometry to investigate oxygen ionic migration and cation redistribution in ionic oxides. The local concentrations of oxygen vacancies and other cation species are visualized by three-dimensional mappings, indicating that oxygen vacancies tend to be ejected toward the surface. An accumulation of oxygen vacancies and ionic redistribution strongly depend on tip polarity, thus corroborating their role in the electrochemical process. This work illustrates the interplay between ionic kinetics and electric switching.

The Underlying Catalytic Role of Oxygen Vacancies in Fatty Acid Methyl Esters Ketonization over TiOx Catalysts

Recently, interest in converting bio-derived fatty acid methyl esters (FAMEs) into added-value products has significantly increased. The selectivity of ketonization reaction in the conversion of the FAMEs has significantly hampered the efficiency of this process. Herein, this work reports the preparation of catalysts with different levels of oxygen vacancies while the crystal phase remained unchanged. The catalyst with the highest level of oxygen vacancy exhibited the maximum selectivity. The density functional theory (DFT) simulation showed an increase in interatomic distances leading to the formation of frustrated Lewis pairs (FLPs) upon the creation of oxygen vacancies. The surface measurements, type and density of acid sites of the catalysts, showed that the Lewis acid sites enhanced the selectivity for ketone production; while Bronsted acid sites increased the formation of by-products. Moreover, the ketone formation rate was directly proportional to acid density. The findings of this research provide a different approach for catalyst design, based on defects engineering and their effect on the surface activity, which could be used for enhancing the catalytic performance of novel metal oxides.

A More Efficient Method for Preparing a MIP-CQDs/ZnO1-x Photodegradant with Highly Selective Adsorption and Photocatalytic Properties

The application of semiconductor photocatalysts in wastewater treatment always has a drawback, which is the lack of selectivity for pollutants, but molecular imprinting technology (MIT) is a remarkable method for preparing highly selective adsorbents for low concentration target pollutants. Up to now, the research of molecular imprinting materials has mainly focused on organic polymers, and there has been little research on inorganic molecular imprinting materials. In the present work, we introduced carbon quantum dots (CQDs) into the flower-like hierarchical ZnO to prepare photocatalysts CQDs/ZnO. Further, with ciprofloxacin (CIP) as the template molecule, a molecular imprinting material MIP-CQDs/ZnO1-x was prepared by introducing both oxygen vacancies and imprinted cavities into CQDs/ZnO by the hydrothermal calcination method. It can not only increase the concentration of oxygen vacancies and broaden the light absorption range of zinc oxide without changing the crystal form of ZnO but also make it have the characteristics of preferential adsorption and degradation of CIP during the degradation process. Under the synergistic effect of CQDs, oxygen vacancies, and molecularly imprinted cavities, the molecularly imprinted material exhibits excellent photocatalytic and selective adsorption performance.

Targeted Delivery of Active Sites by Oxygen Vacancy-Engineered Bimetal Silicate Nanozymes for Intratumoral Aggregation-Potentiated Catalytic Therapy

Biodegradable silicate nanoconstructs have aroused tremendous interest in cancer therapeutics due to their variable framework composition and versatile functions. Nevertheless, low intratumoral retention still limits their practical application. In this study, oxygen vacancy (OV)-enriched bimetallic silicate nanozymes with Fe-Ca dual active sites via modification of oxidized sodium alginate and gallic acid (GA) loading (OFeCaSA-V@GA) were developed for targeted aggregation-potentiated therapy. The band gap of silica markedly decreased from 2.76 to 1.81 eV by codoping of Fe3+ and Ca2+, enabling its excitation by a 650 nm laser to generate reactive oxygen species. The OV that occurred in the hydrothermal synthetic stage of OFeCaSA-V@GA can anchor the metal ions to form an atomic phase, offering a massive fabrication method of single-atom nanozymes. Density functional theory results reveal that the Ca sites can promote the adsorption of H2O2, and Fe sites can accelerate the dissociation of H2O2, thereby realizing a synergetic catalytic effect. More importantly, the targeted delivery of metal ions can induce a morphological transformation at tumor sites, leading to high retention (the highest retention rate is 36.3%) of theranostic components in tumor cells. Thus, this finding may offer an ingenious protocol for designing and engineering highly efficient and long-retention nanodrugs.

Geometrical Stabilities and Electronic Structures of Rh5 Nanoclusters on Rutile TiO2 (110) for Green Hydrogen Production

Addressing the urgent need for sustainable energy sources, this study investigates the intricate relationship between rhodium (Rh5) nanoclusters and TiO2 rutile (110) surfaces, aiming to advance photocatalytic water splitting for green hydrogen production. Motivated by the imperative to transition from conventional fossil fuels, this study employs density functional theory (DFT) with DFT-D3 and HSE06 hybrid functionals to analyse the geometrical stabilities and electronic structures of Rh5 nanoclusters on TiO2 rutile (110). TiO2, a prominent photocatalyst, faces challenges such as limited visible light absorption, leading researchers to explore noble metals like Rh as cocatalysts. Our results show that bipyramidal Rh5 nanoclusters exhibit enhanced stability and charge transfer when adsorbed on TiO2 rutile (110) compared to trapezoidal configurations. The most stable adsorption induces the oxidation of the nanocluster, altering the electronic structure of TiO2. Extending the analysis to defective TiO2 surfaces, this study explores the impact of Rh5 nanoclusters on oxygen vacancy formation, revealing the stabilisation of TiO2 and increased oxygen vacancy formation energy. This theoretical exploration contributes insights into the potential of Rh5 nanoclusters as efficient cocatalysts for TiO2-based photocatalytic systems, laying the foundation for experimental validations and the rational design of highly efficient photocatalysts for sustainable hydrogen production. The observed effects on electronic structures and oxygen vacancy formation emphasize the complex interactions between Rh5 nanoclusters and the TiO2 surface, guiding future research in the quest for clean energy alternatives.