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The BiVO.sub.4 microspheres and Sm.sup.3+-doped BiVO.sub.4 polygons were prepared via a facile hydrothermal method by means of K.sub.6V.sub.10O.sub.28·9H.sub.2O as a novel vanadium source. Optimized temperature and pH value of prepared BiVO.sub.4 were obtained. The polycrystalline BiVO.sub.4 microspheres prepared at T = 140 °C, pH 4, demonstrates the best photocatalytic activities for degrading dyes under UV radiation. This is resulted due to transfers of photogenerated electrons from tetragonal to monoclinic phases. In contrast to the undoped BiVO.sub.4, the photocatalytic activity of Sm.sup.3+-doped BiVO.sub.4 polygons is drastically enhanced not only under UV radiation but also under visible light radiation. The optimized Sm content was found to be 10 %. Enhanced efficiency with the doped sample is attributed to the dopants' role in blocking recombination of photogenerated electron-hole pairs. This work offers a simple route to obtain mixed phase BiVO.sub.4 and provide an effective way to achieve higher photocatalytic activity by doping the Sm.sup.3+ in the semiconductor catalysts.

A series of iron-vanadium mixed oxide catalysts prepared by the coprecipitation method were used for the selective catalytic reduction NO with NH.sub.3. The activity evaluation results exhibited that the activity of Fe.sub.2O.sub.3 was enhanced by addition of a little V, and the Fe-V-O.sub.x catalyst also showed high resistant to the SO.sub.2 and H.sub.2O poisoning in the tested condition. The XRD, NH.sub.3-TPD, H.sub.2-TPR and in situ DRIFTS characterization results displayed that the lower grain size of Fe.sub.2O.sub.3, the reinforced acidity and high redox ability should be the critical factors for the Fe-V-O.sub.x catalyst to achieve the high NH.sub.3-SCR performance.

With the rapid growth of renewable energy, the need for efficient and stable energy storage systems has become increasingly urgent. Aqueous zinc-ion batteries (AZIBs) can offer high safety, abundant zinc supply, and promising electrochemical properties. However, their performance is limited by poor electronic conductivity, slow Zn[sup.2+] diffusion, and structural degradation of conventional cathode materials. To address these issues, an in situ polyaniline (PANI) intercalation strategy for vanadium oxide cathodes is introduced in this paper. The conductive PANI chains play three key roles: (1) expand and stabilize interlayer spacing, (2) enhance electronic conductivity, and (3) provide mechanical support to prevent structural collapse and zinc-dendrite formation. A flower-like PANI-V[sub.2]O[sub.5] hybrid is synthesized via synchronous oxidative polymerization, forming a hierarchical architecture without inert intercalants. The resulting electrode achieves a high specific capacity of 450 mAh·g[sup.−1] at 0.1 A·g[sup.−1] and retains 96.7% of its capacity after 300 cycles at 1 A·g[sup.−1], with excellent rate performance. These findings demonstrate that PANI intercalation enhances ion transport, electronic conductivity, and structural integrity, offering a promising design approach for next-generation AZIBs cathodes.

Synthesizing published data, we provide a quantitative summary of the global biogeochemical cycle of vanadium (V), including both human-derived and natural fluxes. Through mining of V ores (130 × 10⁹ g V/y) and extraction and combustion of fossil fuels (600 × 10⁹ g V/y), humans are the predominant force in the geochemical cycle of V at Earth’s surface. Human emissions of V to the atmosphere are now likely to exceed background emissions by as much as a factor of 1.7, and, presumably, we have altered the deposition of V from the atmosphere by a similar amount. Excessive V in air and water has potential, but poorly documented, consequences for human health. Much of the atmospheric flux probably derives from emissions from the combustion of fossil fuels, but the magnitude of this flux depends on the type of fuel, with relatively low emissions from coal and higher contributions from heavy crude oils, tar sands bitumen, and petroleum coke. Increasing interest in petroleum derived from unconventional deposits is likely to lead to greater emissions of V to the atmosphere in the near future. Our analysis further suggests that the flux of V in rivers has been incremented by about 15% from human activities. Overall, the budget of dissolved V in the oceans is remarkably well balanced—with about 40 × 10⁹ g V/y to 50 × 10⁹ g V/y inputs and outputs, and a mean residence time for dissolved V in seawater of about 130,000 y with respect to inputs from rivers.

Due to safety problems caused by the use of organic electrolytes in lithium-ion batteries and the high production cost brought by the limited lithium resources, water-based zinc-ion batteries have become a new research focus in the field of energy storage due to their low production cost, safety, efficiency, and environmental friendliness. This paper focused on vanadium dioxide and expanded graphite (EG) composite cathode materials. Given the cycling problem caused by the structural fragility of vanadium dioxide in zinc-ion batteries, the feasibility of preparing a new composite material is explored. The EG/VO[sub.2] composites were prepared by a simple hydrothermal method, and compared with the aqueous zinc-ion batteries assembled with a single type of VO[sub.2] under the same conditions, the electrode materials composited with high-purity sulfur-free expanded graphite showed more excellent capacity, cycling performance, and multiplicity performance, and the EG/VO[sub.2] composites possessed a high discharge ratio of 345 mAh g[sup.−1] at 0.1 A g[sup.−1], and the Coulombic efficiency was close to 100%. The EG/VO[sub.2] composite has a high specific discharge capacity of 345 mAh g[sup.−1] at 0.1 A g[sup.−1] with a Coulombic efficiency close to 100%, a capacity retention of 77% after 100 cycles, and 277.8 mAh g[sup.−1] with a capacity retention of 78% at a 20-fold increase in current density. The long cycle test data demonstrated that the composite with expanded graphite effectively improved the cycling performance of vanadium-based materials, and the composite maintained a stable Coulombic efficiency of 100% at a high current density of 2 A/g and still maintained a specific capacity of 108.9 mAh/g after 2000 cycles.

Oxygen vacancy (Vö) is important in the modification of electrode for rechargeable batteries. However, due to the scarcity of suitable preparation strategy with controllable Vö incorporation, the impact of Vö concentration on the electrochemical performances remains unclear. Thus, in this work, Vö-V 2 O 5 -PEDOT (VöVP) with tunable Vö concentration is achieved via a spontaneous polymerization strategy, with the capability of mass-production. The introduction of poly(2,3-dihydrothieno-1,4-dioxin) (PEDOT) not only leads to the formation of Vö in V 2 O 5 , but it also results in a larger interlayer spacing. The as-prepared Vö-V 2 O 5 -PEDOT-20.3% with Vö concentration of 20.3% (denoted as VöVP-20) is able to exhibit high capacity of 449 mAh·g −1 at current density of 0.2 A·g −1 , with excellent cyclic performance of 94.3% after 6,000 cycles. It is shown in the theoretical calculations that excessive Vö in V 2 O 5 will lead to an increase in the band gap, which inhibits the electrochemical kinetics and charge conductivity. This is further demonstrated in the experimental results as the electrochemical performance starts to decline when Vö concentration increases beyond 20.3%. Thus, based on this work, scalable fabrication of high-performance electrode with tunable Vö concentration can be achieved with the proposed strategy.

Snapshots of a phase transitionTime-resolved x-ray scattering can be used to investigate the dynamics of materials during the switch from one structural phase to another. So far, methods provide an ensemble average and may miss crucial aspects of the detailed mechanisms at play. Wall et al. used a total-scattering technique to probe the dynamics of the ultrafast insulator-to-metal transition of vanadium dioxide (VO2) (see the Perspective by Cavalleri). Femtosecond x-ray pulses provide access to the time- and momentum-resolved dynamics of the structural transition. Their results show that the photoinduced transition is of the order-disorder type, driven by an ultrafast change in the lattice potential that suddenly unlocks the vanadium atoms and yields large-amplitude uncorrelated motions, rather than occurring through a coherent displacive mechanism.Science, this issue p. 572; see also p. 525Many ultrafast solid phase transitions are treated as chemical reactions that transform the structures between two different unit cells along a reaction coordinate, but this neglects the role of disorder. Although ultrafast diffraction provides insights into atomic dynamics during such transformations, diffraction alone probes an averaged unit cell and is less sensitive to randomness in the transition pathway. Using total scattering of femtosecond x-ray pulses, we show that atomic disordering in photoexcited vanadium dioxide (VO2) is central to the transition mechanism and that, after photoexcitation, the system explores a large volume of phase space on a time scale comparable to that of a single phonon oscillation. These results overturn the current understanding of an archetypal ultrafast phase transition and provide new microscopic insights into rapid evolution toward equilibrium in photoexcited matter.

Reactive oxygen species (ROS) are generated and consumed in living organism for normal metabolism. Paradoxically, the overproduction and/or mismanagement of ROS have been involved in pathogenesis and progression of various human diseases. Here, we reported a two-dimensional (2D) vanadium carbide (V 2 C) MXene nanoenzyme (MXenzyme) that can mimic up to six naturally-occurring enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione peroxidase (GPx), thiol peroxidase (TPx) and haloperoxidase (HPO). Based on these enzyme-mimicking properties, the constructed 2D V 2 C MXenzyme not only possesses high biocompatibility but also exhibits robust in vitro cytoprotection against oxidative stress. Importantly, 2D V 2 C MXenzyme rebuilds the redox homeostasis without perturbing the endogenous antioxidant status and relieves ROS-induced damage with benign in vivo therapeutic effects, as demonstrated in both inflammation and neurodegeneration animal models. These findings open an avenue to enable the use of MXenzyme as a remedial nanoplatform to treat ROS-mediated inflammatory and neurodegenerative diseases. Materials with enzymatic-like activities are of interest for a wide range of applications. Here, the authors report on 2D vanadium carbide MXene nanozymes capable of mimicking multiple enzymes and demonstrate application to treat reactive oxygen species-mediated inflammatory and neurodegenerative diseases.

Separating structure and electrons in VO2Above 341 kelvin—not far from room temperature—bulk vanadium dioxide (VO2) is a metal. But as soon as the material is cooled below 341 kelvin, VO2 turns into an insulator and, at the same time, changes its crystal structure from rutile to monoclinic. Lee et al. studied the peculiar behavior of a heterostructure consisting of a layer of VO2 placed underneath a layer of the same material that has a bit less oxygen. In the VO2 layer, the structural transition occurred at a higher temperature than the metal-insulator transition. In between those two temperatures, VO2 was a metal with a monoclinic structure—a combination that does not occur in the absence of the adjoining oxygen-poor layer.Science, this issue p. 1037The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.

Vanadium has various oxidation states and multiple crystalline phases that make it interesting for various applications. The oxidation state transition and crystal formation of vanadium oxide (VOx) were affected by growth conditions and annealing temperatures. In this study, VOx nanopowders were prepared by hydrothermal method, and annealing-induced characterizations of VOx were analyzed. The morphologies, structures, composition, and optical properties of VOx were characterized by SEM, XRD, EDX, FTIR, and UV–Vis spectroscopy. The results demonstrated that the annealing temperature significantly affected the transition of oxide states from the VOOH and VOx clusters to V2O5 nanoparticles and the crystal size from amorphous to 38.96 nm which led to an increase in the optical band gap from 2.28, 2.26 to 2.39 and 2.38 eV as increasing calcination temperature and enhanced photocatalytic activity under sunlight irradiation. The energy dispersive X-ray (EDX) spectra reveal that the percentage molar mass between vanadium and oxygen changes due to the oxidation state transition and the formation of oxygen vacancies in V2O5. The relation between nanoparticle size, oxidation state, and crystal size was clarified by comparing EDX and XRD spectra.