Factors Determining the Selectivity of NO Reduction Catalyzed by Copper-Vanadium Oxide Cluster Anions Cu2VO3‒5.

Catalytic NO reduction by CO is imperative to satisfy the increasingly rigorous emission regulations. Identifying the structural characteristic of crucial intermediate that governs the selectivity of NO reduction is pivotal to having a fundamental understanding on real-life catalysis. Herein, benefiting from the state-of-the-art mass spectrometry, we demonstrated experimentally that the Cu2VO3-5- clusters can mediate the catalysis of NO reduction by CO, and two competitive channels to generate N2O and N2 can co-exist. Quantum-chemical calculations were performed to rationalize this selectivity. The formation of the ONNO unit on the Cu2 dimer was demonstrated to be a precursor from which two pathways of NO reduction start to emerge. In the pathway of N2O generation, only the Cu2 dimer was oxidized and the VO3 moiety  functions as a "support", while both moieties have to contribute to anchor oxygen atoms from the ONNO unit and then N2 can be generated. This finding displays a clear picture to elucidate how and why the involvement of VO3 "support" can regulate the selectivity of NO reduction.

Dual Polarization of Ni Sites at VOx-Ni3N Interface Boosts Ethanol Oxidation Reaction.

Substituting thermodynamically favorable ethanol oxidation reaction (EOR) for oxygen evolution reaction (OER) engenders high-efficiency hydrogen production and generates high value-added products as well. However, the main obstacles have been the low activity and the absence of an explicit catalytic mechanism. Herein, a heterostructure composed of amorphous vanadium oxide and crystalline nickel nitride (VOx-Ni3N) is developed. The heterostructure immensely boosts the EOR process, achieving the current density of 50 mA cm-2 at the low potential of 1.38 V versus reversible hydrogen electrode (RHE), far surpassing the sluggish OER (1.65 V vs RHE). Electrochemical impedance spectroscopy indicates that the as-fabricated heterostructure can promote the adsorption of OH- and the generation of the reactive species (O*). Theoretical calculations further outline the dual polarization of the Ni site at the interface, specifically the asymmetric charge redistribution (interfacial polarization) and in-plane polarization. Consequently, the dual polarization modulates the d-band center, which in turn regulates the adsorption/desorption strength of key reaction intermediates, thereby facilitating the entire EOR process. Moreover, a VOx-Ni3N-based electrolyzer, coupling hydrogen evolution reaction (HER) and EOR, attains 50 mA cm-2 at a low cell voltage of ≈1.5 V. This work thus paves the way for creating dual polarization through interface engineering toward broad catalysis.

Flash Joule Heating Synthesis of Layer-Stacked Vanadium Oxide/Graphene Hybrids within Seconds for High-Performance Aqueous Zinc-Ion Batteries.

Vanadium oxides have been regarded as highly promising cathodes for aqueous zinc-ion batteries (ZIBs). However, obtaining high-performance vanadium oxide-based cathodes suitable for industrial application remains a significant challenge due to the need for cost-effective, straightforward, and efficient preparation methods. Herein, we present a facile and rapid synthesis of a composite cathode, consisting of layer-stacked VO2/V2O5 and graphene-like carbon nanosheets, in just 2.5 s by treating the commercial V2O5 powder via a flash Joule heating strategy. When employed as the cathode for ZIBs, the resulting composite delivers a comparable rate capacity of 459 mA h g-1 at 0.2 A g-1 and remarkable cycle stabilities of 355.5 mA h g-1 after 2500 cycles at 1.0 A g-1 and 169.5 mA h g-1 after 10,000 cycles at 10 A g-1, respectively. Further electrochemical analysis reveals that the impressive performance is attributed to the accelerated charge transfer and the alleviated structure degradation, facilitated by the abundant sites and a built-in electric field of the layer-stacked VO2/V2O5 heterostructure, as well as the excellent conductivity of graphene-like carbon nanosheets. This work introduces a unique approach for ultrafast and low-cost fabrication of high-performance vanadium oxide-based composite cathodes toward efficient ZIBs.

Selective Synthesis of 3D Aligned VO2 and V2O5 Carbon Nanotube Hybrid Materials by Chemical Vapor Deposition.

3D carbon nanotube hybrid materials containing VO2 and V2O5 evenly distributed onto vertically aligned carbon nanotubes (VACNTs) is reported. Adjustable loading of particles in controllable sizes onto the VACNTs was developed via a stepwise chemical vapour deposition (CVD) approach. Solid VO(acac)2 is chosen as vanadium source. CO2 acts as reactive gas for the pre-functionalisation of the VACNTs. The process temperature was identified as key parameter to control the deposited vanadium oxide phase. A temperature of 550°C results in monoclinic VO2, while 600 °C results in the deposition of V2O5 onto the VACNT support. The morphology and the amount of deposited material was found to be dependent on the reactor dimensions and the degree of functionalization of the carbon support. An increase of the D/G ratio of the VACNT from 0.75 to 1.08 caused by a CO2 treatment step within the process led to an increase of the particle coverage from a scarce coverage without prior CO2 treatment to a dense coverage of the VACNT support after 15 min of CO2 exposure time. Size and crystallinity of the as deposited particles can be further adjusted by a controlled heat treatment after VO(acac)2 precursor deposition.

Synthesis and characterization of an organic-inorganic hybrid crystal: 2[Co(en)3](V4O13)·4H2O.

Organic-inorganic hybrid crystals have diverse functionalities, for example in energy storage and luminescence, due to their versatile structures. The synthesis and structural characterization of a new cobalt-vanadium-containing compound, 2[Co(en)3]3+(V4O13)6-·4H2O (1) is presented. The crystal structure of 1, consisting of [Co(en)3]3+ complexes and chains of corner-sharing (VO4) tetrahedra, was solved by single-crystal X-ray diffraction in the centrosymmetric space group P1. Phase purity of the bulk material was confirmed by infrared spectroscopy, scanning electron microscopy, elemental analysis and powder X-ray diffraction. The volume expansion of 1 was found to be close to 1% in the reported temperature range from 100 to 300 K, with a volume thermal expansion coefficient of 56 (2) × 10-6 K-1. The electronic band gap of 1 is 2.30 (1) eV, and magnetic susceptibility measurements showed that the compound exhibits a weak paramagnetic response down to 1.8 K, probably due to minor CoII impurities (<1%) on the CoIII site.

Coupling Manipulation of Interfacial Chemistry and Coordination Structure in Vanadium Oxides Enables Rapid Magnesium Ion Diffusion Kinetics.

Rechargeable magnesium batteries (RMBs) are a highly promising energy storage system due to their high volumetric capacity and intrinsic safety. However, the practical development of RMBs is hindered by the sluggish Mg2+ diffusion kinetics, including at the cathode-electrolyte interface (CEI) and within the cathode bulk. Herein, we propose an efficient strategy to manipulate the interfacial chemistry and coordination structure in oligolayered V2O5 (L-V2O5) for achieving rapid Mg2+ diffusion kinetics. In terms of the interfacial chemistry, the specific exposed crystal planes in L-V2O5 possess strong electron donating ability, which helps to promote the degradation dynamics of C-F/C-S bonds in the electrolyte, thereby establishing the inorganic-organic interlocking CEI layer for rapid Mg2+ diffusion. In terms of the coordination structure, the straightened V-O structure in L-V2O5 provides efficient ions diffusion path for accelerating Mg2+ diffusion in the cathode. As a result, the L-V2O5 delivers a high reversible capacity (355.3 mA h g-1 at 0.1 A g-1) and an excellent rate capability (161 mAh g-1 at 1 A g-1). Impressively, the interdigital micro-RMBs is firstly assembled, exhibiting excellent flexibility and practicability. This work gives deeper insights into the interface and interior ions diffusion for developing high-kinetics RMBs.

Miniaturized Hyperspectral Imager Utilizing a Reconfigurable Filter Array for Both High Spatial and Spectral Resolutions.

Miniaturized hyperspectral imaging based on filter arrays has attracted much attention in consumer applications, such as food safety and biomedical applications. In this Letter, we demonstrate a miniaturized hyperspectral imager using a reconfigurable filter array to tackle the existing trade-off issue between the spectral and spatial resolutions. Utilizing tens of intermediate states of a vanadium dioxide cavity, we increase the total number of physical spectral channels by tens of times from a 2 × 2 mosaic filter unit, providing both high spatial and spectral resolutions for spectral imaging. The reconfigurable filter has a good spectral resolvability of 10 nm in the visible range with a wavelength inaccuracy of less than 2.1 nm. Hyperspectral imaging is demonstrated with a frame rate of 4.5 Hz.

Anisotropic Optical Response of Ti-Doped VO2 Single Crystals.

This study delves into the effects of titanium (Ti) doping on the optical properties of vanadium dioxide (VO2), a material well known for its metal-to-insulator transition (MIT) near room temperature. By incorporating Ti into VO2's crystal lattice, we aim to uncover the resultant changes in its physical properties, crucial for enhancing its application in smart devices. Utilizing polarized infrared micro-spectroscopy, we examined TixV1-xO2 single crystals with varying Ti concentrations (x = 0.059, x = 0.082, and x = 0.187) across different crystal phases (the conductive rutile phase and insulating monoclinic phases M1 and M2) from the far-infrared to the visible spectral range. Our findings reveal that Ti doping significantly influences the phononic spectra, introducing absorption peaks not attributed to pure VO2 or TiO2. This is especially notable with polarization along the crystal growth axis, mainly in the x = 0.187 sample. Furthermore, we demonstrate that the electronic contribution to optical conductivity in the metallic phase exhibits strong anisotropy, higher along the c axis than the a-b plane. This anisotropy, coupled with the progressive broadening of the zone center infrared active phonon modes with increasing doping, highlights the complex interplay between structural and electronic dynamics in doped VO2. Our results underscore the potential of Ti doping in fine-tuning VO2's electronic and thermochromic properties, paving the way for its enhanced application in optoelectronic devices and technologies.

Using MXene as a Chemically Induced Initiator to Construct High-Performance Cathodes for Aqueous Zinc-Ion Batteries.

MXene usually exhibits weak pseudo-capacitance behavior in aqueous zinc-ion batteries, which cannot provide sufficient reversible capacity, resulting in the decline of overall capacity when used as the cathode materials. Taking inspiration from polymer electrolyte engineering, we have conceptualized an in situ induced growth strategy based on MXene materials. Herein, 5.25 % MXene was introduced into the nucleation and growth process of vanadium oxide (HVO), providing the heterogeneous nucleation site and serving as an initiator to regulate the morphology and structural of vanadium oxide (T-HVO). The resulted materials can significantly improve the capacity and rate performance of zinc-ion batteries. The growth mechanism of T-HVO was demonstrated by both characterizations and DFT simulations, and the improved performance was systematically investigated through a series of in situ experiments related to dynamic analysis steps. Finally, the evaluation and comparison of various defect introduction strategies revealed the efficient, safety, and high production output characteristics of the in situ induced growth strategy. This work proposes the concept of in situ induced growth strategy and discloses the induced chemical mechanism of MXene materials, which will aid the understanding, development, and application of cathode in aqueous zinc-ion batteries.

Synergistic Theoretical and Experimental Insights into NH4+-Enhanced Vanadium Oxide Cathodes for Aqueous Zinc-Ion Batteries.

This study explores the enhancement of aqueous zinc-ion batteries (AZIBs) using ammonium-enhanced vanadium oxide cathodes. Density Functional Theory (DFT) calculations reveal that NH4+ incorporation into V6O16 lattices significantly facilitates Zn2+ ion diffusion by reducing electrostatic interactions, acting as a structural lubricant. Subsequent experimental validation using (NH4)2V6O16 cathodes synthesized via a hydrothermal method corroborates the DFT findings, demonstrating remarkable electrochemical stability with a capacity retention of 90% after 2000 cycles at 5 A g-1. These results underscore the potential of NH4+ in improving the performance and longevity of AZIBs, providing a pathway for sustainable energy storage solutions.

Calcium-Pillar Boosting Smooth Phase Transition in Potassium Vanadate Nanobelts toward Superior Cycling Performance in Potassium-Ion Batteries.

The depletion of lithium resources has prompted exploration into alternative rechargeable energy storage systems, and potassium-ion batteries (PIBs) have emerged as promising candidates. As an active cathode material for PIBs, potassium vanadate (KxV2O5) usually suffers from structural damage during electrochemical K-ion insertion/extraction and hence leading to unsatisfactory cycling performance. Here, we introduce Ca2+ ions as pillars into the potassium vanadate to enhance its structural stability and smooth its phase transition behavior. The additional Ca2+ not only stabilizes the layered structure but also promotes the rearrangement of interlayer ions and leads to a smooth solid-solution phase transition. The optimal composition K0.36Ca0.05V2O5 (KCVO) exhibits outstanding cyclic stability, delivering a capacity of ∼90 mA h g-1 at 20 mA g-1 with negligible capacity decay even after 700 cycles at 500 mA g-1. Theoretical calculations indicate lower energy barriers for K+ diffusion, promoting rapid reaction kinetics. The excellent performances and detailed investigations offer insights into the structural regulation of layered vanadium cathodes.

In situ Low-Energy Electron Microscopy of Chemical Waves on a Composite V-oxide/Rh(110) Surface.

Chemical wave patterns and V-oxide redistribution in catalytic methanol oxidation on a VOx/Rh(110) surface have been investigated in the 10-4 mbar range with low-energy electron microscopy (LEEM) and micro spot low-energy electron diffraction (micro-LEED) as in situ methods. V coverages of θV=0.2 and 0.4 MLE (monolayer equivalents) were studied. Pulses display a c(2×2) pattern in the reduced part and (1×2) and c(2×8) structures in the oxidized part of the surface. At θV=0.4 MLE (1×2)/(1×4) patterns with streaks along the [001]-direction at the 1/8 positions are present on the oxidized part of the surface. This phase can be assigned to V-oxide. On a tentative basis, an excitation mechanism for pulses is presented, Annealing the surface to 990 K under reaction conditions results in a macroscopic hole pattern in which holes of low VOx coverage are surrounded by a V-oxide layer. Chemical waves propagate inside the holes as well as on the VOx covered parts of the surface. The results demonstrate for the first time that also in supported oxidic overlayers selforganization processes can take place leading to chemical waves and a large scale redistribution of the oxide.

Laser-Scribed Battery Electrodes for Ultrafast Zinc-Ion Energy Storage.

Aqueous Zn batteries are promising for large-scale energy storage but are plagued by the lack of high-performance cathode materials that enable high specific capacity, ultrafast charging, and outstanding cycling stability. Here, a laser-scribed nano-vanadium oxide (LNVO) cathode is designed that can simultaneously achieve these properties. The material stores charge through Faradaic redox reactions on/near the surface at fast rates owing to the small grain size of vanadium oxide and interpenetrating 3D graphene network, displaying a surface-controlled capacity contribution (90%-98%). Multiple characterization techniques unambiguously reveal that zinc and hydronium ions co-insert with minimal lattice change upon cycling. It is demonstrated that a high specific capacity of 553 mAh g-1 is achieved at 0.1 A g-1, and an impressive 264 mAh g-1 capacity is retained at 100 A g-1 within 10 s, showing excellent rate capability. The LNVO/Zn can also reach >90% capacity retention after 3000 cycles at a high rate of 30 A g-1, as well as achieving both high energy (369 Wh kg-1) and power densities (56306 W kg-1). Moreover, the LNVO cathode retains its excellent cycling performance when integrated into quasi-solid-state pouch cells, further demonstrating mechanical stability and its potential for practical application in wearable and grid-scale applications.

Discovering the Order-Disorder Transition in Quinoline Intercalated Vanadium Oxide with Superior Calcium Storage via Polyhedral Distortion.

Calcium-ion batteries (CIBs) are considered as potential next-generation energy storage systems due to their abundant reserves and relatively low cost. However, irreversible structural changes and weak conductivity still hinder in current CIBs cathode materials. Herein, an organic molecular intercalation strategy is proposed, in which V2O5 regulated with quinoline, pyridine, and water molecules are studied as cathode material to provide fast ion diffusion channels, large storage host, and high conductivity for Ca ions. Among them, V2O5-quinoline (QVO) owns the largest interplanar spacing of 1.25 nm and the V-O chains are connected with organic molecular by hydrogen bond, which stabilizes the crystal structure. As a result, QVO exhibits a specific capacity of 168 mAh g-1 at 1 A g-1 and capacity retention of 80% after 500 cycles at 5 A g-1 than the other materials. Furthermore, X-Ray diffraction and X-ray absorption spectroscopy results reveal a reversible order-disorder transformation mechanism of Ca2+ for QVO, which can make full use of the abundant active sites for high capacity and simultaneously achieve fast reaction kinetics for excellent rate performance. These results demonstrate that QVO is a promising cathode material for CIBs, providing more choices for the development of high-performance CIBs.

Tailoring Physicochemical Properties of V2O5 Nanostructures: Influence of Solvent Type in Sol-Gel Synthesis.

The influence of different solvents, including aqueous and nonaqueous types, on the physicochemical properties of V2O5 nanostructures was thoroughly investigated. Various characterization techniques, such as XRD, XPS, FTIR, Raman spectroscopy, UV-vis DRS, SEM, TEM, and BET, were employed to analyze the obtained materials. Additionally, the adsorption properties of the synthesized V2O5 nanostructures for methylene blue were examined, and kinetic parameters of adsorption were calculated. The results demonstrate that the morphology of the obtained crystals can be finely controlled by manipulating water concentration in the solution, showcasing its profound impact on both the structural characteristics and adsorption properties of the nanostructures. Furthermore, the structural changes of the resulting V2O5 material induced by solvents show strong impacts on its photocatalytic properties, making it a promising photocatalyst.

Multi-metal ions co-regulated vanadium oxide cathode toward long-life aqueous zinc-ion batteries.

Interlayer intercalation engineering shows great feasibility to improve the structure stability of the layered oxides. Although high Zn-storage capability has been attained based on the pillar effect of multifarious intercalants, an in-depth understanding the synergistic effect of intercalated multiple metal ions is still in deficiency. Herein, alkali metal ion K+, alkaline earth metal ion Mg2+ and trivalent metal ion Al3+ are introduced into the VO interlayer of V2O5. Due to the different electronegativity and hydrated ion radius of K+, Mg2+ and Al3+, adjusting the relative proportions of these metal ions can achieve an appropriate interlayer spacing, stable layer structure and regular morphology, which facilitates the transport kinetics of Zn2+. Under the synergistic effect of pre-intercalated multi-metal ion, the optimal tri-metal ion intercalated hydrated V2O5 cathode exhibits a high specific capacity of 382.4 mAh g-1 at 0.5 A g-1, and long-term cycling stability with capacity retention of 86 % after 2000 cycles at the high current density of 10 A g-1. Ex-situ and kinetic characterizations reveal the fast charge transfer and reversible Zn2+ intercalation mechanism. The multi-ion engineering strategy provides an effective way to design desirable layered cathode materials for aqueous zinc-ion batteries.

Forming-Free, Low-Voltage, and High-Speed Resistive Switching in Ag/Oxygen-Deficient Vanadium Oxide(VOx)/Pt Device through Two-Step Resistance Change by Ag Filament Formation.

Forming-free, low-voltage, and high-speed resistive switching is demonstrated in an Ag/oxygen-deficient vanadium oxide (VOx)/Pt device via the facilitated formation and rupture of Ag filaments. Direct current (DC) voltage sweep measurements exhibit forming-free switching from a high-resistance state (HRS) to a low-resistance state (LRS), called SET, at an average VSET of +0.23 V. The reverse RESET transition occurs at an average VRESET of -0.07 V with a low RESET current of <1 mA. Reversible switching operations are stable with an HRS/LRS resistance ratio >103 during repeated measurements for thousands of cycles. In pulse measurements, switching occurs within 100 ns at an amplitude of +1.5 V. Notably, a two-step resistance change is observed in the SET operation, where the resistance first partially decreases due to Ag+ ion accumulation in VOx and then further decreases to the LRS after hundreds of nanoseconds upon complete filament formation. The VOx layer deposited to be mostly amorphous with oxygen deficiency from V2O5 has abundant vacancies and expedites Ag+ ion migration, thus realizing forming-free, high-speed, and low-voltage switching. These characteristics of the facilitated Ag filament formation using the substoichiometric VOx layer are highly beneficial for use as stand-alone nonvolatile memory and in-memory computing elements.

N-Doping-Induced Amorphization for Achieving Ultrastable Aqueous Zinc-Ion Batteries.

Vanadium-based oxides, known for their high capacity and low cost, have garnered significant attention as promising cathode candidates in aqueous zinc-ion batteries. Nonetheless, their poor rate performance and limited durability in aqueous electrolytes present a challenge to the realistic implementation of vanadium-based aqueous zinc-ion batteries. Here, we synthesized nitrogen-doped V2O3@C (N-V2O3@N-C) via ammonia treatment of V2O3@C derived from vanadium-based metal-organic framework (V-MOF), aiming to achieve outstanding rate and cycling performance. The N-V2O3@N-C electrode exhibits notable in situ self-transformation into an amorphous state. Density functional theory calculations reveal that the distorted N-V2O3 structure and uneven charge distribution result in the creation of an amorphous state. As expected, Zn/N-V2O3@N-C aqueous zinc-ion batteries can achieve remarkable specific capacity (349.0 mAh g-1 at 0.1 A g-1), along with impressive rate performance, showcasing a capacity of 253.5 mAh g-1 at 5 A g-1 and exceptional durability at 5 A g-1 (96.4% after 1350 cycles). The employed induced amorphization approach offers novel perspectives for designing high-performance cathodes that exhibit both sturdy structures and extended cycling lifespans.

H2O-Mg2+ Waltz-Like Shuttle Enables High-Capacity and Ultralong-Life Magnesium-Ion Batteries.

Mg-ion batteries (MIBs) are promising next-generation secondary batteries, but suffer from sluggish Mg2+ migration kinetics and structural collapse of the cathode materials. Here, an H2O-Mg2+ waltz-like shuttle mechanism in the lamellar cathode, which is realized by the coordination, adaptive rotation and flipping, and co-migration of lattice H2O molecules with inserted Mg2+, leading to the fast Mg2+ migration kinetics, is reported; after Mg2+ extraction, the lattice H2O molecules rearrange to stabilize the lamellar structure, eliminating structural collapse of the cathode. Consequently, the demo cathode of Mg0.75V10O24·nH2O (MVOH) exhibits a high capacity of 350 mAh g-1 at a current density of 50 mA g-1 and maintains a capacity of 70 mAh g-1 at 4 A g-1. The full aqueous MIB based on MVOH delivers an ultralong lifespan of 5000 cycles The reported waltz-like shuttle mechanism of lattice H2O provides a novel strategy to develop high-performance cathodes for MIBs as well as other multivalent-ion batteries.

Multifield-Modulated Spintronic Terahertz Emitter Based on a Vanadium Dioxide Phase Transition.

The efficient generation and active modulation of terahertz (THz) waves are strongly required for the development of various THz applications such as THz imaging/spectroscopy and THz communication. In addition, due to the increasing degree of integration for the THz optoelectronic devices, miniaturizing the complex THz system into a compact unit is also important and necessary. Today, integrating the THz source with the modulator to develop a powerful, easy-to-adjust, and scalable or on-chip THz emitter is still a challenge. As a new type of THz emitter, a spintronic THz emitter has attracted a great deal of attention due to its advantages of high efficiency, ultrawide band, low cost, and easy integration. In this study, we have proposed a multifield-modulated spintronic THz emitter based on the VO2/Ni/Pt multilayer film structure with a wide band region of 0-3 THz. Because of the pronounced phase transition of the integrated VO2 layer, the fabricated THz emitter can be efficiently modulated via thermal or electric stimuli with a modulation depth of about one order of magnitude; the modulation depths under thermal stimulation and electrical stimulation were 91.8% and 97.3%, respectively. It is believed that this multifield modulated spintronic THz emitter will provide various possibilities for the integration of next-generation on-chip THz sources and THz modulators.