Pure V2O5 Research Articles

Lithography-free fabrication of Vanadium Dioxide and its devices using direct laser writing

Vanadium Dioxide (VO2) changes reversibly from metal and insulator phase around the transition temperature (68 °C) causing resistance and reflectance switching. Conventional VO2 device fabrication technology involves VO2 deposition, lithography for film patterning/etching, and contact formation. The overall fabrication process is complex, time-consuming, costly, and requires harmful chemicals. This work demonstrates a lithography-free method to fabricate VO2 devices where the VO2 region synthesis, isolation, and contact formation are all done in continuity using direct laser writing (DLW) on Vanadium (V) thin films. The effect of the laser parameters on oxidation is examined and spots of phase pure VO2 and V2O5 are obtained on the same sample, with VO2 showing ∼ 2 orders of resistance switching. Lines of VO2 are synthesized using DLW on V film, resulting in a V-VO2-V structure which after laser isolation forms a completely laser-written VO2 device exhibiting resistance switching driven by either voltage or temperature. To display the suitability of the fabricated device for circuit applications, a relaxation oscillator circuit is demonstrated. The presented DLW based lithography free approach to synthesize VO2 structures and devices significantly simplifies fabrication compared to traditional semiconductor processing approaches. It can also enable single step fabrication of integrated circuits based on vanadium oxide active regions with V interconnects.

An in-depth photoluminescence investigation of charge carrier transport in ZrO2|V2O5 type I junction: Probing the production of hydroxyl radicals

The determination of the band edge positions turns out to be of particular importance in different fields. We present a comparison of different approaches for the determination of the band edge alignment. For this purpose, we suggested studying the ZrO2|V2O5 heterojunction. The structural properties investigated by means of X-ray diffraction (XRD) revealed the formation of pure V2O5 with an orthorhombic structure. The resulting ZrO2, however, exhibits two different phases (monoclinic and tetragonal). Based on the absorption spectra, the near-band edges for V2O5, ZrO2, and ZrO2|V2O5 were found to be 2.07, 4.9, and 2.12 eV, respectively. The corresponding band gap values determined by the Tauc method were found to be 2.32, 5.16, and 2.35 eV, respectively. The down-conversion photoluminescence (PL) spectra of pure and junctioned materials are discussed in detail. The up-conversion in ZrO2 revealed its band gap value (∼5.14 eV), which is very close to the one obtained by the Tauc method (∼5.16 eV). The band gap alignment of the ZrO2|V2O5 heterojunction was determined using Sanderson method and experimentally using X-ray photoelectron spectroscopy (XPS). In this work, we propose an In-depth photoluminescence study for the confirmation of the type of heterojunction by probing the hydroxyl radical (HO•) production.

Towards Unlocking/Tuning the Mott Transition Temperature in Alkaline-Doped Vanadium Oxide Thermochromic Coatings and Potential Green Air-Conditioning via Room Temperature VxOy-V-VxOy Layered Coatings

In this contribution, we validate for the first time that the near infrared-infrared (NIR-IR) modulation of the optical transmission (DTTRANS = T(T<TMIT) - T(T>TMIT)) of vanadium oxide-based nanomaterials can be controlled or tuned via a genuine approach with a simultaneous drastic reduction of its Mott transition temperature TMIT. More accurately, we report a significant thermochromism in multilayered V2O5/V/V2O5 stacks equivalent to that of pure VO2 thin films but with a far lower transition temperature TMIT. Such a multilayered V2O5/V/V2O5 thermochromic system exhibited a net control or tunability of the optical transmission modulation in the NIR-IR (DTTRANS) via the nano-scaled thickness of the intermediate vanadium layer. In addition, the control of DTTRANS is accompanied by a noteworthy diminution of the Mott transition temperature TMIT from the bulk value of 68.8 °C to the range of 27.5–37.5 °C. The observed peculiar thermochromism in the multilayered V2O5/V/V2O5 is likely to be ascribed to a significant interfacial diffusion or an excessive interfacial stress/strain, and/or to an effective halide (Na, K, Ca) doping. This doping is driven by a significant diffusion from the borosilicate substrate surface towards the V2O5/V/V2O5 stacks. If the upscaling of this approach is validated, the current findings would contribute to advancing thermochromic nanomaterials and their applications in smart windows for managing solar heat and green air-conditioning technologies.

Advancing photocatalysis: Innovative approaches using novel V2O5/ZnO nanocomposites for efficient photocatalytic degradation of tubantin red

Photocatalytic response of V2O5, ZnO, and V2O5/ZnO nanostructures for the degradation of Tubantin red 8BL dye has been reported. Pure V2O5, ZnO, and V2O5/ZnO composite nanostructures were synthesized through a hydrothermal method. UV–Visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray microscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR) characterizations were done to examine their bandgap energy (Eg), morphology, composition, and structure, respectively. These discoveries advance our knowledge of the agglomerated nanoparticles of V2O5, ZnO, and V2O5/ZnO for their prospective photocatalytic uses. The presence of V2O5 and ZnO in composite is confirmed through the analysis of FTIR. Flower shaped morphology was observed in V2O5/ZnO nanocomposite by SEM. The 2.83 eV bandgap energy was observed in composite. The nanocomposite was evaluated for Tubantin red 8BL photodegradation. The efficiencies of pure ZnO nanoparticles after 25 min, 50 min, 75 min, 100 min, 125 min, and 150 min irradiation are 54.54 %, 58.00 %, 61.41 %, 63.84 %, 71.19 %, and 78.53 %; for pure V2O5 nanoparticles, they are 72.72 %, 76.45 %, 80.85 %, 85.42 %, 89.99 %, and 94.32 %. Similarly, the efficiencies (%) of V2O5/ZnO composite nanoparticles are 45.10 %, 53.27 %, 60.75 %, 68.24 %, 79.99 %, 91.74 %, and 99.79 %, respectively. Reusability studies (three cycles) were used to further confirm the photocatalytic efficiency, and the findings of the subsequent characterization revealed an arrangement of crystalline layers which is the cause of the high efficiency. These nanostructures also demonstrated stability across three cycles, suggesting more photocatalytic uses for them in the future.

Development of V2O5@GO (1D/2D) nanohybrid based chemiresistor for low-trace of toluene

A room temperature operated V2O5 nanorods-decorated graphene oxide (GO) nanosheets-nanocomposite based chemiresistor has been fabricated for detecting low-trace of toluene (5–60 ppm). The V2O5 nanorods were grown on GO nanosheets via hydrothermal method. The surface morphological investigation done by SEM and confirmed the decoration of V2O5 nanorods on GO nanosheets. The Rietveld refinement was performed for structural analysis of V2O5 nanorods confirmed the orthorhombic phase structure. At lowest concentration of 5 ppm, the sensor response of V2O5 @GO nanohybrid was 4.90 which was 2.84 and 3.52 times higher than pure GO and V2O5, respectively. The rapid response and recovery time at 5 ppm were observed to be 4.18 s and 5.86 s, respectively. The decoration of V2O5 nanorods on GO nanosheets increased the activated sites and formed p-n heterojunction, resulting in the enhanced sensing performance. The sensor response for the maximum concentration of 60 ppm was 36.25. Also, the V2O5@GO chemiresistor demonstrated high long-term stability and selectivity towards toluene as compared to other interfering volatile organic compounds such as, methanol, ethanol, aniline, formaldehyde, benzene, and acetone. This work opens a novel window for the development of devices that are room temperature operatable, highly sensitive and selective for rapid detection of toluene gas for its commercialization.

Synthesis, Properties, and Applications of Vanadium Pentoxide (V2O5) as Photocatalyst: A Review

Water pollution has increased worldwide, sparking interest in photocatalysis, a viable water treatment approach. Vanadium pentoxide (V2O5) is a good photocatalyst for photocatalytic degradation due to its excellent crystallinity, high yield and recyclability, low cost, photo-corrosion resistance, small band gap (2.3 eV), improved electron mobility, and broad absorption range. Pure V2O5's photocatalytic efficiency is limited by inefficient photonic and quantum processes, and its tiny structure enables photogenerated carriers to recombine, reducing efficiency. This prevents widespread use of V2O5. This mini-review examines V2O5 as a potent visible-light photocatalyst, focusing on its structure, synthesis methods, and modifications that improve its efficiency. Hydrothermal, sol-gel, co-precipitation, solvothermal, and others are reviewed. The methods employed affect the photocatalyst's efficiency. Photogenerated electron-hole separation, charge transfer to catalyst surface or across two-phase catalyst interfaces, and reactive species interaction with hazardous contaminants are all affected. Photoredox uses have been explored for dyes, phenols, and pharmaceutical wastes. According to a review of the past decades, V2O5 has primarily been used for the degradation of dye pollutants, with fewer applications for pharmaceutical wastes and other pollutants. More research on V2O5's capabilities and qualities on diverse target pollutants is needed. This mini-review discusses present obstacles in producing vanadium pentoxide-based systems and future research prospects. Despite its potential as a photocatalyst, V2O5 has not been thoroughly researched as an electron storage material. Numerous investigations have shown that V2O5 can store energy like lithium batteries. This finding will likely motivate researchers and newcomers to explore V2O5's potential to synthesise nanomaterials with increased electron storage capacity, making it a good day-night photocatalyst. This review should improve future V2O5 research.

Ppb-level detection of trimethylamine as biomarker in exhaled gas based on MoO3/V2O5 hierarchical heterostructure

The toxic gas trimethylamine (TMA) with fishy odor can not only be used as an indicator for evaluating seafood spoilage, but also as a biomarker for trimethylaminuria and kidney disease. This paper constructs a ppb-level trimethylamine gas sensor that operates at room temperature based on MoO3/V2O5 nanocomposites, which were fabricated by hydrothermal synthesis process. The adsorption energy of TMA on sensitive materials was calculated through the density functional theory, and the sensing mechanism was explored by simulating the adsorption process of TMA on the sensitive materials. The response (11.37%) of MoO3/V2O5 composites to ultra-low concentration (20 ppb) TMA was better than that of pure MoO3 nanorods (5.49%) and V2O5 nanospheres (6.36%) at room temperature. Compared with pure MoO3 sensors, an n-n heterojunction is formed between MoO3 and V2O5, which enhances the sensing performance of pure sensing material for TMA. In addition, the detection of exhaled gas in simulated kidney disease patients indicates that this sensor has great potential as an effective TMA detection tool in the field of non-invasive disease diagnosis.

Printed and Room Temperature Processed Nanoparticulate VO2 Thin Films Toward Memristive Device Applications

Vanadium dioxide (VO2) has received tremendous research interest in recent years for its versatile electronic application possibilities based on its reversible metal-insulator transition (MIT) behavior, which can be triggered by a large set of stimuli, such as current, electric field, or light. VO2 undergoes a phase transition from a semi-insulating monoclinic to metallic rutile phase at a low critical temperature of 68 °C, which is very close to room temperature, and compatible with any inexpensive flexible substrate. However, owing to the existence of various vanadium oxide polymorphs, the synthesis of the pure monoclinic VO2 (M) phase is a challenge. In fact, the difficulty level increases further when it is to be solution-processed. However, synthesis protocol for phase-pure VO2 (M) following wet chemical routes is essential to obtain high throughput, cost-efficient, and substrate-independent fabrication routine for the large volume of devices. In this regard, in the present study, we report a solution-based synthesis of ultra-small VO2 (M) nanoparticles that are phase-pure and the small nanoparticles may easily be used to formulate inkjet printable VO2 nanoparticulate. The printed VO2 (M) films have been found to be homogeneous, crack-free and the memristor device thus fabricated has demonstrated temperature-dependent phase transition and a resistance change of more than three orders of magnitude around 68 °C; on the other hand, retention of the metallic and insulating state has also been demonstrated for 180 minutes.

Photoelectrodes based on selenium-polypyrrole-vanadium pentoxide nanowire films for high-performance lightweight symmetric photo-supercapacitors: A flexible photo-rechargeable electrical energy storage device

V2O5-PPy, Se-V2O5, and Se-V2O5-PPy films on flexible indium tin oxide electrodes have been used to prepare flexible, lightweight and high-performance flexible photo-supercapacitors. Vanadium pentoxide (V2O5) nanowires, which are excellent electrode compounds for high electrochemical performance and long cycle life photoresponsive supercapacitance, have been synthesized and their photo-assisted supercapacitor performances have been enhanced by selenium and polypyrrole (PPy). The capacitive performances of Se-V2O5-PPy have been improved to 375 mF/cm2 at 0.25 mA.cm−2, which is over 2.1 times that of pure V2O5, 1.5 times those of the corresponding values for V2O5-PPy, 1.6 times of Se-V2O5 and 1.7 times of Se-PPy at identical current densities. Areal capacitance values of 151 mF/cm2 and 375 mF/cm2 (@ 0.25 mA/cm2) have been shown by Se-V2O5-PPy electrodes prepared in the dark and under light irradiation, respectively. Good cycle stability of 91% is shown by the assembled device after 10,000 cycles and its voltage window can be increased to 2.0 V. Furthermore, maximum volumetric energy densities of 16.8 and 41.6 Wh/kg can be obtained in the dark and under light irradiation, respectively. The flexible self-powered photo-supercapacitors show remarkable flexibility while maintaining their supercapacitor performance well even under various bent conditions, which signifies the outstanding flexibility of this device.

Enhancing thermochromic properties of VO2 amorphous films on glass substrates by Sn-W co-doping

Co-doping is an effective method for VO2 films to meet the requirements of smart window applications. In this research, we prepared pure VO2, Sn-doped, and Sn-W co-doped amorphous films on glass substrates. Compared with pure and Sn-doped VO2 films, Sn-W co-doped samples showed better thermochromic properties. For the 4.8 % Sn-2.1 % W co-doped sample, the luminous transmittance (Tlum) reached 76 %, the metal-insulator transition (MIT) temperature (Tc) decreased to 46.7 °C, the solar transmittance modulation capacity (ΔTsol) was maintained at around 5.2 %, and the near-infrared modulation capacity (ΔTIR) was up to 13.5 %. These results show that co-doping Sn and W into VO2 is feasible for smart window applications.

2D V2O5 nanoflakes on 2D p-gC3N4 nanosheets of heterostructure photocatalysts with the enhanced photocatalytic activity of organic pollutants under direct sunlight

The demand for high-performing photocatalysts remains constant as photocatalytic techniques utilizing semiconductors are recognized as a highly effective means of purifying wastewater by eliminating various pollutants. Heterostructure binary nanocomposite photocatalysts possess the remarkable capability of absorbing solar light and effectively transmitting photocarriers, rendering them exceptionally efficient for diverse applications. This manuscript reports the synthesis of V2O5 (VO) and protonated g-C3N4 (PCN) nanocomposite by sol-gel method. The impact of protonated g-C3N4 on the nanocomposite (V2O5/protonated g-C3N4) was investigated by varying the different weight percentages [5% PCN/VO (PV1), 10% PCN/VO (PV2), and 15% PCN/VO (PV3)]. Several characterization techniques, including X-ray Diffraction (XRD),UV–VisDiffuse Reflectance Spectroscopy (UV-DRS), Photoluminescence (PL), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and X-ray Photoelectron spectroscopy (XPS) analysis, were employed systematically to examine the structural, optical, morphological, and chemical compositional properties of the synthesized nanocomposites, respectively. The photocatalytic performance of the pure and nanocomposites was thoroughly assessed by degrading methylene blue (MB) under sunlight irradiation. TEM analysis confirms the intimate interface between VO and PCN in the heterostructure, facilitating efficient charge transfer. Additionally, UV analysis reveals an increased bandgap, indicating enhanced responsiveness to higher wavelength regions. In comparison to pure VO, the PV2 sample significantly increased its photocatalytic activity when exposed to direct sunlight, achieving a degradation efficiency of 97% with k = 0.024 min−1 in 100 min.

First‐Principles Studies of Electronic Structures and Optical Properties of Cobalt‐Doped VO2

First‐principles calculations based on density functional theory (DFT) are used to investigate the phase transition characteristics, electronic structures, and optical properties of pure and Co‐doped VO2 (M1 and R phase). Studies show that the metal‐to‐insulator phase transition temperature of VO2 is significantly reduced after Co doping, which is correlated to the decrease of bandgap value. Besides, the decrease of the energy required for electron transition of M1‐phase Co‐doped VO2 corresponds to the imaginary part of the dielectric peak moving to the low‐energy region. For both the M1‐ and R‐phase VO2, the visible light transmissivity of the Co‐doped VO2 is increased than that of pure VO2, which is beneficial to the application of VO2 film as visible windows. In addition, the absorptivity and reflectivity of Co‐doped R‐phase VO2 in the infrared light range are larger than those of M1‐phase VO2, indicating that the Co‐doped VO2 can block more infrared light at higher temperature to fulfill the purpose of lowering temperature. Overall, these results give new insights for the application of Co‐doped VO2 as a photoenergy material to regulate the room temperature.

Defect controlled diffusion of lithium ions in Mn doped V2O5 for potential applications as cathode material

With a motivation to unravel the effect of cation (Mn) doping-induced modifications in structure, charge transfer resistance, and Li-ion diffusion in V2O5 a systematic study using X-ray diffraction (XRD), Raman Spectroscopy and electrochemical impedance spectroscopy (EIS) has been employed using three electrodes configuration. Structural investigations using XRD suggest the selective diffusion of Mn ion towards the c-axis at a low doping percentage. Raman spectroscopy suggests the shift in 994 cm-1 modes which substantiates the uniaxial diffusion of Mn ions. Nyquist plots show that interfacial charge transfer resistance is highest for the lowest doping i.e., 1% Mn-doped V2O5 and exhibits the lowest diffusion coefficient as compared to other doped V2O5 samples. Specific capacitance calculated from cyclic voltammetry is found to be highest for the 4% Mn-doped V2O5 sample. Moreover, diffusion of Lithium ions improves with an increase in doping concentration due to higher concentration of defects as evident from Δd/d and Nelson–Riley factor (NRF) for pure V2O5 and Mn-doped V2O5.

Non-thermal to thermal electric field effects induced by DC and current pulses in pure and doped VO2 single crystals

Pure VO2, GexV1−xO2 (x < 0.2), and AlxV1−xO2 (x ≤ 0.02) exhibit above room temperature the well-known insulator-metal-transition (IMT) (at TIMT ≅ 340 K). In addition, AlxV1−xO2 exhibits an insulator-insulator-transition (IIT) at TIIT < TIMT. Both transitions can be induced either by external or by Joule heating. Both leave prominent marks on the I–V characteristics of the investigated samples, IIT at low currents and IMT at high currents. Reported herein is a comparative study of the I–V characteristics of needle-like pure and doped VO2 single crystals obtained with pulsed currents of various durations and with DC, in an attempt to separate thermal from non-thermal electric field effects. Identification of the Poole–Frenkel effect (a non-thermal electric field effect) in the I–V characteristics of the doped crystals may play an important role in a long-standing debate on the mechanism of IMT. Such an identification was obtained in this investigation for several Ge- and Al-doped VO2 crystals, so far only in narrow ranges of electric fields (<2000 V/cm) and pulse durations (≤1 ms) above which the non-linear conductivity of the crystals is dominated by Joule heating.

Engineered nitrogen doping on VO2(B) enables fast and reversible zinc-ion storage capability for aqueous zinc-ion batteries

Vanadium-based compounds with high theoretical capacities and relatively stable crystal structures are potential cathodes for aqueous zinc-ion batteries (AZIBs). Nevertheless, their low electronic conductivity and sluggish zinc-ion diffusion kinetics in the crystal lattice are greatly obstructing their practical application. Herein, a general and simple nitrogen doping strategy is proposed to construct nitrogen-doped VO2(B) nanobelts (denoted as VO2-N) by the ammonia heat treatment. Compared with pure VO2(B), VO2-N shows an expanded lattice, reduced grain size, and disordered structure, which facilitates ion transport, provides additional ion storage sites, and improves structural durability, thus presenting much-enhanced zinc-ion storage performance. Density functional theory calculations demonstrate that nitrogen doping in VO2(B) improves its electronic properties and reduces the zinc-ion diffusion barrier. The optimal VO2-N400 electrode exhibits a high specific capacity of 373.7 mA h g−1 after 100 cycles at 0.1 A g−1 and stable cycling performance after 2000 cycles at 5 A g−1. The zinc-ion storage mechanism of VO2-N is identified as a typical intercalation/de-intercalation process.

Sandwich-like MXene bridged heterostructure electrode enables anti-aggregation and superior storage for aqueous zinc-ion batteries

Severe aggregation and sluggish reaction kinetics are the main research challenges that impair the storage performance of cathode materials for aqueous zinc-ion batteries. In this work, we report the concept of sandwich-like Ti3C2Tx MXene-bridged VO2 heterostructure (VO2/Ti3C2Tx) design to simultaneously relieve the self-aggregation and boost the interfacial storage kinetics. When acting as cathode material, such VO2/Ti3C2Tx electrode can deliver a high specific capacity 415 mAh g−1 at 0.1 A g−1 after 110 cycles, as well as 338 mAh g−1 at 1 A g−1 after 300 cycles, much higher than that of the pure VO2 case. Moreover, such electrode also exhibits remarkably rate capability and cyclic stability, which can retain a specific capacity of 170 mAh g−1 at the high current density of 5 A g−1 after 1500 cycles. The superior storage performance should be mainly benefited from the mixed-dimensional heterogeneous engineering. In addition, the evolution of crystal structure and valence state of electrode upon cycling were investigated, thus a storage mechanism can be revealed. That is, single VO2 phase would be transformed into the VO2 and ZnxV2O5·nH2O mixed phase, with a highly reversible H+/Zn2+ insertion/extraction behavior. Such strategy proposed in this work can be also applied for other kinds of cathode materials and promoting the development of aqueous zinc-ion batteries.

Facile Synthesis and Single-Switch Antenna Application of Germanium-Doped Vanadium Dioxide

Materials that undergo a phase transition from metallic to insulating, or metal–insulator transition (MIT), materials have become widely popular for their potential in emerging technologies due to their drastic conductivity change upon transitioning. Notable among the MIT materials is vanadium dioxide (VO2), and ongoing efforts are focused on tuning its MIT phase transition temperature (TMIT). In this report, VO2 germanium-doped nanoparticles with various germanium dopant levels were synthesized via a hydrothermal route and used in a simple single-switch antenna. Powder X-ray diffraction (XRD) analysis shows a monoclinic phase (M1) for both the pure and Ge-doped VO2 nanomaterials at room temperature, with no change in the diffraction pattern in the Ge-doped samples at low doping percentages; the M1 phase for both pure and Ge-doped VO2 was further confirmed by Raman spectroscopy. Energy-dispersive X-ray spectroscopy (EDS) showed Ge uniformly distributed in the nanomaterials. The nanoparticles’ morphology, imaged by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), reveals a morphology change from nanoparticles to nanosheets with increased dopant concentration. Ge-doped VO2 nanoparticle dispersions were used to print a single switch in an antenna solely obtained through a facile printing process. A vector network analyzer used to characterize the antenna performance showed that the germanium doping successfully changed the transition temperature of the material, demonstrating the capability of controlling the antenna operation frequencies as a function of material doping. Density functional theory (DFT) shows that substituting Ge into a V site of the crystal structure distorts the lattice and reduces the band gap at high doping percentages. These results provide insight into the potential of smart switches fabricated from Ge-doped VO2.

Annealing Enhanced Phase Transition in VO2 Thin Films Deposited on Glass Substrates via Chemical Vapor Deposition

In this work, VO2 is deposited on borosilicate glass substrates via a single step Chemical Vapor Deposition (CVD). Though the structural characterization revealed the presence of phase pure polycrystalline VO2 in simple monoclinic crystal structure (P21/c), electrical measurements did not show a sharp transition. To understand the ambiguity, surface characterization was performed with X-ray Photoelectron Spectroscopy (XPS) on the as-deposited VO2 thin films. Vanadium was present in V3+, V4+ and V5+ states. Following these measurements, annealing was performed in ambience at 200 °C for 10 minutes. Subsequent electrical measurements showed an improved phase transition, enhanced by an order of magnitude. We attribute the enhancement in transition to annealing of oxygen vacancies present in VO2 thin films because of the deposition conditions. Decrease in oxygen vacancies was correlated with a decrease in the fraction of V3+ from XPS measurements. The sample annealed at 200°C for 10 minutes exhibited a higher resistance ratio (ΔA = 305) with an optimum hysteresis (4°C) and transition width(12°C), whereas the as-deposited sample exhibited a resistance ratio of ΔA = 32. The thermal treatment affected the characteristics of the transition. A narrow hysteresis of 4°C and a sharp transition width with a reasonable resistance ratio were obtained for the sample annealed at 200°C for 10 minutes. From this study, we understand that our synthesis of VO2 thin films via CVD is prone to be off-stoichiometric and therefore, contains defects such as oxygen vacancies. We could mitigate the effect of these vacancies and engineer the stoichiometry by performing a simple annealing which in turn improved the strength of the phase transition. Drawbacks such as a poor-quality transition, resulting from synthesis parameters can be mitigated if we understand the effect of vanadium and oxygen vacancies.

Organic Molecular Intercalated V3O7·H2O with High Operating Voltage for Long Cycle Life Aqueous Zn‐Ion Batteries

AbstractV3O7·H2O (VO) is an attractive cathode material for high‐capacity aqueous Zn‐ion batteries (AZIBs), but it is limited by slow ion mobility and low working platform voltage. Here, a 1,3‐propane diamine (DP)‐intercalated VO with nanoribbon‐assembled thorn flower‐like structure is fabricated by a facile hydrothermal method, noted as VO‐DP. The study shows that the zinc ion diffusion coefficient in VO‐DP (3.1 × 10−8 cm−2 s−1) is five orders of magnitude higher than that of a pure VO counterpart. Auxiliary density functional theory simulation shows that the embedded energy of zinc ions in VO‐DP significantly decreases from 0.24 to −2.5 eV, thus leading to excellent diffusion kinetics and superior rate performance. Benefiting from these unique properties, AZIBs composed of VO‐DP cathodes exhibit high operating voltage (0.89 V), remarkable capacities of 473 mA h g−1 at 0.05 A g−1, excellent rate capability (144 mA h g−1 at 10 A g−1) and long‐term cycling performance (73% capacity retention over 15 000 cycles at 10 A g−1).

A Facile Hydrothermal Synthesis of S-VO2-Cellulose Nanocomposite for Photocatalytic Degradation of Methylene Blue Dye

A novel UV-light-active MCC/S-VO2 photocatalyst was successfully synthesized by a simple and reliable hydrothermal route. XRD, FT-IR, Raman analysis, XPS, FE-SEM, EDX, TEM, DRS, and thermal analysis techniques were utilized for the characterization of the as-prepared photocatalysts. The photocatalytic activities of the V2O5, doped S-VO2, and MCC/S-VO2 nanostructures were investigated by monitoring the fading out of the methylene blue (MB) concentration under UV-light irradiation. The results revealed that the photocatalytic degradation of MB via MCC/S-VO2 was superior compared with that exhibited by pure V2O5 and doped S-VO2. It was found that 72.3% of MB (100 mL; 20 mg·L−1) was degraded after 6 h in contact with MCC/S-VO2. Interestingly, the photodegradation of MB dye was enhanced dramatically by adding H2O2, while 92.5% of MB was degraded within 55 min. The kinetic studies revealed that the MB degradation followed the pseudo-first-order model with a rate constant (kobs) of 3.9 × 10−2 min−1. The effect of several active species scavengers on the photocatalytic degradation process was investigated. The data exhibited that hydroxyl radicals and positive holes were the key active species during the degradation process. The stability and reusability of the as-prepared nanostructures were examined, and the results displayed its applicability for the removal of MB dye from aqueous media.