Vanadium Doping Research Articles

The electronic and geometric structure modifications of LiFePO4 with vanadium doping to achieve ultrafast discharging capability: The experimental and theoretical investigations

The electrochemical performance of vanadium doped LiFePO4 has been significantly enhanced as a result of improved electron conductivity and lithium ion diffusion capability. These findings enable the utilization of LiFePO4 to power electric vehicles with faster acceleration and reliable long-term cycling stability. Herein, optimization of the band structure of LiFePO4 with effective reduction of forbidden bandwidth after vanadium doping were demonstrated via theoretical calculation. Meanwhile, the decreased energy barrier of lithium ion diffusion enabled a fast transfer. The vanadium doped LiFePO4/C composites were synthesized via a solid state method with iron powder as direct precursor and realized 100% atomic efficiency as well as a higher tap density. The specific capacity and high rate performance were apparently ameliorated, 2% V-doped LiFe0.98V0.02PO4/C measured 141.4 mAh g−1 at 1 C and 93.9 mAh g−1 at 20 C, while the pristine counterpart only performed 130.1 mAh g−1 and 80.5 mAh g−1, respectively. Furthermore, the capacity retention rate after 500 cycles at 1 C was 98.3% for LiFe0.98V0.02PO4/C. Based on these DFT calculation and experimental results, the dramatic improvement of vanadium doped LiFePO4/C materials may provide novel opportunities for the evolution of olivine cathode materials and satisfy the demand in electric vehicles.

V-Doped Cu2 Se Hierarchical Nanotubes Enabling Flow-Cell CO2 Electroreduction to Ethanol with High Efficiency and Selectivity.

CO2 electrocatalytic reduction (CO2 ER) to multicarbon (C2+ ) products is heavily pursued because of their commercial values, and the efficiency and selectivity have both attracted tremendous attention. A flow-cell is a device configuration that can greatly enhance the conversion efficiency but requires catalysts to possess high electrical conductivity and gas permeability; meanwhile, the catalysts should enable the reaction pathway to specific products. Herein, it is reported that V-doped Cu2 Se nanotubes with a hierarchical structure can be perfectly compatible with flow-cells and fulfil such a task, achieving CO2 electroreduction to ethanol with high efficiency and selectivity. As revealed by the experimental characterization and theoretical calculation, the substitutional vanadium doping alters the local charge distribution of Cu2 Se and diversifies the active sites. The unique active sites promote the formation of bridge *COB and its further hydrogenation to *COH, and, as such, the subsequent coupling of *COH and *COL eventually generates ethanol. As a result, the optimal Cu1.22 V0.19 Se nanotubes can electrocatalyze CO2 to ethanol with a Faradaic efficiency of 68.3% and a partial current density of -207.9mA cm-2 for the single liquid product of ethanol at -0.8V in a flow-cell. This work provides insights into the materials design for steering the reaction pathway toward C2+ products, and opens an avenue for flow-cell CO2 ER toward a single C2+ liquid fuel.

Structural, optical, and magnetic properties of V-doped ZnO nanoparticles and the onset of ferromagnetic order

Pure and vanadium (V) doped ZnO nanoparticles (NPs) were successfully synthesized via a modified sol-gel method. The wurtzite crystal structure of ZnO remained intact with the vanadium doping concentrations under the present synthesis environment as confirmed by an array of advanced analytical techniques; such as Rietveld refined X-ray diffraction (XRD) pattern, as well as bond valence sum (BVS) analysis. SEM and TEM techniques were used to examine the morphology of the samples. UV-Vis-NIR spectra showed an absorption band in the UV range with reduction in the band gap from 3.23 eV to 3.20 eV when V content increases. Photoluminescence (PL) shows that doping with V causes the creation of some defects in the band gap of ZnO. The energy position of the obtained PL emission introduces a blue shift when the measurement temperature increases. The M-T curve is successfully fitted using both three dimensional (3D) spin wave model and Curie-Weiss law which attests to the mixed state existence of ferromagnetic (FM) and paramagnetic (PM) phases. The electron paramagnetic resonance (EPR) analysis supports the XRD results and provides evidence of oxygen vacancies (VO). Magnetic interaction is quantitatively studied and explained by polaronic percolation of bound magnetic polarons (BMP) produced by VO defects.

Vanadium doped OMS-2 catalysts for one-pot synthesis of imine from benzyl alcohol and aniline: Effects of vanadium content and precursor

A series of vanadium doped cryptomelane-type manganese oxide (V-OMS-2) catalysts were prepared by a simple, low-cost reflux method, and investigated for one-pot imine synthesis from oxidative coupling of benzyl alcohol and aniline with air. The physicochemical properties of the V-OMS-2 catalysts were characterized by various techniques including XRD, BET, SEM, TEM, XPS, H2-TPR and NH3-TPD. It was found that the surface area, Lewis acid sites, the amount of Mn3+ component and active surface oxygen species were much improved with vanadium doping. Consequently, the activity of V-OMS-2 catalyst for oxidative coupling of benzyl alcohol and aniline to imine was enhanced. The highest conversion and the imine yield were obtained over the 3 mol% V-OMS-2 catalyst, being ∼99% and 92%, respectively. Higher vanadium doping (≥ 6 mol%), however, hindered the preservation of OMS-2 crystal structure, leading to a drop in the catalytic performance. The high specific surface area was suggested to be the key contributor to the high catalytic activity of 3% V-OMS-2(1) catalyst. Among the vanadium precursors studied, the catalyst prepared with vanadium pentoxide exhibited a much higher catalytic activity, which can be attributed to its larger surface area, unique mesoporous structure, increased Lewis acid sites and more readily available surface oxygen species. In addition, the stability and recyclability of the catalyst were also studied, and the reaction mechanism was discussed.

Doping of Vanadium into Bismuth Oxide Nanoparticles for Electrocatalytic CO2 Reduction

Doping of Vanadium into Bismuth Oxide Nanoparticles for Electrocatalytic CO₂ Reduction

Controllable substitutional vanadium doping in wafer-scale molybdenum disulfide films

Controllable substitutional vanadium doping in wafer-scale molybdenum disulfide films

Vanadium-Doped FeBP Microsphere Croissant for Significantly Enhanced Bi-Functional HER and OER Electrocatalyst.

Ultra-fine hydrogen produced by electrochemical water splitting without carbon emission is a high-density energy carrier, which could gradually substitute the usage of traditional fossil fuels. The development of high-performance electrocatalysts at affordable costs is one of the major research priorities in order to achieve the large-scale implementation of a green hydrogen supply chain. In this work, the development of a vanadium-doped FeBP (V-FeBP) microsphere croissant (MSC) electrocatalyst is demonstrated to exhibit efficient bi-functional water splitting for the first time. The FeBP MSC electrode is synthesized by a hydrothermal approach along with the systematic control of growth parameters such as precursor concentration, reaction duration, reaction temperature and post-annealing, etc. Then, the heteroatom doping of vanadium is performed on the best FeBP MSC by a simple soaking approach. The best optimized V-FeBP MSC demonstrates the low HER and OER overpotentials of 52 and 180 mV at 50 mA/cm2 in 1 M KOH in a three-electrode system. In addition, the two-electrode system, i.e., V-FeBP || V-FeBP, demonstrates a comparable water-splitting performance to the benchmark electrodes of Pt/C || RuO2 in 1 M KOH. Similarly, exceptional performance is also observed in natural sea water. The 3D MSC flower-like structure provides a very high surface area that favors rapid mass/electron-transport pathways, which improves the electrocatalytic activity. Further, the V-FeBP electrode is examined in different pH solutions and in terms of its stability under industrial operational conditions at 60 °C in 6 M KOH, and it shows excellent stability.

A vanadium-doped La0.5Sr0.5FeO3-δ perovskite as a promising anode of direct carbon solid oxide fuel cells for brown coal utilization

Direct carbon solid oxide fuel cell (DC-SOFC) is a potential and prospective technology to convert chemical energy from real-world coal fuels into electricity with environment friendliness and high efficiency. However, the limited three-phase reaction boundaries and the challenge of sluggish carbon oxidation activity have always hindered the development and application of DC-SOFCs. On this account, here vanadium-doped B-site-deficient La0.5Sr0.5FeO3-δ (LSFVx, x = 0, 0.05, 0.10, 0.15) perovskite materials are synthesized and developed as the anode of DC-SOFCs for brown coal utilization. The best electrochemical performance at 850 ℃ belongs to the LSFV0.1 cell, delivering a maximum power density of 249 mW cm−2, and the lowest polarization resistance of 0.37 Ω cm2,along with the longest discharging time up to 8.65 h. Compared with the pure LSF, the electrochemical performances of all perovskites doped with vanadium have been greatly promoted, demonstrating that the doping of vanadium can effectively expand the three-phase reaction boundaries of the cell, thus enhance the catalytic activity due to the promotion of oxygen deficiencies and tailing of electronic structures.

Quasi‐Continuous Tuning of Carrier Polarity in Monolayered Molybdenum Dichalcogenides through Substitutional Vanadium Doping

AbstractSemiconducting 2D transition metal dichalcogenides (2D TMDs) with tunable electronic properties are a fundamental prerequisite for the development of next generation advanced electronic/optoelectronic devices. However, controllable and quasi‐continuous tuning carrier polarity of monolayered MoS2 ranging from intrinsic n‐type to p‐type via ambipolarity still remains a challenge. Herein, quasi‐continuous tailoring of carrier polarity of monolayered MoS2 through substitutional doping of molybdenum (Mo) with vanadium (V) atoms is presented. Atomic distribution in real space characterized by spherical aberration‐corrected scanning transmission electron microscopy (Cs‐STEM) reveals that the V atoms randomly substitute Mo in monolayered MoS2, and its doping concentration can be tuned in a wide range from 0.7 to ≈10 at.%. Electrical measurements confirm that the carrier polarity of the monolayered MoS2 can be tuned from intrinsic n‐type to p‐type via ambipolarity depending on the V doping degree, consistent with the density functional theory calculations. Moreover, this doping strategy is demonstrated to extend to other monolayered 2D TMDs by using MoSe2 as a model material, owing to a good universality.

Accelerating electrochemical hydrogen production on binder-free electrodeposited V- doped Ni-Mo-P nanospheres

• V-doped Ni-Mo-P nanostructure was fabricated using electrochemical deposition. • Fabricated electrode exhibited outstanding electrocatalytic HER and OER activity. • Synergistic effect and high surface area was main reason for excellent performance. • Deposited electrode represented outstanding electrocatalytic durability. The emergence and fabrication of cost-effective and active electrodes in the overall water splitting process are one of the most critical challenges for hydrogen production. Here, firstly Ni-P electrodes were generated at different scan rates using the electrochemical deposition method, and then molybdenum was doped in Ni-P structure using the same method and vanadium using hydrothermal deposition method, and V-doped Ni-Mo-P electrode was generated. It was revealed that the synthesized electrode displays outstanding electrochemical properties for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For reaching a current density of 10 mA cm −2 , the optimum sample needed only 65 mV in the HER process and only 261 mV of overpotential in the OER process. In addition, the electrocatalytic stability investigation disclosed that this electrode had excellent durability at the 100 mA cm −2 in HER and OER process after 10 h of electrolysis in which only less than 2 % increase in overpotential was observed, which indicates excellent electrocatalytic stability. Such outstanding electrocatalytic properties were mainly because of increasing the active surface area and the synergistic effect due to doping of molybdenum and vanadium in the electrode structure .

Basal Plane Activation of MoS2 by the Substitutional Doping of Vanadium toward Electrocatalytic Hydrogen Generation

Basal Plane Activation of MoS₂ by the Substitutional Doping of Vanadium toward Electrocatalytic Hydrogen Generation

Improving the Electrocatalytic Activity of a Nickel-Organic Framework toward the Oxygen Evolution Reaction through Vanadium Doping.

Metal-organic frameworks (MOFs) have been considered as potential oxygen evolution reaction (OER) electrocatalysts owning to their ultra-thin structure, adjustable composition, high surface area, and high porosity. Here, we designed and fabricated a vanadium-doped nickel organic framework (V1-x -Nix MOF) system by using a facile two-step solvothermal method on nickel foam (NF). The doping of vanadium remarkably elevates the OER activity of V1-x -Nix MOF, thus demonstrating better performance than the corresponding single metallic Ni-MOF, NiV-MOF and RuO2 catalysts at high current density (>400 mA cm-2 ). V0.09 -Ni0.91 MOF/NF provides a low overpotential of 235 mV and a small Tafel slope of 30.3 mV dec-1 at a current density of 10 mA cm-2 . More importantly, a water-splitting device assembled with Pt/C/NF and V0.09 -Ni0.91 MOF/NF as cathode and anode yielded a cell voltage of 1.96 V@1000 mA cm-2 , thereby outperforming the-state-of-the-art RuO2 (+) ||Pt/C(-) . Our work sheds new insight on preparing stable, efficient OER electrocatalysts and a promising method for designing various MOF-based materials.

Synthesis, characterization, and photocatalytic application of V/ZnO-ZrO<sub>2</sub>

In this work we report the synthesis of ZnO-ZrO2 and vanadium doped ZnO-ZrO2 (V/ZnO-ZrO2) nanocomposite materials by a sol–gel processing technique. The molar ratio between ZnO and ZrO2 is 3 : 4, the molar percentage of vanadium doped (relative to ZrO2) varies from 3% to 9%. The obtained materials were characterized by XRD, SEM, UV-Vis, BET, EDX. XRD data identified phase of the ZnO and phase of ZrO2 in all obtained samples. The average crystallite size of the samples was between 18 to 20 nm. UV-Vis spectra showed that the band gap energy decreased by the doping of Vanadium. The EDX result of ZZV347S indicated doping efficiency equal 91,29%. The photocatalytic activities of nanocompsite materials were evaluated by the photocatalytic degradation of phenol under UV light. The highest photocatalytic efficiency for phenol degradation was achieved through ZZV343S catalyst after 180 minutes.

A new insight characterization analysis and two photon absorption behaviour of pure and doped vanadium oxide

Pure and (7, 12 and 17 wt%) fluorine doped vanadium oxide was synthesized by simple one-step hydrothermal treatment. XRD confirms the formation of mixed phases of orthorhombic V2O5 and monoclinic V3O7. Increasing trend in crystallite size with fluorine content was observed due to the replacement of fluorine in oxygen sites of vanadium oxide lattices. FESEM and EDX analysis ascertains the formation of platelets with uniform doping of vanadium pentoxide. Both samples exhibit maximum absorption in UV region and the band gap slightly decreases due to fluorine doping. The impedance characterization signal was analysed in the specific frequency range from 100 KHz to 0.01 Hz. The dielectric parameters are dependent on the frequency and different dopant ratios. The dielectric dispersion signal shows to decrease in dielectric values as frequency increases. The microstructure properties are successfully studied using Raman and FTIR spectroscopy. Under Q-switched frequency doubled Nd:YAG laser (532 nm, 9 ns, 100 μJ) excitation, both pure and fluorine doped vanadium oxide exhibit reverse saturable absorption. 17 wt% F doped V2O5 possesses a higher 2PA coefficient which arises mainly from the synergetic effect from the contribution of nanoplatelet morphology and incorporation of F as decorative element upon V2O5. Also two-photon absorption induced optical limiting action was witnessed and this makes them potential candidate for fabrication of laser safety googles.

Growth of vanadium doped semi-insulating 4H-SiC epilayer with ultrahigh-resistivity

4H-SiC epitaxial layers with ultrahigh resistivity of over 1010 Ω cm were successfully grown by using a hot wall chemical vapor deposition system with vanadium doping. The resistivity of the vanadium doped epilayer was found to be strongly dependent on the types of dopant impurities. The resistivity of n-type-based vanadium doped semi-insulating 4H-SiC epilayers showed stronger dependence on vanadium incorporation than that of p-type-based epilayers. This means that the carrier trap characteristics of vanadium atoms may differ with respect to electrons and holes. As the result, an ultrahigh resistivity of over 1010 Ω cm was realized on an n-type-based 4H-SiC epilayer with vanadium doping.

Effects of vanadium doping on the charge ordering and low-temperature spin-glass phase in Pr0.45Ca0.55MnO3

We report structural, magnetic, and dielectric properties of the Pr0.45Ca0.55Mn1-xVxO3 (x = 0.05 and 0.1) polycrystalline compounds, prepared by solid state reaction method. Pnma space group and orthorhombic crystal structure of the compounds are confirmed by the Rietveld refinement of X-ray diffraction data. Magnetic study reveals a multiple-phase-separated metastable magnetic behavior with charge ordered phase followed by a spin-glass state at the low-temperature region. For a single change of vanadium content from x = 0.05–0.1, the charge ordering temperature decreases from 245 K to 239 K, the antiferromagnetic ordering temperature decreases from 131 K to 127 K, and the ferromagnetic cluster-glass ordering temperature increases from 41 K to 44 K. This indicates the weakening of charge ordering strength and development of ferromagnetic components in the antiferromagnetic background, which is also confirmed by isothermal hysteresis. Colossal dielectric constant is observed in both samples. In the measured temperature range, an implication of a ferroelectric phase transition around 253 K is observed in Pr0.45Ca0.55Mn0.90V0.10O3 compound. The calculated results indicate that the low-temperature relaxation follows variable range hopping behavior, whereas the high-temperature one takes place according to the Arrhenius model. The fitting parameters ascribe the low-temperature relaxation process to the hopping of polaron charge carriers at localized sites, whereas the high-temperature relaxation is related to Maxwell-Wagner relaxation, caused by blocking of charge carriers at grain boundaries.

Doping-dependent nucleation of basal plane dislocations in 4H-SiC

Basal plane dislocations (BPDs) are one of the most harmful dislocations in 4H silicon carbide (4H-SiC). Understanding the nucleation of BPDs is the basis of reducing the density of BPDs in 4H-SiC. In this work, we investigate the nucleation mechanism of BPDs, as well as the effect of doping on the nucleation of BPDs in 4H-SiC using nanoindentation. It is found that the shear stress plays a dominant role in the nucleation of BPDs in undoped 4H-SiC. This indicates that the shear component of the thermal stress during the growth of 4H-SiC single crystals and that of the mechanical stress during the processing of 4H-SiC wafers both give rise to the nucleation of BPDs. Nitrogen (N) doping is found to facilitate the nucleation of BPDs and decrease the shear stress required for the nucleation of BPDs. In contrast, vanadium (V) doping hinders the nucleation of BPDs, which promotes the polymorph transition from 4H-SiC to 3C-SiC.

Non-oxidative Propane Dehydrogenation over Vanadium Doped Graphitic Carbon Nitride Catalysts

Non-oxidative Propane Dehydrogenation over Vanadium Doped Graphitic Carbon Nitride Catalysts

Theoretical Investigations of Electronic and Optical Properties of Vanadium Doped Wurtzite Zinc Oxide from First Principle Calculation Method

In this study lattice parameters, band structure, and optical characteristics of pure and V-doped ZnO are examined by employing (USP) and (GGA) with the assistance of First-principles calculation (FPC) derived from (DFT). The measurements are performed in the supercell geometry that were optimized. GGA+U, the geometrical structures of all models, are utilized to compute the amount of energy after optimizing all parameters in the models. The volume of the doped system grows as the content of the dopant V is increased. Pure and V-doped ZnO are investigated for band structure and energy bandgaps using the Monkhorst–Pack scheme's k-point sampling techniques in the Brillouin zone (G-A-H-K-G-M-L-H). In the presence of high V content, the bandgap energy decreases from 3.331 to 2.043 eV as seen by the band diagram. PDOS diagram was utilized to get the insight of the electronic structure of the atoms and the amount to which all energy bands contribute to a particular orbit of the atoms. As the V content grew, so did the PDOS for all of the states. The manipulation of bandgaps was carried out in a way that narrowing the bandgaps occurs, resulting in a redshift of the absorption spectrum in the IR region. At lower photon energies, the imaginary and real parts dielectric functions have increased. The effectiveness of V atoms on transmissivity especially in the low energy region of the V-doped ZnO perovskite has been verified compared to the other theoretical results.

Vanadium Incorporation in 3C-SiC Epilayers and its Consequences for Electrical Properties of 3C-SiC Material

The present experimental study demonstrates the feasibility of Vanadium doping of 3CSiC hetero-epitaxial material. Some of Vanadium incorporation trends as well as the influence of Vanadium doping on 3C-SiC resistivity are observed.