Cobalt Vanadium Oxide Research Articles

Rational H2O deintercalation effects on cobalt vanadium oxide hydrates for ultrafast energy storage devices

Pseudocapacitive materials have been employed in supercapacitors owing to their high specific capacitance. Nevertheless, high-level ultrafast capabilities are emphasized to overcome their rapid capacitance degradation under ultrafast-rate ion diffusion conditions. We demonstrated rational H2O deintercalation effects on cobalt vanadium oxide hydrate (CVOH) with increasing temperature. As the temperature increases to 200 ℃, CVOH undergoes a partial amorphization and exists in a mixed state of hydrated and dehydrated phases. As the temperature increases to 500 ℃, CVOH recrystallizes into the CVO phase through a complete deintercalation of H2O molecules. Such acceleration of H2O deintercalation leaves functionalized hydroxyl groups at the vertex oxygens, promoting binding affinity with electrolyte ions. Moreover, the crack propagation is accelerated on the CVO surface, resulting in a nano-split morphology from the surface to the interior of CVO particles that enlarges the contact area between the CVO and electrolyte. As the temperature increases to 800 ℃, H2O molecules re-intercalate and carbon bridged covalent bonds are formed between the CVO interlayers, resulting in particle coarsening. Owing to the rational H2O deintercalation effects on CVOH, CVO subjected to temperature at 500 ℃ maintained notable specific capacitance retention even under the ultrafast ion diffusion conditions (137.9 F/g at 500 mV/s).

Boron-doped carbon nano dot anchored thin film coating on cobalt vanadium oxide for ultrafast energy storage devices

Lithium-ion capacitors (LICs) with ultrafast rate capabilities are required to increase the applicability of rechargeable energy storage devices. Considering that the power density of an LIC is primarily determined by the anode properties, carbon coating onto the anode material is a promising method of accelerating electron transfer between particles and alleviating structural collapse during repeated charge–discharge cycles. In this study, a new coating configuration featuring a boron-doped carbon nano dot-anchored thin film on cobalt vanadium oxide (BC-CVO) was demonstrated. The coating morphology, wherein the carbon nano dots were connected by a thin carbon film, induced nano-scale surface roughness on CVO, expanding the contact area between the functional groups on the coating layer and electrolyte. The boron-doped carbon lattice structure provided ultrafast electron transfer inside the CVO particles, which allowed reversible electron transfer even under ultrafast charge–discharge cycles. This morphological and chemical combination significantly improved the ultrafast-rate capability of the LIC anodes (429.6 mAh/g at 4000 mA/g and 534.3 mAh/g after 1000 cycles at 2000 mAh/g) compared to that of bare CVO. Furthermore, an LIC full cell fabricated with a BC-CVO anode and an activated carbon cathode showed high energy and power densities.

Chemical synthesis of binder-free nanosheet-like cobalt vanadium oxide thin film electrodes for hybrid supercapacitor devices

Morphologically tuned (nanoflakes to nanosheets) CVO thin film electrodes prepared by CBD method as an emergent cathode for high-performing flexible hybrid supercapacitors.

Synergistic Co-N/V-N dual sites in N-doped Co3V2O8 nanosheets: pioneering high-efficiency bifunctional electrolysis for high-current water splitting

Developing affluent dual-metal active sites bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential to achieve large-scale water electrolysis, whereas still remains challenging. Herein, a novel nitrogen-doped cobalt-vanadium oxide with abundant Co-N and V-N dual active sites supported on nickel foam (N-Co3V2O8@NF) is constructed by a controllable impregnation-thermal nitridation strategy. The staggered nanosheet structure ensures optimal exposure of active sites. More importantly, N doping effectively regulates the electronic structure of the metal centers and induces the formation of Co-N and V-N dual active sites, which is conducive to improving the conductivity and hydrophilicity, thus synergistically enhancing the electrocatalytic efficiency. Consequently, the optimized N-Co3V2O8@NF exhibits prominent HER (63 mV@10 mA cm−2) and OER (256 mV@10 mA cm−2) activities, surpassing most contemporary bifunctional electrocatalysts. In practical application, the assembled N-Co3V2O8@NF(+/−) electrolyzer consistently achieved ultra-low cell voltages of 1.97 and 2.03 V at 500 and 1000 mA cm−2, respectively, superior to the benchmark RuO2@NF(+) || Pt/C@NF(–) and showcasing robust durability. This paves the way for its prospective adoption in industrial water electrolysis applications.

Growth Dynamics‐Dependent Chemical Approach to Accomplish Nanostructured Cobalt Vanadium Oxide Thin Film Electrodes with Controlled Surface Area for High‐Performance Solid‐State Hybrid Supercapacitor Devices

Rational designing of electrode materials having high surface area can accomplish the enhanced charge‐storing ability of the electrochemical energy storage devices. Therefore, the surface area of cobalt vanadium oxide (CVO) material is controlled by changing growth dynamics in successive ionic layer adsorption and reaction methods. Structural analysis confirms the formation of hydrous cobalt vanadium oxide nanoparticles (Co3V2O8⋅nH2O) thin film electrodes, and alteration in the surface area with change in growth dynamics is observed in Brunauer–Emmett–Teller analysis. The CVO1:1 thin film electrode prepared at optimal growth dynamics illustrates high specific capacitance (Cs) (capacity) of 793 F g−1 (396.7 C g−1) at 0.5 A g−1, respectively. Moreover, aqueous hybrid supercapacitor devices constructed using CVO1:1 as cathode exhibit high Cs of 133.5 F g−1 at 1.1 A g−1, specific energy (SE) of 47.7 Wh kg−1 with specific power (SP) of 0.90 kW kg−1. The solid‐state hybrid supercapacitor devices also offer high Cs of 102.9 F g−1 at 0.3 A g−1, SE of 36.6 Wh kg−1 at SP of 0.30 kW kg−1. In the SILAR approach, the dipping time plays a critical role in improving the surface area of the material and, consequently, electrochemical performance, as the current work amply indicates.

Bimetallic Co3V2O8 microstructure: A versatile bifunctional electrode for supercapacitor and electrocatalysis applications

Our research focuses on hydrothermally synthesizing a bimetallic cobalt vanadium oxide Co3V2O8 (CVO) microstructure, tailoring it for use in both bifunctional supercapacitor and electrolysis applications. We carefully optimized the molar ratio of Co and V to achieve a hexagonal microstructure for Co3V2O8, confirming it through field emission scanning electron microscopy (FESEM) and High resolution transmission electron microscopy (HRTEM) studies. The optimized electrode exhibited exceptional electrochemical characteristics when utilized in a supercapacitor application. It demonstrated a superior areal capacitance of 3.76 F/cm2 at a current density of 1 mA/cm2. Subsequently, we utilized the optimized electrode in an asymmetric supercapacitor configuration with activated carbon (AC), resulting in an areal capacitance of 126.1 mF/cm2 and an energy density of 29.6 mWh/cm2 at a power density of 2.6 W/cm2. To assess the stability of this configuration, we conducted 5000 cycles at 5 mA/cm2 and observed a retention rate of 87%. Additionally, we investigated the effectiveness of the optimized electrode as an electrocatalyst for water oxidation in a 1 M KOH electrolyte. In this setup, the CVO-4 electrode exhibited a lower overpotential of 226 mV for the hydrogen evolution reaction (HER) and a Tafel slope of 178 mV/dec for HER. Overall, our findings indicate that the as-prepared optimized electrode operates highly efficiently in bifunctional applications, positioning it as a promising candidate for energy conversion and storage operations.

Electronic interconnected CoV2O6 to induce boosted reaction kinetics for highly stable sodium-ion half/full batteries

It is one of the most common methods to improve the performance of sodium-ion batteries (SIBs) by improving the anodes. Vanadium metal oxides, including cobalt vanadate, are potential substitute as new anode material for SIBs due to their high theoretical capacity, variable crystal structure, synergistic effect and interfacial effect between multiple metals. However, although the specific capacity of such anode material is high, the irreversible capacity is often caused by the phase transition process in the charging and discharging process, which leads to a large amount of capacity attenuation. In addition, poor conductivity also limits the rate performance. In this work, bimetallic CoV2O6 (CVO) nanoparticles were modified by using two-dimensional (2D) reduced graphene oxide (rGO) with facile hydrothermal and heat treatment method. Via this construction, the CVO-rGO owns the advantage of porous electronic interconnected network structure, favoring the Na ions/electrons transportation, and suppressing the phase transition during Na+ (de)insertion. Benefiting from the built structure of CVO-rGO, it exhibits excellent performance in SIBs half and full cells. Specifically, CVO-rGO delivers stable 980 mAh g−1 at 0.1 A g−1 after 500 cycles and 98% capacity retention after 1000 cycles at 1 A g−1. Moreover, as anode in SIBs pouch cell, 84.7 mAh g−1 at 2 A g−1 after 1000 cycles (specific capacity retention: 90.3%) can be achieved. Such superior sodium storage of CVO-rGO is confirmed by reaction kinetics analysis and ex-situ XPS/Raman characterization. This work provides a reference for cobalt vanadium oxide to be used as anode material for high performance SIBs.

Cobalt oxide decked with inorganic-sulfur containing vanadium oxide for chromium(vi) reduction and UV-light-assisted methyl orange degradation

Inorganic sulfur containing cobalt vanadium oxide appeared as an efficient catalyst for Cr(vi) reduction and photo decomposition of methyl orange dye.

Fine-tune d-band center of cobalt vanadium oxide nanosheets by N-doping as a robust overall water splitting electrocatalyst

Developing high-activity, long-durability, and noble metal-free oxygen evolution (OER) and hydrogen evolution (HER) cocatalysts are the bottlenecks for efficient overall water splitting (OWS). Here, novel cobalt vanadium oxides doped by nitrogen were synthesized by nitriding Co2V2O7@NF precursor at 300–450 °C for OER and HER reactions. N-Co2V2O7@NF (350 °C) and N-Co2VO4/VO2@NF (400 °C) show remarkable OER and HER performance with overpotentials of 310 mV and 224 mV at high current density (100 mA cm−2). Besides, they also revealed long-term solid stability even after 170 h and 700 h of continuous performance. Furthermore, the N-Co2V2O7@NF(+)||N-Co2VO4/VO2@NF(–) OWS device possesses a cell voltage of 1.93 V at 500 mA cm−2 better than RuO2@NF(+)||Pt/C@NF(–) (2.02 V) and can operate for 60 h with almost no degradation. This extraordinary performance can be attributed to the nanosheet structure, which can maximize the exposure of active sites and accelerate the mass transfer. Moreover, density functional theory (DFT) calculations suggest that N-doping can fine-tune the d-band center and band gap to facilitate intermediate adsorption and electron motion. The method presented here can be applied in other novel N-doped electrocatalysts for the energy field.

Morphological Perspective on Energy Storage Behavior of Cobalt Vanadium Oxide

AbstractCurrently available graphitic‐based anodes for lithium‐ion storage do not meet the present‐day energy requirements. Concerning the upcoming energy demands, it is necessary to discover high‐performance anode materials that are suitable for lithium‐ion energy storage systems. Herein, a CoV2O6 (cobalt vanadium oxide, cobalt vanadate denoted as CV) anode material using a simple solvothermal technique is synthesized. Furthermore, the effects of modifying the molar concentration of the precursor materials are investigated. Interestingly, there is no change in the crystal structure, but there is a morphological evolution in the materials. Due to the morphological variations, the electrochemical performances vary significantly. Among the synthesized materials, the CV‐2 compound performs the best, exhibiting excellent performance for lithium‐ion batteries as an anode. At the end of 500 cycles, the material delivers a specific discharge capacity of 391.03 mAh g−1 with a current density of 500 mA g−1.

Carbon-free hydrated cobalt vanadium oxide as a promising anode for lithium-ion batteries

Recently, cobalt vanadium oxide (CoV2O6 or CVO), a transition metal-incorporated vanadium oxide, is proposed as a promising anode material for lithium-ion batteries (LIBs). Although introducing cobalt ions into vanadium oxide improves the electrical conductivity and structural stability, gradual structural deterioration compromises the long-term performance of CVO. In this study, hydrated CVO (CoV2O6·4H2O or CVO4H) is synthesized through a simple coprecipitation method, where Li-ion insertion/deinsertion is facilitated in the hydrated structure and the diffusion kinetics are enhanced relative to those of plain CVO. The presence of crystal water molecules in CVO4H increases the interplanar spacing of CVO, enhances the structural stability, and facilitates Li-ion diffusion. To systematically verify these characteristics, various electrochemical analyses (electrochemical impedance spectroscopy, galvanostatic intermittent titration technique, and cyclic voltammetry) are performed. As-synthesized CVO4H exhibits high electrochemical performance (1141/1157 and 1078/1090 mAh g−1 at current densities of 100 and 500 mA g−1 after 200 and 300 cycles) with stable Li-cycling life and good rate capability (capacity retention of ∼70% at 10 A g−1 relative to 0.1 A g−1), without added carbon in the active material. Consequently, CVO4H is a promising candidate material for next-generation LIB anodes.

Chirally modified cobalt-vanadate grafted on battery waste derived layered reduced graphene oxide for enantioselective photooxidation of 2-naphthol: Asymmetric induction through non-covalent interaction

The cobalt oxide-vanadium oxide (Co3O4-V2O5) combined with reduced graphene oxide (rGO) having band gap of ∼ 3.3 eV appeared as a suitable photocatalyst for selective oxidation of 2-naphthol to BINOL. C2-symmetric BINOL was achieved with good yield using hydrogen peroxide as the oxidant under UV-light irradiation. The same catalyst was chirally modified with cinchonidine and a newly synthesized chiral Schiff base ligand having a sigma-hole center. The strong interaction of the chiral modifiers with the cobalt-vanadium oxide was truly evident from various spectroscopic studies and DFT calculations. The chirally modified mixed metal oxide transformed the oxidative CC coupling reaction with high enantioselectivity. High enantiomeric excess upto 92 % of R-BINOL was obtained in acetonitrile solvent and hydrogen peroxide as the oxidant. A significant achievement was the formation of S-BINOL in the case of the cinchonidine modified catalyst and R-BINOL with the Schiff base ligand anchored chiral catalyst. The UV-light induced catalytic reaction was found to involve hydroxyl radical as the active reactive species. The spin trapping ESR and fluorescence experiment provided relevant evidence for the formation of such species through photodecomposition of hydrogen peroxide on the catalyst surface. The chiral induction to the resultant product was found to induce through supramolecular interaction like OH…π, H…Br interaction. The presence of sigma hole center was believed to play significant role in naphtholate ion recognition during the catalytic cycle.

Benchmarking of oxygen evolution catalysts on porous nickel supports

Summary Active and inexpensive oxygen evolution reaction (OER) electrocatalysts are needed for energy-efficient electrolysis applications. Objective comparison between OER catalysts has been blurred by the use of different supports and methods to evaluate performance. Here, we selected nine highly active transition-metal-based catalysts and described their synthesis, using a porous nickel foam and a new Ni-based dendritic material as the supports. We designed a standardized protocol to characterize and compare the catalysts in terms of structure, activity, density of active sites, and stability. NiFeSe- and CoFeSe-derived oxides showed the highest activities on our dendritic support, with low overpotentials of η100 ≈ 247 mV at 100 mA cm–2 in 1 M KOH. Stability evaluation showed no surface leaching for 8 h of electrolysis. This work highlights the most active anode materials and provides an easy way to increase the geometric current density of a catalyst by tuning the porosity of its support.

Co3+-O-V4+ cluster in CoVOx nanorods for efficient and stable electrochemical oxygen evolution

The development of cost-efficient and long-term stable catalysts for the oxygen evolution reaction (OER) is crucial to produce clean and sustainable H2 fuels from water. Here we demonstrate a cobalt vanadium oxide (CoVOx-300) working as such an efficient and durable electrocatalyst. Such an active catalyst is beneficial from the balanced Co3+-O-V4+ active species, which show the high surface Co3+ contents with matched V4+ generated by rapid heat treatment. The CoVOx-300 with highest Co3+/Co2+ ratio of 1.4 and corresponding highest V4+/ V5+ ratio of 1.7 exhibits remarkable OER activity with an overpotential of 330 mV at current density of 10 mA cm−2 (η10), a shallow Tafel slope of only 46 mV dec-1 and a current density of 100 mA cm−2 at an overpotential of 0.38 V vs RHE, which is 20 times higher than the active CoOx-300 and 1000 times higher than VOx-300. The catalyst also shows excellent stability for 10 h in alkaline media and a 40 % reduced activation energy to the counterpart, CoOx-300. The overpotential (η10) of CoVOx-300 also shows nearly 70 and 80 mV lower than the corresponding CoOx-300 and CoVOx catalysts, respectively and 20 % lower Tafel slope than the commercial benchmark catalyst RuO2. Thus, this study for the first time demonstrates that surface Co3+-O-V4+ species play a crucial role in improving electrocatalytic properties and stability for water oxidation reaction and the approaches allow the rational design and synthesis of other active transition metal oxides toward efficient OER activity.

Nickel, bismuth, and cobalt vanadium oxides for supercapacitor applications

In today's sophisticated world, the need for electric energy is increasing every day. Therefore, it is essential to manufacture electrode materials to store electric energy. Nickel, bismuth, and cobalt vanadium oxides are considered a member of a group of the best anodes in energy storage applications. In this study, three kinds of anode materials were analyzed for their better electrochemical behavior. Hydrothermal method was preferred for all the synthesis processes. The basic characterization studies such as X-ray diffraction, photoluminescence, Raman, and Fourier transform infrared confirmed the presence of nickel, bismuth, and cobalt vanadium oxides. The highest specific capacitance value of 426.11 F/g in cyclic voltammetry and 285.65 F/g in galvanostatic charge–discharge (GCD) measurements was obtained for the cobalt vanadium oxide samples. Furthermore, stability test in GCD showed its 83.64% capacitive retention over 5000 cycles at a high (5 mA/g) current density.

Integration of Binary Active Sites: Co3V2O8 as Polysulfide Traps and Catalysts for Lithium‐Sulfur Battery with Superior Cycling Stability

Lithium-sulfur (Li-S) batteries as a promising energy storage candidate have attracted attention due to their high energy density (2600 Wh kg-1 ). However, the serious shuttle effect caused by the dissolution of the lithium polysulfides (LiPS) in electrolyte significantly degrades their cycling life and rate performance. Herein, the "binary active sites" concept in a Li-S battery system via the design of a cobalt vanadium oxide (CVO) modified multifunctional separator is designed. In the case of CVO, active vanadium sites simultaneously anchor the LiPS through the chemical affinity and active cobalt sites can dominate a rapid kinetic conversion. Such a synergistic effect contributes to improving the utilization of sulfur in the electrochemical process for the enhanced electrochemical performance. As a result, the Li-S battery with the CVO modified separator possesses a high reversible capacity of 1585.5 mAh g-1 at 0.1 C and superior cycling stability with 0.012% capacity decay cycle-1 after 3000 cycles. More impressively, the assembled soft-packaged Li-S devices can exhibit the excellent stability under bending states. This binary active sites strategy provides a route to design the functional materials for modifying separators of Li-S batteries to improve the performance.

Enhanced Performance of Cobalt Vanadium Oxide upon Doping with Sulfur for Hybrid Supercapacitor Application in Aqueous and Non-Aqueous Medium

Cobalt Vanadate is one of the electroactive material for charge storage application due to earth abundant and environment friendly nature of cobalt. Further, vanadate system renders the material with multiple stable oxidation states, high electrical and ionic conductivity and high rate capability. However, the electrochemical performance of cobalt vanadate is limited either by high resistance of binder material or by the introduction of dead weight during electrode fabrication. This limitation can be circumvented by in-situ synthesis of cabalt vanadate onto current collector. Further, the doping of Sulfur in cobalt vanadate matrix significantly improves the electrochemical performance by improving the electrical conductivity. Herein, we report binder-free synthesis of Sulfur doped cobalt vanadate (S-Co3V2O8) nanosheet arrays on Ni foam using hydrothermal approach. The hydrothermally synthesized S-Co3V2O8 achieves nanosheet morphology with height and thickness of ~200 nm and ~10 nm, respectively wherein the size remains unchanged before and after the doping of sulfur in Co3V2O8. Further, the increased duration of hydrothermal reaction increases the thickness of synthesized nanosheet. We found that the electrochemical performance of Sulfur doped Co3V2O8 is ~25% more as compared to its undoped Co3V2O8 counterpart. In 6M KOH aqueous electrolyte, S-Co3V2O8 nanosheet array shows a specific capacity of 1476 C/g (3690 F/g) at 2 A/g. Further, the material exhibits enhanced rate capability and excellent capacity retention of 94.2% at 5 A/g specific current after 4000 cycles. The introduction of sulfur into vanadate matrix improves the electrochemical performance due to low electronegativity and large size of sulfur as compared to oxygen, which improves the charge transport properties, charge storage capacity with highly robust structure. An asymmetric supercapacitor device fabricated using S-Co3V2O8 as cathode and active carbon (AC) as anode shows specific capacity (or capacitance) of 174.5 C/g (or 116.33 F/g), energy density (36.4 Wh/kg) and power density (740 W/kg) at 2 A/g with 98.4% capacity retention after 4000 cycles. Further, the electrochemical performance of S-Co3V2O8 has been checked in 1M LiPF6 in non-aqueous electrolyte as Li-ion hybrid capacitor. The capacitor fabricated in a CR2032 coin cell exhibits specific capacity of 994 mAh/g with energy density of 695 W/kg at specific current of 1 A/g with good rate capability and 46.5% capacity retention after 100 cycles which makes it a potential candidate for robust high electrochemical energy storage system.

Effect of V2O5 addition on the structural and electrical properties of CoTio3

The present work shows the electric and dielectric study of ceramic composites made from cobalt titanate CoTiO3 (CoTO) and vanadium oxide (V2O5), by complex impedance spectroscopy. The CoTO was obtained by solid state reaction, the structural properties of the CoTO and the composites were discussed using X-ray diffraction and the electric and dielectric study to possible applications in radio frequency was made by measurements analysis of impedance spectroscopy at room temperature and with temperature variation. The analysis of the diffractogram of the CoTO synthesis showed the formation of only a single phase of CoTO without presence of spurious phases and analysis of the diffractograms of the composites after sintering process revealed the formation of a secondary phase [Co3V2O8]. The CoTO study showed the electrical and dielectric properties of impedance (Z′), dielectric permittivity (ε′), conductivity (σ) and activation energy (Ea), where they were studied in the frequency range from 1 Hz to 1 MHz and temperature (280–440 °C). The results indicate that CoTO electroceramics and ceramic composites presented a thermo-activated charge transfer process in the studied temperature range and the electrical results were modeled through equivalent circuit configurations composed of two and three associations in parallel with R-CPE, representing the electric responses of the grain, grain boundary and electrode effect presented by the studied electroceramics.

Correction to Amorphous Cobalt Vanadium Oxide as a Highly Active Electrocatalyst for Oxygen Evolution

Correction to Amorphous Cobalt Vanadium Oxide as a Highly Active Electrocatalyst for Oxygen Evolution

Facile synthesis of V-doped CoP nanoparticles as bifunctional electrocatalyst for efficient water splitting

Abstract Adjusting the intrinsic activity and conductivity of electrocatalysts may be a crucial way for excellent performance for water splitting. Herein, the rational design of vanadium element doped cobalt phosphide (V-doped CoP) nanoparticles has been investigated through a facile gaseous phosphorization using cobalt vanadium oxide or hydroxide (Co-V hydr(oxy)oxide) as precursor. The physical characterization shows that the homogeneous dispersion of V element on V-doped CoP nanoparticles have obtained, which may imply the enhanced electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The electrochemical measurements of the prepared V-doped CoP in alkaline electrolyte demonstrate the superior electrocatalytic activity for both HER (overpotential of 235 mV@10 mA cm−2) and OER (overpotential of 340 mV @10 mA cm−2). Further, V-doped CoP nanoparticles used as anode and cathode simultaneously in a cell require only 370 mV to achieve a current density of 10 mA cm−2. The outstanding electrocatalytic activity may be ascribed to the improved conductivity and intrinsic activity owing to phosphating and the doping of V element. In addition, the long-term stability of V-doped CoP has been obtained. Therefore, metal doping into transition metal-based phosphides may be a promising strategy for the remarkable bifunctional electrocatalyst for water splitting.