Synthesis Of Transition Metal Oxides Research Articles

Deep eutectic solvent-assisted synthesis of transition metal oxide and its integration into polymer matrix for supercapacitor

Transition metal oxide-based materials continue to attract interest in energy and environmental applications due to their unique characteristics. However, their integration with polymers needs to be explored to achieve enhanced capacitance values. To address this issue, two step strategy is utilized wherein the first step involves preparation of a pristine transition metal oxide (Co3O4) by a deep eutectic solvent (DES) consisting of choline chloride and hydrogen donor ethyelene glycol in the ratio of 2:1. In the second step the environmentally friendly high energy ball milling is utilized with strong mechanical forces producing desired poly-3-dodecyl thiophene (P3DDT)-wrapped cobalt oxide (Co3O4). The structural and morphological properties of the prepared Co3O4 and its composite (P3DDT-Co3O4) are determined by aid of X-ray diffraction (XRD) studies, Field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS). The synthesized Co3O4 exhibited petal-like morphology, whereas in P3DDT-Co3O4 the polymer appears to be completely wrapped on transition metal oxide. The electrochemical characteristics of electrodes were studied. The P3DDT-Co3O4 exhibited higher specific capacitance (294F/g) than pristine Co3O4 (174F/g) at a current density of 1 A/g and its retention capacity increased (96%) and then decreased (93%) over 5000 cycles in a three-electrode cell assembly. The lowest capacitance (136F/g) was obtained for P3DDT. Experimental results demonstrate that the design is suitable for upgrading favorably active electrochemical spots in Co3O4 during the incorporation of P3DDT by the ball-milling procedure, showing outstanding performance in energy-storage applications.

Cold plasma activated Ni0/Ni2+ interface catalysts for efficient electrocatalytic methane oxidation to low-carbon alcohols

To stabilize Ni0/Ni2+ during the CH4OR process, herein, we have successfully developed a general oxidation strategy for the direct synthesis of transition metal oxides by O2 cold plasma treatment of Ni0, including NiO, to generate a Ni0/Ni2+-on-Cu interface.

A Review on Microwave Assisted Synthesis of Transition Metal Oxides and their Potent Application as Supercapacitors

AbstractPreparation of transition metal oxides and mixed metal oxides via a microwave‐assisted method that permits processes to be completed in a quicker reaction time with the formation of homogenous and well‐dispersed nanoparticles. Recently, due to the environmentally friendly nature of this technique, it has become an important approach to green chemistry. The major advantage of microwave‐assisted synthesis includes clean, fast, efficient, less time‐consuming, highly accelerated rate, high yield, and an economic method. In this review, we have discussed the process of microwave synthesis and also compared this with other synthetic methods. A discussion of transition metal oxides in groups was performed where we have discussed their synthetic route and reaction conditions along with the effect on morphology and other properties. Additionally, the application of transition metal oxides as supercapacitors was also discussed. Since then, researchers have gained a lot of interest in transition metal oxides as energy storage devices due to their low‐cost, energy efficient, long cycle life, and improved electrical, thermal, and chemical stability, variable oxidation states and excellent redox properties. However, they cannot meet the need for high‐performance energy devices due to their low conductivity.

A novel template processing method for preparing spinel oxides with various morphologies to assemble high-performance supercapacitors

With the increasing complexity of the application scenarios of nanomaterials, transition metal oxides (TMOs) have shown excellent development potential. However, the synthesis of TMOs with customized morphologies for different application environments is still challenging. Herein, an acid-alcohol treatment based on the different intensities of the redox reactions between nitric acid and ethanol was developed to prepare different carbon templates. Through impregnation and annealing of the templates, NiCo2O4 (NCO) materials with hollow spherical (NCO-HS), multi-shell spherical (NCO-MS), and lamellar (NCO-L) morphologies were obtained. The characterization was performed through different analytical methods, which revealed various structures, morphologies, and surface chemistry of the materials. NCO-HS, NCO-MS, and NCO-L were tested for supercapacitor applications and exhibited a high specific capacitance of 402.6, 1037.1, and 531.4 F g−1, respectively. Overall, the proposed method can be used to customize the synthesis of functional materials with various morphologies for future advanced applications.

Facile synthesis of transition metal oxide SnO2/MnO2 hierarchical nanostructure: As an efficient electrocatalyst for robust oxygen evolution reaction

One of main areas of the current research into the electrochemical water oxidation mechanism for the production of clean energy is the production of less cost, more efficient, and protracted consistent electrocatalyst. For oxygen evolution reaction (OER) in a basic electrolyte, cost effective metal oxides based have proven more advantageous than other media. As their strong electrical characteristics and the promised synergistic result, the MnO2-based composites are the more appealing components for the water oxidation reaction among these transition metal oxides. This is because the materials' surface properties, will be drastically altered to support electrocatalysis. Herein, we report the synthesis of SnO2/MnO2 nanocomposite via a hydrothermal approach employed toward the OER process using Cu foam as a conductive substrate. The vertically aligned irregularly shaped nanocube tin oxide and nanosphere of manganese oxide are connected to create hierarchical nanostructures. The impact of bimetallic oxide for OER performance has been thoroughly investigated. For OER in alkaline atmosphere, SnO2/MnO2 nanocomposite confirms Tafel slope mechanism of 38.9 mV dec−1 and less overpotential (η) of 360 mV @ 10 mA cm−2. In order to enhance OER commotion, this effort validates the value of nanocrystalline catalysts with logically controlled hierarchical designs.

The valance state of vanadium-key factor in the flexibility of potassium vanadates structure as cathode materials in Li-ion batteries

Potassium hexavanadate (K2V6O16·nH2O) nanobelts have been synthesized by the LPE-IonEx method, which is dedicated to synthesis of transition metal oxide bronzes with controlled morphology and structure. The electrochemical performance of K2V6O16·nH2O as a cathode material for lithium-ion batteries has been evaluated. The KVO nanobelts demonstrated a high discharge capacity of 260 mAh g−1, and long-term cyclic stability up to 100 cycles at 1 A g−1. The effect of the vanadium valence state and unusual construction of the nanobelts, composed of crystalline and amorphous domains arranged alternately were also discussed in this work. The ex-situ measurements of discharged electrode materials by XRD, MP-AES, XAS and XPS show that during the subsequent charge/discharge cycle the potassium in the K2V6O16·nH2O structure are replacing by lithium. The structural stability of the potassium hexavandate during cycling depends on the initial vanadium valence state on the sample surface and the presence of the “fringe free” domains in the K2V6O16·nH2O nanobelts.

Enhanced Electrocatalysts Fabricated via Quenched Ultrafast Sintering: Physicochemical Properties and Water Oxidation Applications

AbstractThe synthesis of transition metal oxides is typically time‐ and energy‐consuming. Recently, fast sintering methods have demonstrated great potential in reducing ceramic sintering time and energy use, improving the commercial prospects of these materials. In this article, a quenched ultrafast high‐temperature sintering (qUHS) technique is developed to sinter metastable brownmillerite SrCoO2.5 (SCO) in less than a minute. Surprisingly, SCO fabricated by qUHS shows higher activity for the oxygen evolution reaction (OER) than solid‐state‐reaction‐synthesized SCO. Comparing samples produced by these two techniques, the increased OER performance of SCO qUHS is likely due to the synergistic combination of surface Co chemical state, higher mesoporosity, and enhanced hydroxyl ion (OH–) adsorption. This work demonstrates the potential of qUHS for producing high‐performance electrocatalysts and provides detailed insights into the impact of ultrafast sintering on the materials’ physical properties and electrocatalytic activity.

Structural and Morphological Studies of V2O5/MWCNTs and ZrO2/MWCNTs Composites as Photocatalysts

The present study outlines the synthesis of transition metal oxide- (TMO-) multiwall carbon nanotubes- (MWCNTs-) based composites for photocatalytic application. MWCNTs were functionalized/purified by treating with H2SO4 and HNO3 to improve their dispersion in water. The TMOs (ZrO2, V2O5) were decorated on MWCNTs by the hydrothermal method to yield V2O5/MWCNTs and ZrO2/MWCNTs composites. Subsequently, these composites were characterized for their structural/morphological studies by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Photocatalytic activities of TMO/MWCNTs composites were investigated by degradation phenomenon of methylene blue (MB) dye in aqueous solution. It was observed that the prepared composites best performed in the presence of H2O2 under ultraviolet irradiation. The maximum observed degradation efficiencies for ZrO2/MWCNTs and V2O5/MWCNTs were 49% and 96%, respectively.

Synthesis of transition metal oxide incorporated MOF-5 and NH2-MOF-5 as efficient photoanode for oxygen evolution reaction

Synthesis of transition metal oxide incorporated MOF-5 and NH2-MOF-5 as efficient photoanode for oxygen evolution reaction

Low-temperature synthesis of sea urchin-like Co-Ni oxide on graphene oxide for supercapacitor electrodes

Transition metal oxides are ideal electrode materials used for supercapacitors. However, the synthesis of transition metal oxides suffers from drawbacks such as high reaction temperature and energy consumption. Herein, we report the synthesis of sea urchin-like Co3O4-NiO composites supported on graphene oxide (GO) using a hydrothermal method followed by calcination with a low temperature (250 °C). The obtained Co3O4-NiO/GO composite demonstrates a high specific capacitance of 883 F g−1 at 1 A g−1. Furthermore, upon coupling with an activated carbon (AC) positive electrode, an asymmetric cell of Co3O4-NiO/GO//AC exhibits outstanding stability reflected by the high capacitance retention of 82% at a high current density of 10 A g−1. The excellent electrochemical properties of the composite may be attributed to the good synergistic effect of Co3O4 and NiO, as well as the assembly of Co3O4 and NiO into a sea urchin structure, which results in increased electron conductivity and more exposed electroactive sites leading to the promotion of the Faradaic redox process.

Facile Synthesis of NiO/Nitrogen-doped Reduced Graphene Oxide Nanocomposites for the Application in Supercapacitors

Coupling the merits of transition metal-oxide with graphene for the application in energy-storage has received great attention. Herein, NiO loaded nitrogen-doped reduced graphene oxide (NiO/N-rGO) composites were synthesized through facile and effective hydrothermal method. The as-synthesized NiO/N-rGO were designed as high effective electrode materials for the application in a supercapacitor. Electrochemical performance of the as-synthesized NiO/N-rGO composites displays that the specific capacitances reach up to 233 F g–1 at 1 A g–1 in 6 M KOH. This paper may support a facile method for the synthesis of transition metal oxide and graphene composites which may be applied as electrode materials for supercapacitors.

In-situ phase transition to form porous h-MoO3@C nanofibers with high stability for Li+/Na+ storage

Porous h-MoO3@C nanofibers with a large specific surface area of 400.2 m2 g−1 were successfully synthesized with hot HNO3 oxidizing MoO2@C nanofibers without obvious damage to carbon shells. As anodes for lithium ion batteries (LIBs), the porous h-MoO3@C nanofibers electrodes show a reversible capacity of 302.9 mA h g−1 at 2 A g−1 after 500 cycles. As anodes for sodium ion batteries (SIBs), they also can deliver a good rate capacity and hold 108.9 mA h g−1 at 2 A g−1 after 500 cycles, even can have 91 mA h g−1 at 5 A g−1 after 1200 cycles. The excellent electrochemical performances of the porous h-MoO3@C nanofibers are attributed to the unique structure which not only can maintain the structure stability but also provide enough active sites for Li+/Na+. At the same time, the tunnel structure of h-MoO3 can lead to separate electron–hole and offer a great deal of special positions for cation (Li+/Na+) insertion/extraction. The present method may be helpful for the synthesis of transition metal oxides (TMOs)-carbon composites with high valence metal atoms in the field of batteries and catalysts.

Molten Salt Synthesis of Transition Metal Oxides doped Li4Ti5O12 as Anode Material of Li-Ion Battery

Co3O4 doped Li4Ti5O12 compounds with protuberant nanoparticles are synthesized by molten salts method. Co3O4 doping greatly decreases particle size of Li4Ti5O12. Combining with the result of Fe2O3 doped Li4Ti5O12 and as interstitial and substitutional atoms, transition metal atoms homogenously distribute in the crystal lattice of Li4Ti5O12 and do not change the cubic spinel structure of Li4Ti5O12. As the substitutional atoms, the mixed valence of Co3+ and Co2+ co-exists in Li4Ti5O12 causing O32e or Li8a,16d vacant sites thereby improving the electronic conductivity of Li4Ti5O12. The doped Li4Ti5O12 exhibits a large first discharge capacity (173.5 mAh g-1) at 0.2 C rate, 144.8 mAh g-1 at 1 C rate with the capacity loss of 8.8% after 100 charge/discharge cycles and 106 mAh g-1 at 10 C. EIS analysis indicates the doped Li4Ti5O12 electrode exhibits lower charge transfer resistance and lithium ions diffusion resistance, as optimized amounts of Co3O4 produces appropriate lattice distortion and interstitial atoms in Li4Ti5O12.

WO3-x Nanoplates Grown on Carbon Nanofibers for an Efficient Electrocatalytic Hydrogen Evolution Reaction.

The search for non-noble metal catalysts with high activity for the hydrogen evolution reaction (HER) is crucial for efficient hydrogen production at low cost and on a large scale. Herein, we report a novel WO3-x catalyst synthesized on carbon nanofiber mats (CFMs) by electrospinning and followed by a carbonization process in a tubal furnace. The morphology and composition of the catalysts were tailored via a simple method, and the hybrid catalyst mats were used directly as cathodes to investigate their HER performance. Notably, the as-prepared catalysts exhibit substantially enhanced activity for the HER, demonstrating a small overpotential, a high exchange current density, and a large cathodic current density. The remarkable electrocatalytic performances result from the poor crystallinity of WO3-x, the high electrical conductivity of WO3-x, and the use of electrospun CNFs. The present work outlines a straightforward approach for the synthesis of transition metal oxide (TMO)-based carbon nanofiber mats with promising applications for the HER.

Synthesis of Cu nanopowders by condensation from the gas phase

In order to determine the most efficient regimes of copper nanoparticles synthesis, a series of experiments were conducted by evaporation and subsequent condensation of the raw material in an argon atmosphere. During the tests it was found that an increase of evaporation rate increases significantly the average size of the synthesized particles. However, the study of the dependence of dimensional parameters of the produced clusters on the intensity of the buffer gas flow rate has encountered significant difficulties associated because the results significantly divergent from the previously conducted experiments on the synthesis of transition metal oxides. In order to solve this contradiction the computer simulation was held of copper atoms condensation from the gas phase for the three different cooling rates and for the two final temperatures T = 373 K and T = 77 K. It was found after analysis that the rate of cooling of the gas mixture and the final temperature directly influences the number and the size of particles produced. For instance, with the 10 times of cooling rate decreases the average size of the particles obtained had increased by 2.7 times at a final temperature of 77 K and by 3.1 times at Tf = 373 K.

English

Recent developments in the synthesis of transition metal oxides in the form of thin films have opened up opportunities in the construction of electrochromic devices with enhanced properties. Transition metal oxides like WO3 and MoO3 have good electrochromic properties and these oxides can also change their optical properties when a voltage pulse is applied. These electrochromic materials are used for displays, gas sensors, rear-view mirrors and smart windows for energy saving applications. There are numbers of different techniques used for the deposition of stable thin films of these oxide materials. Tungsten Oxide (WO3) is the best suited material for energy conservation applications. Thin films of WO3 are deposited by various techniques that offers flexibility, allows the fabrication of required topographical, physical, crystallographic, desired geometrical and metallurgical structures. This review paper is aimed to summarize applications of WO3 thin films as an electrochromic material and the effect of various deposition techniques on its electrochromic and optical properties.

A Novel Sonochemical Synthesis of Metal Oxides Based Bhasmas

Metal oxides form part of inorganic medicines called Bhasmas, which has been used in a non-allopathic medicine system practiced in India called Ayurveda. Bhasmas may be classified under the nanomedicines of ancient India. The traditional preparation methods involve time consuming and complicated preparation procedures. This paper highlights a novel ultrasound assisted technique called sonochemical synthesis of transition metal oxides in a facile, faster, inherently safer and environmentally benign (green chemistry) way which could be considered to be used for the synthesis of metal oxides such as copper oxide which form part of the copper based Ayurvedic nanomedicine called tamra bhasma, which is copper in its oxide form and used therapeutically as a source of copper. The synthesis procedure outlined here could be considered for the preparation of other types of Bhasmas also.

Synthesis of Transition Metal Oxide Based MgO Nanocomposites by a Simple Precursor Approach

MgO based nanocomposites possess a wide range of applications in various catalytic reactions. Transition metal oxide based MgO nanocomposites are expected to be useful in spintronics. MgO has been chosen due to its less interaction with magnetic nanoparticles and also it provides stability to the magnetic nanoparticles. In the present study, MgO–Co3O4 and MgO–NiO nanocomposites have been synthesized by a simple precursor approach. Firstly, magnesium oxychloride precursors were prepared using aqueous solutions of magnesium chloride, cobalt chloride (or nickel chloride) and nanocrystalline MgO which on calcination at 500°C led to MgO–Co3O4 and MgO–NiO nanocomposites. The nanocomposites were characterized by XRD, FE-SEM, EDXA, TEM and magnetic measurements. The XRD results indicate the formation of Co3O4 and NiO along with MgO on calcination of the precursors. The SEM and TEM images indicate the presence of MgO particles along with transition metal oxide nanoparticles. Magnetic measurements of both the nanocomposites (M-H) indicate superparamagnetic behavior at 5 K.

High-Quality Metal Oxide Core/Shell Nanowire Arrays on Conductive Substrates for Electrochemical Energy Storage

The high performance of a pseudocapacitor electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. We present a powerful two-step solution-based method for the fabrication of transition metal oxide core/shell nanostructure arrays on various conductive substrates. Demonstrated examples include Co(3)O(4) or ZnO nanowire core and NiO nanoflake shells with a hierarchical and porous morphology. The "oriented attachment" and "self-assembly" crystal growth mechanisms are proposed to explain the formation of the NiO nanoflake shell. Supercapacitor electrodes based on the Co(3)O(4)/NiO nanowire arrays on 3D macroporous nickel foam are thoroughly characterized. The electrodes exhibit a high specific capacitance of 853 F/g at 2 A/g after 6000 cycles and an excellent cycling stability, owing to the unique porous core/shell nanowire array architecture, and a rational combination of two electrochemically active materials. Our growth approach offers a new technique for the design and synthesis of transition metal oxide or hydroxide hierarchical nanoarrays that are promising for electrochemical energy storage, catalysis, and gas sensing applications.

Electrochromic Devices Based on Porous Tungsten Oxide Thin Films

Recent developments in the synthesis of transition metal oxides in the form of porous thin films have opened up opportunities in the construction of electrochromic devices with enhanced properties. In this paper, synthesis, characterization and electrochromic applications of porous WO3 thin films with different nanocrystalline phases, such as hexagonal, monoclinic, and orthorhombic, are presented. Asymmetric electrochromic devices have been constructed based on these porous WO3 thin films. XRD measurements of the intercalation/deintercalation of Li+ into/from the WO3 layer of the device as a function of applied coloration/bleaching voltages show systematic changes in the lattice parameters associated with structural phase transitions in LixWO3. Micro‐Raman studies show systematic crystalline phase changes in the spectra of WO3 layers during Li+ ion intercalation and deintercalation, which agree with the XRD data. These devices exhibit interesting optical modulation (up to ~70%) due to intercalation/deintercalation of Li ions into/from the WO3 layer of the devices as a function of applied coloration/bleaching voltages. The obtained optical modulation of the electrochromic devices indicates that, they are suitable for applications in electrochromic smart windows.