Binary Transition Metal Oxides Research Articles

Fabrication of NiO-CuO/RGO Composite for Lithium Storage Property

The lithium storage performance of binary transition metal oxide/graphene composites as anode materials has been attracting more interest from researchers, based on the fact that binary transition metal oxides and graphene are expected to create a synergistic effect and exhibit improved lithium storage characteristics. In this work, a NiO-CuO/reduced graphene oxide composite (NiO-CuO/RGO) was prepared by an ultrasonic agitation process. When the NiO-CuO/RGO is applied to the anode material for lithium-ion batteries (LIBs), the batteries display high discharge capacities (at 730 mA h/g after 100 cycles at 100 mA/g), high-rate performance (311 mA h/g with 5000 mA/g), and excellent stable cyclability (375 mA h/g within 2000 mA/g after 400 cycles). Such results indicate that the combination of NiO-CuO and RGO leads to enhanced lithium storage performance, for the RGO sheets inhibit the large volume change of binary NiO-CuO and enhance the fast transport of both lithium ions and electrons during the repeated lithium cycling processes.

Fabrication of NiO-CuO/RGO Composite for Lithium Storage Property

The lithium storage performance of binary transition metal oxide/graphene composites as anode materials has been attracting more interest from researchers, based on the fact that binary transition metal oxides and graphene are expected to create a synergistic effect and exhibit improved lithium storage characteristics. In this work, a NiO-CuO/reduced graphene oxide composite (NiO-CuO/RGO) was prepared by an ultrasonic agitation process. When the NiO-CuO/RGO is applied to the anode material for lithium-ion batteries (LIBs), the batteries display high discharge capacities (at 730 mA h/g after 100 cycles at 100 mA/g), high-rate performance (311 mA h/g with 5000 mA/g), and excellent stable cyclability (375 mA h/g within 2000 mA/g after 400 cycles). Such results indicate that the combination of NiO-CuO and RGO leads to enhanced lithium storage performance, for the RGO sheets inhibit the large volume change of binary NiO-CuO and enhance the fast transport of both lithium ions and electrons during the repeated lithium cycling processes.

Nanostructured binary transition-metal-sulfides and nanocomposites as high-performance electrodes for hybrid supercapacitors

Supercapacitors (SCs) are attractive as promising energy storage devices because of their distinctive attributes, such as high power density, good current charge/discharge ability, excellent cyclic stability, reasonable safety, and low cost. Electrode materials play key roles in achieving excellent performance of these SCs. Among them, binary transition metal sulfides (BTMSs) have received significant attention, attributed to their high conductivity, abundant active sites, and excellent electrochemical properties. This topic review aims to summarize recent advances in principles, design, and evaluation of the electrochemical performance for nanostructured BTMSs (including nickel–cobalt sulfides, zinc–cobalt sulfides, and copper–cobalt sulfides.) and their nanocomposites (including those carbon nanomaterials, transition metal oxides, binary transition metal oxides, transition metal sulfides, and polymers). Nanostructuring of these BTMSs and nanocomposites as well as their effects on the performance were discussed, including nanoparticles, nanospheres, nanosheets, nanowires, nanorods, nanotubes, nanoarrays, and hierarchitectured nanostructures. Their electrochemical performance has further been reviewed including specific capacitance, conductivity, rate capability, and cycling stability. In addition, the performance of hybrid supercapacitors (HSCs) assembled using the nanostructured BTMSs as the cathodes also have been summarized and compared. Finally, challenges and further prospects in the HSCs-based BTMS electrodes are presented.

Enhanced Energy Storage Performance through Controlled Composition and Synthesis of 3D Mixed Metal-Oxide Microspheres.

Binary transition metal oxide complexes (BTMOCs) in three-dimensional (3D) layered structures show great promise as electrodes for supercapacitors (SCs) due to their diverse oxidation states, which contribute to high specific capacitance. However, the synthesis of BTMOCs with 3D structures remains challenging yet crucial for their application. In this study, we present a novel approach utilizing a single-step hydrothermal technique to fabricate flower-shaped microspheres composed of a NiCo-based complex. Each microsphere consists of nanosheets with a mesoporous structure, enhancing the specific surface area to 23.66 m2 g-1 and facilitating efficient redox reactions. When employed as the working electrode for supercapacitors, the composite exhibits remarkable specific capacitance, achieving 888.8 F g-1 at 1 A g-1. Furthermore, it demonstrates notable electrochemical stability, retaining 52.08% capacitance after 10,000 cycles, and offers a high-power density of 225 W·kg-1, along with an energy density of 25 Wh·kg-1, showcasing its potential for energy storage applications. Additionally, an aqueous asymmetric supercapacitor (ASC) was assembled using NiCo microspheres-based complex and activated carbon (AC). Remarkably, the NiCo microspheres complex/AC configuration delivers a high specific capacitance of 250 F g-1 at 1 A g-1, with a high energy density of 88 Wh kg-1, for a power density of 800 W kg-1. The ASC also exhibits excellent long-term cyclability with 69% retention over 10,000 charge-discharge cycles. Furthermore, a series of two ASC devices demonstrated the capability to power commercial blue LEDs for a duration of at least 40 s. The simplicity of the synthesis process and the exceptional performance exhibited by the developed electrode materials hold considerable promise for applications in energy storage.

In-situ synthesis of coral reef-like synergistic zinc cobalt oxide and zinc manganese oxide composite as a battery-type electrode material for supercapacitors

Recently, in-situ preparation of metal oxide composite structures has gained much importance in fabricating electrode materials for energy storage and conversion devices because of its advantageous properties of beneficial interfacial contact, high conductivity, good synergism, short ion diffusion distance, better electrochemical performance, etc. Binary transition metal oxides (BTMOs) are given great attention for their significant electrochemical performances over primary MOs because of the two metal ions with different valent states for the redox reactions. In this study, we synthesize zinc cobalt oxide (ZnCo2O4) and zinc manganese oxide (ZnMn2O4) composite via a solvothermal synthetic method. The existence of both phases is identified using an X-ray diffraction analysis (XRD). The unique coral reef-like structures of the composite electrode are analysed via field emission scanning electron microscopy, and the nanostructure was identified using transmission electron microscopy. The X-ray photoelectron spectroscopy confirms the surface oxidation states of the composite and supports the XRD analysis. The synergetic composite electrode provides a large surface area of 50.86 m2 g−1 with many pores. The composite electrode has a specific capacity of 250 C g−1 at 1 A g−1. The ZCO/ZMO composite demonstrated impressive stability, retaining a specific capacity of 180 C g−1 at 6 A g−1 over 5000 cycles.

Spin-selective evolution of the Zhang-Rice state in binary transition metal oxide MnO(001) film

Spin-selective evolution of the Zhang-Rice state in binary transition metal oxide MnO(001) film

Carbamide-mediated facile sol-gel synthesis of porous flower-like ZnCo2O4 microspheres for high-performance asymmetric coin cell supercapacitors

The design and development of ultrahigh-performance nanomaterials possessing novel characteristics are needed to achieve reliable energy storage performance. To satisfy the needs, diverse electrode materials are explored. Even though carbon-based materials hold high surface area and conductivity, their specific capacitance value fails to deliver high-performance applications. Therefore, pseudocapacitive transition metal oxide is adopted to overcome these issues. Among all Zinc Cobaltite, a binary transition metal oxide is widely explored owing to its fascinating electrochemical properties. As most of the synthesis of these kinds of materials requires the hydro/solvothermal method, herein, we have proposed the concept of a facile sol-gel method to prepare this class of materials by using Carbamide as both structure director and fuel to achieve the porous flower-like Zinc Cobaltite. The prepared material delivers the notable gravimetric specific capacitance of 513.3 F g−1. Owing to its unique morphology and porous structure, ion channelization is feasible, which will enhance the electrochemical reaction. Constructed asymmetric coin cell supercapacitor showed an extraordinary specific capacitance of 106.5 F g−1 and energy density of 56.2 Wh kg−1, demonstrating an impressive ability to retain 89.6 % of its capacitance after 4000 cycles at a current density of 6 A g−1. Due to the remarkable electrochemical behavior, this work can act as a guiding tool for designing efficient and cost-effective energy storage devices that will hold prodigious potential in commercial energy storage applications.

A heterostructured ternary transition metal oxide composite as an efficient electrocatalyst for the hydrogen evolution reaction

A key method for hydrogen production is water electrolysis involving the oxygen and hydrogen evolution reactions. The efficiency of these processes is largely dependent on the use of effective electrode catalysts. Despite the high water-splitting catalytic activity of noble metals such as Pt, Ru, and Ir, their scarcity and costliness pose significant challenges. Although Fe and Fe-based compounds have recently been identified as promising alternative catalysts due to their abundance, affordability, and low toxicity, particularly under the alkaline conditions required for the hydrogen evolution reaction, both can be reduced to unstable forms during the reaction. To address this, the focus of the present study is on developing a ternary transition metal oxide electrocatalyst comprising Ni, Fe, and Co oxides. Thereby, we leveraged the synergistic interactions among them to provide a heterogeneous electrocatalyst for the hydrogen evolution reaction with a sufficiently low overpotential of 45 mV and suitably high Tafel kinetics of 44.99 mV dec−1 and long-term stability. The ternary transition metal oxide electrode showcased superior performance compared to one comprising binary transition metal oxides by achieving a lower overpotential and a better Tafel slope while maintaining catalytic stability even for 100 h at a current density of 1000 mA cm−2. This innovative approach offers a highly efficient alternative catalyst to Fe, which is known to have stability issues for hydrogen production, especially at high current density.

Hollow CuCo2O4 nanocages engineered by Kirkendall effect for room-temperature sensing of ammonia gas

Recently, binary transition metal oxide (BTMO)-based gas sensors have gained significant interest in detecting harmful gases in the atmosphere. Herein, we report a p-type BTMO, hollow CuCO2O4 (CCO) nanocages, for ammonia (NH3) gas sensing at room temperature (RT). Hollow CCO nanocages were fabricated using a two-step process, including hydrothermal synthesis followed by annealing. The sensor exhibited responses of 2.8 % and 13.6 % towards 1 and 100 ppm NH3, respectively. Furthermore, it demonstrated good selectivity and repeatability for NH3 gas. Although the response decreased in the presence of humidity, it showed a high response to NH3 in a humid atmosphere. Additionally, a flexible sensor was fabricated on a PET substrate and subjected to bending (45, 90, and 190°) and twisting (30, 60, and 90°). Generally, the sensor showed a higher response after 100 cycles of bending compared to 100 cycles of twisting. Therefore, with the promising results obtained in this study, the present sensor can be used for selective RT detection of NH3 gas in flexible applications where the sensor is subjected to bending at different angles under rapid and harsh conditions.

Porous NiMoO4 Nanosheet Films and a Device with Ultralarge Optical Modulation for Electrochromic Energy-Storage Applications.

Reducing building energy consumption, improving aesthetics, and improving occupant privacy as well as comfort by dynamically adjusting solar radiation are important application areas for electrochromic (EC) smart windows. However, the current transition metal oxides still cannot meet the requirements of neutral coloration and large optical modulation. We report NiMoO4 nanosheet films directly grown on fluorine-doped tin oxide glasses. The as-grown NiMoO4 film not only achieves neutral coloration from transparent to dark brown but also shows an ultralarge optical modulation (86.8% at 480 nm) and excellent cycling stability (99.4% retention of maximum optical modulation after 1500 cycles). Meanwhile, an EC device demonstrating good EC performance was constructed. These results will greatly promote the research and development of binary transition metal oxides for both EC and energy-storage applications, and NiMoO4 films may be an excellent candidate to replace NiO films as ion-storage layers in complementary EC devices with WO3 films as EC layers.

Surface‐Modified ZnCo2O4 Nanoparticles as Binder‐Free Electrode for All Solid‐State Asymmetric Supercapacitor

AbstractChoice of electrode material is crucial to the development of high‐performance supercapacitors. Since surface properties are key to the performance of an electrode material for supercapacitors, surface chemical treatment of electrode materials is an interesting topic of research. ZnCo2O4 (ZCO) is a low‐cost binary transition metal oxide with high theoretical conductivity and charge storage capacity making it a good choice for supercapacitor electrode. Herein, we present a systematic investigation of the influence of four different surface modifier (3 surfactants, 1 mineralizer) on ZCO electrode directly grown on Ni foam to compare the relative influence on the performance of the modified ZCO electrode. Analyses of the modified ZCO electrodes revealed the formation of cubic spinel phase of ZCO with average particle size of ~30 nm. The sodium dodecyl sulfate (ZCO−S) modified electrode (ZCO−S) exhibited the best electrochemical performance with specific capacitance of 1988 F/g at 1 A/g and 87 % capacity retention after 7000 cycles at 10 A/g. Further, an all‐solid‐state asymmetric supercapacitor (ASC) was fabricated with ZCO−S on Ni foam and carbon nanotube combination which exhibited specific capacitance of 102 F/g at 1 A/g corresponding to power density of ~1599 W‐kg−1 establishing ZCO−S as a very good electrode material for supercapacitor.

Self-assembled carbon wrapped manganese cobaltite nano-composite with promising electrochemical performance for symmetric and asymmetric supercapacitor device

The growing energy requirements of modern society have led to an intensive search for advanced supercapacitor (SC) electrode materials. Binary transition metal oxides with excellent supercapacitive performance are among the most promising materials. However, the phase transformation of these metal oxides during repeated charging/discharging is a major concern, which depletes their cyclic performance. Coating metal oxides with carbon can provide structural stability to the metal oxide, thereby increasing their cyclic life. In addition, the highly conductive carbon enhances the capacitance of metal oxides by allowing the effective transfer of charges from MnCo2O4 to the current collector. In this study, self-assembled carbon-wrapped MnCo2O4 composite has been prepared through a two-step process involving hydrothermal and solution-mixing processes. The structural/electrochemical performances of the composites have been investigated. The optimized composite offered a maximum capacitance of 626.8 Fg−1 withholding 98 % of capacitance for 6000 cycles. Furthermore, the electrochemical performance of the composite has also been tested in an all-redox symmetric SC (SSC) as well asymmetric (ASC) configuration. In the symmetric cell, 30.2 Whkg−1 of energy is reported for 1.6 kWkg−1 of power. The asymmetric cell with the optimized composite as a cathode and MnO2/Activated carbon as an anode was fabricated. The ASC displayed 45.5 Whkg−1 of energy corresponding to 10 kWkg−1. Three SSCs/ASCs in series illuminated a panel of 39 red-LEDs for 9 and 15 min, respectively. The results suggest the promising performance of such composites for hybrid supercapacitors. Thus, the fabrication of all-redox-type SSCs/ASCs can be a futuristic approach for hybrid storage systems.

Fabrication of NiCo2O4@polyaniline heterostructure as positive electrode for asymmetrical supercapacitor

AbstractNiCo2O4, as a low‐cost and high‐performance binary transition metal oxide material, has been widely used in the fabrication of supercapacitor electrodes. However, the low energy density of binary metal oxides limits their large‐scale practical applications in supercapacitors, so it is highly desirable to design the structure of the NiCo2O4‐based supercapacitor. Therefore, in this paper, NiCo2O4 is compounded with polyaniline (PANI) to improve its electrochemical performance by exploiting the synergistic effect. The NiCo2O4@PANI composite electrode exhibits a specific capacitance of 561.2 F/g at 10 mV/s. In this study, asymmetric supercapacitors are assembled with NiCo2O4@PANI as the positive electrode and MXene as the negative electrode. The NiCo2O4@PANI‐CC//MXene‐CC supercapacitor has a specific capacitance of 31.95 F/g at a scan rate of 10 mV/s and a good cycle retention capacity of 86.2% after 3000 cycles. The excellent electrochemical performances are attributed to the dynamic equilibrium and fast redox kinetics of the two electrodes.

Rod-like CoMoO4 grows on lamellar Fe-MOF to assemble the composite electrocatalyst for efficient oxygen evolution reaction

There is an urgent need to design effective and affordable noble metal-free oxygen evolution electrocatalysts for the realization of hydrogen production technology through overall water splitting. In this work, we synthesized CoMoO4/Fe-MOF composite catalysts on nickel foam by solvothermal method and explored them as electrodes towards oxygen evolution reaction. At 10 mA cm-2, CoMoO4/Fe-MOF demonstrated a small overpotential of 238 mV, with a relatively small Tafel slope of 49.22 mV dec-1 and exhibited excellent stability after 30 h of testing. The enhanced OER activity and good durability of CoMoO4/Fe-MOF could be attributed to the self-supported growth of Fe-MOF nanosheets as well as the tight binding to the rod-like CoMoO4. The coupling of CoMoO4 with Fe-MOF established a rich boundary, thus improving conductivity, increasing specific surface area and exposing more active sites. These results suggested that the combination of MOFs with binary transition metal oxides provided an effective route to develop robust and efficient electrocatalysts.

Experimental and computational study of binary transition metal oxides NaNi1/2 X1/2 O2 (X=Cr, Fe, Co and Cu) for energy storage applications

For novel applications as cathodes in sodium-ion batteries, layered transition metal oxides have been reported to have an appropriate voltage window that results higher specific capacity and energy density. In the present work, a series of binary layered transition metal oxides: NaNi1/2Cr1/2O2, NaNi1/2Fe1/2O2, NaNi1/2Co1/2O2, and NaNi1/2Cu1/2O2 were prepared using sol-gel technique. XRD analysis confirmed that all the synthesized materials stabilize a hexagonal structure with an R3m space group. SEM micrographs showed the formation of well-separated particles of varying shapes. FTIR spectra indicated the presence of metal oxygen absorption bands. Using density functional theory (DFT), crystal structure was generated using the lattice parameters worked out using XRD. The spin polarized electronic band structures and density of states (DOS) computed for all four compounds revealed half metallic character. Average intercalation voltages (AIV) were calculated theoretically from the total energies of the optimized compounds and their de-sodianted phases. Volume changes were also calculated to study its minimal values for the compounds, to identify them as of good structural stability. Both experimental findings and theoretical calculations show that the investigated binary layered transition metal oxides are suitable cathode materials for coin cell fabrications.

Fabrication of SrWO4/PPy composite as electrode material for high-performance supercapacitors

The societal major concern of the moment is energy storage, energy production and global warming. Researchers are striving to create novel, highly efficient energy storage materials for developing faster, safer as well as more effective energy storage systems. One effective method to improve the electrochemical performance of supercapacitors (SCs) is the construction of highly efficient electro active materials, employing multivalent binary transition metal oxides (BTMOs) with electrical conducting polymers (CPs). For the first time, we report SrWO4/PPy composite synthesized by In-situ chemical polymerization route. The physio-chemical characteristics of the synthesized material was extensively examined with spectral and analytical techniques. SrWO4/PPy composite on Ni foil was fabricated as an alternate electrode material and was investigated for its capacitive behaviour. SrWO4/PPy electrode achieved a high specific capacitance of 747 Fg-1 at 5 mVs−1 and a remarkable cyclic stability of 93.8% even after 5000 cycles at 1 Ag-1. The notable electrochemical property of the electrode was attributed to its distinctive composite morphology, which is crucial in facilitating high conductivity, quick electron transfer, short ion diffusion distance and excellent active sites for enhanced electrochemical performance. The substantial capacitive behaviour can be attributed to the synergetic effect of SrWO4 and PPy. This work introduces platform to design efficient electrodes for the energy storage devices as well as for wearable electronics.

Selective and sensitive phenothiazine sensor based on hexagonal CuO/Co3O4 decorated on reduced graphene oxide catalyst

Binary transition metal oxides with conducting carbon materials are increasingly accepted in electrochemistry. Here, a highly effective binary CuO/Co3O4 metal oxide electrocatalyst with hexagonal morphology was synthesized directly on cobalt and copper containing solid precursors by a facile hydrothermal method. Further, the activity of CuO/Co3O4 was enhanced by combination with conductive reduced graphene oxide (rGO). The physical properties of the resulting material (CuO/Co3O4@rGO) were investigated using various spectroscopic and microscopic techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). CuO/Co3O4@rGO coated on a screen-printed carbon electrode (SPCE) was used as an electrode for the detection of antipsychotic drug phenothiazine (PTZ) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (PBS, pH 5.0). The CuO/Co3O4@rGO/SPCE showed a wide linear range of 0.01–2.1 μM with a detection limit of 0.64 * 10−9 mol/L and a sensitivity of 1.8 μA/μM cm2 for PTZ detection. In addition, the PTZ sensor has reliable selectivity, stability and accuracy. Finally, the practicality of the fabricated sensor was tested in human serum and urine samples with acceptable recoveries.

Hybrid nanostructures made of porous binary transition metal oxides for high performance asymmetric supercapacitor application

The present work is an experimental comparison of various binary transition metal oxides (BTMOs) and their application as electrode material for supercapaitor (SC). The possibility of Molybdenum oxides and their nanostructures are explored in the field of energy storage devices however, very few works have been reported analyzing the potential of BTMOs as electrode materials for energy applications. Herein, CoMoO4, NiMoO4, MnMoO4 and CuMoO4 nanostructures were synthesized and implicated as an electrode for coin-cell based SC. The electrode materials were tested in both three and two-electrode system to conclude the suitable electrode for commercial application. Coin-cell device based on XMoO4║NrGO/CNT was fabricated and compared in this study. This comparative experimental study investigated the influence of the intrinsic properties of electrodes on specific capacitance. NiMoO4║NrGO/CNT delivered a capacitance of 261 F g−1 and capacity retention of 80 %. Also, depicted an energy density of 45.23 Wh kg−1 at a power density of 7500 W kg−1. This excellent electrochemical performance of the NiMoO4 electrode implies it will be a prospective candidate for supercapacitor application.

A portable electrochemical sensor based on binary transition metal oxide (CoO/ZnO) for the evaluation of eugenol in real-time samples

We report a one-step hydrothermal synthesis route of synthesizing the binary transition metal oxide-based composite using zinc acetate and cobalt acetate precursors. A synthesized binary transition metal oxide-based composite is characterized to understand features of crystalline and structural arrangements, functionality, chemical composition, and surface morphologies using the XRD, FT-IR, XPS, FESEM, & HR-TEM techniques. The composite materials tend to show excellent morphology with spherical morphology. Owing to this, the synthesized binary transition metal oxide composite is then modified over the surface of the glassy carbon electrode (GCE) towards the electrochemical sensing of Eugenol (EUG). In this regard, the CoO/ZnO/GCE composite delivers much more improved electrocatalytic activity because of the synergistic features offered by the binary transition metal oxides due to their unique structural morphology, high surface area, and increased active sites which afford rapid electron transfer rate to the CoO/ZnO/GCE when compared to other electrodes. CoO/ZnO/GCE sensor of determining the (EUG) with a wider linear range of 0.049 – 179.8 µM possessed nanomolar level detection (LOD) of under DPV & LSV is calculated to be 4 nM & 7 nM along with sensitivity found to be 1.366 µA µM−1 cm−2 & 1.01 µA µM−1 cm−2. The proposed CoO/ZnO/GCE has better selectivity over interference studies, with practical feasibility features of repeatability, reproducibility, and storage stability. Real-time sample practical applicability with exceptional recoveries of 99 % for the clove sample and urine samples.

A Facile Microwave Hydrothermal Synthesis of ZnFe2O4/rGO Nanocomposites for Supercapacitor Electrodes

As a typical binary transition metal oxide, ZnFe2O4 has attracted considerable attention for supercapacitor electrodes due to its high theoretical specific capacitance. However, the reported synthesis processes of ZnFe2O4 are complicated and ZnFe2O4 nanoparticles are easily agglomerated, leading to poor cycle life and unfavorable capacity. Herein, a facile microwave hydrothermal process was used to prepare ZnFe2O4/reduced graphene oxide (rGO) nanocomposites in this work. The influence of rGO content on the morphology, structure, and electrochemical performance of ZnFe2O4/rGO nanocomposites was systematically investigated. Due to the uniform distribution of ZnFe2O4 nanoparticles on the rGO surface and the high specific surface area and rich pore structures, the as-prepared ZnFe2O4/rGO electrode with 44.3 wt.% rGO content exhibits a high specific capacitance of 628 F g-1 and long cycle life of 89% retention over 2500 cycles at 1 A g-1. This work provides a new process for synthesizing binary transition metal oxide and developing a new strategy for realizing high-performance composites for supercapacitor electrodes.