Nanostructured Transition Metal Research Articles

Nanostructured Transition Metal Oxides on Carbon Fibers for Supercapacitor and Li-Ion Battery Electrodes: An Overview

Nowadays, owing to the new technological and industrial requirements for equipment, such as flexibility or multifunctionally, the development of all-solid-state supercapacitors and Li-ion batteries has become a goal for researchers. For these purposes, the composite material approach has been widely proposed due to the promising features of woven carbon fiber as a substrate material for this type of material. Carbon fiber displays excellent mechanical properties, flexibility, and high electrical conductivity, allowing it to act as a substrate and a collector at the same time. However, carbon fiber’s energy-storage capability is limited. Several coatings have been proposed for this, with nanostructured transition metal oxides being one of the most popular due to their high theoretical capacity and surface area. In this overview, the main techniques used to achieve these coatings—such as solvothermal synthesis, MOF-derived obtention, and electrochemical deposition—are summarized, as well as the main strategies for alleviating the low electrical conductivity of transition metal oxides, which is the main drawback of these materials.

Nanostructured transition metal dichalcogenides-based colorimetric sensors: Synthesis, characterization, and emerging applications.

Nanostructured transition metal dichalcogenides (TMDCs) have garnered significant attention as prospective materials for the development of highly sensitive and versatile colorimetric sensors. This work explores the synthesis, characterization, and emerging applications of TMDC-based sensors, focusing on their unique structural aspects and inherent properties. The synthesis methods involve tailored fabrication techniques, such as chemical vapor deposition and hydrothermal processes, aimed at producing well-defined nanostructures that enhance sensor performance. Characterization techniques, including microscopy, spectroscopy, and surface analysis, are employed to elucidate the structural and chemical features of the nanostructured TMDCs. These analyses provide insights into the correlation between the material's morphology and its sensing capabilities. The colorimetric sensing mechanism relies on the modulation of optical properties in response to specific analytes, enabling rapid and visual detection. The emerging applications of TMDC-based colorimetric sensors span diverse fields, including environmental monitoring, healthcare, and industrial processes. The sensors exhibit high sensitivity, selectivity, and real-time response, making them ideal candidates for detecting various target analytes. Furthermore, their integration with complementary technologies such as microfluidics, can facilitate the development of on-site and point-of-care applications. This work highlights the interdisciplinary significance of nanostructured TMDC-based colorimetric sensors and underscores their potential contributions to addressing contemporary challenges in sensing technology.

Enhancing oxygen evolution reaction through self-reconstruction of 2D nanoarrays on nickel foam

The synthesis of nanostructured transition metal compounds with adjustable components are often challenging due to the involvement of multiple synthetic procedures or complex manipulations. In this work, a one-step self-regulating acid-etching strategy is employed for nickel iron-layered double hydroxide (NiFe LDH). A two-dimensional (2D) NiFe LDH nanosheet is speedy and efficiently formed. This as-prepared NiFe LDH exhibits electrocatalytic activity for oxygen evolution reaction (OER). This approach avoids numerous structural design challenges and provides highly active sites and a robust interface between catalyst and support. As a result, 2D NiFe LDH electrodes demonstrate highly efficient OER performance with a low overpotential of 300 mV and a Tafel slope of 70.6 mV dec−1 at a current density of 100 mA cm−2.

Design, synthesis, and pharmacological efficacy of sonication-irradiated nanostructured transition metal (II) designed macrocyclic complexes

The synthesis of transition metal (II) complexes from aspartic acid was accomplished by using sonication irradiation in this work. Sonication irradiation is a straightforward and efficient technique for synthesis. Physiological and spectroscopic studies were carried out to investigate the process of assembling nanostructured complexes. Using the serial dilution (2-fold) and free radical scavenging (DPPH) procedures, the antioxidant and antibacterial activity were assessed, respectively. Various bacteria, including Gram-positive and Gram-negative strains and fungi, were tested to determine the antimicrobial efficacies of the macrocyclic ligand and its accompanying metal complexes. The inhibitory results on microbes showed that metal complexes had more potent antibacterial effects than their Schiff base ligands. The findings demonstrated that the biological activity had a positive impact. Sonication irradiation of some complexes increased the movement of those complexes at concentrations ranging from 3.125 to 6.250 μg/ml (MIC). The Gaussian 09 software was utilized to simulate the three-dimensional structure of the complexes, the chemical reactivity of the produced macrocyclic ligand, and the binding energy of its complexes’ EHOMO and ELUMO energies using the B3LYP Density Functional Theory (DFT) method. This method is well-suited for pharmaceutical applications in the real world since it requires little effort to set up, produces a high yield, and requires a relatively small amount of solvent.

Designing intimately interconnected neuron-shaped nickel-copper(I) sulfide nanocomposites as cathode material for supercapacitors

Nanostructured transition metal sulfides have attracted significant attention as pseudocapacitance materials owing to their high specific capacitance and improved conductivity compared to oxides. Bimetallic nickel‑copper(I) (NiCu) sulfides are promising candidates for use in asymmetric supercapacitors because of their high specific capacitance, wide voltage range, and high conductivity. In this study, we synthesize neuron-shaped Ni-Cu(I) sulfide nanocomposites with intimate interconnectivity via the sulfidation and ion exchange of Ni-Cu(I) carbonate hydroxide, prepared by a straightforward hydrothermal process. The product's unique structure, featuring a neuronal network, exhibits a high specific capacitance of 1226.5 F g−1 at 1 A g−1 and an excellent cycling stability (88.97 % capacitance retention after 5000 cycles), which is attributed to the coexistence of bimetallic components and an inherently interconnected neuron-shaped configuration that prevents structural collapse and self-aggregation, while providing easy electrolyte accessibility. Furthermore, an asymmetric supercapacitor with a Ni-Cu(I) sulfide cathode material demonstrates a maximum power and energy densities of 9000 W kg−1 and 23.99 Wh kg−1, respectively, with an initial capacity retention rate of 83.69 % after 5000 cycles. The distinctive structural features of Ni-Cu(I) sulfides enhance the energy storage capabilities of the nanomaterials, enabling the development of portable electronic devices.

Top‐Down Preparation and Magnetic Properties of MnSe2 Nanoparticles

Nanostructured transition metal dichalcogenide MnSe2 has attracted much attention due to its fascinating magnetic properties. In this article, a series of MnSe2 nanoparticles with different particle sizes are successfully prepared by a facile top‐down method of solid‐state reaction combined with ball milling, and the effects of ball milling on the phase composition, microstructure and magnetic properties of the MnSe2 are systematically studied. The results show that pure MnSe2 microparticles are obtained by the solid‐state reaction, however, partial MnSe2 is decomposed after ball milling for 16 h. The average particle size of the MnSe2 gradually decreases with the increase of milling time. MnSe2 nanoparticles with average particle size approximately 65 nm are obtained after milling for 40 h. After milling, the antiferromagnetic MnSe2 nanoparticles exhibit weak ferromagnetic characteristics due to the surface effect and the microstrain induced by ball milling. The residual magnetization (Mr) and coercivity (Hc) of the sample gradually increase as the particle size decreases. The Mr and Hc of the sample milled for 40 h reach 70.13 × 10−4 emu g−1 and 67.47 Oe, respectively.

Augmented ammonia sensing of ion-beam modified MoSe2

Gas sensors based on nanostructured transition metal dichalcogenides, such as MoSe2, are increasingly becoming important due to their low band gap, good electrical conductivity and selectivity. However, some of the parameters related to the gas adsorption can be tuned to enhance the overall sensing performance. The change of response sometimes remains low because of small number of active interaction sites on the surface. There are challenges related to slow response and slow recovery of the sensor. Furthermore, if the surface is hydrophilic, it can attract moisture, which may reduce interactions with the target gas and may also reduce the lifetime of the sensor. In this study we have used ion irradiation technique to overcome these challenges and exploit theoretical models to explain the physics behind enhanced sensing performance of 3D nanostructured MoSe2. A low energy (5 keV) argon ions have been used to induce structural and morphological modification of MoSe2. The irradiation leads to formation of Mo and Se vacancies, which is predicted by ion-solid interaction simulation and corroborated with various characterization techniques. The surface becomes superhydrophobic after irradiation and a significant increase of electrical conductivity takes place. We found that the ammonia sensing response increases by about 60 % due to the irradiation. There are further significant gains of response and recovery time of the sensor, post-irradiation. The response of irradiated samples shows more stability as compared to the pristine sample over a period of 180 days. First principles-based calculation points out that the charge transfer happens from surface to ammonia during the interaction and ion irradiation induced vacancies lead to better adsorption of ammonia in case of irradiated sample than that of the pristine sample.

Armoring hydrophilic wood-structured ultrathick electrode with bimetallic nitride enables high energy-density supercapacitor

Thick electrodes can reduce the ratio of inactive constituents in a holistic energy storage system while improving energy and power densities. Unfortunately, traditional slurry-casting electrodes induce high-tortuous ionic diffusion routes that directly depress the capacitance with a thickening design. To overcome this, a novel 3D low-tortuosity, self-supporting, wood-structured ultrathick electrode (NiMoN@WC, a thickness of ∼1400 μm) with hierarchical porosity and artificial array-distributed small holes was constructed via anchoring bimetallic nitrides into the monolithic wood carbons. Accompanying the embedded NiMoN nanoclusters with well-designed geometric and electronic structure, the vertically low-tortuous channels, enlarged specific surface area and pore volume, superhydrophilic interface, and excellent charge conductivities, a superior capacitance of NiMoN@WC thick electrodes (∼5350 mF cm−2 and 184.5 F g−1) is achieved without the structural deformation. In especial, monolithic wood carbons with gradient porous network not only function as the high-flux matrices to ameliorate the NiMoN loading via cell wall engineering but also allow fully-exposed electroactive substance and efficient current collection, thereby deliver an acceptable rate capability over 75% retention even at a high sweep rate of 20 mA cm−2. Additionally, an asymmetric NiMoN@WC//WC supercapacitor with an available working voltage of 1.0–1.8 V is assembled to demonstrate a maximum energy density of ∼2.04 mWh cm−2 (17.4 Wh kg−1) at a power density of 1620 mW cm−2, along with a decent long-term lifespan over 10,000 charging-discharging cycles. As a guideline, the rational design of wood ultrathick electrode with nanostructured transition metal nitrides sketch a promising blueprint for alleviating global energy scarcity while expanding carbon-neutral technologies.

A facile synthesis of 2D bimetallic solid solution nitrides for robust stability in lithium-ion battery

Nanostructured transition metal nitrides (TMNs) demonstrate immense promise for lithium-ion battery applications owing to their outstanding conductivity and high theoretical capacity. However, challenges such as the expansion of volume, aggregation concerns, and rapid capacity decay still need to be effectively addressed. Herein, a facile synthesis of 2D nitrides, including TiVN, NbVN and TiNbN, is achieved through nitriding their corresponding MXenes. The distinct 2D layered structure enables them fast lithium-ion transport and inhibits volume variation, thereby improving rate performance and stability. Moreover, the incorporation of bimetallic elements in solid solution induces lattice distortion, creating lattice vacancies and increasing lithium storage capacity. Atomic-level interactions within solid solutions, confirming by the shifts of binding energy, contribute to improved structural stability and accelerated charge transfer. The theoretical calculation further proves that the bimetallic solid solution structure elevates the d-band center and increases the Li+ adsorption energy. Consequently, the synthesized TiVN, NbVN and TiNbN demonstrate remarkable lithium storage performance. Especially, NbVN with a porous morphology stands out by achieving a specific capacity of 216.6 mAh/g after 1,400 cycles at 1 A/g, significantly outperforming Nb4N5 and VN. This work may provide valuable insights for the efficient synthesis and electrochemical applications of two-dimensional solid-solution nitrides.

Simple and affordable synthesis of a binder-free nickel-zinc sulfide electrode for high-performance supercapacitors

Due to the increasing demand for renewable energy solutions, aqueous energy systems have emerged as promising and sustainable technologies. Nanostructured transition metal sulfides, renowned for their exceptional properties, are prime candidates for electrochemical supercapacitors. In this study, we present the synthesis of nickel-zinc sulfide (Ni-Zn-S) as a binder-free supercapacitor material using the affordable successive ionic layer adsorption and reaction simple technique. The active nanomaterial was directly deposited onto a 3D Ni foam current collector substrate, negating the need for a binder. The synergistic combination of Ni and Zn enhances the electrode capacitance. Various electrochemical techniques were used to evaluate the loaded active material as a binder-free supercapacitor electrode in a 6 M KOH electrolyte. Results indicate pseudocapacitive performance, achieving a high specific capacitance of 400F/g at 0.7 A/g. This material retains 97 % of its capacity, even after 2000 cycles, showcasing exceptional long-term cycling stability. These findings underscore the potential of the Ni-Zn-S electrode for delivering low-cost, high-performance supercapacitors.

FeNi alloys encapsulated with N-doped porous carbon nanotubes as highly efficient and durable CO2 reduction electrocatalyst

The development of highly efficient, cost-effective, and robustly stable electrocatalysts for CO2 reduction remains a significant challenge. In this study, a promising CO2 reduction electrocatalyst composed of nanostructured transition metal alloys (i.e., FeNi, FeCo, or CoNi) nanoparticles encapsulated on N-doped porous carbon material is reported. Among the different compositions, FeNi@N-CNTs-1100 exhibited the most efficient CO2ER activity and exceptional stability. It demonstrated a high CO Faradaic efficiency of over 90 % in a wide potential range (–0.47 to –0.97 V (vs. RHE)), with a CO partial current density of 20.18 mA cm−2 at –0.97 V (vs. RHE). Notably, it achieved a long-term stability of 35 h at –0.77 V (vs. RHE) in an H-cell with 0.5 M KHCO3 electrolyte. Various characterization techniques and designed experiments revealed that FeNi@N-CNTs-1100 exhibited enhanced intrinsic catalytic activity and CO selectivity due to optimized *COOH adsorption and *CO desorption compared to the other catalysts studied.

Intrinsic Properties Affecting the Catalytic Activity toward Oxygen Reduction Reaction of Nanostructured Transition Metal Nitrides as Catalysts for Hybrid Na-Air Batteries

Nanostructured transition metal nitrides (TMNs) have been considered as a promising substitute for precious metal catalysts toward ORR due to their multi-electron orbitals, metallic properties, and low cost. To design TMN catalysts with high catalytic activity toward ORR, the intrinsic features of the influencing factor on the catalytic activity toward ORR of nanostructured TMNs need to be investigated. In this paper, titanium nitride (TiN), zirconium nitride (ZrN), and hafnium nitride (HfN) nanoparticles (NPs) are highly efficient and synthesized in one step by the direct current arc plasma. TiN, ZrN, and HfN NPs with an oxidation layer are applied as the catalysts of hybrid sodium–air batteries (HSABs). The effect of the composition and structural attributes of TMNs on ORR catalysis is defined as follows: (i) composition effect. With the increase in the oxygen content, the catalytic ORR capability of TMNs decreases progressively due to the reduction in oxygen adsorption capacity; (ii) structure effect. The redistribution of the density of states (DOS) of ZrN indicates higher ORR activity than TiN and HfN. HSABs with ZrN exhibit an excellent cyclic stability up to 137 cycles (about 140 h), an outstanding rate performance, and a specific capacity of 2817 mAh·g−1 at 1.0 mA·cm−2.

Promoting the activity of Ni3S2-x/Ni2P fuzzy-like nanorods as a bifunctional electrocatalyst for efficient overall water splitting through dealloying and active site design strategy

High-efficiency bifunctional electrocatalysts can reduce the hydrogen and oxygen evolution reaction (HER/OER) overpotential, which is of great significance for hydrogen production by water splitting. However, issues remain with large-scale preparation and a bottleneck for design separation. In this work, we reported on a facile method using a nanostructured transition metal sulfide (TMS) Ni3S2-Vs-Ps nanorod (NSVP NR) bifunctional catalyst material, which was prepared by dealloying and doping to obtain novel fuzzy-like NRs with heterostructures in triphasic points. The experimental results and first-principles calculations both revealed that the P-dopants changed the coordination environment between the inner S-vacancy Ni3S2-x NRs and outer Ni2P nanoparticles in the heterojunctions of the triphasic points, which as active sites could accelerate the movement of electron charges in the metal catalyst. The NVSP NRs showed excellent adsorption energy results, which on the Ni site were ΔGH* at 0.12 eV for HER and ΔGmax at 0.48 eV for OER. The optimized NSVP NRs demonstrated a current density of 100 mA/cm2 at the lowest overpotential of only 148 mV for HER and 311 mV for OER. Moreover, a cell voltage of 1.565 V could achieve 10 mA/cm2 when assembled in 1 M KOH solution for overall water splitting (OWS). Therefore, these findings provide a novel route from traditional dealloying corrosion for creating nanostructures and for producing new energy, offering insight into bifunctional catalyst design and application.

Nanotechnology in Advanced 2D and 3D Nanostructured Transition Metal Oxide Based Flexible Supercapacitors: A Review

AbstractFlexible supercapacitors (FSCs) can be power sources for the next generation of flexible and wearable electronic devices. Recent breakthroughs in nanotechnology have opened new opportunities in the energy industry to improve the performance of FSCs by providing high energy density, high power density, and excellent flexibility. Due to their higher surface area, larger contact area between electrode and electrolyte, and shorter ion‐diffusion pathways, low‐dimensional materials with a wide variety of morphologies play a key role in improving the performance of FSCs. Especially nanostructured transition metal oxides (TMOs) are of great interest for the application of SCs due to their superior specific capacitance, high energy density, high redox reversibility, easy availability, and environmental safety. However, the low electrical conductivity, low power density, poor cycle stability, and rigid properties of TMOs have limited their wide applications for FSCs. Therefore, the fabrication of nanostructured TMO‐based composites with conducting carbon, polymers, and other materials with large surface areas, pore and layer structures, etc., improves the electrical and mechanical properties. This review provides a brief overview of the current developments in 2D and 3D TMO‐based nanomaterials and their preparation techniques, design, structure, and fundamental understanding of nanoscale capacitive behavior for advanced flexible energy storage applications.

Intercalation of Potassium Ions in Molybdenum Sulfide as Catalyst for CO2 Reduction

The increasing CO2 emission during the last decades highly contributed to global warming and as a consequence, we are facing the disruption of nature and more and more extreme weather conditions nowadays [1]. One way of dealing with the emitted excess CO2 is to create a synthetic carbon cycle, where the emitted CO2 is captured and turned into fuel using electrocatalysis and green energy. However, in order to achieve this, the exploration of new electrocatalysts is needed for the sake of cost and process efficiency and environmental friendliness.Two dimensional materials have a promising future as catalysts due to their high surface-to-volume ratio. A potential catalyst material for CO2 reduction is molybdenite (MoS2), a cheap, layered semiconductor which already showed selectivity towards CO2 reduction in non-aqueous media [2,3]. Its layered structure allows not only to have a high specific surface area but also makes the intercalation of different ions possible. These features enable us to enhance the conductivity of the material via electron donation by the intercalated species [4]. The improved conductivity and the changed band gap can contribute to a higher efficiency of electrochemical processes.Our research investigates the intercalation mechanism of potassium ions into MoS2 layers and the effects of the intercalated potassium on the CO2 reduction efficiency. The intercalation process is studied experimentally through electrochemical impedance spectroscopy (EIS) and confirmed by X-ray diffraction (XRD). Furthermore, the Gibbs free energy profile of the intercalation is obtained by Molecular Dynamics (MD) simulations using umbrella sampling. The electronic properties are measured with X-ray photoelectron spectroscopy (XPS) and the products of the CO2 reduction reaction is measured with gas chromatography (GC). The results suggest that the potassium intercalation improves the conductivity of the MoS2 and consequently the CO2 reduction efficiency.[1] McCrystall et al. New climate models reveal faster and larger increases in Arctic precipitation than previously projected. Nat. Commun. 12:6765, 2021.[2] Asadi et al. Robust carbon dioxide reduction on molybdenum disulphide edges. Nature Communications, 5(1), 2014.[3] Asadi et al. Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid. Science, 353(6298):467–470, 2016.[4] Wang et al. Atomic-scale clarification of structural transition of MoS2 upon sodium intercalation. ACS Nano, 8(11):11394– 11400, 2014.

Pd-doped flower like magnetic MnFe2O4 spinel ferrit nanoparticles: Synthesis, structural characterization and catalytic performance in the hydrazine-borane methanolysis

MnFe2O4 nanoparticles, an important member of nanostructured transition metal oxides, also known as spinel ferrites, find wide use in many applications, especially medicine and catalysis, due to their fascinating properties. In this research article, MnFe2O4 and MnFe2O4 supported Pd0 nanoparticles were primarily prepared by solvothermal and impregnation/reduction methods, respectively. After the structural and morphological examination of the MnFe2O4 decorated Pd0 nanoparticles (Pd@MnFe2O4), their catalytic activity was tested in the release of hydrogen from the methanolysis of hydrazine-borane. The morphological characterizations of Pd@MnFe2O4 catalyst show that Pd0 nanoparticles were successfully decorated (average particle size ∼2.83 nm) on the flower-like MnFe2O4 spinel ferrite nanoparticles. The Pd@MnFe2O4 catalyst presented high catalytic performance in the H2 production via the methanolysis of hydrazine-borane, and the turn-over frequency value at 298 K was 47.2 min−1, which is the highest catalytic systems in the literature for this purpose. The Pd@MnFe2O4 catalyst displaying good activity in ten consecutive catalytic runs can be considered a good heterogeneous catalyst for the hydrogen production from the methanolysis of hydrazine-borane.

Promoting active species generation by sculpting Co3S4/Co(OH)2 nanotubes with rich sulfide/hydroxide interfaces for efficient oxygen evolution reaction

Nanostructured transition metal sulfides (TMSs) have attracted great attention owing to their superior electric conductivity and easy redox reaction properties in oxygen evolution reaction (OER) catalysts. However, the strong metal-metalloid bonds (M−S) and metalloid-metalloid (SS) bonds in the crystal structure of TMSs are difficult to break, which might result in the insufficient formation of electrocatalytically active metal hydroxide species on the surface and prevent the realization of their full OER potential. Herein, we demonstrate an approach by sculpting Co(OH)2 on Co3S4 nanotubes (Co3S4/Co(OH)2) as highly reactive and stable electrocatalysts for efficient OER. The electron transfer between cobalt and sulfur and the pre-sculpted Co(OH)2 promote the formation of rich hydroxide active species on the surface of Co3S4/Co(OH)2. The optimized Co3S4/Co(OH)2–0.8 catalyst possesses excellent electrocatalytic activity for OER in an alkaline medium, with a relatively low OER overpotential of 269 mV (at 10 mA cm−2) and a Tafel slope of 95.2 mV dec-1. This work provides a new sight of designing TMS electrocatalysts for practical application in efficient water splitting.

A Highly Conductive and Supercapacitive MXene/N-CNT Electrode Material Derived from a MXene-Co-Melamine Precursor

MXene is a two-dimensional nanostructured transition metal carbon/nitride and carbon nanotubes (CNTs) are a one-dimensional graphitized carbon material, which are widely exploited for their large specific surface and excellent electrical conductivity, but the easy aggregation limits their performance. In this work, a MXene-Co-melamine precursor is elaborately assembled by coordination bonds and a highly dispersed MXene/N-CNT composite material is ultimately constructed via a segmental pyrolysis of the MXene-Co-melamine precursor. This strategy synchronously relieves the self-restacking problem of MXene and N-CNTs. The optimal 0.60-MXene/N-CNT is composed of abundant and homogeneous CNTs with a high nitrogen dosage of 5.879 wt %. And it has a large BJH adsorption average pore size of 11.5 nm, a high microporous–mesoporous distribution of 1.94% micropores and 61.67% mesopores, and a well-matched hierarchical pore structure. Due to the orderly assembled porous structure of MXene and N-CNTs, the 0.60-MXene/N-CNT exhibits a high specific capacitance of 167.2 F g–1 at 0.5 A g–1. The assembled 0.60-MXene/N-CNT//AC asymmetric supercapacitor maintains a high capacitance retention of 73.2% after 10,000 cycles at 5 A g–1 current density and a high Coulomb efficiency of 97.5%. Its energy density also can reach 12.1 Wh kg–1 at a power density of 195.4 W kg–1.

Microwave-assisted synthesis of ternary transition metal ferrite: Structural, morphological, optical, magnetic and electrochemical properties

Transition metal oxides are promising materials in photocatalysts, sensors, photovoltaics, and especially as supercapacitor electrodes for their rapid, reversible faradaic redox reactions. Nanosized ternary transition metal ferrite (NiMnFe 2 O 4 ) has been synthesized using an easy and inexpensive microwave-assisted combustion method. The powder XRD confirms the nanoparticles as in spinal cubic structure with space group Fd-3m. FTIR has analyzed to understand the vibration of metal ions in the prepared NiMnFe 2 O 4 . The elemental composition and surface morphology of the nanoparticles have been studied by scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray (EDX) analysis. The UV–Visible diffuse reflectance spectra are used to examine the optical properties and to calculate the band gap energy of NiMnFe 2 O 4 , which is found to be 1.08 eV. The electrochemical properties of the prepared metal ferrite have been studied by electrochemical impedance spectroscopy (EIS), Galvanostatic charge-discharge (GCD) and cyclic voltammetry (CV). The specific capacitance of the modified electrode is found to exhibit the highest value of 476 F/g at 5 mV/s. • Nanostructured ternary transition metal ferrite has been prepared by a low-cost Microwave-assisted combustion method. • SEM analysis exhibit the irregular shape morphology. • The prepared NiMnFe 2 O 4 electrode revealed a higher energy density of 1.226 W h/Kg and superior power density of 1125 W/kg. • Cyclic stability of the NiMnFe 2 O 4 exhibits capacity retention of 83.67%.

A binder-free three-dimensional Ni foam supported hollow Co3O4/NiCo2O4 sensor for efficient monitoring of 4-chlorophenol

Nanostructured transition metal oxides with fine morphological tuning are considered excellent electrode materials for manufacturing electrochemical sensors. To explore a novel functional electroactive material having higher sensitivity and stability with a low limit of detection in a wider linear range and reliable selectivity for 4-chlorophenol (4-CP) monitoring in aqueous media, zeolitic imidazolate framework-67-derived hollow porous Co3O4/NiCo2O4 bimetallic nanostructure on Ni foam was assembled successfully via a simple and facile method. The optimized nano architectural Co3O4/NiCo2O4@NF electrode showed remarkable results in terms of sensitivity (0.47 μA μM−1 cm−2), ultra-low detection limit (0.08) in a wider linear range (0.3–133 μM), and excellent performance in complex environment for reliable 4-CP monitoring with the application of an appropriate applied potential. The prepared sensor has not only tremendous durability (∼35 days) and reproducibility but also a great capability to detect 4-CP in real-water environment. The applied sensor showed superior electroconductivity, abundant active sites on the larger surface area, efficient electron transfer because of the availability of numerous short pathways for ion diffusion owing to the hollow porous structure. This works offers not only a rationally designed electrode by bimetallic oxides for excellent monitoring of 4-CP but also promising electrode materials for the detection of other pollutants.