Zinc cobalt sulfide nanoparticles as high performance electrode material for asymmetric supercapacitor

Study on the performance and mechanism of cobaltous ion removal from water by a high-efficiency strontium-doped hydroxyapatite adsorbent

In this study, a high-efficiency strontium-doped hydroxyapatite (Sr-HAP) adsorbent was synthesized by a sol-gel method for removing cobaltous ions (Co(II)) from water. The effects of adsorbent dose, initial solution pH, initial Co(II) concentration and temperature on the removal performance of Co(II) were investigated. Experimental results indicated that the optimum Sr-HAP dose was 0.30 g/50 mL solution, the Sr-HAP adsorbent could effectively remove Co(II) in a wide pH range of 3-8. Increasing temperature was conducive to the adsorption, and the maximum Co(II) adsorption capacity by Sr-HAP reached 48.467 mg/g at 45 °C. The adsorption of Co(II) followed the pseudo-second-order kinetic model, indicating that the Co(II) adsorption by Sr-HAP was attributed mainly to chemisorption. The isothermal adsorption results showed that at lower Co(II) equilibrium concentration, the Langmuir model fitted the data better than the Freundlich model but opposite at higher Co(II) equilibrium concentration. Therefore, the adsorption of Co(II) was a process from monolayer adsorption to multilayer adsorption with the increase of the Co(II) equilibrium concentration. The diffusion analysis of Co(II) to Sr-HAP indicated that the internal diffusion and surface adsorption were the rate-controlled steps of Co(II) adsorption. Thermodynamic study demonstrated that the Co(II) adsorption process was spontaneous and endothermic. The mechanism study revealed that in addition to chemisorption, Sr-HAP also removed Co(II) ions from water via ion exchange and surface complexation.

Effectively Reinforced α-Bi2O3 MPs/PDA-RGO Sensor for Selective Modality Sensing of a Hazardous Phenolic Compound

The phenolic compound trichlorophenol (TCP) is an ingredient in fungicides and herbicides. This compound's high stability, bioaccumulation, toxicity, and poor biodegradability result in severe environmental and biological health issues. Consequently, it is crucial to have an affordable and sensitive method for detecting TCP in environmental samples. In this study, α-phase bismuth oxide microplates and polydopamine-functionalized reduced graphene oxide (α-Bi2O3 MPs/PDA-RGO) were synthesized using a simple ultrasonic method and characterized with various analytical and physical characterizations. The conversion of the catechol moieties present in the resulting PDA-RGO material into quinones facilitates productive interactions with diverse functional groups, such as hydroxyl, amine, and imine. Consequently, the compounds 2,4,6-trichlorophenol (TCP) engages in electrochemical interactions with the aforementioned functional groups. As a result, TCP shows more excellent selectivity on the designed α-Bi2O3 MPs/PDA-RGO/SPCE sensor. Under the optimized conditions, the sensor demonstrated a lower detection limit (0.0042 μM), a limit of quantification (0.0078 μM), good sensitivity (2.24 μA μM-1 cm2), a wide linear range (0.019-190.7 and 212.7-1649 μM), and pinpoint specificity. The efficacy of the sensor is additionally validated through the accurate identification of TCP residues in water, soil, and food samples.

A heterostructure of NiMn-LDH nanosheets assembled on ZIF-L-derived ZnCoS hollow nanosheets with a built-in electric field enables boosted electrochemical energy storage

Supercapacitors (SCs) have emerged as an efficient technology toward the utilization of renewable energy, which demands high-performance electrode materials. Transition-metal sulfides (TMSs) and layered double hydroxides (LDHs) rich in active sites and valence states are very promising electrode materials, but they still suffer from inherent defects, such as low electric conductivity, sluggish reaction kinetics and large volume change during electrochemical reactions. In this work, NiMn-LDH nanosheets are assembled on the surfaces of ZnCoS hollow nanosheet arrays derived from a zeolitic imidazolate framework-L (ZIF-L) to form a ZnCoS@NiMn-LDH heterostructure (ZCS@LDH) with a built-in electric field. The unique structure gives rise to abundant exposed active sites and improved ion diffusion. More importantly, the built-in electric field can enhance conductivity and charge transfer by modulating the electronic structures. With these merits, the optimal ZCS@LDH-6 electrode displays outstanding specific capacitance (2102.2 F g-1 at 1 A g-1) and remarkable rate performance (68.1% at 10 A g-1). The assembled asymmetric supercapacitor (ASC) using the ZCS@LDH-6 electrode shows high energy storage capacity (41.7 W h kg-1 at 850.0 W kg-1), satisfactory cycle life (92.2% capacitance retention after 10 000 cycles) and high coulombic efficiency (95.8%). This work will shed light on designing high-performance electrode materials via heterostructure and morphology engineering.

Bos taurus (A-2) urine assisted bioactive cobalt oxide anchored ZnO: a novel nanoscale approach

In this study, a novel synthetic method for cobalt oxide (Co3O4) nanoparticles using Bos taurus (A-2) urine as a reducing agent was developed. In addition to this ZnO nanorods were produced hydrothermally and a nanocomposite is formed through a solid-state reaction. The synthesized materials were characterized through modern characterization techniques such as XRD, FE-SEM with EDS, DLS, zeta potential, FT-IR, Raman spectroscopic analysis, and TGA with DSC. The free radical destructive activity was determined using two different methods viz. ABTS and DPPH. The potential for BSA denaturation in vitro, which is measured in comparison to heat-induced denaturation of egg albumin and results in anti-inflammatory effects of nanomaterial was studied. All synthesized nanomaterials have excellent antibacterial properties, particularly against Salmonella typhi and Staphylococcus aureus. The composite exhibits excellent antioxidant and anti-inflammatory activities in comparison to pure nanomaterials. This reveals that these nanomaterials are advantageous in medicine and drug administration.

Hierarchically nanostructured Zn0.76C0.24S@Co(OH)2 for high-performance hybrid supercapacitor

It is a great challenge to achieve both high specific capacity and high energy density of supercapacitors by designing and constructing hybrid electrode materials through a simple but effective process. In this paper, we proposed a hierarchically nanostructured hybrid material combining Zn_0.76Co_0.24S (ZCS) nanoparticles and Co(OH)₂ (CH) nanosheets using a two-step hydrothermal synthesis strategy. Synergistic effects between ZCS nanoparticles and CH nanosheets result in efficient ion transports during the charge-discharge process, thus achieving a good electrochemical performance of the supercapacitor. The synthesized ZCS@CH hybrid exhibits a high specific capacity of 1152.0 C g^-1 at a current density of 0.5 A g^-1 in 2 M KOH electrolyte. Its capacity retention rate is maintained at ∼ 70.0% when the current density is changed from 1 A g^-1 to 10 A g^-1. A hybrid supercapacitor (HSC) assembled from ZCS@CH as the cathode and active carbon (AC) as the anode displays a capacitance of 155.7 F g^-1 at 0.5 A g^-1, with a remarkable cycling stability of 91.3% after 12,000cycles. Meanwhile, this HSC shows a high energy density of 62.5 Wh kg^-1 at a power density of 425.0 W kg^-1, proving that the developed ZCS@CH is a promising electrode material for energy storage applications.

Facile synthesis of g-C3N4 quantum dots/graphene hydrogel nanocomposites for high-performance supercapacitor

This work demonstrates a facile one-pot method for preparing graphitic carbon nitride (g-C₃N₄) quantum dots/graphene hydrogel (CNQ/GH) nanocomposites using a hydrothermal process, in which graphene sheets of a graphene hydrogel (GH) are decorated with g-C₃N₄ quantum dots (CNQDs) and have a 3D hierarchical and interconnected structure through a typical self-assembly process. The obtained CNQ/GH nanocomposite demonstrates improved electrochemical performances of a supercapacitor with a specific capacitance of 243.2 F g⁻¹ at a current density of 0.2 A g⁻¹. In addition, the fabricated symmetric supercapacitor (SSC) using CNQ/GH electrodes exhibits a high energy density of 22.5 W h kg⁻¹ at a power density of 250 W kg⁻¹ and a superior cycling stability with a capacitance retention of 89.5% after 15 000 cycles. The observed improvements in the electrochemical performance of CNQ/GH electrodes are attributed to the large surface area with abundant mesopores and various C–N bonds in CNQDs, which promote efficient ion diffusion of electrolyte and electron transfer and provide more active sites for faradaic reactions. These obtained results demonstrate a facile and efficient route to develop potential electrode materials for high-performance energy storage device applications.

This work demonstrates a facile one-pot synthesis of graphitic carbon nitride (g-C₃N₄) quantum dots/graphene hydrogel (CNQ/GH) nanocomposites using a hydrothermal process, which shows excellent electrochemical performances for supercapacitors.

MnCo2O4/Ni3S4 nanocomposite for hybrid supercapacitor with superior energy density and long-term cycling stability

MnCo₂O₄ is regarded as a good electrode material for supercapacitor due to its high specific capacity and good structural stability. However, its poor electrical conductivity limits its wide-range applications. To solve this issue, we integrated the MnCo₂O₄ with Ni₃S₄, which has a good electrical conductivity, and synthesized a MnCo₂O₄/Ni₃S₄ nanocomposite using a two-step hydrothermal process. Comparing with individual MnCo₂O₄ and Ni₃S₄, the MnCo₂O₄/Ni₃S₄ nanocomposite showed a higher specific capacity and a better cycling stability as the electrode for the supercapacitor. The specific capacity value of the MnCo₂O₄/Ni₃S₄ electrode was 904.7 C g^-1 at 1 A g^-1 with a potential window of 0-0.55 V. A hybrid supercapacitor (HSC), assembled using MnCo₂O₄/Ni₃S₄ and active carbon as the cathode and anode, respectively, showed a capacitance of 116.4 F g^-1 at 1 A g^-1, and a high energy density of 50.7 Wh kg^-1 at 405.8 W kg^-1. Long-term electrochemical stability tests showed an obvious increase of the HSC's capacitance after 5500 charge/discharge cycles, reached a maximum value of ∼162.7% of its initial value after 25,000 cycles, and then remained a stable value up to 64,000 cycles. Simultaneously, its energy density was increased to 54.2 Wh kg^-1 at 380.3 W kg^-1 after 64,000 cycles.

Hierarchically urchin-like hollow NiCo2S4 prepared by a facile template-free method for high-performance supercapacitors

Hollow structures draw much attention for high energy density supercapacitors due to their large hollow cavities, high specific surface area, and low interfacial contact resistance. However, constructing hierarchical hollow structures remains a challenge. Herein, we reported a facile template-free method for a novel urchin-like hollow nickel cobalt sulfide (NiCo₂S₄). The hollow interior and urchin exterior remarkably improved the specific capacitance and accommodated structural collapse caused by electrochemical reactions. Owing to these features, the urchin-like hollow NiCo₂S₄ spheres exhibited an impressive capacitance of 1398F g^-1 at 1 A g^-1 and maintained 1110F g^-1 with a large current density of 10 A g^-1. The hybrid supercapacitor fabricated by NiCo₂S₄ and active carbon possesses an energy density of 39.3 Wh kg^-1 at a power density of 749.6 W kg^-1 and an outstanding cycling stability of 74.4% retention after 5000 cycles. Our work presents a facile method of constructing a hollow structure of binary sulfide materials and also makes progress on highly efficient supercapacitors.

Enhanced Supercapacitor Performance Using a Co3 O4 @Co3 S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes

To avoid an enormous energy crisis in the not-too-distant future, it be emergent to establish high-performance energy storage devices such as supercapacitors. For this purpose, a three-dimensional (3D) heterostructure of Co₃ O₄ and Co₃ S₄ on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro-deposited on rGO/Ni foam by applying cyclic-voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co₃ O₄ @Co₃ S₄ nanocomposite, the nanostructure of Co₃ S₄ was fabricated from Co₃ O₄ nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm^-2 (5651.24 F g^-1 ) at a current density of 6 mA cm^-2 compared to the Co₃ O₄ /rGO/NF electrode with a capacitance of 3.06 F cm^-2 (1230.77 F g^-1 ) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg^-1 , specific power density of 6048.03 W kg^-1 and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s^-1 ). Finally, by using Co₃ O₄ @Co₃ S₄ /rGO/NF and the activated carbon-based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm^-2 at the applied current density of 1 mA cm^-2 , and delivered an energy density of 0.143 Wh kg^-1 at the power density of 5.42 W kg^-1 .

Supercapacitor electrode materials: addressing challenges in mechanism and charge storage

In recent years, rapid technological advances have required the development of energy-related devices. In this regard, Supercapacitors (SCs) have been reported to be one of the most potential candidates to meet the demands of human’s sustainable development owing to their unique properties such as outstanding cycling life, safe operation, low processing cost, and high power density compared to the batteries. This review describes the concise aspects of SCs including charge-storage mechanisms and scientific principles design of SCs as well as energy-related performance. In addition, the most important performance parameters of SCs, such as the operating potential window, electrolyte, and full cell voltage, are reviewed. Researches on electrode materials are crucial to SCs because they play a pivotal role in the performance of SCs. This review outlines recent research progress of carbon-based materials, transition metal oxides, sulfides, hydroxides, MXenes, and metal nitrides. Finally, we give a brief outline of SCs’ strategic direction for future growth.

Cobalt(II)-ion-exchanged Zn-bio-MOF-1 derived CoS/ZnS composites modified electrochemical sensor for chloroneb detection by differential pulse voltammetry

For the first time CoS-nanoparticles attached ZnS rods (CoS/ZnS composites) have been synthesized using cobalt(II)-ion-exchanged zinc-based biological metal-organic framework-1 (Zn-bio-MOF-1) as precursors by a solvothermal method. Among them, the cobalt(II)-ion-exchanged Zn-bio-MOF-1 was obtained by exchanging the dimethylammonium cations (Me₂NH₂⁺) of Zn-bio-MOF-1 with cobalt ions. A novel electrochemical sensor based on CoS/ZnS composites and molecularly imprinted polymers (MIPs) was proposed for rapid, sensitive, and highly selective detection of organochlorine pesticide chloroneb. The MIP film was obtained by cyclic voltammetry (CV), and differential pulse voltammetry (DPV) was used to detect chloroneb. Under the optimal conditions, the oxidation peak current density of chloroneb was linearly related to the concentration from 0.003 to 0.2 μM and 0.2 to 3.2 μM with a detection limit of 0.87 nM (S/N = 3) and a sensitivity of 52.27 μA·μM^-1·cm^-2. The proposed sensor exhibits a favorable selectivity, stability, and reproducibility, and was applied to detect chloroneb residues in licorice, cucumber, river water, and soil samples with satisfactory results.Graphical abstract.

Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

N-Doped carbon as the anode and ZnCo2O4/N-doped carbon nanocomposite as the cathode for high-performance asymmetric supercapacitor application

Herein, we report a one-pot hydrothermal assisted synthesis of ZnCo₂O₄/N-doped carbon nanocomposite (ZC/NC) for high-performance asymmetric supercapacitor applications.

Cu-MOF derived Cu-C nanocomposites towards high performance electrochemical supercapacitors

For the development of asymmetric supercapacitors with higher energy density, the study of new electrode materials with high capacitance is a priority. Herein, the electrochemical behavior of nano copper in alkaline electrolyte is first discovered. It is found that there are two obvious reversible redox symmetric peaks in the range of -0.8-0.2 V in the alkaline electrolyte, corresponding to the conversion of copper into cuprous ions, and then converting cuprous ions into copper ions, indicating that the nanocomposite electrode has the characteristics of a pseudocapacitive reaction. It has a specific capacitance of up to 318 F g-1 at a current density of 1 A g-1, which remains at nearly 100% after 10 000 cycles at the same current density. When assembled with a Ni(OH)2-based electrode into an asymmetric supercapacitor, the device shows excellent capacitive behavior and good reaction reversibility. At 0.4 A g-1, the supercapacitor delivers a reversible capacity of 8.33 F g-1 with an energy density of 13.5 mW h g-1. This study first discovers the electrochemical behavior of nano copper, which can provide a new research idea for further expanding the negative electrodes of supercapacitors with higher energy density.

Rational design of flower-like cobalt–manganese-sulfide nanosheets for high performance supercapacitor electrode materials

The design and development of composite materials with novel structures is one of the effective ways to enhance the electrochemical properties of supercapacitors.