Co3O4/SiO2 nanocomposites for supercapacitor application

Magnetic cobalt oxide supported organosilica-sulfonic acid as a powerful nanocatalyst for the synthesis of tetrahydrobenzo[a]xanthen-11-ones

A novel core-shell structured magnetic cobalt oxide supported organosilica-sulfonic acid (Co3O4@SiO2/OS-SO3H) nanocomposite is prepared through a low-cost, simple, and clean method. The characterization of Co3O4@SiO2/OS-SO3H was performed by using Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD), energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and transmission electron microscopy (TEM). The TGA and FT-IR results illustrate the high stability of the designed nanocomposite. The SEM image showed a size of about 40 nm for the Co3O4@SiO2/OS-SO3H nanoparticles. Furthermore, according to the result of VSM analysis, the saturation magnetization of this nanocomposite was about 25 emu/g. This novel material was used as an efficient nanocatalyst for the synthesis of biologically active tetrahydrobenzo[a]xanthen-11-one derivatives. These products were obtained in high to excellent yields under green conditions. The recoverability and reusability of this catalyst were also investigated under applied conditions.

The supercapattery designed with a binary composite of niobium silver sulfide (NbAg2S) and activated carbon for enhanced electrochemical performance

A supercapattery is a hybrid device that is a combination of a battery and a capacitor. Niobium sulfide (NbS), silver sulfide (Ag₂S), and niobium silver sulfide (NbAg₂S) were synthesized by a simple hydrothermal method. NbAg₂S (50/50 wt% ratio) had a specific capacity of 654 C g^-1, which was higher than the combined specific capacities of NbS (440 C g^-1) and Ag₂S (232 C g^-1), as determined by the electrochemical investigation of a three-cell assembly. Activated carbon and NbAg₂S were combined to develop the asymmetric device (NbAg₂S//AC). A maximum specific capacity of 142 C g^-1 was delivered by the supercapattery (NbAg₂S//AC). The supercapattery (NbAg₂S/AC) provided 43.06 W h kg^-1 energy density while retaining 750 W kg^-1 power density. The stability of the NbAg₂S//AC device was evaluated by subjecting it to 5000 cycles. After 5000 cycles, the (NbAg₂S/AC) device still had 93% of its initial capacity. This research indicates that merging NbS and Ag₂S (50/50 wt% ratio) may be the best choice for future energy storage technologies.

Formation of MXene-Derived/NiCoFe-LDH Heterostructures for Supercapacitor Applications

In this study, MXene-derived/NiCoFe-LDH heterostructures with three-dimensional interconnected porous network microstructures were prepared, leveraging the excellent electrical conductivity and growth platform provided by the MXene material. The remarkable specific capacitance of metal oxides was fully exploited. The composite exhibited high specific capacitance and excellent stability, with a specific capacitance of 1305 F g^-1 at 1 A g^-1 and a capacitance of 85.7% of the initial performance after 6000 charge/discharge tests at 10 A g^-1. A two-electrode assembly was constructed using activated carbon as the negative electrode material corresponding to 49.5 Wh kg^-1 at 800 W kg^-1, indicating that the electrodes could achieve rapid charge/discharge. The findings of this study indicate that the composite material comprising LDH/MXene has significant potential for supercapacitor applications.

Semi-Embedding Zn-Co3O4 Derived from Hybrid ZIFs into Wood-Derived Carbon for High-Performance Supercapacitors

Transition metal oxides (TMOs) can provide high theoretical capacitance due to the change of multiple valence states of transition metals. However, their intrinsic drawbacks, including poor electrical conductivity, lower energy density, and huge volume expansion, will result in the pulverization of electrode materials and restricted electrochemical kinetics, thus leading to poor rate capability and rapid capacity fading. Composite electrodes based on transition metal oxides and carbon-based materials are considered to be promising candidates for overcoming these limitations. Herein, we reported a preparation method of hybrid ZIFs derived Zn-doped Co3O4/carbon (Zn-Co3O4/C-230) particles semi-embedded in wood-derived carbon skeleton for integrated electrodes. A large specific surface area, excellent conductivity, and electrochemical stability provide a larger electrochemical activity and potential window for the electrode. Prepared Zn-Co3O4@CW-230 electrode (0.6 mm thick) displays ultrahigh area specific capacitances of 7.83 and 6.46 F cm-2 at the current densities of 5 and 30 mA cm-2, respectively. Moreover, a symmetric supercapacitor assembled by two identical Zn-Co3O4@CW-230 electrodes delivers a superior area-specific capacitance of 2.61 F cm-2 at the current densities of 5 mA cm-2 and great energy densities of 0.36 mWh cm-2 (6.0 mWh cm-3) at 2.5 mW cm-2, while maintaining 97.3% of initial capacitance over 10,000 cycles. It notably outperforms those of most carbon-based metal oxides, endowing the Zn-Co3O4@CW-230 with extensive prospects for practical application.

A Review of Cobalt-Containing Nanomaterials, Carbon Nanomaterials and Their Composites in Preparation Methods and Application

With the increasing demand for sustainable and green energy, electric energy storage technologies have received enough attention and extensive research. Among them, Li-ion batteries (LIBs) are widely used because of their excellent performance, but in practical applications, the electrochemical performance of electrode materials is not satisfactory. Carbon-based materials with high chemical stability, strong conductivity, high specific surface area, and good capacity retention are traditional anode materials in electrochemical energy storage devices, while cobalt-based nano-materials have been widely used in LIBs anodes because of their high theoretical specific capacity. This paper gives a systematic summary of the state of research of cobalt-containing nanomaterials, carbon nanomaterials, and their composites in LIBs anodes. Moreover, the preparation methods of electrode materials and measures to improve electrochemical performance are also summarized. The electrochemical performance of anode materials can be significantly improved by compounding carbon nanomaterials with cobalt nanomaterials. Composite materials have better electrical conductivity, as well as higher cycle ability and reversibility than single materials, and the synergistic effect between them can explain this phenomenon. In addition, the electrochemical performance of materials can be significantly improved by adjusting the microstructure of materials (especially preparing them into porous structures). Among the different microscopic morphologies of materials, porous structure can provide more positions for chimerism of lithium ions, shorten the diffusion distance between electrons and ions, and thus promote the transfer of lithium ions and the diffusion of electrolytes.

Development of a Kinetic Model for the Redox Reactions of Co2.4Ni0.6O4 and SiO2/Co2.4Ni0.6O4 Oxides for Thermochemical Energy Storage

One of the possible solutions for the transition of the actual energetic model is the use of thermal energy storage technologies. Among them, thermochemical energy storage based on redox reactions involving metal oxides is very promising due to its high energy density. This paper deals with the development of the kinetic study based on data extracted from the thermogravimetric analysis of a cobalt-nickel mixed oxide (Co_2.4Ni_0.6O₄) without and with the addition of SiO₂ particles to improve the cyclability. The results show that in the reduction reaction the activation energy is not affected by the addition of SiO₂ particles while in the oxidation reaction an increase in the activation energy is observed. The theoretical models fitting with the experimental data are different for each material in the reduction reaction. The mixed oxide is controlled by a nucleation and growth mechanism for conversion ratios higher than 0.5, while the added material is controlled by diffusion mechanisms. In the oxidation reaction, the two materials are controlled by a nucleation and growth mechanism for conversion ratios higher than 0.5.

Electrochemical Performance of Iron-Doped Cobalt Oxide Hierarchical Nanostructure

In this study, hydrothermally produced Fe-doped Co3O4 nanostructured particles are investigated as electrocatalysts for the water-splitting process and electrode materials for supercapacitor devices. The results of the experiments demonstrated that the surface area, specific capacitance, and electrochemical performance of Co3O4 are all influenced by Fe3+ content. The FexCo3-xO4 with x = 1 sample exhibits a higher BET surface (87.45 m2/g) than that of the pristine Co3O4 (59.4 m2/g). Electrochemical measurements of the electrode carried out in 3 M KOH reveal a high specific capacitance of 153 F/g at a current density of 1 A/g for x = 0.6 and 684 F/g at a 2 mV/s scan rate for x = 1.0 samples. In terms of electrocatalytic performance, the electrode (x = 1.0) displayed a low overpotential of 266 mV (at a current density of 10 mA/cm2) along with 52 mV/dec Tafel slopes in the oxygen evolution reaction. Additionally, the overpotential of 132 mV (at a current density of 10 mA/cm2) and 109 mV with 52 mV/dec Tafel slope were obtained for x = 0.6 sample towards hydrogen evolution reaction (HER). According to electrochemical impedance spectroscopy (EIS) measurements and the density functional theory (DFT) study, the addition of Fe3+ increased the conductivity at the electrode–electrolyte interface, which substantially impacted the high activity of the iron-doped cobalt oxide. The electrochemical results revealed that the mesoporous Fe-doped Co3O4 nanostructure could be used as potential electrode material in the high-performance electrochemical capacitor and water-splitting catalysts.

Electrochemical Performance of Aluminum Doped Ni1−xAlxCo2O4 Hierarchical Nanostructure: Experimental and Theoretical Study

For electrochemical supercapacitors, nickel cobaltite (NiCo2O4) has emerged as a new energy storage material. The electrocapacitive performance of metal oxides is significantly influenced by their morphology and electrical characteristics. The synthesis route can modulate the morphological structure, while their energy band gaps and defects can vary the electrical properties. In addition to modifying the energy band gap, doping can improve crystal stability and refine grain size, providing much-needed surface area for high specific capacitance. This study evaluates the electrochemical performance of aluminum-doped Ni1−xAlxCo2O4 (0 ≤ x ≤ 0.8) compounds. The Ni1−xAlxCo2O4 samples were synthesized through a hydrothermal method by varying the Al to Ni molar ratio. The physical, morphological, and electrochemical properties of Ni1−xAlxCo2O4 are observed to vary with Al3+ content. A morphological change from urchin-like spheres to nanoplate-like structures with a concomitant increase in the surface area, reaching up to 189 m2/g for x = 0.8, was observed with increasing Al3+ content in Ni1−xAlxCo2O4. The electrochemical performance of Ni1−xAlxCo2O4 as an electrode was assessed in a 3M KOH solution. The high specific capacitance of 512 F/g at a 2 mV/s scan rate, 268 F/g at a current density of 0.5 A/g, and energy density of 12.4 Wh/kg was observed for the x = 0.0 sample, which was reduced upon further Al3+ substitution. The as-synthesized Ni1−xAlxCo2O4 electrode exhibited a maximum energy density of 12.4 W h kg−1 with an outstanding high-power density of approximately 6316.6 W h kg−1 for x = 0.0 and an energy density of 8.7 W h kg−1 with an outstanding high-power density of approximately 6670.9 W h kg−1 for x = 0.6. The capacitance retention of 97% and 108.52% and the Coulombic efficiency of 100% and 99.24% were observed for x = 0.0 and x = 0.8, respectively. First-principles density functional theory (DFT) calculations show that the band-gap energy of Ni1−xAlxCo2O4 remained largely invariant with the Al3+ substitution for low Al3+ content. Although the capacitance performance is reduced upon Al3+ doping, overall, the Al3+ doped Ni1−xAlxCo2O4 displayed good energy, powder density, and retention performance. Thus, Al3+ could be a cost-effective alternative in replacing Ni with the performance trade off.

The Recent Progress on Silver Nanoparticles: Synthesis and Electronic Applications

Nanoscience enables researchers to develop new and cost-effective nanomaterials for energy, healthcare, and medical applications. Silver nanoparticles (Ag NPs) are currently increasingly synthesized for their superior physicochemical and electronic properties. Good knowledge of these characteristics allows the development of applications in all sensitive and essential fields in the service of humans and the environment. This review aims to summarize the Ag NPs synthesis methods, properties, applications, and future challenges. Generally, Ag NPs can be synthesized using physical, chemical, and biological routes. Due to the great and increasing demand for metal and metal oxide nanoparticles, researchers have invented a new, environmentally friendly, inexpensive synthetic method that replaces other methods with many defects. Studies of Ag NPs have increased after clear and substantial support from governments to develop nanotechnology. Ag NPs are the most widely due to their various potent properties. Thus, this comprehensive review discusses the different synthesis procedures and electronic applications of Ag NPs.

Recent Advances of Nanoremediation Technologies for Soil and Groundwater Remediation: A Review

Nanotechnology has been widely used in many fields including in soil and groundwater remediation. Nanoremediation has emerged as an effective, rapid, and efficient technology for soil and groundwater contaminated with petroleum pollutants and heavy metals. This review provides an overview of the application of nanomaterials for environmental cleanup, such as soil and groundwater remediation. Four types of nanomaterials, namely nanoscale zero-valent iron (nZVI), carbon nanotubes (CNTs), and metallic and magnetic nanoparticles (MNPs), are presented and discussed. In addition, the potential environmental risks of the nanomaterial application in soil remediation are highlighted. Moreover, this review provides insight into the combination of nanoremediation with other remediation technologies. The study demonstrates that nZVI had been widely studied for high-efficiency environmental remediation due to its high reactivity and excellent contaminant immobilization capability. CNTs have received more attention for remediation of organic and inorganic contaminants because of their unique adsorption characteristics. Environmental remediations using metal and MNPs are also favorable due to their facile magnetic separation and unique metal-ion adsorption. The modified nZVI showed less toxicity towards soil bacteria than bare nZVI; thus, modifying or coating nZVI could reduce its ecotoxicity. The combination of nanoremediation with other remediation technology is shown to be a valuable soil remediation technique as the synergetic effects may increase the sustainability of the applied process towards green technology for soil remediation.

Solution Processing of Topochemically Converted Layered WO3 for Multifunctional Applications

Solution processing of nanomaterials is a promising technique for use in various applications owing to its simplicity and scalability. However, the studies on liquid-phase exfoliation (LPE) of tungsten oxide (WO₃ ) are limited, unlike others, by a lack of commercial availability of bulk WO₃ with layered structures. Herein, a one-step topochemical synthesis approach to obtain bulk layered WO₃ from commercially available layered tungsten disulfide (WS₂ ) by optimizing various parameters like reaction time and temperature is reported. Detailed microscopic and spectroscopic techniques confirmed the conversion process. Further, LPE was carried out on topochemically converted bulk layered WO₃ in 22 different solvents; among the solvents studied, the propan-2-ol/water (1 : 1) co-solvent system appeared to be the best. This indicates that the possible values of surface tension and Hansen solubility parameters for bulk WO₃ could be close to that of the co-solvent system. The obtained WO₃ dispersions in a low-boiling-point solvent enable thin films of various thickness to be fabricated by using spray coating. The obtained thin films were used as active materials in supercapacitors without any conductive additives/binders and exhibited an areal capacitance of 31.7 mF cm^-2 at 5 mV s^-1 . Photo-electrochemical measurements revealed that these thin films can also be used as photoanodes for photo-electrochemical water oxidation.

Synthesis, Characterization and Applications of Spinel Cobaltite Nanomaterials

Recently, spinel structures (AB₂O₄) Nanoparticles (NPs) having binary and ternary mixtures of metal oxides have been established as promising redox catalysts. Due to the presence of two mixed valence metal cations, transport of electrons takes place easily between multiple transition-metal cations with relatively low energy of activation. Among these, spinel cobaltite (MCo₂O₄) is very attractive due to its low cost, non-toxicity, higher stability, higher electronic conductivity and electrochemical property. To date, MCo₂O₄ has been used in the fabrication of supercapacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. A variety of MMCo₂O₄materials have been synthesized, characterized, and utilized in the fabrication of super capacitors, electrodes for oxygen evolution reaction, and electrochemical sensors for glucose. The progress in the field of the spinel MCo₂O₄ materials opens the door to novel and efficient applications in the nanoscience and nanotechnology, and elctrochemistry.

Improving the Supercapacitor Performance by Dispersing SiO2 Microspheres in Electrodes

This paper describes a simple, reproducible, and scalable procedure for the preparation of a SiO₂-containing supercapacitor with high cycle stability. A carbon mesoporous material (CMM) with a high specific surface area, CMK-3, was adopted as an electric double-layer capacitor (EDLC) active material for the preparation of electrodes for the supercapacitor. The optimized SiO₂ content decreased as the microsphere diameter decreased, and the optimal specific capacitance was obtained with 6 wt % SiO₂ microspheres (100 nm size). The capacitance improved from 133 to 298 F/g. The corresponding capacitance retention rate after 1000 cycles increased from 68.04 to 91.53%. In addition, the energy density increased from 21.05 to 26.25 Wh/kg with a current density of 1 A/g. Finally, similar results based on active carbon, CeO₂/CMK-3, and graphene/CNT/MnO_v composite electrodes demonstrated that the proposed method exhibits wide compatibility with diverse electrode materials.

An autocatalytic route of CuO/Co3O4@SiO2 nanocapsules as excellent performance supercapacitor materials

Nanocapsules prepared with silica as a carrier and coated with Co₃O₄ and CuO nanoparticles are used for high-performance supercapacitors.

Simultaneous Electrochemical Deposition of Cobalt Complex and Poly(pyrrole) Thin Films for Supercapacitor Electrodes

Supercapacitors are beneficial as energy storage devices and can obtain high capacitance values greater than conventional capacitors and high power densities compared to batteries. However, in order to improve upon the overall cost, energy density, and charge-discharge rates, the electrode material of supercapacitors needs to be fine-tuned with an inexpensive, high conducting source. We prepared a Co(III) complex and polypyrrole (PPy) composite thin films (CoN₄-PPy) that was electrochemically deposited on the surface of a glassy carbon working electrode. Cyclic voltammetry studies indicate the superior performance of CoN₄-PPy in charge storage in acidic electrolyte compared to alkaline and organic solutions. The CoN₄-PPy material generated the highest amount of specific capacitance (up to 721.9 F/g) followed by Co salt and PPy (Co-PPy) material and PPy alone. Cyclic performance studies showed the excellent electrochemical stability of the CoN₄-PPy film in the acidic medium. Simply electrochemically depositing an inexpensive Co(III) complex with a high electrically conducting polymer of PPy delivered a superior electrode material for supercapacitor applications. Therefore, the results indicate that novel thin films derived from Co(III) metal complex and PPy can store a large amount of energy and maintain high stability over many cycles, revealing its excellent potential in supercapacitor devices.

Carbon nanospheres derived from Lablab purpureus for high performance supercapacitor electrodes: a green approach

Carbon nanospheres derived from a natural source using a green approach were reported. Lablab purpureus seeds were pyrolyzed at different temperatures to produce carbon nanospheres for supercapacitor electrode materials. The synthesized carbon nanospheres were analyzed using SEM, TEM, FTIR, TGA, Raman spectroscopy, BET and XRD. They were later fabricated into electrodes for cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy testing. The specific capacitances were found to be 300, 265 and 175 F g^-1 in 5 M KOH electrolyte for carbon nanospheres synthesized at 800, 700 and 500 °C, respectively. These are on a par with those of prior electrodes made of biologically derived carbon nanospheres but the cycle lives were remarkably higher than those of any previous efforts. The electrodes showed 94% capacitance retention even after 5200 charge/discharge cycles entailing excellent recycling durability. In addition, the practical symmetrical supercapacitor showed good electrochemical behaviour under a potential window up to 1.7 V. This brings us one step closer to fabricating a commercial green electrode which exhibits high performance for supercapacitors. This is also a waste to wealth approach based carbon material for cost effective supercapacitors with high performance for power storage devices.

Metal organic framework-derived Zn1−xCox-ZIF@Zn1−xCoxO hybrid photocatalyst with enhanced photocatalytic activity through synergistic effect

A Zn_1−xCo_x-ZIF@Zn_1−xCo_xO hybrid photocatalyst, doped with different amounts of Co, was successfully fabricated through a novel metal organic framework (MOF)-derived method.

Design and Synthesis of Hierarchical SiO2@C/TiO2 Hollow Spheres for High-Performance Supercapacitors

TiO₂ has been widely investigated as an electrode material because of its long cycle life and good durability, but the relatively low theoretical capacity restricts its practical application. Herein, we design and synthesize novel hierarchical SiO₂@C/TiO₂ (HSCT) hollow spheres via a template-directed method. These unique HSCT hollow spheres combine advantages from both TiO₂ such as cycle stability and SiO₂ with a high accessible area and ionic transport. In particular, the existence of a C layer is able to enhance the electrical conductivity. The SiO₂ layer with a porous structure can increase the ion diffusion channels and accelerate the ion transfer from the outer to the inner layers. The electrochemical measurements demonstrate that the HSCT-hollow-sphere-based electrode manifests a high specific capacitance of 1018 F g^-1 at 1 A g^-1 which is higher than those for hollow TiO₂ (113 F g^-1) and SiO₂/TiO₂ (252 F g^-1) electrodes, and substantially higher than those of all the previously reported TiO₂-based electrodes.

3,4-Diaminotoluene sensor development based on hydrothermally prepared MnCoxOy nanoparticles

A facile hydrothermal process was used to prepare MnCo_xO_y nanoparticles (NPs) in alkaline medium (pH~10.5) at room temperature. The NPs were characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV/vis), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and powder X-ray diffraction (XRD). A thin layer of NPs film as a chemical sensor was fabricated on a glassy carbon electrode (GCE) with the help of a conducting binder. The sensor was implemented successfully for the detection 3,4-DAT with reliable I-V approach at low potential. The sensor-features include good sensitivity (0.37 mAµmolL^-1cm^-2), low detection limit (LOD=0.26±0.01 pmolL^-1 at a signal to noise ratio of 3), low limit of quantification (LOQ=7.80±0.01 pmolL^-1), good reliability, good reproducibility, ease of integration, and long-term stability were investigated. The sensor response towards 3,4-DAT is linear in logarithmic scale over a large concentration range (1.0 pmolL^-1 to 1.0 µmolL^-1). This work is introduced a route for future sensitive sensor development based on MnCo_xO_y NPs by reliable I-V method for the detection of hazardous and carcinogenic toxins in environmental and health care fields.

Facile synthesis of Co3O4 porous nanosheets/reduced graphene oxide composites and their excellent supercapacitor performance

Porous Co₃O₄ nanosheets/RGO composite with excellent capacitive performance was prepared through a facile two-step strategy.