Controllable ZnFe2O4/reduced graphene oxide hybrid for high-performance supercapacitor electrode

Hierarchical NiCo2O4@CuS composite electrode with enhanced surface area for high-performance hybrid supercapacitors

Hierarchical binder-free NiCo2O4@CuS composite electrodes have been successfully fabricated on a nickel foam surface using a facile hydrothermal method and directly used as a battery-type electrode material for supercapacitor applications. The surface morphological studies reveal that the composite electrode exhibited porous NiCo2O4 nanograss-like structures with CuS nanostructures. The surface area of the composite is significantly enhanced (91.38 m2 g-1) compared to NiCo2O4 (52.16 m2 g-1), with a predominant pore size of 3-6 nm. This synergistic combination enhanced the electrode's electrochemical properties. The NiCo2O4@CuS electrode delivered an impressive specific capacitance of 141.13 mA h g-1 at 1 A g-1, surpassing the performance of the bare NiCo2O4 electrode. The composite electrode also exhibited excellent rate capability and cycling stability, retaining 87.49% of its initial capacity at high current densities and 88.62% after 3000 cycles. A hybrid supercapacitor (HSC) device assembled using NiCo2O4@CuS and G-ink electrodes attained a peak energy density of 28.85 W h kg-1 at a power density of 238.2 W kg-1, outperforming many reported HSCs. Additionally, the HSC device demonstrated exceptional cycling stability, retaining 87.59% of its initial capacitance after 4000 cycles. The superior performance of the NiCo2O4@CuS composite electrode is attributed to the synergistic combination of NiCo2O4 and CuS, which promotes interfacial electron separation and facilitates rapid electron transfer.

Electrical, optical, and electrochemical performances of phosphate-glasses-doped with ZnO and CuO and their composite with polyaniline

Phosphate-based glasses (PBG) with appropriate doping agents have been used as solid electrolytes in solid-state ionic devices. Therefore, more light was shed on the electrical, optical, and electrochemical behavior of the phosphate-based glasses (PBG), containing ZnO or CuO in the absence and existence of conductive polyaniline (PANI), since no publications are available concerning this work. The glass samples were prepared by the rapid quenching method, then mixing phosphate glass and polyaniline (PANI) with metal oxide (ZnO, CuO). They were characterized by different techniques; diffuse reflectance spectrophotometer (DRS), broadband dielectric spectrometer (BDS), cyclic voltammetry (CV), and charge-discharge techniques. In the DRS study, the direct and indirect band gap were calculated from Tauc's relationship where CuO-doped glasses have higher values than ZnO-doped glasses. In the BDS study, the permittivity of all glass compositions decreased while AC conductivity increased with increasing frequency. AC conductivity of PBG doped with metal oxides and mixed with PANI exhibited semiconducting features (6.8 × 10-4 S/cm). Further, these composites exhibited lower loss tangent (0.11), and giant permittivity (186,000) compared to the pure PBG. Also, the electrochemical study exhibited that the composite with 7% CuO content has the highest specific capacitance value (82.3 F/g at 1.0 A/g) which increased to about 113% of its first cycle and then decreased to about 55% after 2500 cycles and finally increased again to 77% after 4500 cycles, indicating its good stability. The combination of optical, electrical, and electrochemical features of these composites suggests their use for energy generation and storage devices.

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.

An inorganic-organic hybrid nanomaterial with a core-shell structure constructed by using Mn-BTC and Ag5[BW12O40] for supercapacitors and photocatalytic dye degradation

Creating inorganic-organic hybrids with polyoxometalates (POMs) and metal-organic frameworks (MOFs) as energy storage and dye-degradation materials remains challenging. Here, a new hybrid nanomaterial Mn-BTC@Ag₅[BW₁₂O₄₀] is synthesized by using Ag₅[BW₁₂O₄₀] and Mn₃(BTC)₂(H₂O)₆ (Mn-BTC, BTC = 1,3,5-benzenetricarboxylic acid) through a plain grinding method. The structure and morphology characterization by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) shows that the synthetic products have core-shell construction. Due to its unique structure wherein the core is Mn-BTC and the shell is Ag₅[BW₁₂O₄₀], it exhibits excellent capacitance performance. In a three-electrode system where nickel foam is a collector, at a current density of 1 A g^-1, its specific capacitance is 198.09 F g^-1; after 5000 cycles, the capacitance retention rate is 94.4%. When the power density is 503.1 W kg^-1, the symmetrical supercapacitor reveals a high energy density which is 10.9 W h kg^-1. At the same time, the capacitance retention is 92.9% after 5000 cycles which showed good cycle stability. The photocatalytic degradation efficiencies of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) dyes exceed 90% after 140 min, and the degradation results remained unchanged after five photocatalytic cycles. The photocatalytic degradation mechanism shows that ˙OH has a major effect. The results show that this research provides a fresh idea for the development of energy storage and dye photocatalytic degradation materials.

Binder-Free Zinc-Iron Oxide as a High-Performance Negative Electrode Material for Pseudocapacitors

The interaction between cathode and anode materials is critical for developing a high-performance asymmetric supercapacitor (SC). Significant advances have been made for cathode materials, while the anode is comparatively less explored for SC applications. Herein, we proposed a high-performance binder-free anode material composed of two-dimensional ZnFe₂O₄ nanoflakes supported on carbon cloth (ZFO-NF@CC). The electrochemical performance of ZFO-NF@CC as an anode material for supercapacitor application was examined in a KOH solution via a three-electrode configuration. The ZFO-NF@CC electrode demonstrated a specific capacitance of 509 F g^-1 at 1.5 A g^-1 and was retained 94.2% after 10,000 GCD cycles. The ZFO-NF@CC electrode showed exceptional charge storage properties by attaining high pseudocapacitive-type storage. Furthermore, an asymmetric SC device was fabricated using ZFO-NF@CC as an anode and activated carbon on CC (AC@CC) as a cathode with a KOH-based aqueous electrolyte (ZFO-NF@CC||AC@CC). The ZFO-NF@CC||AC@CC yielded a high specific capacitance of 122.2 F g^-1 at a current density of 2 A g^-1, a high energy density of 55.044 Wh kg^-1 at a power density of 1801.44 W kg^-1, with a remarkable retention rate of 96.5% even after 4000 cycles was attained. Thus, our results showed that the enhanced electrochemical performance of ZFO-NF@CC used as an anode in high-performance SC applications can open new research directions for replacing carbon-based anode materials.

Highly efficient removal of Sb(V) from water by franklinite-containing nano-FeZn composites

The existence of toxic and carcinogenic pentavalent antimony in water is a great safety problem. In order to remove antimony(V) from water, the purpose of this study was to prepare a novel graphene nano iron zinc (rGO/NZV-FeZn) photocatalyst via hydrothermal method followed by ultrasonication. Herein, weakly magnetic nano-Fe–Zn materials (NZV-FeZn, GAC^SP/NZV-FeZn, and rGO/NZV-FeZn) capable of rapid and efficient Sb(V) adsorption from water were prepared and characterised. In particular, rGO/NZV-FeZn was shown to comprise franklinite, Fe⁰, and graphite. Adsorption data were fitted by a quasi-second-order kinetic equation and Langmuir model, revealing that among these materials, NZV-FeZn exhibited the best Sb removal performance (543.9 mg_Sb g_NZV-FeZn⁻¹, R² = 0.951). In a practical decontamination test, Sb removal efficiency of 99.38% was obtained for a reaction column filled with 3.5 g of rGO/NZV-FeZn. Column regenerability was tested at an initial concentration of 0.8111 mg_Sb L⁻¹, and the treated water obtained after five consecutive runs complied with the GB5749-2006 requirement for Sb. rGO/NZV-FeZn was suggested to remove Sb(V) through adsorption-photocatalytic reduction and flocculation sedimentation mechanisms and, in view of its high cost performance, stability, and upscalable synthesis, was concluded to hold great promise for source water and wastewater treatment.

Facile Synthesis of Coral Reef-Like ZnO/CoS2 Nanostructure on Nickel Foam as an Advanced Electrode Material for High-Performance Supercapacitors

Nanocomposite electrodes receive much attention because of their excellent energy storage nature. Electrodes for supercapacitors have come a major source of interest. In this pursuit, the current work elucidates binder-free coral reefs resembling ZnO/CoS2 nanoarchitectures synthesized on the surface of Ni foams employing the cost-effective hydrothermal route. The Zno/CoS2 nanocomposite demonstrated excellent battery-type behavior, which can be employed for supercapcitor application. Various analyses were carried out in the current study, such as X-ray diffraction and high-resolution scanning electron microscopy, which allowed defining the crystalline nature and morphology of surface with ZnO/CoS2 nanoarchitectures. Electrochemical measures such as cyclic voltammetry, galvanostatic charge discharge, and potentiostatic impedance spectroscopy confirmed the battery-type behavior of the material. The synthesized precursors of binder-free ZnO/CoS2 nanostructures depicted an excellent specific capacity of 400.25 C·g−1 at 1 A·g−1, with a predominant cycling capacity of 88. 2% and retention holding of 68% at 10 A·g−1 and 2 A·g−1, even after 4000 cycles, representing an improvement compared to the pristine ZnO and CoS2 electroactive materials. Therefore, the electrochemical and morphological analyses suggest the excellent behavior of the ZnO/CoS2 nanoarchitectures, making them promising for supercapacitors.

Enhanced electrochemical performance of MnNi2O4/rGO nanocomposite as pseudocapacitor electrode material and methanol electro-oxidation catalyst

Binary transition metal oxides with encouraging electrocatalyst properties have been suggested as electrode materials for supercapacitors and methanol oxidation. Hence, in this work, a binary mixed metal oxide based on nickel and manganese (MnNi₂O₄) and its hybrid with reduced graphene oxide were synthesized by a one-step hydrothermal method. After physical and morphological characterization, the potential of these nanostructures was investigated for use as supercapacitor electrodes and methanol electro-oxidation. The results of the electrochemical analysis showed a substantial effect of adding rGO to the MnNi₂O₄. The MnNi₂O₄/rGO hybrid electrode supercapacitor exhibited good stability of 93% after 2000 consecutive CV cycles and a specific capacitance of 575 F g^-1at the current density of 0.5 A g^-1. Furthermore, the application of this hybrid nanomaterial in the methanol electro-oxidation reaction (MOR) indicated its appropriate electrochemical efficiency and stability in methanol oxidation. Our results show that MnNi₂O₄/rGO can be considered as a promising electrode material for energy applications.

Design of a ZnMoO4 porous nanosheet with oxygen vacancies as a better performance electrode material for supercapacitors

A ZnMoO₄ porous nanosheet with oxygen vacancies (ZnMoO₄-OV) was synthesized which delivers a preferable energy storage performance.

Boosting the performance of cobalt molybdate nanorods by introducing nanoflake-like cobalt boride to form a heterostructure for aqueous hybrid supercapacitors

Binary transition metal oxides have received extensive attention because of their multiple oxidation states. However, due to the inherent vices of poor electronic/ionic conductivities, their practical performance as supercapacitor material is limited. Herein, a cobalt molybdate/cobalt boride (CoMoO₄/Co-B) composite is constructed with cobalt boride nanoflake-like as a conductive additive in CoMoO₄ nanorods using a facile water bath deposition process and liquid-phase reduction method. The effects of CoMoO₄/Co-B mass ratios on its electrochemical performance are investigated. Remarkably, the CoMoO₄/Co-B composite obtained at a mass ratio of 2:1 shows highly enhanced electrochemical performance relative to those obtained at other ratios and exhibits an optimum specific capacity of 436 F g^-1 at 0.5 A g^-1. This kind of composite could also display great rate capacity (294 F g^-1 at 10 A g^-1) and outstanding long cycle performance (90.5% capacitance retention over 10 000 cycles at 5 A g^-1). Also, the asymmetric supercapacitor device is prepared by using CoMoO₄/Co-B composite as the anode with the active carbon as the cathode. Such a device demonstrates an outstanding energy density of 23.18 Wh kg^-1 and superior long-term stability with 100% initial specific capacity retained after 10,000 cycles. The superior electrochemical properties show that the CoMoO₄/Co-B electrode material has tremendous potential in energy storage equipment applications.

Current progress achieved in novel materials for supercapacitor electrodes: mini review

Supercapacitors are highly attractive for a large number of emerging mobile devices for addressing energy storage and harvesting issues. This mini review presents a summary of recent developments in supercapacitor research and technology, including all kinds of supercapacitor design techniques using various electrode materials and production methods. It also covers the current progress achieved in novel materials for supercapacitor electrodes. The latest produced EDLC/hybrid/pseudo-supercapacitors have also been described. In particular, metal oxides, specifically ZnO, used as electrode materials are in focus here. Eventually, future developments, prospects, and challenges in supercapacitor research have been elaborated on.

A high-performance asymmetric supercapacitor electrode based on a three-dimensional ZnMoO4/CoO nanohybrid on nickel foam

A two-step hydrothermal route was employed to fabricate a ZnMoO₄/CoO nanohybrid supported on Ni foam. The ZnMoO₄/CoO nanohybrid shows a three-dimensional criss-crossed structure. The specific surface area is enhanced from 45 m² g^-1 of ZnMoO₄ to 67 m² g^-1 of the ZnMoO₄/CoO nanohybrid. Furthermore, the existence of electroactive CoO is in favor of reducing the charge transport resistance. The ZnMoO₄/CoO nanohybrid electrode possesses a high capacitance of 4.47 F cm^-2 at 2 mA cm^-2, which is much higher than those of ZnMoO₄ (1.07 F cm^-2) and CoO (2.47 F cm^-2). The ZnMoO₄/CoO nanohybrid electrode also exhibits an ultrahigh cycling stability with 100.5% capacitance retention after 5000 cycles at 20 mA cm^-2. In addition, an asymmetric all-solid-state supercapacitor was assembled using the ZnMoO₄/CoO nanohybrid as the positive electrode and exfoliated graphite carbon paper as the negative electrode. The asymmetric supercapacitor exhibits a superior energy density of 58.6 W h kg^-1 at a power density of 800 W kg^-1 and a considerable cycling stability with 81.8% capacitance retention after 5000 cycles at 5 A g^-1. The ZnMoO₄/CoO nanohybrid demonstrates its tremendous advantages and possibilities as a positive electrode material in energy storage applications. Moreover, for a better understanding of the electrochemical behavior, a combined study of experimental measurements and density functional theory calculations is also applied to illustrate the high-performance of the ZnMoO₄/CoO nanohybrid.

Fabrication of cobalt gallium oxide with zinc iron oxide on nickel foam for a high-performance asymmetric supercapacitor

A straightforward method is proposed for the synthesis of CoGa₂O₄ on nickel foam with excellent durability for practical applications in asymmetric supercapacitors.