CuCo 2 O 4 flowers/Ni-foam architecture as a battery type positive electrode for high performance hybrid supercapacitor applications

CuCo2O4 nanoneedle arrays growth on carbon cloth as a non-enzymatic electrochemical sensor with low detection limit ketoprofen recognition

An electrochemical sensor for detecting ketoprofen was constructed by in-situ grown copper cobaltate (CuCo2O4) nanoneedle arrays on a carbon cloth (CC) substrate. The resulting porous nanoneedle arrays not only expose numerous electrochemically active sites but also significantly enhance the electrochemical apparent active area and current transmission efficiency. By leveraging its electrochemical properties, the sensor achieves an impressive detection limit for ketoprofen of 0.7 pM, with a linear range spanning from 2 pM ~ 2 µM. Furthermore, the sensor exhibits remarkable reproducibility, anti-interference capabilities, and stability. Notably, the developed sensor also performed ketoprofen detection on real samples (including drug formulations and wastewater) and demonstrated excellent recognition ability. These exceptional performances can be attributed to the direct growth of CuCo2O4 nanoneedle arrays on the CC substrate, which facilitates a robust electrical connection, provides abundant electrocatalytic active sites, and expands the apparent active area. Consequently, these improvements contribute to the efficient trace detection capabilities of the ketoprofen sensor.

Rod-Like Nanostructured Cu-Co Spinel with Rich Oxygen Vacancies for Efficient Electrocatalytic Dechlorination

Dichloromethane (CH₂Cl₂) hydrodechlorination to methane (CH₄) is a promising approach to remove the halogenated contaminants and generate clean energy. In this work, rod-like nanostructured CuCo₂O₄ spinels with rich oxygen vacancies are designed for highly efficient electrochemical reduction dechlorination of dichloromethane. Microscopy characterizations revealed that the special rod-like nanostructure and rich oxygen vacancies can efficiently enhance surface area, electronic/ionic transport, and expose more active sites. The experimental tests demonstrated that CuCo₂O₄-3 with rod-like nanostructures outperformed other morphology of CuCo₂O₄ spinel nanostructures in catalytic activity and product selectivity. The highest methane production of 148.84 μmol in 4 h with a Faradaic efficiency of 21.61% at -2.94 V (vs SCE) is shown. Furthermore, the density function theory proved oxygen vacancies significantly decreased the energy barrier to promote the catalyst in the reaction and O_v-Cu was the main active site in dichloromethane hydrodechlorination. This work explores a promising way to synthesize the highly efficient electrocatalysts, which may be an effective catalyst for dichloromethane hydrodechlorination to methane.

Rationally Designed Bimetallic Co-Ni Sulfide Microspheres as High-Performance Battery-Type Electrode for Hybrid Supercapacitors

Rational designing of electrode materials is of great interest for improving the performance of battery-type supercapacitors. The bimetallic NiCo₂S₄ (NCS) and CoNi₂S₄ (CNS) electrode materials have received much attention for supercapacitors due to their rich electrochemical characteristics. However, the comparative electrochemical performances of NCS and CNS electrodes were never studied for supercapacitor application. In this work, microsphere-like bimetallic NCS and CNS structures were synthesized via a facile one-step hydrothermal method by controlling the molar ratio of Ni and Co precursors. The physico-chemical results confirmed that microsphere-like structures with cubic spinel-type NCS and CNS materials were successfully fabricated by this method. When tested as the supercapacitor electrode materials, both NCS and CNS electrodes exhibited battery-type behavior in a three-electrode configuration with outstanding electrochemical performances such as specific capacity, rate performance and cycle stability. Impressively, the CNS electrode delivered a high specific capacity of 430.1 C g^-1 at 1 A g^-1, which is higher than 345.9 C g^-1 of the NCS electrode. Furthermore, the NCS and CNS electrodes showed a decent cycling stability with 75.70 and 84.70% capacity retention after 10,000 cycles. Benefiting from the electrochemical advantage of CNS microspheres, we fabricated a hybrid supercapacitor (HSC) device based on CNS microspheres (positive electrode) and activated carbon (AC, negative electrode), which is named as CNS//AC. The assembled CNS//AC HSC device showed a large energy density of 41.98 Wh kg^-1 at a power density of 800.04 W kg^-1 and displayed a remarkable cycling stability with a capacity retention of 91.79% after 15,000 cycles. These excellent electrochemical performances demonstrate that both bimetallic NCS and CNS microspheres may provide potential electrode materials for high performance battery-type supercapacitors.

Effective regeneration of mixed composition of spent lithium-ion batteries electrodes towards building supercapacitor

Recycling of different manufacturers of spent lithium-ion batteries cathode and anode via a simple regeneration process has an opportunity to fabricate new energy devices. In this study, the different manufacturers of spent LIB cathode pieces were subjected to lixiviation process and found the best-optimized conditions such as tartaric acid concentration (2.5 M), H₂O₂ concentration (7.5 vol%), solid-liquid ratio (80 g/L), temperature (80 °C), and lixiviation time (80 min) for maximum ~ 99% extraction efficiency of metals. Further, 3D-MnCo₂O₄ (MCO) spheres were regenerated from the cathode lixivium containing metal ions via hydrothermal technique. Besides, anode graphite and Al foils after cathode lixiviation were exploited to prepare reduced graphene oxide (RGO) at room temperature in a simple method. The electrochemical performance of both regenerated electrodes from spent LIBs was explored in the half-cell configuration using the 1 M Na₂SO₄ electrolyte. Additionally, the constructed MCO//RGO asymmetric supercapacitor device offers an operational voltage of 1.8 V and displays a high energy density of ~ 23.9 Wh kg^-1 at 450 W kg^-1 with 8000 cycles. This alternative recycling method proposes the possibility to construct high-energy storage devices from different compositions of spent LIBs.

Recent Advancements of Polyaniline/Metal Organic Framework (PANI/MOF) Composite Electrodes for Supercapacitor Applications: A Critical Review

Supercapacitors (SCs), also known as ultracapacitors, should be one of the most promising contenders for meeting the needs of human viable growth owing to their advantages: for example, excellent capacitance and rate efficiency, extended durability, and cheap materials price. Supercapacitor research on electrode materials is significant because it plays a vital part in the performance of SCs. Polyaniline (PANI) is an exceptional candidate for energy-storage applications owing to its tunable structure, multiple oxidation/reduction reactions, cheap price, environmental stability, and ease of handling. With their exceptional morphology, suitable functional linkers, metal sites, and high specific surface area, metal–organic frameworks (MOFs) are outstanding materials for electrodes fabrication in electrochemical energy storage systems. The combination of PANI and MOF (PANI/MOF composites) as electrode materials demonstrates additional benefits, which are worthy of exploration. The positive impacts of the two various electrode materials can improve the resultant electrochemical performances. Recently, these kinds of conducting polymers with MOFs composites are predicted to become the next-generation electrode materials for the development of efficient and well-organized SCs. The recent achievements in the use of PANI/MOFs-based electrode materials for supercapacitor applications are critically reviewed in this paper. Furthermore, we discuss the existing issues with PANI/MOF composites and their analogues in the field of supercapacitor electrodes in addition to potential future improvements.

PPy coated nanoflower like CuCo2O4based onin situgrowth of nanoporous copper for high-performance supercapacitor electrodes

General CuCo₂O₄electrodes suffer a very low reversible capacity and poor cycling stability because of easily fading phenomena and volume change during cycling. To optimize the electrode, a facile method is conducted to fabricate a novel electrode of Cu@CuCo₂O₄@polypyrrole nanoflowers. Due to larger specific surface area and more electrochemical reactive areas of CuCo₂O₄@polypyrrole nanoflowers, the pseudocapacitance of thein situgrown CuCo₂O₄@polypyrrole (912 F g^-1at 2 A g^-1) is much higher than the pristine CuCo₂O₄(618 F g^-1at 2 A g^-1). Remarkably, the CuCo₂O₄@polypyrrole (cathode) and active carbon (anode) are used to assemble an asymmetric supercapacitor, which exhibits a relatively high energy density of 90 Wh kg^-1at a power density of 2519 W kg^-1and 35 Wh kg^-1at a high-power density of 9109 W kg^-1, and excellent cycling stability (about 90.4% capacitance retention over 10 000 cycles). The prominent performance of CuCo₂O₄@polypyrrole makes it as a potential electrode for supercapacitor.

A Comparative Study of the Influence of Nitrogen Content and Structural Characteristics of NiS/Nitrogen-Doped Carbon Nanocomposites on Capacitive Performances in Alkaline Medium

Supercapacitors (SCs) have been regarded as alternative electrochemical energy storage devices; however, optimizing the electrode materials to further enhance their specific energy and retain their rate capability is highly essential. Herein, the influence of nitrogen content and structural characteristics (i.e., porous and non-porous) of the NiS/nitrogen-doped carbon nanocomposites on their electrochemical performances in an alkaline electrolyte is explored. Due to their distinctive surface and the structural features of the porous carbon (A-PVP-NC), the as-synthesized NiS/A-PVP-NC nanocomposites not only reveal a high wettability with 6 M KOH electrolyte and less polarization but also exhibit remarkable rate capability (101 C/g at 1 A/g and 74 C/g at 10 A/g). Although non-porous carbon (PI-NC) possesses more nitrogen content than the A-PVP-NC, the specific capacity output from the latter at 10 A/g is 3.7 times higher than that of the NiS/PI-NC. Consequently, our findings suggest that the surface nature and porous architectures that exist in carbon materials would be significant factors affecting the electrochemical behavior of electrode materials compared to nitrogen content.

NiCo2O4/RGO Hybrid Nanostructures on Surface-Modified Ni Core for Flexible Wire-Shaped Supercapacitor

In this work, we report surface-modified nickel (Ni) wire/NiCo2O4/reduced graphene oxide (Ni/NCO/RGO) electrodes fabricated by a combination of facile solvothermal and hydrothermal deposition methods for wire-shaped supercapacitor application. The effect of Ni wire etching on the microstructural, surface morphological and electrochemical properties of Ni/NCO/RGO electrodes was investigated in detail. On account of the improved hybrid nanostructure and the synergistic effect between spinel-NiCo2O4 hollow microspheres and RGO nanoflakes, the electrode obtained from Ni wire etched for 10 min, i.e., Ni10/NCO/RGO exhibits the lowest initial equivalent resistance (1.68 Ω), and displays a good rate capability with a volumetric capacitance (2.64 F/cm3) and areal capacitance (25.3 mF/cm2). Additionally, the volumetric specific capacitance calculated by considering only active material volume was found to be as high as 253 F/cm3. It is revealed that the diffusion-controlled process related to faradaic volume processes (battery type) contributed significantly to the surface-controlled process of the Ni10/NCO/RGO electrode compared to other electrodes that led to the optimum electrochemical performance. Furthermore, the wire-shaped supercapacitor (WSC) was fabricated by assembling two optimum electrodes in-twisted structure with gel electrolyte and the device exhibited 10 μWh/cm3 (54 mWh/kg) energy density and 4.95 mW/cm3 (27 W/kg) power density at 200 μA. Finally, the repeatability, flexibility, and scalability of WSCs were successfully demonstrated at various device lengths and bending angles.

Beyond hierarchical mixed nickel-cobalt hydroxide and ferric oxide formation onto the green carbons for energy storage applications

To attain superior energy density concurrently with high power density, high-performance supercapacitors have been developed. Herein an innovative strategy has been adopted to fabricate unique binder-free electrodes composed of a unique porous structure of binary metal carbonate hydroxide nanomace-decorated hydrothermal porous carbon spheres (PCSs). Hierarchical nickel-cobalt carbonate hydroxide (NiCOCH) nanomaces, directly grown on PCSs, are used as positive electrodes for supercapacitors fabrication. Furthermore, Fe₂O₃@PCS composites, having benefits of highly reversible redox reaction in the negative potential window and highly porous structure, are employed as the negative electrode in the fabrication of the asymmetric supercapacitors (ASCs). The assembled NiCoCH@PCS// Fe₂O₃@PCS asymmetric devices with a wide electrochemical potential window not only have the merit of high energy and power densities but also receive benefits from remarkable cycle stability. These encouraging outcomes that are mutually beneficial, make these fabricated ASCs significantly ideal for high-performance electronics.

Three-dimensional hierarchical core-shell CuCo2O4@Co(OH)2 nanoflakes as high-performance electrode materials for flexible supercapacitors

Rational design of composite electrode materials with novel nanostructures plays an important role in improving both high energy density and structure stability of flexible and wearable supercapacitors. Herein, numerous peculiar three-dimensional hierarchical core-shell CuCo₂O₄@Co(OH)₂ nanoflakes directly grown on Ni foam are synthesized via a facile hydrothermal method and subsequent electrodeposition technique. Ultrathin Co(OH)₂ nanosheets arrays vertically anchored on CuCo₂O₄ nanoflakes can not only improve the electrical conductivity, but also provide interconnected channels for ion diffusion and enrich electrochemical active sites to boost faradaic redox reaction, leading to the enhanced electrochemical behavior. Excellent electrochemical performance of CuCo₂O₄@Co(OH)₂ electrode can be reflected on a higher specific capacitance of 1558 F/g and lower resistance compared with that of the pristine CuCo₂O₄ electrode. The asymmetric flexible supercapacitor assembled by the optimized CuCo₂O₄@Co(OH)₂ electrode and activated carbon exhibits high energy density of 62.5 Wh/kg at 893 W/kg, outstanding cycle stability of 88.6% capacitance retention after 10,000 cycles and remarkable mechanical flexibility, performing the best electrochemical behavior among various metal oxides based asymmetric supercapacitors. All above results indicate that the resulted hierarchical core-shell CuCo₂O₄@Co(OH)₂ electrode can be a promising candidate for flexible energy storage devices.

In situ microwave-assisted solvothermal synthesis via morphological transformation of ZnCo2O4 3D nanoflowers and nanopetals to 1D nanowires for hybrid supercapacitors

Over recent decades, the conversion of energy and its storage have been in the lime light due to the depletion of fossil resources. The electrochemical energy storage devices like supercapacitors and batteries, and their materials and fabrication methods have been extensively evaluated, which is the best solution for the energy crisis. Herein, zinc cobaltite (ZnCo2O4; ZCO) nanostructures grown on nickel (Ni) foam by microwave-assisted solvothermal fabrication for hybrid supercapacitors are reported. Two different structures/samples, ZCO-15/Ni (nanoflowers) and ZCO-30/Ni (nanowires), were obtained by simply adjusting the reaction time. The electrochemical and physicochemical properties of the as-prepared samples were systematically determined. Particularly, ZCO-15/Ni exhibits excellent structural stability due to its dual morphologies: nanoflowers and nanopetals, and exhibits a large electroactive surface area (25.61 m2 g-1), pore diameter (48.38 nm), and robust adhesion to Ni foam, enabling ion and electron transport. ZCO-15/Ni foam electrode delivers an excellent specific capacity of 650.27 C g-1 at 0.5 A g-1 and admirable cyclic performance of 91% capacitance retention after 5000 cycles compared to ZCO-30/Ni electrode. The excellent electrochemical performance of ZCO makes them promising electrode materials for batteries, hybrid supercapacitors, and other alternative energy storage applications.

Constructed Ag NW@Bi/Al core-shell nano-architectures for high-performance flexible and transparent energy storage device

Flexible and transparent energy storage devices (FTESDs) have recently attracted much attention for use in wearable and portable electronics. Herein, we developed an Ag nanowire (NW) @Bi/Al nanostructure as a transparent negative electrode for FTESDs. In the core-shell nanoarchitecture, the Ag NW percolation network with excellent conductivity contributes superior electron transport pathways, while the unique nanostructure provides an effective interface contact between the current collector and electroactive material. As a result, the electrode delivers a high capacity of 12.36 mF cm-2 (3.43 μA h cm-2) at 0.2 mA cm-2. With a minor addition of Al, the coulombic efficiency of the electrode remarkably increases from 65.1% to 83.9% and the capacity retention rate improves from 53.8% to 91.9% after 2000 cycles. Moreover, a maximum energy density of 319.5 μW h cm-2 and a power density of 27.5 mW cm-2 were realized by an interdigital structured device with a transmittance of 58% and a potential window of 1.6 V. This work provides a new negative electrode material for high-performance FTESDs in the next-generation integrated electronics market.

Facile preparation of porous sheet-sheet hierarchical nanostructure NiO/Ni-Co-Mn-O x with enhanced specific capacity and cycling stability for high performance supercapacitors

NiO, Ni–Co–Mn–O_x and NiO/Ni–Co–Mn–O_x on nickel foam substrates were prepared via a chemical bath deposition–calcination. The thermodynamic behavior was observed by TG/DTA. The chemical structure and composition, phase structure and microstructures were tested by XPS, XRD, FE-SEM and TEM. The electrochemical performance was measured by CV, GCD and EIS. The mechanism for formation and enhancing electrochemical performance is also discussed. Firstly, the precursors such as NiOOH, CoOOH and MnOOH grow on nickel foam substrates from a homogeneous mixed solution via chemical bath deposition. Thereafter, these precursors are calcined and decomposed into NiO, Co₃O₄ and MnO₂ respectively under different temperatures in a muffle furnace. Notably, NiO/Ni–Co–Mn–O_x on nickel foam substrates reveals a high specific capacity with 1023.50 C g⁻¹ at 1 A g⁻¹ and an excellent capacitance retention with 103.94% at 5 A g⁻¹ after 3000 cycles in 2 M KOH, its outstanding electrochemical performance and cycling stability are mainly attributed to a porous sheet–sheet hierarchical nanostructure and synergistic effects of pseudo-capacitive materials and excellent redox reversibility. Therefore, this research offers a facile synthesis route to transition metal oxides for high performance supercapacitors.

NiO, Ni–Co–Mn–O_x and NiO/Ni–Co–Mn–O_x on nickel foam substrates were prepared via a chemical bath deposition–calcination.

Dandelion-like CuCo2O4 arrays on Ni foam as advanced positive electrode material for high-performance hybrid supercapacitors

In this paper, CuCo₂O₄ dandelion arrays grown on nickel foam (CuCo₂O₄/NF) was successfully synthesized by a simple hydrothermal route with post-heat-treatment for emolying as a high-performance positive electrode material for hybrid supercapacitors. Due to the unique tree-dimension porous (3D) microstructure and binder-free electrode architecture, the CuCo₂O₄/NF electrode deliveries a large specific capacitance of 2656.7 F g^-1 at an areal current density of 1 mA cm^-2. Moreover, it has an outstanding rate performance, as well as striking cycling stability. Additionally, a hybrid supercapacitors (HSCs) was fabricated using CuCo₂O₄ as positive electrode and corals-like N-doping porous carbon (N-CCs) as negative electrode. The device exhibited a broad potential window of 1.55 V and a high specific capacitance of 273.9 F g^-1, which result in a largest energy density of 91.4 Wh kg^-1 and a maximum power density of 13.4 kW kg^-1. Finally, the assembled device manifests a preeminent electrochemical stability which maintained a 92.32% capacitance retention after 5000 cycles. The practical application was visually validated by lighting a blue light-emitting diode.

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.

Novel mesoporous electrode materials for symmetric, asymmetric and hybrid supercapacitors

Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due to their potential applications ranging from microelectronic devices to hybrid electric vehicles. Supercapacitors can provide high power densities but their inherently low energy density remains a great challenge. The high-performance supercapacitors utilize large electrode surface area for electrochemical double-layer capacitance and/or pseudocapacitance. To enhance the performance of supercapacitors, various strategies have been adopted such as electrode nanostructuring, hybrid electrode designs using nanocomposite electrodes and hybrid supercapacitor (HSC) configurations. Nanoarchitecturing of electrode-active materials is an effective way of enhancing the performance of supercapacitors as it increases the effective electrode surface area for enhanced electrode/electrolyte interaction. In this review, we focus on the recent developments in the novel electrode materials and various hybrid designs used in supercapacitors for obtaining high specific capacitance and energy density. A family of electrode-active materials including carbon nanomaterials, transition metal-oxides, transition metal-nitrides, transition metal-hydroxides, electronically conducting polymers, and their nanocomposites are discussed in detail. The HSC configurations for attaining enhanced supercapacitor performance as well as strategies to integrate with other microelectronic devices/wearable fabrics are also included.

In situ preparation of MgCo2O4 nanosheets on Ni-foam as a binder-free electrode for high performance hybrid supercapacitors

MgCo₂O₄ nanosheets grown on Ni-foam exhibited a maximum specific capacity of 947 C g⁻¹ at 2 A g⁻¹.

A high performance asymmetric supercapacitor based on in situ prepared CuCo2O4 nanowires and PPy nanoparticles on a two-ply carbon nanotube yarn

A two-ply CNT yarn asymmetric supercapacitor was fabricated by assembling a CuCo₂O₄ nanowire positive electrode and a PPy nanoparticle negative electrode. The full cell exhibits a high specific capacitance of 59.55 mF cm⁻² and a high energy density of 0.02 mW h cm⁻².

Terephthalate-based cobalt hydroxide: a new electrode material for supercapacitors with ultrahigh capacitance

Terephthalate-based cobalt hydroxide, a layered hydroxyl derivative, is grown on Ni foam and first applied in supercapacitors with ultrahigh capacitances.