Nickel-cobalt Layered Double Hydroxide Nanosheets Research Articles

Efficient photocatalytic hydrogen production of Ni-Co layered double hydroxides (Ni-Co LDHs) anchored with reduced graphene oxide (rGO) hybrid composite

Using a suitable co-catalyst to boost photocatalytic H2 evolution from water splitting is crucial. Herein, we designed pristine NiCo-LDH and reduced graphene-oxide supported nickel-cobalt layered double hydroxide nanosheets (NiCo-LDH/rGO) as photocatalyst for the first time to evaluate the hydrogen production performance. Adding graphene has the potential to significantly increase electrical conductivity, and the supported NiCo-LDH has the potential to significantly reduce the likelihood of graphene self-aggregation. The effectiveness of its photocatalytic hydrogen generation was analyzed using a set of characterizations. The H2 evolution rates for pure rGO were 345.2 μmolh-1g-1, whereas those for Ni-Co LDH/rGO were 578.2 μmolh-1g-1. Average hydrogen generation per hour for the Ni-Co LDH/rGO composite material was 2032.1 μmolh-1g-1, which was 5.8 and 3.5 times that of rGO and Ni-Co LDH/rGO, respectively, NiCo-LDH@rGO's synergistic impact on the NiCo-LDH boosts the H2 generation pathway by increasing the catalyst's stability as well as performance by exposing active sites and speeding up electron transport. The produced nanocomposite shows excellent spatial charge separation and quicker electron transport across the conductive network of rGO, as shown by the photocurrent response test and photoluminescence (PL) spectra. The results of this study provide a fresh perspective on the practical use and synthesis of the inexpensive and effective NiCo-LDH/rGO, demonstrating the standard deviation of logical planning and preparation of high-performance photocatalysts.

Nickel aerogel @ ultra-thin NiCo-LDH nanosheets integrated freestanding film as a collaborative adsorption and accelerated conversion cathode to improve the rate performance of lithium sulfur batteries

It is a great challenge to develop freestanding ultralight cathodes for lithium–sulfur battery exhibiting good electrochemical performances. Herein, ultrathin porous nickel–cobalt layered double hydroxide (NiCo-LDH) nanosheets were grown on the surface of ultra-light nickel microwire aerogels (NMWAs), and there is capillary action in the gaps formed by the ordered arrangement due to the presence of magnetic filed in the preparation process, which has the advantages of synergistic adsorption and accelerated conversion kinetics of lithium polysulfide. Because of the abundant hydrophilic hydroxyl groups on the surface of NiCo-LDH and the capillary action of NMWAs, the integrated freestanding film cathode sulfur host (NMWAs@NiCo-LDH/S) provides excellent rate performance as well as cycling stability. The film cathode has an ultra-high initial specific capacity of 1238.4 mAh g−1 at 0.1C and an excellent reversible capacity of 805.8 mAh/g at 5.0C. Even after 700 cycles at a high current density of 5.0C, it still provides a reversible capacity of 647.1 mAh g−1 with a capacity decay rate of only 0.018 % per cycle. This work provides a simple and new way for the design of high rate lithium–sulfur battery film cathodes with good cycle stability.

Electrochemical detection of carmoisine in the presence of tartrazine on the surface of screen printed graphite electrode modified with nickel-cobalt layered double hydroxide ultrathin nanosheets

Toxic effluents containing azo dyes are discharged from various industries and they adversely affect water resoures, soil and aquatic ecosystems. Also, excessive use of food azo dyes can be carcinogenic, toxic, and adversely affect human health. Therefore, the determination of food azo dyes is significant from the perspective of human health and aquatic organisms. In the present work, nickel-cobalt layered double hydroxide nanosheets were prepared and analyzed by various techniques (field emission-scanning electron microscopy, X-ray diffraction, and Fourier Transform-Infrared spectroscopy). Then, the screen printed graphite electrode modified with nickel-cobalt layered double hydroxide nanosheets was used for the detection of carmoisine. The nickel-cobalt layered double hydroxide nanosheets/screen printed graphite electrode significantly improved the oxidation of carmoisine by increasing the response current and lowering potentials compared to unmodified screen printed graphite electrode. Based on the findings from differential pulse voltammetry, the nickel-cobalt layered double hydroxide nanosheets/screen printed graphite electrode sensor response towards carmoisine was linear (0.3–125.0 μM) with a detection limit of 0.09 μM. A sensitivity of 0.3088 μA μM−1 was achieved. Also, the nickel-cobalt layered double hydroxide nanosheets/screen printed graphite electrode was used for voltammetric detection of carmoisine in the presence of tartrazine. Due to the catalytic activity of prepared layered double hydroxide, the prepared sensor exhibited remarkable separation of the peaks when carmoisine and tartrazine coexist. In addition, the prepared sensor showed good stability. Finally, the proposed sensor had promising applicability for analysis of study analytes in powdered juice and lemon juice, with commendable recoveries between 96.9%-104.8%.

Potential modulation of Nickel-Cobalt hydroxide nanosheets with conductive Poly(3,4-Ethylenedioxythiophene) skin for aqueous hybrid supercapacitors

Transition metal hydroxides with tuned structure and superior electrochemical activities are of potential as positive electrodes for aqueous hybrid supercapacitors (AHSs), yet their conductivities and stacking behaviors need to be optimized to further improve the electrical potential distribution from the electronic multi-contact border to the electroactive center. Herein, we report a new approach to coat poly(3,4-ethylenedioxythiophene) (PEDOT) skin with a controlled thickness on nickel–cobalt layered double hydroxide (NiCo-LDH) nanosheets via a simple yet efficient oxidative chemical vapor deposition (oCVD). The conductive PEDOT skin is ionically permeable, resulting in uniform distribution of the electrical potential and fast transport of ions to active sites. The density functional theory (DFT) calculations reveal that the PEDOT layer can build an embedded electric field at the interface and enable a low desorption energy of hydrogen for electrochemical redox reactions. The as-obtained NiCo-LDH nanosheets with the PEDOT skin of 10 nm thick (LDH/PEDOT-10) as the battery-type electrode deliver a high specific capacity of 167 mAh g−1 (1250F g−1) with a greatly improved rate capability of 79 % at 50 A g−1 and cycling stability of 92 % for 6000 cycles, which endows AHS devices with superior charge-storage performance. This study has demonstrated for the first time that the modulation of electrical potential for redox electrodes via an interface engineering strategy can achieve simultaneously fast reaction kinetics and excellent structure stability for aqueous energy-storage devices.

Hierarchical Nickel–Cobalt Hydroxide Composite Nanosheets-Incorporated Nitrogen-Doped Carbon Nanotubes Embedded with Nickel–Cobalt Alloy Nanoparticles for Driving a 2 V Asymmetric Supercapacitor

A class of electrode materials with favorable structures and compositions and powerful electrochemical (EC) properties are needed to boost the supercapacitor capacity significantly. In this study, an inventive technique was established to produce a well-aligned nickel-cobalt alloy nanoparticles-encapsulated N-doped carbon nanotubes with porous structure and good conductivity on carbon cloth (NiCo@NCNTs/CC) as a substrate. Then, nanosheets of nickel-cobalt layered double hydroxide (NiCo-LDH) were grown on NiCo@NCNTs/CC via a simple EC deposition method to construct a self-supported monolithic hierarchical nanosheets/nanotubes composite electrode of NiCo-LDH/NiCo@NCNTs/CC. In such a composite electrode, the NiCo@NCNTs can act as a good conductor and structural scaffold to grow NiCo-LDH nanosheets with a three-dimensional open and porous structure, which helps to improve the electron/ion-transfer performance, increase the number of exposed reactive sites, and inhibit the aggregation of NiCo-LDH nanosheets, thereby boosting the capacitance and stability. As a positive electrode, the NiCo-LDH/NiCo@NCNTs/CC hierarchical nanosheets/nanotubes electrode displays 1898 mF cm-2 (1262 A g-1) of high capacitance, long-term stability with a capacitance retention of around 100% after 8000 cycles, and nearly 103% Coulombic efficiency. After assembling into an asymmetric supercapacitor with a Co(OH)2/NiCo@NCNTs/CC negative electrode, 2 V of operating voltage with 73.1 μW h cm-2 (52.8 W h kg-1) of energy density was achieved. Our investigation gives a potential approach for constructing the integrated composite electrode of transition-metal compounds-carbon materials for high-performance supercapacitors.

Honeycomb nickel-cobalt layered double hydroxides supported on carbon skeleton as high-performance electrodes in supercapacitors

Nickel-cobalt layered double hydroxide (NiCo-LDH) is an attractive electrode material for supercapacitors (SCs) due to its high theoretical capacitance. However, the poor electrical conductivity greatly limits the charge transfer characteristic of NiCo-LDH, preventing its wide applications. Herein, the honeycomb NiCo-LDH nanosheet supported by carbonized polydopamine (PDA-C/NiCo-LDH) is constructed by polymerization, carbonization and electrodeposition. The active NiCo-LDH nanosheets are tightly embedded on the conductive framework of PDA-C, which can hinder the aggregation of NiCo-LDH nanosheets and accelerate the charge transfer and redox reactions. Benefiting from the honeycomb structure of NiCo-LDH and conductive framework of PDA-C, the optimal PDA-C/NiCo-LDH electrode exhibits a high capacitance of 2458.1 F g−1 at 1 A g−1, along with superior rate performance and cyclic stability. Furthermore, an asymmetric supercapacitor (ASC) is assembled with the PDA-C/NiCo-LDH as cathode and active carbon (AC) as anode. The ASC exhibits a high energy density of 62.7 Wh kg−1 at a power density of 714.3 W kg−1 and exceptional cyclic performance (92.5 % retention after 10,000 cycles), indicating a huge potential of the PDA-C/NiCo-LDH electrode in energy storage fields.

Phosphate ion-functionalized nickel-cobalt layered double hydroxide nanosheets derived from metal-organic framework compounds for high-performance asymmetric supercapacitors

The modification by functionalized ions (surface modification or doping) presents facile and efficient access to enhance the electrochemical performance of electrode materials. However, the effect of functionalized ions on the structure-performance relationship of electrode materials is not yet apparent. Herein, we develop a novel phosphate ion-functionalized nickel-cobalt layered double hydroxide nanosheet (Ni-Co-P80) derived from metal-organic framework compounds prepared as anode material for supercapacitors. The obtained Ni-Co-P80 not only remains characterized by high specific surface area and porosity, but also possesses more active sites and higher electrical conductivity with phosphate modification, thus improving the charge transfer kinetics. The electrochemical test results show that the highest specific capacitance of Ni-Co-P80 modified with phosphate ions increases by 49.7% compared to pure phase LDH. More impressively, the assembled asymmetric supercapacitor exhibits an excellent energy density of 64.89 Wh kg-1 at a power density of 1600 W kg-1 with an ultralong cyclic performance of 77.78% capacitance retention after 5000 cycles. This study explicitly demonstrates the remarkable enhancement of specific capacitance of layered double hydroxide following modification with phosphate ions. It brings a prospective pathway toward the rational design of LDH-based high-performance asymmetric supercapacitors.

Sheet-like NiCo-layered double hydroxide anchored on N self-doped hierarchical porous carbon aerogel from chitosan for high-performance supercapacitors

Smart use of renewable and biodegradable biomass materials to partially replace other synthetic materials can bring huge economic benefit and environmental improvement. Herein, a highly graphitized N self-doped hierarchical porous carbon aerogel (HPCA) conductive frame is prepared using biomass chitosan particle as the precursor. Subsequently, nickel-cobalt layered double hydroxide (NiCo-LDH) nanosheets with desired pseudocapacitance properties are uniformly anchored on HPCA. Generally, a porous carbon skeleton with high conductivity and a large surface area brings a lot of active sites and channels for rapid electron and ion transport, and can control the growth morphology of NiCo-LDH nanosheets. As a result, compared with NiCo-LDH/HPCA-10, NiCo-LDH/HPCA-50 and pure NiCo-LDH, the optimized NiCo-LDH/HPCA-30 composite exhibits a large specific capacitance (1504 F g−1 at 1 A g−1) and excellent capacitance retention rate (85.9% after 5000 cycles) in a three-electrode system. In addition, the assembled NiCo-LDH/HPCA-30//AC asymmetric supercapacitor can bring a high energy density (33.33 Wh kg−1) and an outstanding cycle retention rate (90.76% after 3000 cycles). Therefore, the new NiCo-LDH/HPCA-30 composite with excellent electrochemical properties is expected to give full play to the application advantages of high-performance energy storage devices.

Metal-Organic Framework Derived Nickel-Cobalt Layered Double Hydroxide Nanosheets Cleverly Constructed on Interconnected Nano-Porous Carbon for High-Performance Supercapacitors

Metal-Organic Framework Derived Nickel-Cobalt Layered Double Hydroxide Nanosheets Cleverly Constructed on Interconnected Nano-Porous Carbon for High-Performance Supercapacitors

3D NiCo-Layered double Hydroxide@Ni nanotube networks as integrated free-standing electrodes for nonenzymatic glucose sensing

Nickel cobalt layered double hydroxide (NiCo-LDH)-based materials have recently emerged as catalysts for important electrochemical applications. However, they frequently suffer from low electrical conductivity and agglomeration, which in turn impairs their performance. Herein, we present a catalyst design based on integrated, self-supported nickel nanotube networks (Ni-NTNWs) loaded with NiCo-LDH nanosheets, which represents a binder-free, hierarchically nanostructured electrode architecture combining continuous conduction paths and openly accessible macropores of low tortuosity with an ultrahigh density of active sites. Similar to macroscale metallic foams, the NTNWs serve as three-dimensionally interconnected, robust frameworks for the deposition of active material, but are structured in the submicron range. Our synthesis is solely based on scalable approaches, namely templating with commercial track-etched membranes, electroless plating, and electrodeposition. Morphological and compositional characterization proved the successful decoration of the inner and outer nanotube surfaces with a conformal NiCo-LDH layer. Ni-NTNW electrodes and hydroxide-decorated variants showed excellent performance in glucose sensing. The highest activity was achieved for the catalyst augmented with NiCo-LDH nanosheets, which surpassed the modification with pure Ni(OH)2. Despite its low thickness of 20 µm, the optimized catalyst layer provided an outstanding sensitivity of 4.6 mA mM−1 cm−2, a low detection limit of 0.2 µM, a fast response time of 5.3 s, high selectivity and stability, and two linear ranges covering four orders of magnitude, up to 2.5 mM analyte. As such, derivatized interconnected metal nano-networks represent a promising design paradigm for highly miniaturized yet effective catalyst electrodes and electrochemical sensors.

Synthesis of reduced graphene oxide supported nickel-cobalt-layered double hydroxide nanosheets for supercapacitors

Supercapacitors are deemed as reliable power sources for portable devices and electric vehicles. Electrode materials with high energy and power densities are greatly needed. Herein, we designed reduced-graphene-oxide supported nickel-cobalt layered double hydroxide nanosheets (NiCo-LDH/rGO) as electrode materials. The introduction of graphene could largely enhance the conductivity, and the supported NiCo-LDH could effectively prevent graphene from self-aggregation. Thanks to the synergistic effect of conductive graphene and electro-active LDH, the nanocomposites delivered a capacitance of 1675 F g−1 at 1 A g−1 and decent rate performance (capacitance retention of 83.8% at 10 A g−1); while NiCo-LDH could only exhibited a capacitance of 920 F g−1 at 1 A g−1 and 81.5% of the capacitance remained at 10 A g−1. The asymmetric supercapacitors assembled with NiCo-LDH/rGO and activated carbon (AC) delivered high energy density and power density, up to 49.9 Wh kg−1 and 3747.9 W kg−1, respectively. The appealing electrochemical performance indicates its huge application potential in supercapacitors.

Advanced core-shell nanostructures based on porous NiCo-P nanodiscs shelled with NiCo-LDH nanosheets as a high-performance electrochemical sensing platform

The development of robust and efficient earth-abundant electrocatalysts based on complex core-shell arrays with ordered two-dimensional nano-architectures for different electrochemical technologies is an ongoing challenge. In this matter, the fabrication of core-shell arrays with a core of bimetallic phosphides nanodisc-like building blocks has not been reported yet. Herein, advanced core-shell nanostructures consisting of porous nickel-cobalt phosphide nanodiscs (NiCo-P NDs) shelled with nickel-cobalt layered double hydroxide nanosheets (NiCo-LDH NSs) were rationally designed (NiCo-P@NiCo-LDH). The NiCo-P@NiCo-LDH core-shell nanodiscs/nanosheets have unique features such as high conductivity, large specific surface area, more contact area between nanomaterials and analyte, and numerous active sites for enhancing electrochemical performance. The electrocatalytic performance of fabricated core-shell arrays was evaluated toward electrochemical sensing of isoprenaline (IPN) as a templet. Some competencies of glassy carbon electrode coated with NiCo-P@NiCo-LDH core-shell arrays (NiCo-P@NiCo-LDH/GCE) to IPN determination are including speedy response time (∆t <1s), low detection limit (0.17 µM), wide linear range (0.5–2110 µM), long-term stability, good reproducibility, low cost, and portability. This report is promising for application in other electrochemical technologies and it will pave the way for the development of new core-shell nanostructures based on multi-metallic phosphide nanodiscs.

Hierarchical molybdenum disulfide nanosheet arrays stemmed from nickel-cobalt layered double hydroxide/carbon cloth for highly-efficient hydrogen evolution reaction

The hierarchical molybdenum disulfide nanosheet arrays on carbon cloth are synthesized using layered double hydroxides as a growth template for highly efficient hydrogen evolution reaction. The hierarchical structure of molybdenum disulfide (MoS 2 ) nanosheet arrays stemmed from nickel-cobalt layered double hydroxide (NiCo-LDH)/carbon cloth was prepared by growing the MoS 2 nanosheet arrays onto the NiCo-LDH template which was pre-deposited onto the carbon cloth substrate. In this electrode configuration, carbon cloth is the three dimensional and conductive skeleton; NiCo-LDH nanosheets, as the template, ensure the oriented growth of MoS 2 nanosheet arrays. Therefore, more MoS 2 active sites are exposed and the catalyst exhibits good hydrogen evolution reaction activity.

Co-ZIF derived porous NiCo-LDH nanosheets/N doped carbon foam for high-performance supercapacitor

The three-dimensional (3D) interconnected structure is desirable for high-performance supercapacitor since it can provide more exposed electroactive sites as well as accelerate the electron and ion transfer. Herein, nitrogen doped carbon foams with good hydrophilicity and mechanical property are first prepared from cheap melamine foams via the heat-treatment at low temperature in the air, which can serve as an ideal substrate for growing nickel cobalt layered double hydroxide nanosheets (NiCo-LDH) derived from cobalt zeolitic imidazole frameworks (Co-ZIF). The as-prepared NiCo-LDH/N doped carbon foam (NiCo-LDH/NCF) exhibits high specific capacity of 756 C g−1 at a current density of 0.5 A g−1, and still retains the specific capacity of 414 C g−1 at a current density of 20 A g−1, indicating the excellent rate capability. Furthermore, the assembled NiCo-LDH@NCF//activated carbon asymmetrical supercapacitor device achieves a high energy density of 41.5 Wh kg−1 at a power density of 750 W kg−1, and an excellent cyclic stability of 80.4% retention over 10000 cycles. The remarkable capacitive performance of NiCo-LDH@NCF is assigned to the self-supporting 3D interconnected architecture of NCF that makes the uniform distribution of NiCo-LDH nanosheets and also provides the rapid channels for electron and ion transfer. The results indicate that NiCo-LDH@NCF will be a promising candidate for high-performance supercapacitors.

Facile Synthesis of Nickel Cobalt Layered Double Hydroxide Nanosheets Intercalated with Sulfate Anion for High-Performance Supercapacitor.

Nickel-cobalt layered double hydroxide nanosheets intercalated with sulfate anion were fabricated via a facile hydrothermal method and investigated as high-performance electrode materials for supercapacitors. The morphology and electrochemical properties of the obtained samples could be controlled by changing molar ratios of the Ni and Co precursors. NiCo-LDHs with Ni/Co molar ratio of 0.35:0.65 exhibited high specific capacitance of 1551.1 F/g at the current density of 1 A/g and good cycling stability of 84.0% retention after 1000 charge/discharge cycles. On this basic, aqueous asymmetric supercapacitor (AAS) was successfully constructed by using the Ni0.35Co0.65-LDHs as the positive electrode and the activated carbon as the negative electrode. The as-built AAS was able to work in a working voltage window of 0~1.4 V and exhibited outstanding electrochemical performance. The Ni0.35Co0.65-LDHs//KOH activated cotton-derived carbon (ACDC) AAS showed the highest specific capacitance of 157.5 F/g, the satisfactory capacitance retention of 78.62% after 5000 cycles, the maximum energy density of 42.88 Wh/kg, and preferable combination of energy density of 30.63 Wh/kg with power density of 4.9 kW/kg at a current density of 7 A/g.

Three-dimensional porous MXene/NiCo-LDH composite for high performance non-enzymatic glucose sensor

In this paper, Nickel–Cobalt layered double hydroxide (NiCo-LDH) nanosheets were first in situ synthesized on MXene (Ti3C2) via a simple hydrothermal method, then glucose sensing performance based on three-dimensional porous MXene/NiCo-LDH nanocomposite was explored. At a working potential of 0.45 V (vs. SCE), the glucose sensor exhibits a wide linearity range (0.002 mM–4.096 mM), a low limit of detection (0.53 μM) and a rapid response (<3 s). Moreover, good selectivity, reproducibility and stability were also obtained. And the excellent performance can attribute to large area of contact of materials surface with glucose, fast electron transfer rate and easy diffusion of electrolyte provided by the novel 3D porous NiCo-LDH nanosheets on the conductive MXene substrate. Therefore, MXene/NiCo-LDH composites will be a candidate for electrochemical detection of glucose.

Self-templated transformation of MOFs into layered double hydroxide nanoarrays with selectively formed Co9S8 for high-performance asymmetric supercapacitors

Metal-organic frameworks (MOFs) with tunable pore size, stable porous architectures and large specific surface areas have been widely used as precursors for supercapacitor electrode materials. Herein, MOF-derived hollow nickel cobalt layered double hydroxide (NiCo-LDH) nanoarrays embedded with selectively formed Co9S8 nanoparticles on flexible carbon fibers (CC@NiCo-LDH/Co9S8) are reported. The 2D hollow NiCo-LDH framework from self-templated transformation of MOFs enhances the flow efficiency of ions at interlayers to further reduce the resistance of ion transportation. Significantly, the embedded Co9S8 nanoparticles from selective sulfurization of Co exhibit rich active sites and intimate contact of LDH/Co9S8, which effectively improves the electrochemical properties of CC@NiCo-LDH/Co9S8 hybrids, such as electrical conductivity, capacity performance and structural stability. Due to synergistic interaction of NiCo-LDH nanosheets and embedded Co9S8 nanoparticles, the as-prepared CC@NiCo-LDH/Co9S8 electrode material exhibits an ultrahigh capacitance of 2438 F g−1 at 5 A g−1. Furthermore, the as-assembled asymmetric supercapacitor (ASC) device of CC@NiCo-LDH/Co9S8//activated carbon (AC) achieves a maximum energy density of 38.0 Wh kg−1 at 800.0 W kg−1 and outstanding cycling stability with 93.1％ retention of the initial capacitance after 5000 cycles.

Highly dispersed ultrafine Pt nanoparticles on nickel-cobalt layered double hydroxide nanoarray for enhanced electrocatalytic methanol oxidation

Highly dispersed ultrafine Pt nanoparticles (NPs) were loaded on a nickel-cobalt layered double hydroxide (NiCo-LDH) nanoarray that was grown on Ni foam (NF) via an in situ redox reaction without any external agent between Co2+ (Co(OH)2) in NiCo-LDH and PtCl62-. The obtained Pt/NiCoLDH/NF composite was used as a catalyst for methanol oxidation in alkaline media, showing much higher electrocatalytic activity and better anti-poisoning ability and stability for methanol oxidation than commercial Pt/C, mainly because of the uniform dispersion of ultrafine Pt NPs, the synergistic effect and stable support of NiCoLDH. The NiCoLDH nanoarray effectively increased the specific surface area and location sites for supporting Pt NPs and enhanced the catalytic performance and tolerance to intermediate species. This enhancement was probably due to the synergistic effect between Pt and the NiCo-LDH nanosheets, in which the LDH can provide adequate OH−ads species for accelerating the methanol oxidation reaction (MOR).

Conductive silver nanowires-fenced carbon cloth fibers-supported layered double hydroxide nanosheets as a flexible and binder-free electrode for high-performance asymmetric supercapacitors

Silver nanowires (Ag NWs) have attracted particular interest in the development of various electronic and energy storage devices due to their one-dimensional structure, good conductivity, fast charge transportation and direct contact to the current collector. Herein, we have successfully deposited the binder-free nickel-cobalt layered double hydroxide nanosheets on Ag NWs-fenced carbon cloth (NC LDH NSs@Ag@CC) by a facile electrochemical deposition method with a chronoamperometry voltage of −1.0V for 120s. The electrically conductive and superhydrophilic nature of the hybrid nanocomposite electrode led to relatively high areal capacitance (1133.3 mF cm−2 at 1mAcm−2) and good cycling stability (80.47% after 2000 cycles) compared to the electrode prepared without Ag NWs. Using such hierarchical NC LDH NSs@Ag@CC as a positive electrode, we further fabricated a flexible asymmetric supercapacitor (ASC) with activated carbon coated CC as a negative electrode. The as-assembled ASC exhibited maximum operational potential window of 1.6V, high areal capacitance of 230.2 mF cm−2 and excellent cycling stability of 88.1% with remarkable energy densities at all the charge-discharge conditions (78.8 μWh cm−2 at the power density of 785 μW cm−2 and 40 μWh cm−2 at the high power density of 12.1mWcm−2, respectively)

Acetate anion-intercalated nickel-cobalt layered double hydroxide nanosheets supported on Ni foam for high-performance supercapacitors with excellent long-term cycling stability

As a widely concerned material for supercapacitors, nickel cobalt layered double hydroxides (NiCo-LDHs) often suffer from the inferior rate capability and cycling stability due to the low electrical conductivity and easy agglomeration. To address these shortcomings, a simple in-situ hydrolysis approach is successfully developed to construct a binder-free system consisting of acetate anion-intercalated nickel cobalt layered double hydroxides (A-NiCo-LDHs) and Ni foam (NF) without additional alkali sources. The resulting A-NiCoLDH/NF electrodes exhibited obviously enhanced capacitive properties owing to the unique nanostructure and strong synergistic effects. It is worth noting that the optimized A-Ni5Co5-LDH/NF electrode delivered the highest performance among the electrodes studied, including ultrahigh specific capacitance (2445Fg−1 at 0.5Ag−1) and superior rate capability (1644Fg−1 and 1383Fg−1 at 20Ag−1 and 50Ag−1, respectively), as well as satisfactory long-term endurance (∼93% capacitance retention after 10,000 cycles at 20Ag−1). The attractive performances and facile fabrication make the A-Ni5Co5-LDH/NF system a promising candidate for low-cost high-performance energy storage devices.