Nickel-cobalt Layered Double Hydroxide Research Articles

Preparation and evaluation of S-rGO/ZnFe2O4/NiCoLDH nanocomposite electrocatalyst in oxygen reduction reaction

This study introduces a novel combination of sulfur-doped reduced graphene oxide (S-rGO), zinc ferrite (ZnFe2O4) and nickel cobalt layered double hydroxide (NiCoLDH) as an efficient and low-cost electrocatalyst for oxygen reduction reaction (ORR) for the first time. The hydrothermal method is used to synthesize all samples including graphene oxide (GO), S-rGO, NiCoLDH, ZnFe2O4 and S-rGO/ZnFe2O4/NiCoLDH hybrids. X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), energy dispersive x-ray analysis (EDX), electrochemical surface area (ECSA), and fourier transform infrared spectroscopy (FTIR) analysis are used to determine the structure of synthesized electrocatalysts, physical properties, and morphology. The electrochemical measurements are carried out using cyclic voltammetry (CV), linear scanning voltammetry (LSV), chronoamperometry (ChA), and electrochemical impedance spectroscopy (EIS). The results for all samples are compared with the Pt/C commercial catalyst. According to the electrochemical results, the S-rGO/ZnFe2O4/NiCoLDH electrocatalyst has the best electrochemical performance. Moreover, the nanocomposite exhibited better electrocatalysis, a high diffusion limiting current density of −5.4 mA cm−2 and an onset potential of 0.03 V. Based on the results of this study, the LDH enhances electrical conductivity, electrocatalytic activity, active surface area, and stability of the catalyst for ORR after combining with carbon bases and ferrite.

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.

Simple preparation of V-doped NiCo-LDH as cathode of high energy density supercapacitor

One of the most promising cathode materials for supercapacitors is nickel-cobalt layered double hydroxide (NiCo-LDH). Doping atoms are widely used to solve the problems of poor electrical conductivity and structural defects of electrode materials. Vanadium (V) has received widespread attention due to its multiple oxidation states and low cost. In this article, we use one-step hydrothermal method to synthesize V-doped NiCo-LDH (V-NC1.5). By regulating the doping amount of V, 2V-NC1.5 exhibits superb specific capacitance of 1835 F g−1 at 1 A g−1. An asymmetric aqueous supercapacitor was assembled with 2V-NC1.5 and activated carbon. Its maximum energy density can reach 60.9 Wh kg−1 at 800 W kg−1 of power density. When the two units are connected in series, they can effectively power a white LED bulb and maintain its brightness for more than 30 min. This result provides a potential opportunity for the efficient deployment of innovative energy storage technologies in the coming years.

Compositionally engineered NiCoLDH@rGO as bifunctional cathode catalyst for rechargeable Li-O2/Li-CO2 battery

Compositionally tuned nickel-cobalt layered double hydroxides (NCLDHs) and NCLDH@reduced graphene-oxide (NCLDH@rGO) were synthesized through a facile solvothermal synthesis route. The formation of the synthesized NCLDH and the NCLDH@rGO with the intercalated carbonate and nitrate anions, has been confirmed utilizing different characterization techniques. Microscopic results revealed the flaky morphology with thickness about 30 nm. Rotating ring disc electrode (RRDE) voltammetry was utilized to analyze the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CO2RR) kinetics on each of the pristine (1:1), (2:1), (3:1) and (4:1) NCLDH catalysts and the NCLDH@rGO composites. The RRDE data revealed that the electrochemical activity towards ORR/OER/CO2RR could be largely increased by tuning mole ratio of the (Ni2+/Co3+) or the amount of the rGO in the NCLDH. It turned out that among the pristine electrocatalysts, the (1:1) NCLDH catalyst exhibited enhanced ORR/OER kinetics. While the NCLDH acted as a catalyst center, the rGO provided conductive network that facilitated passable overpotential with increased current density for the ORR/OER/ CO2RR. Better adsorption of O2 and CO2 on the NCLDH@rGO catalyst also contributed for the electrocatalytic activity. Consequently, the NCLDH@rGO composites as cathode catalyst for Li-O2 battery in the CR2032 prototype coin-cell exhibited a stable open circuit voltage (OCV). Among the NCLDH@rGO composites, the NCLDH with 15 wt.% rGO (NCRGO15) exhibited a high discharge capacity of 3616 mAh g−1 at 50 Ag−1 for the Li-O2 battery and a discharge capacity of 45 mAh g−1 at a current density of 100 Ag−1 for the CR2032 coin-type Li-CO2 battery. As a practical use, a commercial 2.8 V green LED bulb was lit continuously for about 20 h using the fabricated Li-O2 battery that consisted of lithium anode and (1:1) NCLDH@rGO15 wt.% (NCRGO15) air-breathing cathode.

Effect of synthesis temperature on the structural morphology of a metal–organic framework and the capacitor performance of derived cobalt–nickel layered double hydroxides

Three-dimensional interconnected nickel–cobalt layered double hydroxides (NiCo-LDHs) were prepared on nickel foam by ion exchange using a cobalt-based metal–organic framework (Co-MOF) as a template at different temperatures. The effects of the Co-MOF preparation temperature on the growth, mass, morphology, and electrochemical properties of the Co-MOF and derived NiCo-LDH samples were studied. The synthesis temperature from 30 to 50 °C gradually increased the mass of the active material and the thickness of the Co-MOF sheets grown on the nickel foam. The higher the temperature is, the larger the proportion of Co3+. β-Cobalt hydroxide (β-Co(OH)2) sheets were generated above 60 °C. The morphology and mass loading pattern of the derived flocculent layer clusters of NiCo-LDH were inherited from metal-organic frameworks (MOFs). The areal capacitance of NiCo-LDH shows an inverted U-shaped curve trend with increasing temperature. The electrode material synthesized at 50 °C had a tremendous specific capacitance of 7631 mF·cm−2 at a current density of 2 mA·cm−2. The asymmetric supercapacitor assembled with the sample and active carbon (AC) achieved an energy density of 55.0 Wh·kg−1 at a power density of 800.0 W·kg−1, demonstrating the great potential of the NiCo-LDH material for energy storage. This work presents a new strategy for designing and fabricating advanced green supercapacitor materials with large power and energy densities.

Nickel-cobalt layer double hydroxide @ lignin-based hollow carbon quasi core-shell structure for high-performance supercapacitors

The physicochemical properties of an advanced supercapacitor electrode material can be co-tailored by incorporating various active materials into a hierarchical micro-/nano-architecture with a core-shell structure. Herein, we presented the development of high-performance supercapacitor electrode materials of quasi core-shell architectures based on nickel-cobalt layered double hydroxides supported on lignin-based hollow carbon (NiCoLDH@LHC) nanocomposites. The synthesis involves a novel approach combining enzymatic hydrolysis lignin (EHL) as a carbon source and magnesium oxide (MgO) as a template, utilizing evaporation-induced self-assembly (EISA) followed by carbonization. The manipulation of the mass ratio of NiCoLDH/LHC can induce alterations in its apparent morphology, stratified porosity, and active site, thereby an influence on its electrochemical performance. The optimal NiCoLDH@LHC90 nanocomposites display a unique flower-like spherical structure with open pores, a substantial specific surface area (SSA), and numerous electrochemically active sites. In addition, the density functional theory (DFT) calculations demonstrate that the higher density of Ni3+/Co3+ cations induced by the incorporation of LHC can increase the conductivity of NiCoLDH materials. Notably, these nanocomposites exhibit a remarkable specific capacitance of up to 640 C g−1 at 1 A g−1, with exceptional cycling stability (93.66% retention over 10,000 cycles). Furthermore, an assembled NiCoLDH@LHC90//LHC asymmetric supercapacitor demonstrates an impressive energy density (power density) of 35.44 Wh kg−1 (200.01 W kg−1). The physicochemical properties of an advanced supercapacitor electrode material can be finely tuned by incorporating various active materials into a hierarchical micro-/nano-architecture with a core-shell structure.

C3N4 improved nickel-cobalt layered double hydroxide (NiCoLDH) supercapacitive property

A flower-like composite of NiCoLDH/C3N4 is prepared using a simple one-step hydrothermal method. The morphologies and structure information of samples are observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical properties are measured by an electrochemical workstation and Land. The effects of the C3N4 mass loading on the capacitance of NiCoLDH/C3N4 composite are studied. The results show that the NiCoLDH/C3N4 composite exhibits a flower-like morphology and presents an impressive specific capacitance of 2677 F g−1 at 1 A g−1 for the optimized sample with C3N4 mass loading of 5 mg, higher than that of the pristine NiCoLDH (1676 F g−1). In addition, the assembled NiCoLDH/C3N4//YP50 supercapacitor device could achieve a maximum energy density of 33 Wh kg−1 and show a good capacitance retention of 97 % after 9000 cycles.

NiCo-compounds inside and outside N-doped carbon nanotubes to construct a double-enhanced hierarchical structure for high energy density supercapacitors.

Attaining a high energy density that aligns with practical application requirements is a crucial indicator in the advancement of supercapacitors. In this paper, a hybrid hierarchical electrode structure of N-doped carbon nanotube (NCNT) spheres encapsulated with NiCo-Se nanoparticles (NPs) and coated with nickel-cobalt layered double hydroxide (NiCo-LDH) multilayer nanosheets was successfully synthesized on a nickel foam (NF) substrate. The self-supporting strategy enables nickel-cobalt Prussian blue analogues (Ni-Co PBAs) to be directly attached to the NF surface, which results in fluffy NCNTs with a high length-diameter ratio and considerable yield and greatly enhances the conductivity of the electrode material. The synergistic interaction between the dual transition metal compounds inside and outside the NCNTs enables the hybrid electrode material to achieve an impressive specific capacity of 1899 F g-1 (211.0 mA h g-1) at 1 A g-1. The asymmetric supercapacitor (ASC) exhibits an excellent energy density of 57.6 W h kg-1 at a power density of 798 W kg-1. This study not only provides an attractive strategy for obtaining CNTs with excellent properties from Ni-Co PBA and synthesizing hybrid electrodes with efficient synergistic effects, but also achieves a high energy density that aligns with the practical application demands of supercapacitors.

Tunable capacitive charge storage of NiCoLDH@rGO for high-energy capacitor: Performance of flexible solid-state capacitor

The compositionally tunned pristine nickel cobalt layered double hydroxides (NiCoLDHs) and NiCoLDH@reduced graphene-oxide (NiCoLDH@rGO) composites generated via the simple single-pot solvothermal method. The synthesized NiCoLDH and the NiCoLDH@rGO composites were characterized through powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transformed infra-red (FT-IR) spectroscopy, scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX), high-resolution transmission electron microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The XRD, Raman and FT-IR data confirmed the formation of the NiCoLDH with presence of carbonate and nitrate ions in the basal space. Enhanced basal length was observed for the NiCoLDH@rGO composites. The three-electrode system was constructed to analyse the cyclic voltammetry and Galvanostatic charge-discharge studies in 1 M KOH confirmed that the pristine LDHs and the composites are electrochemically active, and the capacity could be tuned by varying (Ni2+/Co3+) mole ratio or the rGO content. The charge storage kinetics in NiCoLDH@rGO was performed through Dunn's approaches and the Power Law, affirmed as the (Ni2+/Co3+) ratio or the rGO content is increased in the composite the capacitive contribution is increased for the charge storage. The NC@RG10 (NiCoLDH with 10 wt% rGO) composite electrode could deliver an enhanced specific capacity of 963C g−1 at a current rate of 1.5 A g−1. Consequently, pristine LDH or composites as positive electrode and rGO as negative electrode was fabricated using the CR-2032 coin-type hybrid capacitor. The laboratory prototype pristine hybrid capacitor (NiCoLDH|1 M KOH|rGO) delivered an enhanced specific energy of 56 Wh kg−1 at specific power of 810 W kg−1, whereas the composite hybrid device (NC@RG10|1 M KOH|rGO) having NC@RG10 electrode delivered an enhanced specific energy of 166 Wh kg−1 at specific power of 638 W kg−1. The NC@RG10 composite-based hybrid device exhibited excellent stability with coulombic efficiency as high as 99 % even at the 10,000th charge−discharge cycle. Reduced aggregation and enhanced conductivity leading to significant capacitive contribution in the NC@RG10 composite is due to the existence of rGO and responsible for the excellent charge storage performance. The fabricated hybrid capacitor powered a red LED on a single charge for 40 min. Fascinatingly, a flexible solid-state hybrid capacitor was also fabricated that delivered an impressive specific energy of 28 Wh kg−1 at a specific power of 553 W kg−1 at a 180° bent angle.

NiSe2-CoSe2 hollow polyhedron as counter electrode catalyst for high-efficiency dye-sensitized solar cells

The design of efficient counter electrode (CE) materials for dye sensitized solar cells (DSSCs) strongly depend on the microstructure construction and the effective combination of different active components. In this study, a hollow polyhedral structured NiSe2-CoSe2 composite electrode was synthesized through the direct selenization of the hollow nanocage morphology nickel-cobalt layered double hydroxide (NiCo-LDH) ultrathin nanosheets, which was derived from ZIF-67 nanocrystals. Notably, owing to the unique hollow structure and synergistic effect of the Ni-Co bimetallic selenides, the hollow polyhedral NiSe2-CoSe2 CE exhibited the expected electrochemical catalytic activity in the reduction of triiodide, as revealed by electrochemical impedance spectroscopy, cyclic voltammetry and Tafel polarization measurements. The photovoltaic results revealed that the PCE of the NiSe2-CoSe2 CE reached 8.21 %, which was higher than those of the Pt and CoSe2 CEs (7.62 % and 6.78 %, respectively). Moreover, the hollow NiSe2-CoSe2 CE exhibited a favourable photocurrent response upon light on-and-off cycling and improved stability over multiple start. This study provides a meaningful reference for the construction of hollow polymetallic transition-metal selenides for DSSC devices.

NiCo-LDH Hollow Nanocage Oxygen Evolution Reaction Promotes Luminol Electrochemiluminescence.

Conventional luminol co-reactant electrochemiluminescence (ECL) systems suffer from low stability and accuracy due to factors such as the ease of decomposition of hydrogen peroxide and inefficient generation of reactive oxygen species (ROS) from dissolved oxygen. Inspired by the luminol ECL mechanism mediated by oxygen evolution reaction (OER), the nickel-cobalt layered double hydroxide (NiCo-LDH) hollow nanocages with hollow structure and defect state are used as co-reaction promoters to enhance the ECL emission from the luminol-H2 O system. Thanks to the hollow structure and defect state, NiCo-LDH hollow nanocages show excellent OER catalytic activity, which can stabilize and efficiently produce ROS and enhance the ECL emission. Additionally, mechanistic exploration suggests that the ROS involved in the co-reaction of the luminol-H2 O system are derived from the OER reaction process, and there is a positive correlation between ECL intensity and the OER catalytic activity of the co-reaction promoter. The selection of catalysts with excellent OER catalytic activity is a key factor in improving ECL emission. Finally, a dual-mode immunosensor is constructed for the detection and analysis of alpha-fetoprotein (AFP) based on the promoting effect of NiCo-LDH hollow nanocages on the luminol-H2 O ECL system.

Cobalt coordinated carbon quantum dots boosting the performance of NiCo-LDH for energy storage

Transition metal layered double hydroxides have extremely high specific capacitances but suffer from poor rate performance and cycling stability due to their low conductivity and structural stability. In this study, cobalt-coordinated carbon quantum dots (CoCQDs) were designed and synthesized to enhance the energy storage performance of nickel–cobalt layered double hydroxides (NiCo-LDH). Nickel and cobalt ions were co-electrodeposited with the CoCQDs to form a NiCo-LDH based composite electrode (denoted as CoC@LDH). Since the CoCQDs participated in the formation of the NiCo-LDH, the carbon quantum dots could be strongly bonded to the NiCo-LDH nanosheets through coordination interactions. Thus, the conductivity as well as the structure stability of the NiCo-LDH was effectively improved, which greatly boosted the cycle stability and rate performance of the NiCo-LDH. Several CoCQDs with different Co contents (nCoCQDs, n = 0.5, 1.0, 2.0) were fabricated and their effects on the performance of the resultant electrodes nCoC@LDH were investigated. The 1.0CoC@LDH electrode exhibited an impressive specific capacitance of 1867 F g–1 at 1 A-g–1, along with a significantly enhanced capacitance retention of 84.6 % after 6000 cycles at 5 A g–1 (benchmark 49.5 %). This ingenious design provides a new avenue for fabricating pseudo-capacitive materials with unprecedented high performance.

Regulating the Oxygen Vacancy and Electronic Structure of NiCo Layered Double Hydroxides by Molybdenum Doping for High-Power Hybrid Supercapacitors.

Amelioration of nickel-cobalt layered double hydroxides (NiCo-LDH) with a high specific theoretical capacitance is of great desire for high-power supercapacitors. Herein, a molybdenum (Mo) doping strategy is proposed to improve the charge-storage performance of NiCo-LDH nanosheets growing on carbon cloth (CC) via a rapid microwave process. The regulation of the electronic structure and oxygen vacancy of the LDH is consolidated by the density functional theory (DFT) calculation, which demonstrates that Mo doping narrows the band gap, reduces the formation energy of hydroxyl vacancies, and promotes ionic and charge transfer as well as electrolyte adsorption on the electrode surface. The optimal Mo-doped NiCo-LDH electrode (MoNiCo-LDH-0.05/CC) has an amazing specific capacity of 471.1mA h g-1 at 1 A g-1 , and excellent capacity retention of 84.8% at 32 A g-1 , far superior to NiCo-LDH/CC (258.3mA h g-1 and 76.4%). The constructed hybrid supercapacitor delivers an energy density of 103.3W h kg-1 at a power density of 750W kg-1 and retains the cycle retention of 85.2% after 5000 cycles. Two assembled devices in series can drive thirty LED lamps, revealing a potential application prospect of the rationally synthesized MoNiCo-LDH/CC as an energy-storage electrode material.

Enhanced electrochemical properties of nickel-cobalt hydroxide nanosheet by high-gravity liquid phase modification

Nickel-cobalt layered double hydroxide (Ni-Co LDH) nanosheet has a low specific capacity and poor rate capability. This study uses an anionic surfactant to modify Ni-Co LDH by the high-gravity liquid-phase method. The results reveal that the sodium dodecyl benzene sulfonate (SDBS) adsorption and intercalation can increase electrode interface area, enlarge interlayer spacing of Ni-Co LDH, accelerate the diffusion of electrolyte ions, and thus improve its specific capacity and rate capability. Compared with the stirred flow field, the high gravity further intensifies the surface adsorption and substitution intercalation of SDBS, resulting in a bigger interface area and interlayer spacing of Ni-Co LDH, which is more favorable to its specific capacity and rate capability. The specific capacity of Ni-Co LDH after high-gravity modification is 984 C g−1 (2187 F g−1, 2 A g−1), and its capacity retention rate reached 80 % (1–30 A g−1), significantly higher than that of the untreated one. Besides, an electrochemical kinetic study shows that a high gravity modification substantially enhances the ion diffusion rate. The modified materials under a high gravity field are utilized as anode materials and activated carbons (ACs) as cathode materials to construct supercapacitors. The Ni-Co LDHs//AC has a 50 Wh kg−1 energy density with well cycling stability. The paper proposes a high-gravity liquid-phase modification method to explore potential high-performance electrode materials.

Revealing the potential of hierarchical heterostructure of tri-metallic selenide and MOFs etched layered hydroxide dodecahedron laminated with rGO-Ni foam for a hybrid supercapacitor applications

Inaugurating the multistage hierarchical hybrid structure with ample surface area and synergistic contribution from polymetallic selenide and layered hydroxide in a conductive 3D substrate has been supposed to be appealing and highly-rated electrode material to enhance the general electrochemical parameters of supercapacitors (SCs), thanks to exclusive structural features, immense electronic states and relatively paramount electrical conductivity of the final product. In this work, hydrothermal assisted zinc‑nickel‑cobalt-selenide (ZNC-Se) nanosheets have been uniformly prepared onto the conductive rGO decorated Ni foam substrate, chased by uniform decoration of metal organic frameworks (MOFs) templated nickel‑cobalt-layered double hydroxide (NC-LDH) onto tri-metallic (ZNC-Se) nanosheets to achieve the hierarchical hybrid structure of [email protected]@rGO-NF. The as-prepared hierarchical [email protected]@rGO-NF delivers remarkable specific capacity value along with outstanding cycle stability. The proposed [email protected]@rGO-NF and MOFs derived open and hollow carbon structure (MDOHCS)-based hybrid device disclosed remarkable cyclic life and an energy/power density of 80.3 W h kg−1/15970.9 W kg−1.

Hierarchically porous cellulose nanofibril aerogel decorated with polypyrrole and nickel-cobalt layered double hydroxide for high-performance nonenzymatic glucose sensors

Hierarchically porous cellulose nanofibril aerogel decorated with polypyrrole and nickel-cobalt layered double hydroxide for high-performance nonenzymatic glucose sensors

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.

High mass-loading of nickel‑cobalt layered double hydroxide on 3D-printed electrode for cathode of asymmetric supercapacitor

To achieve high-performance supercapacitors, the fabrication of electrodes with a high mass loading of active species without sluggish ion diffusion is a key process. Herein, we report nickel‑cobalt layered double hydroxide (NiCo-LDH) electrodeposited on 3D-printed electrodes (3D-PEs) prepared via 3D printing fused deposition modeling (FDM) technique after the surface modification of 3D PEs to achieve high loading mass cathode electrode (NiCo-LDH@3D-PEs) for asymmetric supercapacitor. As fabricated 1.6 mm-thick NiCo-LDH@3D-PE exhibits high mass loading (15.3 mg cm−2) with a capacitance of 25.9 F cm−2 (1690 F g−1) at 10 mA cm−2 current density. These improved activities are mainly due to the intrinsic properties of multilayered 3D-PEs which increase the number of ion-accessible sites and shorten the ion diffusion because of multiple orthogonal layers. Furthermore, an asymmetric supercapacitor was also examined with acid-treated carbon cloth (ATCC) as a negative and NiCo-LDH@3D-PE as a positive electrode. As we expected, the NiCo-LDH@3D-PE//ATCC device resulted in high energy density (1.26 mWh cm−2) and power density (4.74 mW cm−2). In addition, 93 % of its initial capacitance was observed after 10,000 cycles respectively. The outstanding performance of NiCo-LDH@3D-PEs authorizing the 3D printing FDM technique efficiently supports high mass-loading cathodes for asymmetric supercapacitors.