Nickel-cobalt Layered Double Hydroxide Research Articles

Flexible and binder-free nickel-cobalt layered double hydroxides for high specific capacity supercapacitor applications

The development of advanced energy storage materials is crucial for the evolution of high-performance supercapacitors. Recently, nickel-cobalt layered double hydroxides (NiCo LDHs) stand out due to their synergistic effects and abundant redox-active sites, which contribute to superior electrochemical performance. Herein, we design simple cyclic voltammetry-assisted electrochemical synthesis of thin-film NiCo LDHs on stainless steel mesh as a binder-free electrode, which demonstrates enhanced redox-type charge storage and excellent durability. Specifically, the synthesized NiCo LDHs exhibits a porous, sheet-like architecture, confirmed through various structural characterization techniques. Electrochemical measurements in 1M KOH electrolyte showed significant diffusion-contributed capacity in the NiCo LDHs thin films, demonstrating high specific capacitance of 1406.7 F/g (633 C/g) and excellent cycling stability 83%. Moreover, the NiCo LDHs exhibited high energy density of 97.6 Wh/g at a power density of 1666.7 W/kg, respectively. Our work provides the facile cyclic voltammetry method for direct, scalable deposition, providing a straightforward route to optimize redox-active LDHs for efficient supercapacitor applications, highlighting the potential for advanced energy storage solutions.

Nickel–Cobalt Layered Double Hydroxide Nanosheet-Decorated 3D Interconnected Porous Ni/SiC Skeleton for Supercapacitor

In this study, a three-dimensional (3D) interconnected porous Ni/SiC skeleton (3D Ni/SiC) was synthesized by binder-free hydrogen bubble template-assisted electrodeposition in an electrolyte containing Ni2+ ions and SiC nanopowders. This 3D Ni/SiC skeleton served as a substrate for directly synthesizing nickel–cobalt layered double hydroxide (LDH) nanosheets via electrodeposition, allowing the formation of a nickel–cobalt LDH nanosheet-decorated 3D Ni/SiC skeleton (NiCo@3D Ni/SiC). The multiscale hierarchical structure of NiCo@3D Ni/SiC was attributed to the synergistic interaction between the pseudocapacitor (3D Ni skeleton and Ni–Co LDH) and electrochemical double-layer capacitor (SiC nanopowders). It provided a large specific surface area to expose numerous active Ni and Co sites for Faradaic redox reactions, resulting in an enhanced pseudocapacitance. The as-fabricated NiCo@3D Ni/SiC structure demonstrated excellent rate capability with a high areal capacitance of 1565 mF cm−2 at a current density of 1 mA cm−2. Additionally, symmetrical supercapacitor devices based on this structure successfully powered commercial light-emitting diodes, indicating the potential of as-fabricated NiCo@3D Ni/SiC in practical energy storage applications.

Multishell hierarchical GCNF/PANI/NiCo-LDH nanofibers film for high-performance supercapacitors

In the domain of supercapacitor investigation, nickel cobalt layered double hydroxides (NiCo-LDH), regarded as a promising battery material, have garnered significant attention. However, the inherent drawbacks of low conductivity and pronounced agglomeration in single-component NiCo-LDH hinder the achievement of satisfactory overall performance. Thus, a key challenge remains in the rational design of multi-component composite materials incorporating NiCo-LDH, carbon materials, and conductive polymers to enhance their electrochemical properties. In this study, we successfully fabricated multishell hierarchical fiber films of GCNF/PANI/NiCo-LDH through simple wet-chemical approach. This novel architecture features graphene-coated electrospun carbon nanofibers (GCNF) serving as a self-supporting carbon framework, polyaniline (PANI) acting as the conductive layer, and NiCo-LDH contributing a high faraday capacity. Utilizing the enhanced cooperative effects between the various components, the enhanced GCNF/PANI/NiCo-LDH electrode exhibits remarkable specific capacity (347.1 mAh g-1, 2499 F g-1 at 1 A g-1) alongside exceptional rate performance (maintaining 56.5% capacity at 20 A g-1). Moreover, when an asymmetric supercapacitor (ACS) is constructed using active carbon (AC) as the cathode and GCNF/PANI/NiCo-LDH as the anode, it demonstrates remarkable energy storage capabilities. Specifically, it achieves an impressive energy capacity of 43.8 Wh kg-1, along with a high power exceptional durability, with a capacitance retention of 88.8% even after 2000 cycles. This study presents a novel approach for designing high-performance density of 937.5 W kg-1. Additionally, it exhibits core-triple-shelled hierarchical materials in the field of energy storage devices.

Enhanced Electrochemical Performance of NiCo‐Layered Double Hydroxides: Optimal Synthesis Conditions and Supercapacitor Applications

AbstractIn the quest for high‐performance supercapacitor electrode materials, layered double hydroxides (LDHs) containing transition metals, particularly nickel–cobalt layered double hydroxides (NiCo‐LDH), have garnered significant attention due to their distinctive structural and electrochemical properties. In this study, five different temperatures, five distinct reaction times, and four varied Ni:Co ratios to determine the optimal reaction conditions are established. Utilizing these parameters, NiCo‐LDH via a one‐step hydrothermal method is synthesized. Under optimal conditions the specific capacitance reaches 400.2 C g−1 at a current density of 1 A g−1. The assembled supercapacitor has a high energy density of 51.59 µWh cm−2 at a power density of 1.125 mW cm−2. After 10 000 cycles, the capacity retention is 70%, indicating good cycling stability and demonstrating potential for application in supercapacitors. These tests provide theoretical and data‐based support for subsequent experiments and present new opportunities for advancing energy storage and conversion technologies.

One step glow-discharge electrolysis-based preparation of Al doped Ni-Co layered double hydroxide/ graphene oxide as supercapacitor electrode material

Nickel-cobalt layered double hydroxides (LDHs) are promising materials for supercapacitor electrodes; however, they face challenges in terms of cycling stability and rate capability owing to agglomeration and low conductivity. In this study, Ni(III)CoAlx-LDH/GO with an extended layer spacing and excellent electronic conductivity was synthesized by one-step glow discharge electrolysis. A nickel–cobalt alloy was used as the anode, a graphite rod as the cathode, and sodium chloride as the electrolyte. In addition, incorporating an appropriate amount of aluminum chloride into the electrolyte can alter the microstructure of the electrode material, leading to enhanced electrochemical performance. Ni(III)CoAl0.2-LDH/GO, synthesized using 0.2 g AlCl3, demonstrated exceptional electrochemical performance of 1014C g−1 at 2 A/g. At a current density of 5 A/g, the capacitance retention rate was 85.3 % after 10,000 cycles, indicating strong cyclic stability. Moreover, an asymmetric supercapacitor built with Ni(III)CoAl0.2-LDH/GO as the anode and commercial activated carbon as the cathode achieved a specific capacitance of 146.2F/g at a current density of 1 A/g. This device demonstrated outstanding circular stability, retaining 85.07 % of its capacitance after 10,000 cycles. In addition, the device achieves relatively high energy density and power density (energy density of 66.63 Wh kg−1 at a power density of 1022.23 W kg−1). This study introduces a novel synthesis method for the preparation of high-performance electrode materials aimed at advancing energy storage devices.

Insights into kinetic and transfer mechanisms for alkaline decoupled water electrolysis based on distribution of relaxation times

Electrochemical water splitting is crucial for the decarbonization of industrial processes and the coupling of renewable energy sources. Evaluation of individual HER and OER contributions to the transfer process is essential for optimizing electrolysis system performance. This study uses nickel-cobalt layered double hydroxide (NiCo-LDH) as a solid-state redox mediator (SRM), achieving efficient H2 and O2 separation. This study provides an in-depth analysis of kinetic and ion/charge/mass transfer mechanisms linked to various characteristic impedances in alkaline decoupled water electrolysis (DWE) system by integrating Electrochemical Impedance Spectroscopy (EIS) and Distribution of Relaxation Times (DRT) methods. The characteristic frequency evolution is consistent with the charge-discharge state of SRM and mass transfer frequency is related to the bubble size and gas diffusion rate of electrocatalysts at different current densities. The charge transfer Rct dominates the total polarization impedance in decoupled HER, and mass transfer Rm decreases remarkably in decoupled OER. OER shows lower Rct with Fe species existence and lower total polarization impedance than HER. Rm in decoupled HER increases by 38.24% and OER by 29.82% during prolonged decoupled test. This study provides valuable insights into the impedance contributions and kinetic mechanisms through novel electrolysis approaches, guiding further optimization of decoupled electrolyzer and electrode.

Utilizing cationic vacancies to enhance nickel-cobalt layered double hydroxides for efficient electrocatalytic urea oxidation reaction

Electrocatalytic urea oxidation reaction (UOR) is a promising approach for urea-rich wastewater splitting, which benefits for reducing energy consumption in hydrogen production accompanying environmental protection and sustainable energy development. To address the limitations posed by the self-oxidation of nickel-based catalysts on the activity of UOR, we here developed a NiCo LDH nanosheet catalyst with abundant Ni vacancies to initiate the UOR process prior to nickel oxidation. Electrochemical impedance spectroscopy and In-situ spectroscopic characterizations confirm that the UOR process primarily occurs on the surface of the catalyst, rather than being driven by nickel oxidation products. The favorable electronic structure modulation induced by Ni vacancies makes the catalyst more energetically favorable for the UOR compared to nickel self-oxidation. The catalyst exhibits excellent UOR activity, only requiring 1.27 V vs. RHE at 10 mA cm−2 and 1.34 V vs. RHE at 100 mA cm−2, with no significant decay observed after over 120 h of operation. Furthermore, it can function as a bifunctional catalyst, requiring only 1.66 V to achieve 100 mA cm−2 for the UOR||HER system. This study expands the pathway for the application of cationic vacancies in UOR.

Plasmonic Au-NPs photodecorated on NiCoLDH nanosheets as a flexible SERS sensor for the real-time detection of fipronil

Rapid extraction and detection of probe molecules from curved surfaces is critical for on-site and real-time detection. In this study, a flexible platform was developed using carbon cloth (CC) to create honeycomb-like nickel cobalt layered double hydroxides (NiCoLDH) nanosheets via a simple electrodeposition technique, which were then decorated with gold nanoparticles (Au-NPs) via photodeposition process. The Au-NPs/NiCoLDH/CC was designed as a surface-enhanced Raman scattering (SERS) substrate for detecting the broad-spectrum insecticide, Fipronil (FP). The fabricated sensor achieves a superior SERS activity due to the electrodeposited NiCoLDH, which provides the charge-transfer effect, and the photodeposited Au-NPs, which generate efficient SERS hotspots through the electromagnetic effect. The Density Functional Theory (DFT) calculation was used to estimate the optimal geometry and frontier molecular orbital diagrams of the FP molecules. The influence of electrodeposition time on NiCoLDH production and Au-NPs decorating quantity was investigated in detail. Furthermore, the flexible SERS sensor has excellent sensitivity, homogeneity, a low limit of detection (LOD), and high reproducibility for FP detection. Even after 40 cycles of bending and torsion, the SERS substrate maintained excellent mechanical endurance. Through a direct-sampling approach, FP molecules on the surfaces and mesocarp region of grapes and tomatoes were successfully detected with lower LOD. These findings highlight the outstanding potential of the produced flexible SERS sensor for real-time and on-site insecticide detection, making it valuable for food security analysis and monitoring.

In situ construction of sea urchin-like structural NiCo-LDH coated cobalt‑nitrogen co-doped carbon as high-performance electrode for supercapacitor

Nickel‑cobalt layered double hydroxide (NiCo-LDH) has received much attention in the field of supercapacitor electrodes due to its multiple oxidation states and good electrochemical activity. However, NiCo-LDH often suffers from structural instability and low conductivity in practical applications. In this study, sea urchin-like structural NiCo-LDH coated cobalt‑nitrogen co-doped carbon (NiCo-LDH@Co-NC-x) electrode materials were prepared by in situ growth of NiCo-LDH on the surface of cobalt‑nitrogen co-doped carbon nanosheets (Co-NC) using a one-step hydrothermal method. The results show that the NiCo-LDH@Co-NC-2 electrode material exhibits excellent electrochemical performance, its specific capacitance is up to 1909 F g−1 at a current density of 1 A g−1, and capacitance retention of 69.5 % (only 26.2 % for NiCo-LDH) can be achieved after 10,000 cycles at a current density of 10 A g−1. This is because the abundant and uniformly distributed Co nanoparticles on Co-NC provide nucleation sites for the in-situ growth of NiCo-LDH, effectively improving the interface binding between Co-NC and NiCo-LDH, enhancing the structural stability of NiCo-LDH, and ensuring highly efficient electron transport throughout the NiCo-LDH@Co-NC-2 electrode. An asymmetric supercapacitor (NiCo-LDH@Co-NC-2//AC) was further assembled with NiCo-LDH@Co-NC-2 and activated carbon (AC) as positive and negative electrodes, respectively, achieving an energy density as high as 36.8 Wh kg−1 at a power density of 750 W kg−1. These findings suggest that the NiCo-LDH@Co-NC-2 composite can be a promising candidate for high-performance supercapacitor electrode.

Oxygen vacancies are generated in the inner layer of the core-shell structure by in-situ electrochemical activation to promote electrochemical energy storage

Alkaline zinc ion batteries have attracted attention as potential energy storage devices but remain challenging due to the low utilization rate of active substances, poor conductivity, and few active sites. In order to solve these shortcomings, we grow ultrathin nickel-cobalt layered double hydroxides (NiCo LDH) by electrodeposition on Co3O4 surfaces, and generated abundant oxygen vacancies in the inner layer of the core-shell structure by electrochemical method. The special core-shell structure improves the contact between the active material and the electrolyte, bringing a positive effect on ion diffusion and charge transfer during the energy storage process. At the same time, the abundant oxygen vacancies not only effectively improve the conductivity and the number of active sites of the material, but also improve the valence state conversion ability of the cobalt element. As expected Co3O4-OV/NiCo LDH exhibits a specific capacity of 338.47 mAh g−1 at a current density of 1 A g−1 and a high average discharge potential of 1.65 V relative to Zn2+/Zn. Furthermore, the characterizations combined with density functional theory (DFT) calculations indicate that the generation of oxygen vacancies improves the conductivity and the number of active sites which results in excellent reversible electrochemical activity. This work not only provides new insight into designing advanced electrodes by introducing oxygen vacancies but also opens up avenues for the development of high-performance zinc-cobalt batteries.

Designing a Microstructure of NiCo-LDH@CNTs@Carbon Foam for Efficient Electromagnetic Wave Absorption and Excellent Environmental Tolerance.

The constantly evolving environment imposes increasingly stringent demands on the mechanical qualities of materials employed for absorbing electromagnetic waves (EMWs). Therefore, there is an urgent need for advanced materials capable of efficiently absorbing EMWs and withstanding harsh electromagnetic conditions. In this study, the electrodeposition method was effectively used to synthesize nickel-cobalt layered double hydroxides (NiCo-LDHs) in a controlled manner on a composite structure of carbon nanotubes and carbon foam, creating an exquisite construction. The manipulation of the electrodeposition time facilitated the regulation of the density of the layered structure within the composite material, thereby significantly enhancing its polarization relaxation performance. Increased defect sites and interface polarization enhance impedance matching and the attenuation constant, resulting in greatly improved absorption performance. The optimized sample demonstrated exceptional wave-absorbing performance in comparative experimental analysis, attaining a maximum reflection loss of -58.18 dB. It also has an effective absorption bandwidth of 5.36 GHz at a wavelength of 2.28 mm. The exceptional isolation effect of LDH, coupled with the outstanding insulation ability of the porous carbon skeleton, confers remarkable corrosion resistance and thermal insulation performance on the composite material. Hence, this discovery offers novel insights into designing environmentally tolerant absorbent materials.

Regulating the microstructure and catalytic activity of metal selenides via calcination strategy for lithium-sulfur battery

Metal selenides obtain a series of advantages such as high electronic conductivity, excellent catalytic activity and facile fabrication approach, which are considered as promising catalysts in lithium sulfur (Li-S) battery. Traditional research based on metal selenides focuses on designing novel/complex microstructures or composites, however, the catalytic ability can be greatly affected by internal properties such as defect or vacancy. In this work, hollow nickel-cobalt layered double hydroxide (NiCo-LDH) is first fabricated and applied as a precursor to fabricate NiCoSe, and Se vacancy accompanied with crystal phase, microstructure and catalytic activity can be regulated by simply adjusting selenization atmosphere and temperature. Involving the application of NiCoSe in Li-S battery, the optimum fabrication parameter is perform the selenization at 600 °C under argon/5 % hydrogen, and the battery can exhibit a high discharge specific capacity of 1042.8 mAh g−1, excellent cycling performance of 500 cycles with a decay rate of 0.083 % at 1 C. This work highlights the importance of calcination process and also provides reference for further modifying the microstructure and performance of metal selenides in Li-S battery.

Facile synthesis and electrochemical performance of bacterial cellulose/reduced graphene oxide/NiCo-layered double hydroxide composite film for self-standing supercapacitor electrode

This study employs a cost-efficient method to create a pliable BC/rGO-NiCo-LDH electrode film on a bacterial cellulose base. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analyses verified the incorporation of reduced graphene oxide (rGO) and nickel–cobalt layered double hydroxide (NiCo-LDH) into the bacterial cellulose structure. The BC/rGO-NiCo-LDH composite material exhibited high-temperature stability and achieved a specific capacitance of 311 F g−1 at a scan rate of 0.1 mV/s, surpassing that of earlier cellulose electrodes. The electrode film showed exceptional mechanical capabilities, displaying flexibility and load resistance without any structural damage. The film’s flexibility and lightweight properties were improved due to the low density of 0.656 g cm−3, which is a result of the nanoporous structure and intrinsic low density of rGO and cellulose. A retention ratio of 0.40 for storage modulus at a glass transition temperature of around 90°C demonstrated positive mechanical performance. This cost-effective and uncomplicated synthesis approach produced a BC/rGO-NiCo-LDH electrode with potential. The material possessed favourable mechanical and electrochemical characteristics, making it suitable for wearable electronics.

Hollow dodecahedral Zn0.3Cd0.7S@NiCo-mixed metal oxide p-n heterojunction with high-efficiency photocatalytic hydrogen production activity

The growing demand for clean and sustainable energy has driven extensive research into efficient photocatalysts for hydrogen production. However, many semiconductor photocatalysts in this field still face the challenges such as wide band gap, limited visible light absorption, and inefficient separation and transport of photoinduced charges. In this study, nickel–cobalt layered double hydroxide (NiCo-LDH) was synthesized using an “etch-and-grow” method with zeolitic imidazolate framework-67 (ZIF-67) as a sacrificial template, followed by high-temperature calcination to produce nickel–cobalt mixed metal oxide (NiCo-MMO). Zn0.3Cd0.7S quantum dots were used to modify NiCo-MMO resulting in a hollow dodecahedral Zn0.3Cd0.7S@NiCo-MMO composite photocatalyst. In hydrogen production performance test, the optimized Zn0.3Cd0.7S@NiCo-MMO exhibited excellent performance (8177.5 μmol·g−1·h−1) and demonstrated good cycling stability. The hollow dodecahedral structure of the Zn0.3Cd0.7S@NiCo-MMO enhanced the light trapping ability and provided large surface area. The p-n heterojunction formed within Zn0.3Cd0.7S@NiCo-MMO accelerated carrier separation and transfer, effectively inhibited the recombination of photogenerated electrons and holes, and significantly improved the hydrogen production activity.

Hierarchical triplet-metallic oxide/carbon nanocomposites constructed from 2D layered double hydroxides and metal-organic frameworks for high-performance microwave absorption

In the face of increasingly severe electromagnetic wave radiation and interference, it is of great significance to design and prepare excellent absorbing materials. Particularly, hierarchical structure has emerged with enhanced physicochemical properties, offering enormous potential for designing absorbing materials. Here, a hierarchical structure composite constructed by ZIF-8 and fungus-like nickel-cobalt layered double hydroxide (Ni, Co-LDH) nanosheets were synthesized by in-situ self-assembly growth process. A series of Zn@NiCo-Lc composites were obtained by calcination under air. Calcined derivatives of dielectric and magnetic metallic oxides and carbon give rise to multiple polarizations and magnetic losses. The matching of the dielectric and magnetic losses of the hybrid material is further tuned by varying the feed ratio of the bimetallic LDH nanosheets, resulting in a sample with tunable EMA performance. All samples exhibit comparable EMA performance, especially large EABmax of above 5.5 GHz, and Zn@NiCo-Lc-2 has the strongest EMA intensity performance (RLmin is −67.61 dB at an ultra-thin thickness of 1.71 mm). This study provides a tractable method for the fabrication of hierarchical structural composites of high-performance MOF/LDH-derived absorbers, further broadening the application and development of novel electromagnetic wave absorption materials.

Synergistic SERS enhancement of NiCo-LDHs microurchins and silver nanoparticles for ultra-sensitive and reusable detection of thiabendazole

Two-dimensional layered semiconductor materials as a distinctive class of materials are comprehensively explored for widespread applications due to narrow bandgap, controllable morphology, and tunable metal cation composition. Herein, we constructed a sensing platform of surface enhanced Raman spectroscopy (SERS) by combination of nickel‑cobalt layered double hydroxide (NiCo-LDH) microurchins and plasmonic silver nanoparticles (Ag NPs) for fungicide detection of thiabendazole (TBZ). The NiCo-LDHs/Ag-NPs microcomposites consist of NiCo-LDHs microurchins having a large number of nanoneedles deposited with photoreduced Ag NPs. The SERS platform with NiCo-LDHs/Ag-NPs shows an excellent SERS performance for TBZ detection, including an ultra-low detection limit of 1.49 × 10−11 M, a sublime enhancement factor of 1.71 × 109, high uniformity, good reproducibility, and long-term storage stability. The ultrahigh SERS activity of NiCo-LDH/Ag-NPs can be attributed to strong electromagnetic enhancement in the nanoscale gaps between Ag NPs, massive charge transfer through large-area NiCo-LDH/Ag-NPs interfaces, and the synergistic action of electromagnetic and charge transfer mechanisms. Besides, the unique morphology of NiCo-LDHs/Ag-NPs microcomposite provides a broad surface area for adsorption of TBZ molecules for further Raman signal enhancement. The practicability of the proposed SERS platform is confirmed by detecting TBZ in the real samples of apple juice and river water. The exceptional self-cleaning capability of the NiCo-LDHs/Ag-NPs microcomposite with an retention rate of 81.97 % even after the fifth degradation cycle underscores its impressive sustainable reusability and cost-effectiveness. The findings in this work lay the foundation for the development of high-performance SERS platforms to ensure food safety and environmental protection.

NiCo-LDH sheets and Ag3PO4 nanoparticles decorated on graphitic carbon nitride for efficient oxygen evolution reaction

Ternary heterostructure engineering enables highly efficient interfacial charge transfer, which can enhance the efficiency of electrocatalysts for the oxygen evolution reaction (OER), and has thus attracted widespread interest in electrocatalysis. NiCo-LDH/CN/AgPO was synthesized via ultrasonication and subjected to morphological analyses using X-ray diffraction, scanning electron microscopy, and (high-resolution) transmission electron microscopy. The synergistic effects in the ternary heterostructured NiCo-LDH/CN/AgPO nanocomposite comprising 2D nickel-cobalt layered double hydroxide (NiCo-LDH) and silver phosphate (Ag3PO4) nanospecies anchored on graphitic carbon nitride (g-C3N4) nanosheets will provide promising features as an electrode for the alkaline oxygen evolution reaction (OER). The NiCo-LDH/CN/AgPO heterostructure demonstrated exceptional electrocatalytic OER performance compared to AgPO/NiCo-LDH, AgPO/CN, and CN, achieving a low overpotential of 289 mV for the OER at 10 mA cm−2 in 1.0 M KOH. This superior catalytic activity is attributed to the relatively large electroactive surface area, rapid charge transfer capability, and intimate interactions between the components. The innovative design and synthesis of the NiCo-LDH/CN/AgPO heterostructure provide significant potential for constructing electrocatalysts with superior efficacy in oxygen evolution reactions.

Hydrothermal synthesis of Ni, Co hydroxide nanosheet array on vertically suspended carbon cloth for flexible high-performance supercapacitors

The investigation of Ni(OH)2 electrode materials has been a prominent issue in the field of electrochemical energy. The slow ion diffusion kinetics and inherent low electronic conductivity of Ni(OH)2 restrict its electrochemical performance and application in practice. In this work, mixed-phase nickel-cobalt layered double hydroxide (NiCoLDH) array structures are successfully grown directly on vertically suspended carbon cloth (CC). In contrast to the traditional hydrothermal method, the vertically suspended carbon cloth affordes adequate reaction sites to ensure optimum array structure growth. This unique structure realizes a large mass loading of the active material. Meanwhile, the introduction of flexible electrode substrate carbon cloth effectively enhances the mechanical properties of the electrode. Due to the powerful electrochemistry kinetics, NiCoLDH/CC-1.5 exhibites a great capacitive and excellent rate performance of 1516.5 F g−1 at 1 A g−1 and 1073.75 F g−1 even at 20 A g−1. The assembled asymmetric supercapacitor demonstrates a favorable cycling stability (capacitance retention of 90.11 % after 10,000 cycles at 5 A g−1).

Introduction of bimetallic oxide-modified carbon nanotubes for boosting the energy storage performance of NiCo-LDH based in-plane micro-supercapacitors on paper

In-plane micro-supercapacitors (IMSCs) have greater promise for use in flexible wearable electronics than traditional stacked configurations due to their ease of integration and conformability. Nickel-cobalt layered double hydroxide (NiCo-LDH) has garnered significant interest as a stellar material for supercapacitors because of its affordable price, regular morphology, and high theoretical capacity. Unfortunately, the intrinsic poor conductivity of LDH materials prevents supercapacitors from achieving long-term stable cycling and the desired energy density. This research successfully applies the self-templated approach to prepare carbon nanotubes (CNTs) with heterogeneous architectures and numerous phase interfaces, thereby mitigating this disadvantage. Carbon nanosheets adorned with WO2 and MoO2 nanoparticles assemble the CNT with a typical three-dimensional structure. When combined with LDH in a suitable ratio, the composite electrode’s conductivity significantly improves, providing increased capacity and cycling stability. Compared to commercial CNTs, the larger size of the prepared WO2/MoO2@P, N-CNTs serves a superior supporting and connecting role, thereby preventing the NiCo-LDH from aggregating. Under the best conditions, the composite electrode demonstrates a capacity of 1237 C/g at 1 A g−1 and an optimal capacity retention of more than 92%. For the IMSC devices, the composite materials as the positive electrode achieve an energy density of 0.0590 mWh cm−2, and no capacity degradation is observed after 10,000 cycles. In addition, bending tests have demonstrated the mechanical stability of the IMSCs. Therefore, this strategy of mixing highly conductive WO2/MoO2@P, N-CNTs can effectively improve the conductivity of the composite material and the mechanical properties of the overall device. Furthermore, this concept can be further extended to the preparation and application of other wearable devices.

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.