Cobalt Double Hydroxide Research Articles

Enhancing supercapacitor electrochemical performance through acetate-ion intercalation in layered nickel–cobalt double hydroxides

Enhancing the performance of layered nickel–cobalt double hydroxides (NiCo-LDH) as electrode materials for supercapacitors represents a promising strategy for optimizing energy storage systems. However, the complexity of the preparation method for electrode materials with enhanced electrochemical performance and the inherent defects of nickel–cobalt LDH remain formidable challenges. In this study, we synthesized acetate-ion-intercalated NiCo-LDH (NCLA) through a simple one-step hydrothermal method. The physical and chemical structural properties and supercapacitor characteristics of the as-prepared NCLA were systematically characterized. The results indicated that the introduction of Ac− engendered a distinctive tetragonal crystal structure in NiCo-LDH, concomitant with a reduced interlayer spacing, thus enhancing structural stability. Electrochemical measurements revealed that NCLA-8 exhibited a specific capacitance of 1032.2 F g−1 at a current density of 1 A g−1 and a high specific capacitance of 922 F g−1 at 10 A g−1, demonstrating a rate performance of 89.3%. Furthermore, NCLA-8 was used to construct the positive electrode of an asymmetric supercapacitor, while the negative electrode was composed of activated carbon. This configuration resulted in an energy density of 67.7 Wh kg−1 at a power density of 800 W kg−1. Remarkably, the asymmetric supercapacitor retained 82.8% of its initial capacitance following 3000 charge–discharge cycles at a current density of 10 A g−1. Thus, this study demonstrates the efficacy of acetate-ion intercalation in enhancing the electrochemical performance of NiCo-LDH, establishing it as a viable electrode material for supercapacitors.

Improving the composite-structured supercapacitor assembled with Ni–Co-layered double hydroxide and polymer cement electrolyte through structural optimization

The optimized nickel–cobalt double hydroxide electrode by electrodeposition has a high specific area capacitance of 10.53 F cm−2. Capacitors assembled using the optimized electrodes have a specific capacitance of up to 1.442 F cm−2.

NiCo Prussian-Blue-Derived Cobalt–Nickel-Layered Double Hydroxide with High Electrochemical Performance for Supercapacitor Electrodes

High-performance electrode materials are crucial to the improvement of the supercapacitor performance index. Ni2Co1HCF@CoNi-LDH composites with a core–shell structure were prepared by a combination of coprecipitation and constant potential electrodeposition, and the microscopic morphology and phase composition of the composites were characterized by XRD, SEM, FTIR and XPS. The results showed that the NiCo Prussian blue (Ni2Co1HCF) was grown on the nickel foam (NF) substrate by in situ etching, while the nickel–cobalt double hydroxide (CoNi-LDH) was covered on the NiCo Prussian blue surface by electrodeposition, and the composite still retained the cubic skeleton morphology of the NiCo Prussian blue. The electrochemical properties of the composites were investigated using a three-electrode system in 2 M KOH. The results showed that their discharge specific capacity was as high as 1937 F·g−1 at a current density of 1 A·g−1 and still had 81.3% capacity retention at 10 A·g−1, and they exhibited an excellent rate capability. The capacity retention rate was 87.1% after 1000 cycles at 5 A·g−1 and, thus, the composite material has good application prospects as a supercapacitor electrode material.

Fabrication of flexible, binder-free, and self-standing nickel cobalt double hydroxide/graphene films for advanced alkaline batteries

Rechargeable alkaline Ni-Zn batteries possess high promising in large-scale energy storage systems, and wearable flexible devices due to their low cost, high safety, and high energy density compared with other aqueous batteries. However, the traditional preparation method together with the use of bulky Ni mesh current collector has limited their applications. Herein, a simple dry pressing process without the using of any organic solvents is developed to prepare Binder-free, flexible, and lightweight Nickel Cobalt double hydroxide (NiCo-DH) based films, NiCo-DH/GNP@rGO, where NiCo-DH is prepared as active material, graphene nanoplatelets powder (GNP) is used as both conductive and supporting frame, and reduced graphene oxide (rGO) is coated as protective layer of the films. Areal mass of the flexible film is only about 4.2 mg cm−2, and mass loading of NiCo-DH is about 33%. In a three-electrode system, the NiCo-DH/GNP@rGO delivers a high specific capacity of 213 mAh g−1, and outstanding cycling performance (88.8% capacity retention after 1000 cycles’ running at 1 A g−1). Assembled into a full cell using Zn foil as anode, a discharge voltage of 1.6 V is realized. The flexible films prepared here exhibit a promising application prospect in portable and wearable electronic devices.

In Situ Transformation of Metal-Organic Frameworks into Hollow Nickel-Cobalt Double Hydroxide Arrays for Efficient Water Oxidation.

Developing earth-abundant electrocatalysts for efficient oxygen evolution reaction (OER) is of paramount significance for electrochemical water splitting. Herein, an efficient in situ etching-deposition growth strategy is employed to transform pristine two-dimensional (2D) Co-metal-organic frameworks into hollow Ni/Co double hydroxide arrays (denoted as Ni/Co-DH), which not only yields a larger surface area and exposes more active sites but also decreases the activation energy to the OER. With structural and compositional benefits, the Ni/Co-DH exhibits high performance with an overpotential of 229 mV at 10 mA cm-2 and exceptional long-term stability of over 90 h in 1 M KOH medium for OER, comparable to most non-noble oxygen evolution catalysts reported so far. In addition, a two-electrode Ni/Co-DH∥Pt/C electrolyzer also requires a considerably low voltage of 1.58 V at 10 mA cm-2 for overall water splitting. This study affords a rational strategy to develop water-alkali electrolyzers with great complexity for large-scale water-splitting systems.

Multicomponent architectured battery-type flexible yarns for high-performance wearable supercapatteries

Rational design of light weight, flexible and wearable yarn-type electrodes with selectively designed battery-type materials has attracted a promising research interest for the development of high-performance miniatured energy storage devices. However, the relatively lower energy storage performance caused by poor mass loading of existing fiber/yarn-based devices limits their practical applicability in a wide range. Herein, an unique plaiting approach is demonstrated to design flexible and wearable yarn-type supercapatteries (YSCs) with high electrochemical performance. With ubiquitous polyester fabric fibers (PFs) in a plaiting form, PFs are converted into highly conductive plaited PFs via dual layered metallization with superior surface roughness. Upon deposition of carbon nanotubes and nickel cobalt double hydroxides on metallized PFs, an efficient battery-type electrode is designed, which exhibits a high specific capacity of 162.8 mAh g−1 with an excellent cycling stability of 93.3% in alkaline electrolyte. The two-electrode system-based solid-state YSCs are further assembled using multicomponent architectured battery-type and capacitive-type activated carbon electrodes, which enables a high potential of 1.55 V with superior energy and power densities (30.49 Wh kg−1 and 1137.26 W kg−1), respectively. By capitalizing high energy storage, the solar charging-based YSC is practically examined to be able to energize various wearable electronics.

Flexible nickel–cobalt double hydroxides micro-nano arrays for cellular secreted hydrogen peroxide in-situ electrochemical detection

It is critical to detect cellular secreted hydrogen peroxide (H2O2) in situ for clinical diagnosis, biomedical research and cancer treatment. Herein, the electrochemical determination of H2O2 released by cancer cells grown on the surface of carbon cloth supported NiCo-DH/AuPt micro-nano arrays to elevate the capability of in situ signal collection was achieved. NiCo-DH/AuPt @CC was successfully prepared using the cobalt based metal–organic framework (Co-MOF) as a presoma after in situ etching growth onto the CC and electrodeposition of gold and platinum nanoparticles (AuPt NPs). Under the optimal conditions, owing to the excellent catalytic efficiency of NiCo-DH and AuPt NPs, the designed sensor performs a relatively wider linear range to H2O2 concentration from 10 μM to 22.08 mM, and the limit of detection is 0.145 μM. Accordingly, the as-prepared sensing system was also applied to determine H2O2 secreted by living cells which grown on the surface of NiCo-DH/AuPt @CC with satisfactory consequences. In possession of the superior sensitivity, selectivity, reproducibility, the NiCo-DH/AuPt @CC is a luciferous platform for the real time detection of H2O2 in the area of biomedical and clinical diagnosis.

Sulfur-Doped Nickel–Cobalt Double Hydroxide Electrodes for High-Performance Asymmetric Supercapacitors

In this work, an effective strategy was proposed to improve the electrochemical performance of nickel–cobalt layered double hydroxide (NiCo-LDH) by controlling the sulfur doping. The prepared NiCo-...

High-capacity charge storage electrodes based on nickel oxide and nickel–cobalt double hydroxide nanocomposites on 3D nickel foam prepared by sparking and electrodeposition

Abstract In the present work, nickel oxide (NiO) and nickel-cobalt double hydroxide (NiCo-DH) nanocomposites on Ni foams were synthesized for the first time and systemically optimized for charge storage applications. NiO nanoparticles were sparked on Ni foams followed by the electrodeposition of NiCo-DH with various times ranging from 50 to 400 s. Structural characterization results by electron microscopy, Raman spectroscopy and X-ray spectroscopy revealed that 5–10 nm sparked NiO nanoparticles acted as the nucleation seeds for the formation of smaller NiCo-DH nanostructures resulting in an increase of surface area at a moderate electrodeposition times of 100 s and induced metallic Ni and Co species on the composite layer. From electrochemical measurements, the optimal electrodeposition time of 100 s provided a moderate mass loading of 0.6 mg cm−2 and a high specific capacity of 938 C g−1 (1876 F g−1) @ 1 A g−1 with a good rate capability of 69% (647.5 C g−1) @ 20 A g−1. Additionally, a decent capacity retention of 97% was attained after 1000 cycles @ 4 A g−1. The results could be attributed to high surface capacity of NiO + NiCo-DH nanocomposite structures and high electrical conductivity with a low effective series resistance of 0.39 Ω.

A Hydrogen-Deficient Nickel-Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting.

Developing highly efficient and low-cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel-cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble-metal co-catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so-called L-NiCo nanosheets with a nonstoichiometric composition and O2- /Co3+ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O2- and Co3+ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H2 evolution rate of 1.7 μmol h-1 under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.

A Hydrogen‐Deficient Nickel–Cobalt Double Hydroxide for Photocatalytic Overall Water Splitting

AbstractDeveloping highly efficient and low‐cost photocatalysts for overall water splitting has long been a pursuit for converting solar power into clean hydrogen energy. Herein, we demonstrate that a nonstoichiometric nickel–cobalt double hydroxide can achieve overall water splitting by itself upon solar light irradiation, avoiding the consumption of noble‐metal co‐catalysts. We employed an intensive laser to ablate a NiCo alloy target immersed in alkaline solution, and produced so‐called L‐NiCo nanosheets with a nonstoichiometric composition and O2−/Co3+ ions exposed on the surface. The nonstoichiometric composition broadens the band gap, while O2− and Co3+ ions boost hydrogen and oxygen evolution, respectively. As such, the photocatalyst achieves a H2 evolution rate of 1.7 μmol h−1 under AM 1.5G sunlight irradiation and an apparent quantum yield (AQE) of 1.38 % at 380 nm.

New insight into the electrodeposition of NiCo layered double hydroxide and its capacitive evaluation

Although the peculiarities of electrodeposition in the preparation of metal hydroxides is quite attractive, adequate interpretation of this process still lacks. Here, a novel interpretation of the electrodeposition of nickel cobalt double layered hydroxides (NiCo-LDHs) is proposed. Different from the traditional strategies implemented in the pure nitrate or nitrate-assisted electrolytic baths, the sulfate solution with thiourea (TU) additive is used. Benefited from the chelating and inducing effects of TU, honeycomb-shaped NiCo-LDH nanosheets can be successfully electrodeposited on nickel foam (NF). When performed as free-standing electrodes, these integrated electrodes show a robust capacitive performance. Specifically, NC2S12-15/NF (deposition for 15 min) electrode can deliver remarkable electrochemical properties, such as large capacity (1198 F g−1 at 1 A g−1), excellent rate performance (1000 F g−1 at 100 A g−1) and good cycling stability. Additionally, the NC2S12-15/NF//activated carbon (AC) hybrid capacitor (HC) can sustain extraordinary cycle life (88.3% retention for 10,000 cycles) and high energy density (29.1 Wh kg−1), further demonstrating the qualified capacitive behavior of NC2S12-15/NF electrode. This work provides a new insight into the electrodeposition of metal LDHs based on the design of the electrolyte solution.

Sustainable Hydrogen Generation by Catalytic Hydrolysis of NaBH4 Using Tailored Nanostructured Urchin-like CuCo2O4 Spinel Catalyst

The present study describes the hydrogen production as a future energy source via hydrolysis of NaBH4 catalyzed by urchin-like CuCo2O4 spinel catalyst prepared by urea-assisted hydrothermal synthesis method. The as-synthesized copper–cobalt double hydroxide precursor and the resultant CuCo2O4 spinel were characterized by using various analytical, spectroscopic and microscopic techniques in order to understand their physiochemical and morphological aspects. The detail characterization results confirmed the successful formation of CuCo2O4 spinel phase with urchin-like morphology. The CuCo2O4 spinel catalyst was then tested for its application in hydrogen generation from NaBH4 hydrolysis by performing the reaction using 10 wt% of CuCo2O4 spinel catalyst and 0.5 g NaBH4 at room temperature. The CuCo2O4 spinel catalyst with tailored architecture displayed high catalytic activity with H2 generation rate of 1370 mL min−1 g−1 (1438 mL in 21 min). Major factors affecting the hydrolysis of NaBH4 reaction such as catalyst loading, NaOH concentration and temperature variation was also studied and discussed in detail. Correspondingly, the low activation energy of 22 kJ mol−1 was obtained from the Arrhenius plot and kinetic studies revealed that the hydrolysis of NaBH4 followed first order kinetics. Further, recyclability study of CuCo2O4 spinel catalyst was also performed which displayed good catalytic activity and stability even after five successive recycles. Characterization data of reused catalyst revealed that physiochemical properties of fresh CuCo2O4 spinel catalyst were well-preserved in the reused catalyst as well. Therefore, nanostructured CuCo2O4 spinel can be demonstrated as one of the most efficient, cost effective bimetallic spinel catalyst so far for application in the hydrogen generation.

Design and synthesis of sandwich-like CoNi2S4@C@NiCo-LDH microspheres for supercapacitors

Novel sandwich-like hollow nickel cobalt sulfides@carbon@nickel cobalt double hydroxides (CoNi2S4@C@NiCo-LDH) are synthesized using a facile microwave-assisted hydrothermal method and investigated as promising electrode materials for supercapacitors. The in-between highly conductive carbon layer simultaneously serves as uniform cover for CoNi2S4 and large-area support for ultrathin NiCo-LDH, which can restrain the microstructure change during the cyclic charge-discharge process and enhance the transmission rate of electrons and electrolyte ions. The especially nanostructured CoNi2S4@C@NiCo-LDH nanocomposites exhibit outstanding supercapacitive performances including excellent gravimetric specific capacitance (1183 mAh g−1 at 1 A g−1) and high rate capability (85.8% retention rate at 20 A g−1). More importantly, the assembled CoNi2S4@C@NiCo-LDH//graphene asymmetric supercapacitor can deliver a superhigh specific capacitance of 550 mAh g−1 at 1 A g−1, prominent energy density of 111.9 Wh kg−1 and long cycling stability with 93.8% of its initial capacitance after 10,000 cycles at 5 A g−1.

Unique 3D flower-on-sheet nanostructure of NiCo LDHs: Controllable microwave-assisted synthesis and its application for advanced supercapacitors

Two-dimensional (2D) nanostructures, though promising in energy storage, suffer from aggregation and subsequent deterioration of performance in practical applications. Hence, assembly of 2D nanostructures into three-dimensional (3D) architectures is highly desirable. Here, we report a microwave-assisted approach to the controllable synthesis of 2D materials with tunable 3D structures simply by adjusting the ratio of water/ethylene glycol (H2O/EG). Novel flower-on-sheet 3D hierarchical structures of nickel cobalt double hydroxide (NiCo LDHs) are obtained at EG content of 40%, while microspheres and 2D nanosheets are obtained when the EG content is 0% and 75%, respectively. We propose that under microwave irradiation, EG molecules disperse the nuclei and facilitate the initial formation of 2D sheets. Subsequently, the dominating hydrophobicity of the assembling results in the formation of nanoflowers on the sheets. When tested as electrode materials in supercapacitors, the flower-on-sheet NiCo LDH exhibits superior capacitance (1187.2 F g−1 at 1 A g−1), good rate capability (71% retention at 30 A g−1), and high stability (only 0.3% cyclic decay per cycle with respect to the first charge capacitance), which is ascribed to that ‘sheet’ could act as buffer substrate while ‘flower’ expose more active site. Our results demonstrate an energy-saving and one-pot approach for controllable construction of 2D derived 3D nanostructure that can be applied in next-generation energy storage materials.

Comparative Study on Morphological and Electrochemical Properties of Nickel–Cobalt Double Hydroxide, Cobalt Hydroxide, and Nickel Hydroxide

The morphological and electrochemical properties of nickel–cobalt double hydroxide (Ni-Co DH), cobalt hydroxide [Co(OH)2], and nickel hydroxide [Ni(OH)2] prepared directly on a transparent conductive oxide substrate via a simple one-pot wet-chemical method have been investigated and compared. All samples were composed of nanosheets vertically aligned on the substrate. Comparison of the results showed that Ni-Co DH with submicrometer-scale pores had more compact structure than Ni(OH)2 or Co(OH)2. Moreover, the highly symmetric cyclic voltammetry (CV) curves of Ni-Co DH indicated its good electrochemical reversibility. The specific capacitance value of Ni-Co DH was ∼ 286 F/g and ∼ 210 F/g at scan rate of 2 mV/s and 100 mV/s, respectively, indicating its better rate capability, particularly at high scan rate, than Ni(OH)2 or Co(OH)2. In addition, after CV cycling test, the Ni-Co DH nanosheets showed no noticeable morphological change. Furthermore, the electrochromic performance of Ni-Co DH was sustained over 10000 s. Thus, Ni-Co DH prepared via a facile one-step process exhibited promising characteristics as a cost-effective functional material for use in electrochemical devices.

Hierarchical Micro-Nano Sheet Arrays of Nickel-Cobalt Double Hydroxides for High-Rate Ni-Zn Batteries.

The rational design of nickel‐based cathodes with highly ordered micro‐nano hierarchical architectures by a facile process is fantastic but challenging to achieve for high‐capacity and high‐rate Ni–Zn batteries. Herein, a one‐step etching–deposition–growth process is demonstrated to prepare hierarchical micro‐nano sheet arrays for Ni–Zn batteries with outstanding performance and high rate. The fabrication process is conducted at room temperature without any need of heating and stirring, and the as‐grown nickel–cobalt double hydroxide (NiCo‐DH) supported on conductive nickel substrate is endowed with a unique 3D hierarchical architecture of micro‐nano sheet arrays, which empower the effective exposure of active materials, easy electrolyte access, fast ion diffusion, and rapid electron transfer. Benefiting from these merits in combination, the NiCo‐DH electrode delivers a high specific capacity of 303.6 mAh g−1 and outstanding rate performance (80% retention after 20‐fold current increase), which outperforms the electrodes made of single Ni(OH)2 and Co(OH)2, and other similar materials. The NiCo‐DH electrode, when employed as the cathode for a Ni–Zn battery, demonstrates a high specific capacity of 329 mAh g−1. Moreover, the NiCo‐DH//Zn battery also exhibits high electrochemical energy conversion efficiency, excellent rate capability (62% retention after 30‐fold current increase), ultrafast charge characteristics, and strong tolerance to the high‐speed conversion reaction.

Porous nanorods of nickel–cobalt double hydroxide prepared by electrochemical co-deposition for high-performance supercapacitors

Nickel-cobalt double hydroxides (Ni-Co DHs) combined with cost-effectively commercial expanded graphite (EG) was prepared via a facile in-situ electrodeposition in mixed solvents of N,N-dimethylformamide and water. By simply adjust molar ratios of Ni2+/Co2+, a Ni-Co DHs/EG electrode in which Ni-Co DHs showing a porous-nanorod microstructure was fabricated. Thanks to synergistic effects between Ni(OH)2 and Co(OH)2 as well as the unique morphology of porous nanorods, an optimal Ni-Co DHs/EG electrode with a total mass loading of 4.0 mg cm−2 can deliver a specific capacitance of 1246 F g−1 at 1 A g−1, a rate capability of 91.8% as the discharging current density increasing from 1 to 10 A g−1, and a capacitance retention of 80.1% after 1000 cycles charged/discharged at 10 A g−1. Thus we can draw a conclusion that the Ni-Co DHs/EG electrode possesses a satisfactory specific capacitance, extremely superior rate performance, and good cycle stability, therefore it can be very competitive for practical applications in supercapacitors.

Li–S Batteries: Nickel–Cobalt Double Hydroxide as a Multifunctional Mediator for Ultrahigh‐Rate and Ultralong‐Life Li–S Batteries (Adv. Energy Mater. 35/2018)

In article number 1802431, Hongbin Lu and co-authors demonstrate a multifunctional mediator based on a nickel cobalt double hydroxide (NiCo-DH) composite for Li–S batteries. The NiCo-DH plays an important role in suppressing the shuttle effect and accelerating the redox kinetics of LiPSs. The composite electrode can load high contents of sulfur (>85 wt%) and exhibit a superior capacity, ultrahigh rate performance, and ultralong life, with a decay rate of 0.015% per cycle.

Nickel–Cobalt Double Hydroxide as a Multifunctional Mediator for Ultrahigh‐Rate and Ultralong‐Life Li–S Batteries

AbstractThe performance of lithium–sulfur (Li–S) batteries is largely hindered by the shuttle effect caused by the dissolution of lithium polysulfides (LiPSs) and the sluggish reaction kinetics of LiPSs. Here, it is demonstrated that the nickel–cobalt double hydroxide (NiCo‐DH) shells that encapsulate sulfur nanoparticles can play multiple roles in suppressing the shuttle effect and accelerating the redox kinetics of LiPSs by combining with graphene and carbon nanotubes to construct the conductive networks. The NiCo‐DH shell that intimately contacts with sulfur physically confines the loss of sulfur and promotes the charge transfer and ion diffusion. More importantly, it can react with LiPSs to produce the surface‐bound intermediates, which are able to anchor the soluble LiPSs and accelerate the redox kinetics. Such composite electrodes can load high contents of sulfur (>85 wt%) and the resulting Li–S battery exhibits a superior capacity (1348.1 mAh g−1 at 0.1 C), ultrahigh rate performance (697.7 mAh g−1 at 5 C), and ultralong cycle life (1500 cycles) with a decay rate of 0.015% per cycle.