Ni-Co LDH Research Articles

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.

Construction of LDH-derived CoNiP modified W/Z-CdS homojunction for improved photocatalytic hydrogen evolution: Achieving broad solar light response and multiple phases charge transfer

Heterojunction engineering represents a robust strategy for accelerating carrier transfer, thereby enhancing the activity of photocatalytic hydrogen evolution. In this work, a series of innovative CoNiP@W/Z-CdS heterojunctions were prepared for the purpose of investigating the photocatalytic hydrogen evolution activity under visible light-driven. To achieve high efficiency, lamellar CoNiP was first synthesized through the phosphatisation of CoNi LDH precursor. Subsequently, the W/Z-CdS homojunction was in-situ grown on the CoNiP via the hydrothermal method, resulting in the formation of the CoNiP@W/Z-CdS homojunction/heterojunction. The hydrogen evolution rate of 3% CoNiP@W/Z-CdS composite reaches 60.6 mmol/g/h, which is 3.6 times, 7.0 times and 11.9 times higher than that of W/Z-CdS, W-CdS and Z-CdS, respectively. The enhanced photocatalytic performance of 3% CoNiP@W/Z-CdS can be attributed to the introduction of an ultra-thin CoNiP bimetallic phosphide as cocatalyst, which increases the specific surface area to provide a large number of active sites for the catalytic reaction, and broadens the absorption range of sunlight. In particular, the synergistic effect between homojunction and Schottky junction in 3% CoNiP@W/Z-CdS further accelerates separation and migration rate of double interfacial carriers, improving photocatalytic H2 rate. This work offers a new perspective for the rational design of three-phase binary photocatalysts with high activity and stability.

Interface engineering of NiCo LDH and 2D materials for advanced non-invasive glucose sensors

Interface engineering of NiCo LDH and 2D materials for advanced non-invasive glucose sensors

MXene introduced between CoNi LDH and NiMoO4 nanorods arrays: A bifunctional multistage composite for OER catalyst and supercapacitors

To improve the electrochemical activity and electrochemical energy storage performance of the catalyst, one of the best approaches is to adjust materials structure reasonably and design of micro-array to enhance specific surface area and expose more active sites. In this work, CoNi-LDH/MXene@NiMoO4 electrode with multistage structure was successfully designed, in which CoNi-LDH was vertically arranged on NiMoO4 nanorods coated with MXene. Oxygen evolution reaction (OER) performance was improved through the adjustment of LDH by MXene. The electrode has an excellent OER activity, which the overpotential is 222 mV at 100 mA cm−2. In addition, it can maintain high efficiency and stable operation for 120 h. The overall water-splitting (OWS) electrolytic cell was assembled with CoNi-LDH/MXene@NiMoO4 electrodes, which exhibited a low cell voltage (1.56 V) at 10 mA cm−2. Moreover, the assembled OWS electrolytic cell can operate stably under the low voltage by small-scale solar power generation and thermal power generation. Furthermore, CoNi-LDH/MXene@NiMoO4 electrode also showed good potential in electrochemical energy storage. This work opened a new avenue for MXene to regulate the activity of transition metal-based catalysts. The efficient preparation of clean energy by the interaction of MXene and transition metal groups show great prospects.

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.

Mitigating self-discharge in supercapacitors through strategic mesoporous structural modification of NiCo layered double hydroxides

Nickel - Cobalt layered double hydroxide (NiCo LDH) based supercapacitors suffer from severe self-discharge due to their uneven charge distribution, which affects the application of supercapacitors (SCs) in real life. In this paper, three-dimensional self-supported mesoporous NiCo layered double hydroxide mesoporous on nickel foam (NF) (NiCo LDHMs/NF) was prepared by H2O2 etching. The self-discharge phenomenon of supercapacitors assembled using the reaction-derived NiCo LDHMs/NF as the positive electrode and activated carbon as the negative electrode is significantly suppressed. Comparing with the original NiCo LDH devices, the successful construction of mesoporous structures in NiCo LDH resulted in slower open-circuit voltage (OCV) decay (0.93 V vs. 0.59 V in the range of open-circuit voltage of 1.8 V for the same time of 7200 S), and lower leakage current (0.09 mA vs. 0.18 mA at 1.8 V). Due to the formation of mesoporous structure, the charged ions adsorbed on the electrode have more storage sites. Which reduces the movement or loss of charged ions to inhibit the charge redistribution, so it has a high specific capacitance and the self-discharge phenomenon has been greatly reduced.

Synthesis of zinc doped nickel cobaltite nanoparticles through homogeneous precipitation method for catalytic oxidation of styrene

The present study reports homogeneous precipitation method for the preparation of Zn2+ substituted Ni-Co LDH precursors and their subsequent conversion to Ni1−xZnxCo2O4 nanoparticles (NPs) via calcination. Different analytical techniques were used for characterization of the precursors and the Ni1−xZnxCo2O4 NPs. After characterization, catalytic activity of the Ni1−xZnxCo2O4 NPs was investigated towards oxidation of styrene. The effect of reaction time and amount of catalyst on the oxidation of styrene was also investigated. The Ni1−xZnxCo2O4 NPs exhibit better performance as catalyst for the styrene oxidation compared to undoped NiCo2O4 NPs.

Introducing Ce into the interface of NiCo LDH@PBAs to build multi core–shell electrode with superior stability of supercapacitor

Core-shell electrodes have been used in many fields, however, the poor conductivity caused by the weak interfacial interaction limits the practical application of the composites. Herein, a novel multi core–shell material (NiCo-Ce@PBAs) used as electrode in supercapacitor is prepared using Ce as bridge to connect the core (NiCo LDH) and shell (NiCo PBAs). Benefiting from the gradient orbital coupling of 2p-4f-π derived from O-Ce-C≡N unit sites in NiCo-Ce@PBAs, the composite shows enhanced covalency and determines to delocalize the electronic expansion in the interaction. Besides, the redox pair of Ce3+-Ce4+ also makes great contribution to expedite the charge transfer as well as enhancing the binding energies of metals in core and shell. Overall, the optimized core–shell electrodes show excellent electrochemical performance with high area-specific capacitance of 1847 F g−1 at 1 A g−1, which is much higher than that of LDH-based electrodes ever reported. In addition, the electrode is found better cyclic performance than the others (95.7 % even after 10,000 cycles), which is due to the fact that the special 4f empty orbits can store partial electrons, thus decreasing the polarization phenomenon. It also shows great practical application when using commercial activated carbon as cathode. This work illustrates a new strategy to construct core–shell electrodes with strong interfacial interaction as well as revealing the important role of orbital theory in the design of multi core–shell electrodes.

Ni and Co Active Site Transition and Competition in Fluorine-Doped NiCo(OH)2 LDH Electrocatalysts for Oxygen Evolution Reaction.

The oxygen evolution reaction (OER) performance of NiCo LDH electrocatalysts can be improved through fluorine doping. The roles of Ni and Co active sites in such catalysts remain ambiguous and controversial. In addressing the issue, this study draws upon the molecular orbital theory and proposes the active center competitive mechanism between Ni and Co. The doped F-atoms can directly impact the valence state of metal atoms or exert an indirect influence through the dehydrogenation, thereby modulating the active center. As the F-atoms are progressively aggregate, the eg orbitals of Ni and Co transition from e2 g to e1 g, and subsequently to e0 g. The corresponding valence state elevates from +2 to +3, and then to +4, signifying an initial increase followed by a subsequent decrease in the electrocatalytic performance. Furthermore, a series of F-NiCo LDH catalysts are synthesized to verify the eg orbital occupancy analysis, and the catalytic OER overpotentials are 303, 243, 240, and 246mV at the current density of 10mA cm-2, respectively, which coincides well with the theoretical prediction. This investigation not only provides novel mechanistic insights into the transition and competition of Ni and Co in F-NiCo LDH catalysts but also establishes a foundation for the design of high-performancecatalysts.

MXene-mediated Interfacial Growth of 2D-2D Heterostructured Nanomaterials as Cathodes for Zn-based Aqueous Batteries.

In this study, we introduce a novel approach for synthesizing two-dimensional (2D) MXene heterostructures featuring a sandwiched and cross-linked network structure. This method addresses the common issue of activity degradation in 2D nanomaterials caused by inevitable aggregation. By utilizing the distinct surface characteristics of MXene, we successfully induced the growth of various 2D nanomaterials on MXene substrates. This strategy effectively mitigates self-stacking defects and augments the exposure of surface areas. In particular, the obtained 2D-2D MXene@NiCo-layered double hydroxide (MH-NiCo) heterostructures exhibit enhanced structural stability, improved chemical reversibility, and heightened charge transfer efficiency, outperforming pure NiCo LDH. The aqueous MH-Ni4Co1//Zn@carbon cloth (MH-Ni4Co1//Zn@CC) battery demonstrates exceptional performance with a remarkable specific capacity of 0.61 mAh cm-2, maintaining 96.6 % capacitance after 2300 cycles. Additionally, it achieves an energy density of 1.047 mWh cm-2 and a power density of 32.899 mW cm-2. This research not only paves the way for new design paradigms in energy-related nanomaterials but also offers invaluable insights for the application and optimization of 2D-2D heterostructures in advanced electrochemical devices.

MXene‐mediated Interfacial Growth of 2D‐2D Heterostructured Nanomaterials as Cathodes for Zn‐based Aqueous Batteries

AbstractIn this study, we introduce a novel approach for synthesizing two‐dimensional (2D) MXene heterostructures featuring a sandwiched and cross‐linked network structure. This method addresses the common issue of activity degradation in 2D nanomaterials caused by inevitable aggregation. By utilizing the distinct surface characteristics of MXene, we successfully induced the growth of various 2D nanomaterials on MXene substrates. This strategy effectively mitigates self‐stacking defects and augments the exposure of surface areas. In particular, the obtained 2D‐2D MXene@NiCo‐layered double hydroxide (MH−NiCo) heterostructures exhibit enhanced structural stability, improved chemical reversibility, and heightened charge transfer efficiency, outperforming pure NiCo LDH. The aqueous MH−Ni4Co1//Zn@carbon cloth (MH−Ni4Co1//Zn@CC) battery demonstrates exceptional performance with a remarkable specific capacity of 0.61 mAh cm−2, maintaining 96.6 % capacitance after 2300 cycles. Additionally, it achieves an energy density of 1.047 mWh cm−2 and a power density of 32.899 mW cm−2. This research not only paves the way for new design paradigms in energy‐related nanomaterials but also offers invaluable insights for the application and optimization of 2D‐2D heterostructures in advanced electrochemical devices.

Synergy of Mo doping and heterostructures in FeCo2S4@Mo-NiCo LDH/NF as durable and corrosion-resistance bifunctional electrocatalyst towards seawater electrolysis at industrial current density

Electrolysis of seawater to produce hydrogen is a replenished way to utilize sustainable hydrogen energy. However, it remains a challenge to develop electrocatalysts with high chloride corrosion resistance and meet the industrial-required low overpotential at large current density. Here, a heterostructure FeCo2S4@Mo-NiCo LDH/NF (FCS@M-NC LDH/NF) catalyst consisting of Mo-doped NiCo LDH nanosheets on FeCo2S4 nanorods grown on nickel foam is demonstrated as a large-current–density electrocatalyst for seawater electrolysis. The hierarchical structure endows FCS@M-NC LDH/NF with abundant active sites and hydrophilic and aerophobic surfaces, which promotes the adsorption of OH− and accelerates gas-release capabilities during water electrolysis. Moreover, the incorporation of high-valence Mo species and the presence of heterostructures contribute to the outstanding corrosion resistance, selectivity, and activity of FCS@M-NC LDH/NF, which only requires 314 mV (HER) and 307 mV (OER) overpotential to achieve a large current density of 1000 mA cm−2 in alkaline electrolysis of seawater. Impressively, it maintains stable operation for 140 h at a current density of 500 mA cm−2 without the production of hypochlorite. Furthermore, density functional theory calculations demonstrate that Mo doping and formation of heterostructures decrease the adsorption energy barrier for intermediate on FCS@M-NC LDH/NF, which promotes electrocatalytic activity. The robust electronic interaction between FCS and M-NC LDH/NF promotes the redistribution of charges on the interface, boosting electrical conductivity and charge transfer in the FCS@M-NC LDH/NF. This study offers a mild way to create a bifunctional electrocatalyst with exceptional corrosion resistance and stability in industrial high-alkaline natural seawater electrolysis.

Advanced hybrid supercapacitors assembled with CoNi LDH nanoflowers and nanosheets as high-performance cathode materials

In this work, CoNi layered double hydroxide with flower-like nanostructures (CoNi LDH NFs) and nanosheet-based shape (CoNi LDH NSs) were respectively prepared through a facile solvothermal approach, during which a mixed solvent of deionized water and ethylene glycol with different volume ratio was used. The NFs possessed a specific surface area of 101.28 m2 g−1 and was larger than the 38.54 m2 g−1 for NSs. The electrochemical performance of these CoNi LDHs was investigated in three-electrode & two-electrode systems, respectively, and they exhibited the battery-type electrochemical response. The CoNi LDH NFs delivered a specific capacity of 768.3C g−1 at 1 A g−1 and 643.1C g−1 at 10 A g−1, in contrast, the CoNi LDH NSs exhibited an inferior capacity of 669.3C g−1. To evaluate the practical application potential in the field of supercapacitor, the hybrid supercapacitor (HSC) device was assembled with these CoNi LDHs as cathode and activated carbon (AC) as anode. The CoNi LDH NFs//AC HSC delivered an energy density (ED) of 37.1 W h kg−1 at the power density (PD) of 748.0 W kg−1, which was higher than the 31.0 W h kg−1 for NSs-based HSC. The cycling performance and structural stability of such LDHs were investigated over 4000 cycles at a high current density of 10 A g−1, and just a little capacity decay at the end of cycling was found. The CoNi LDH NFs & NSs may serve as battery-grade electrode materials with high performance and probably have great application potential in electrochemical energy storage. Besides, the present synthetic method is simple and can be extended to the preparation of other LDHs for the assembly of advanced HSC device with superior electrochemical performance.

NH3 plasma synthesis of amino modified NiCo layered double hydroxide nanoflowers for carbon dioxide photoreduction

Photoreduction as the paramount ingredient of CO2 catalytic conversion plays an eminent role in greenhouse gas treatment. As a promising catalyst, layered double hydroxide has been widely studied because of its rich variety, low hazard and easy availability. In an effort to improve the productivity of photocatalytic CO2 reduction, the preparation of efficient photocatalysts becomes the key to solve this challenge. Thin nickel-cobalt bimetallic hydroxides (NiCo LDH) were prepared by the hydrothermal method of glycerol and methanol. Amino groups were grafting onto NiCo LDH nanosheets in an ammonia atmosphere by low-temperature plasma. The photocatalytic reduction performance of NH2-NiCo LDH was optimized by adjusting the time of plate dielectric barrier discharge plasma treatment. This work provides theoretical basics for modification of layered double hydroxide.

Room-temperature fluoride ion batteries based on LDH@PPy composites

Fluoride-ion (F−) batteries (FIBs) are a high-energy, cost-effective and safe alternative to lithium-ion batteries because of multiple-electron redox reactions, abundance of resources and absence of dendrite issues. Layered double hydroxides based on transition metals offer intriguing promise as F−-storage electrodes but suffer from poor electrical conductivity. Herein, a new cathode material of FIBs was synthesized by in situ polymerization of pyrrole monomers on the surface of F− intercalated CoNi LDH (CoNi-F−-LDH) platelets. Without destroying its 2D channel and anion storage capacity, the overall electrical conductivity of CoNi-F−-LDH is improved. The resulting polypyrrole (PPy) coated CoNi-F−-LDH exhibits a reversible capacity of ∼ 60 mAh/g over 100 cycles at room-temperature, with a capacity retention of 86 %, superior to most of previously reported cathodes for FIBs. This work illustrates a potential pathway for updating LDH electrodes for room-temperature FIB chemistries.

Recent advancements of NiCo LDH and graphene based nanohybrids for supercapacitor application

Recent advancements of NiCo LDH and graphene based nanohybrids for supercapacitor application

Three-dimensional spherical NiCoOX@NiCo layered double hydroxides nanosheets for high-performance all-solid-state supercapacitors

The low conductivity of cobalt-based oxides greatly limits its application in supercapacitors (SCs). Recently, construction of heterogeneous structural materials has emerged as an effective way to solve this problem. Herein, nickel‑cobalt oxide @ nickel‑cobalt layered double hydroxides (NiCoOX@NiCo LDH) heterostructure is synthesized by an electrodeposition-annealing-electrodeposition step, in which the inner nickel‑cobalt oxide (NiCoOX) layer is firstly deposited on the carbon cloth with a subsequent annealing process, and the outer nickel‑cobalt layered double hydroxides (NiCo LDH) layer is electrodeposited on the prepared NiCoOX layer. Benefiting from the multi-channel structure and extensive specific surface area produced by the heterogeneous structure material, as same as its synergistic effect, at 1 A g−1, NiCoOX@NiCo LDH exhibits an extremely advanced specific capacitance (2451 F g−1). It is much better than pure NiCoOX and pure NiCo LDH. Meanwhile, its specific capacitance retention rate still keeps 62.8 % even at 20 A g−1, indicating its excellent rate property. Furthermore, the assembled all-solid-state asymmetric SCs with NiCoOX@NiCo LDH//Active carbon (AC) exhibits a high energy density of 34.9 Wh kg−1 when the power density is 800 W kg−1. Meanwhile, it has a high capacitance retention of 81.79 % (10 A g−1) after 10,000 cycles, which indicates a remarkable cycle life.

A potential-driven NiO/NiCo LDH film electrode for highly efficient extraction of Br- via electrochemical coordination and anion exchange

A potential-driven nickel oxide/NiCo layered double hydroxide (NiO/NiCo LDH) composite film was deposited within the stainless steel wire mesh, showing excellent Br− extraction in an electrochemically switched ion exchange (ESIX) system. In this composite film, NiO with a high specific surface area and porous structure served as the lower layer to improve the electrical conductivity and ion storage capacity of the film, while NiCo LDH served as the main selective separation layer to selectively adsorb the target Br−. The film electrode extracted Br− up to 159.25 mg·g−1 and the separation factors of Br−/Cl−, Br−/NO3−, and Br−/I− were 2.04, 8.89, and 5.45, respectively. The film electrode showed excellent adsorption–desorption cyclability and electrochemical stability since the NiO increased the binding force and electrical conductivity between NiCo LDH and substrate, and its porous structure accommodated Br−. The highly efficient extraction of Br− in neutral solution was attributed to the electrochemical coordination and interlayer anion exchange sites of NiO/NiCo LDH. This study provided a deep understanding of the ion selective extraction mechanism of LDH-based materials by ESIX technology and the novel electrochemical reaction design of electrodes, which could be used in other fields such as supercapacitors, sensors, and batteries.

Iron doped cobalt nickel layered double hydroxide supported on nickel foam as a robust electrocatalyst for highly efficient water oxidation in alkaline sea water

The seawater electrolysis is an economically favorable approach for water splitting application because seawater is one of the plentiful abundant natural resources on our earth. In water splitting pathway, the anodic half-cell reaction from seawater stills a challenging task due to anodic corrosion and the competitive chloride oxidation process. In the current study, we prepared flower-shaped porous nanorods of iron doped cobalt nickel layered double hydroxide supported on nickel foam (Fe0.05 CoNi LDH/NF), which require very less oxygen evolution reaction (OER) overpotential in 1M KOH (212mV) and alkaline seawater (287mV) to deliver 10 mAcm−2 current density and exhibited remarkable 14h durability. At the same time, post treated sample reveals the better OER activity after chronopotentiometry analysis, because of superior conductivity and corrosion-resistance of the electrocatalyst. The doping of Fe cation in catalysis improves the OER selectivity and kinetics. Meanwhile, CoNi LDH serves as an active OER centers and NF increase the conductivity of the catalyst. Our findings suggests that Fe-doped CoNi LDH on NF provides an effective pathway towards durable and high performance OER electrocatalysts for seawater electrolysis.

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.