Large-Scale Self-Assembly of 3D Flower-like Hierarchical Ni/Co-LDHs Microspheres for High-Performance Flexible Asymmetric Supercapacitors

Hierarchical organic microspheres from diverse molecular building blocks

Microspherical structures find broad application in chemistry and materials science, including in separations and purifications, energy storage and conversion, organic and biocatalysis, and as artificial and bioactive scaffolds. Despite this utility, the systematic diversification of their morphology and function remains hindered by the limited range of their molecular building blocks. Drawing upon the design principles of reticular synthesis, where diverse organic molecules generate varied porous frameworks, we show herein how analogous microspherical structures can be generated under mild conditions. The assembly of simple organic molecules into microspherical structures with advanced morphologies represents a grand challenge. Beginning with a partially condensed Schiff base which self-assembles into a hierarchical organic microsphere, we systematically synthesized sixteen microspheres from diverse molecular building blocks. We subsequently explicate the mechanism of hierarchical assembly through which these hierarchical organic microspheres are produced, isolating the initial monomer, intermediate substructures, and eventual microspheres. Furthermore, the open cavities present on the surfaces of these constructs provided distinctive adsorptive properties, which we harnessed for the immobilization of enzymes and bacteriophages. Holistically, these hierarchical organic microspheres provide an approach for designing multi-functional superstructures with advanced morphologies derived from simple organic molecules, revealing an extended length scale for reticular synthesis.

One-Step Cooperative Growth of High Reaction Kinetics Composite Homogeneous Core-Shell Heterostructure

Reaction kinetics can be improved by the enhanced electrical contact between different components growing symbiotically. But so far, due to the necessity for material synthesis conditions match, the component structures of cooperative growth are similar, and the materials are of the same type. The collaborative growth of high-reaction kinetics composite homogeneous core-shell heterostructure between various materials is innovatively proposed with different structures in one step. The NiCo-LDH and PPy successfully symbiotically grow on activated carbon fiber fabric in one step. The open channel structure of the NiCo-LDH nanosheets is preserved while PPy effectively wrapped around the NiCo-LDH. The well-defined nanostructure with abundant active sites and convenient ion diffusion paths is favorable for electrolyte entry into the entire nanoarrays. In addition, owing to the enhanced electronic interaction between different components through XPS analysis, the NiCo-LDH@PPy electrode shows outstanding reaction kinetics and structural stability. The as-synthesized NiCo-LDH@PPy exhibited excellent super-capacitive storage capabilities, robust capacitive activity, and good rate survival. Furthermore, an asymmetric supercapacitor (ASC) device made of NiCo-LDH@PPy and activated carbon (AC) is able to maintain a long cycle life while achieving high power and energy densities.

Heterostructure design of one-dimensional ZnO@CoNi/C multilayered nanorods for high-efficiency microwave absorption

Dimensional design and heterogeneous interface engineering are promising approaches for the fabrication of superior absorbers with high loss performance and a wide effective bandwidth. Therein, ZnO nanorods were successfully synthesized and combined with CoNi nanosheets by hydrothermal method, and PDA was then encapsulated on the surface of the material to form a unique one dimensional (1D) core-sheath structure. The extensive defects and residual functional groups are present in the calcined material, as well as the multiple heterogeneous interfaces enhance the dielectric loss induced by polarization. Simultaneously, the 1D structure wrapped with PDA offers an efficient pathway for electron transfer, hence facilitating the enhancement of conductive loss. In addition, the CoNi-LDHs sheet layer stacked on the surface not only causes multiple scattering and reflections of electromagnetic waves, but also provides magnetic losses to optimize the impedance matching. Finally, radar cross section (RCS) simulations further reveal that the composite can dissipate electromagnetic energy in practical applications. Consequently, the 1D multilayer ZnO@CoNi/C composite exhibits an optimal reflection loss of -55 dB with a thickness of 2.3 mm and an effective absorption bandwidth (EAB) value of 6.8 GHz when the filling ratio is only 20 wt%. In summary, this paper provides a new direction for the fabrication of 1D multilayer nonhomogeneous interfacial absorbers with excellent performance.

Construction of Binder-Free, Self-Supported, Hetero-Core-Shell Honeycomb Structured CuCo2 O4 @Ni0.5 Co0.5 (OH)2 with Abundant Mesopores and High Conductivity for High-Performance Energy Storage

Clever and rational design of structural hierarchy, along with precise component adjustment, holds profound significance for the construction of high-performance supercapacitor electrode materials. In this study, a binder-free self-supported CCO@N0.5 C0.5 OH/NF cathode material is constructed with hierarchical hetero-core-shell honeycomb nanostructure by first growing CuCo2 O4 (CCO) nanopin arrays uniformly on highly conductive nickel foam (NF) substrate, and then anchoring Ni0.5 Co0.5 (OH)2 (N0.5 C0.5 OH) bimetallic hydroxide nanosheet arrays on the CCO nanopin arrays by adjusting the molar ratio of Ni(OH)2 and Co(OH)2 . The constructed CCO@N0.5 C0.5 OH/NF electrode material showcases a wealth of multivalent metal ions and mesopores, along with good electrical conductivity, excellent electrochemical reaction rates, and robust long-term performance (capacitance retention rate of 87.2%). The CCO@N0.5 C0.5 OH/NF electrode, benefiting from the hierarchical structure of the material and the exceptional synergy between multiple components, demonstrates an excellent specific capacitance (2553.6 F g-1 at 1 A g-1 ). Furthermore, the assembled asymmetric CCO@N0.5 C0.5 OH/NF//AC/NF supercapacitor demonstrates a high energy density (70.1 Wh kg-1 at 850 W kg-1 ), and maintains robust capacitance cycling stability performance (83.7%) after undergoing 10 000 successive charges and discharges. It is noteworthy that the assembled supercapacitor exhibits an operating voltage (1.7 V) that is well above the theoretical value (1.5 V).

Converting Nanoflower-like Layered Double Hydroxides into Solvent-Free Nanofluids for CO2 Capture

Due to the flexibility and versatility of the layered crystal structure of layered double hydroxides (LDHs), they have shown great potential in various fields. However, LDH nanosheets (LDH-NSs) are easy to agglomerate, leading to the problem of accumulation, which hinders their further application. Accordingly, once LDHs are combined with solvent-free nanofluids (SFNs), the advantages of LDHs and SFNs could be combined to achieve an extraordinary performance. However, the stacked structure of traditional LDHs is not conducive to the exposure of hydroxyl functional groups, and hydroxyl sites are key to the conversion of LDHs to SFNs. Therefore, in this work, nanoflower-like LDHs (NFLs) with abundant exposed hydroxyl groups were prepared and combined with organic oligomers to achieve a solid-to-liquid transition. The formation mechanism of NFLs and the grafting mechanism of OS-PEA on their surface were identified. The prepared NFL-F3 still has good fluidity and dispersion stability in different solvents after storage for 100 days. The high-saturated grafting density on the surface of NFLs increased the steric hindrance effect of the nanoparticles, thereby improving the dispersion stability and reducing the viscosity of NFL-F3. Notably, the CO2 sorption performance of NFL-F3 is significantly improved, which is attributed to the voids between polymers, physical sorption, and good fluidity caused by high-saturation grafting on the surface of NFL-F3. Finally, by combining the sorption behavior and model fitting, it was confirmed that the physical effect was dominant in CO2 sorption by the NFL-F, which saved energy for the sorption-desorption process of its industrial application. Moreover, NFL-F3 has a good CO2/N2 separation performance and cycle stability. We envision that this general strategy will open up new insights into the construction of innovative low-viscosity LDH-based SFNs with high CO2 capacity and facilitate CO2/N2 selectivity and offer new directions for LDH utilizations.

Terephthalic Acid Intercalated CoNi-LDH Materials for Improved Li-O2 Battery

CoNi-LDH (layered CoNi double hydroxides) hollow nanocages with specific morphology are obtained by Ni ion etching of ZIF-67 (Zeolitic imidazolate framework-67). The structure of the layered materials is further modified by molecular intercalation. The original interlayer anions are replaced by the ion exchange effect of terephthalic acid, which helps to increase the interlayer distance of the material. The intercalated cage-like structures not only benefit for the storage of oxygen, and the discharge product reaction, but also have more support between the material layers. The experimental results show that the excessive use of intercalation agent will affect structural stability of the intercalated CoNi-LDH. By adjusting the amount of terephthalic acid, the intercalated CoNi-LDH-2 (with 0.02 mmol terephthalic acid intercalated) is not easy to collapse after 209 cycles and shows the best electrochemical performance in Li-O2 battery.

Electrode Materials, Structural Design, and Storage Mechanisms in Hybrid Supercapacitors

Currently, energy storage systems are of great importance in daily life due to our dependence on portable electronic devices and hybrid electric vehicles. Among these energy storage systems, hybrid supercapacitor devices, constructed from a battery-type positive electrode and a capacitor-type negative electrode, have attracted widespread interest due to their potential applications. In general, they have a high energy density, a long cycling life, high safety, and environmental friendliness. This review first addresses the recent developments in state-of-the-art electrode materials, the structural design of electrodes, and the optimization of electrode performance. Then we summarize the possible classification of hybrid supercapacitor devices, and their potential applications. Finally, the fundamental theoretical aspects, charge-storage mechanism, and future developing trends are discussed. This review is intended to provide future research directions for the next generation of high-performance energy storage devices.

A visualized sensor based on layered double hydroxides with peroxidase-like activity for sensitive acetylcholinesterase assay

Acetylcholinesterase (AChE) plays a crucial role in biological neurotransmission. The aberrant expression of AChE is associated with various neurodegenerative diseases. Therefore, it is of great significance to develop a simple and highly sensitive AChE analysis platform. Herein, a simple colorimetric sensor was constructed for sensitive detection of AChE based on the peroxidase-like catalytic activity of Ni/Co layered double hydroxides (Ni/Co LDHs). In this sensor, the fabricated Ni/Co LDHs possess high peroxidase-like activity, enabling rapid catalysis of o-phenylenediamine (OPD) to produce yellow oxOPD in the presence of H₂O₂. This peroxidase-like activity of Ni/Co LDHs was found to be effectively inhibited by the presence of AChE. It is speculated that the combination of AChE on the outer surface of Ni/Co LDHs through non-covalent interaction may cover the active sites and hinder their adsorption to the substrates, leading to the failure of OPD oxidation. As a result, the yellow color from oxOPD is related to the AChE concentration, enabling the direct AChE assay in an equipment-free manner. In addition, the fabricated Ni/Co LDHs could be modified on a paper surface to obtain a paper-based analytical device for visualized colorimetric detection of AChE. The as-proposed sensor shows high sensitivity to AChE with a detection limit down to 6.6 μU mL^-1. Therefore, this naked-eye paper-based sensor is capable of on-site and real-time detection of AChE, and has outstanding application prospects in clinical diagnosis and biomedical fields.

Controllable Architecture of ZnO/FeNi Composites Derived from Trimetallic ZnFeNi Layered Double Hydroxides for High-Performance Electromagnetic Wave Absorbers

The optimization design of micro-structure and composition is an important strategy to obtain high-performance metal-based electromagnetic (EM) wave absorption materials. In this work, ZnO/FeNi composites derived from ZnFeNi layered double hydroxides are prepared by a one-step hydrothermal method and subsequent pyrolysis process, and can be employed as an effective alternative for high-performance EM wave absorber. A series of ZnO/FeNi composites with different structures are obtained by varying the molar ratios of Zn²⁺ /Fe³⁺ /Ni²⁺ , and the ZnO/FeNi composites with a Zn²⁺ /Fe³⁺ /Ni²⁺ molar ratio of 6:1:3 show a hierarchical flower-like structure. Owing to the strong synergistic loss mechanism of dielectric-magnetic components and favorable structural features, this hierarchical flower-like ZnO/FeNi sample supplies the optimal EM wave absorption performance with the highest reflection loss of -52.08 dB and the widest effective absorption bandwidth of 6.56 GHz. The EM simulation further demonstrates that impedance matching plays a determining role in EM wave absorption performance. This work provides a new way for the fabrication of a high-performance metal-based EM wave absorber.

Foldable and wearable supercapacitors for powering healthcare monitoring applications with improved performance based on hierarchically co-assembled CoO/NiCo networks

Small-scale and high-performance energy storage devices have drawn tremendous attention with their portable, lightweight, and multi-functionalized features. Here, we present a foldable supercapacitor with affordable flexibility by adopting a developed design and electrode material system as a way to extend usability. Notably, to resolve the limited energy density of conventional capacitors, we successfully synthesize the CoO/NiCo-layered double hydroxide (LDH) core-shell nanostructure on Ni framework as a cathode material. Further, glucose-based activated carbon (GBAC) is utilized for the anode. The CoO/NiCo-LDH electrodes exhibited a high specific capacitance of ∼284.8 mAh g^-1 at 1 A g^-1, and GBAC delivers a high specific capacitance of ∼166 F g^-1 at 1 A g^-1. In the following, the combinatorial integration of these materials enabled the asymmetric supercapacitor (ASC) to increase the energy density by enhancing the capacitance and the voltage window, in which a hydrogel-based electrolyte was facilitated for the foldable and wearable capability. The energy density of the ASC device was ∼24.9 Wh kg^-1 at a power density of ∼779.5 W kg^-1 with a voltage window of ∼1.6 V. As demonstrated, a self-powered energy source was demonstrated by a serially connected multi-ASC device with a help of a commercial solar cell, which was employed for powering wearable healthcare monitoring devices, including personal alarms for patients and recording the human body's electrical signals. The present work offers a viable approach to preparing potential candidates for high-performance electrodes of supercapacitors with deformable configurations to extend the powering capability of other electronic devices with physical functionalities used in wearable electronics.

Controllable formation of amorphous structure to improve the oxygen evolution reaction performance of a CoNi LDH

The morphology design of layered double hydroxides (LDHs) is an important way to determine the catalytic performance of LDH materials. A novel structure of CoNi LDH sheets with amorphous structure on the edge was prepared by electrooxidation. It was characterized by XRD, SEM, TEM and XPS. It was found that during the electrooxidation, some of the Co²⁺ ions were oxidized to Co³⁺ to form amorphous CoOOH intermediates, which promoted the OER performance. The electrochemical test results show that CoNi LDH treated by electrooxidation for 6 hours has an ultra-low overpotential of 206 mV at a current density of 10 mA cm^-2, and can work stably under alkaline conditions for more than 10 hours. This work suggests that introducing an amorphous structure on LDH through electrooxidation produces abundant active sites, which is an easy and efficient method to improve the OER performance of CoNi LDHs.

Formation of a CoMn-Layered Double Hydroxide/Graphite Supercapacitor by a Single Electrochemical Step

Hybrid electric storage systems that combine capacitive and faradaic materials need to be well designed to benefit from the advantages of batteries and supercapacitors. The ultimate capacitive material is graphite (GR), yet high capacitance is usually not achieved due to restacking of its sheets. Therefore, an appealing approach to achieve high power and energy systems is to embed a faradaic 2D material in between the graphite sheets. Here, a simple one-step approach was developed, whereby a faradaic material [layered double hydroxide (LDH)] was electrochemically formed inside electrochemically exfoliated graphite. Specifically, GR was exfoliated under negative potentials by Co^II and, in the presence of Mn^II , formed GR-CoMn-LDH, which exhibited a high areal capacitance and energy density. The high areal capacitance was attributed to the exfoliation of the graphite at very negative potentials to form a 3D foam-like structure driven by hydrogen evolution as well as the deposition of CoMn-LDH due to hydroxide ion generation inside the GR sheets. The ratio between the Co^II and Mn^II in the CoMn-LDH was optimized and analyzed, and the electrochemical performance was studied. Analysis of a cross-section of the GR-CoMn-LDH confirmed the deposition of LDH inside the GR layers. The areal capacitance of the electrode was 186 mF cm^-2 at a scan rate of 2 mV s^-1 . Finally, an asymmetric supercapacitor was assembled with GR-CoMn-LDH and exfoliated graphite as the positive and negative electrodes, respectively, yielding an energy density of 96.1 μWh cm^-3 and a power density of 5 mW cm^-3 .

Hierarchical Nanocages Assembled by NiCo-Layered Double Hydroxide Nanosheets for a High-Performance Hybrid Supercapacitor

Layered double hydroxides (LDHs) have attracted broad attention as cathode materials for hybrid supercapacitors (HSCs) because of their ultrahigh theoretical specific capacitance, high compositional flexibility, and adjustable interlayer spacing. However, as reported, specific capacitance of LDHs is still far below the theoretical value, inspiring countless efforts to these ongoing challenges. Herein, a hierarchical nanocage structure assembled by NiCo-LDH nanosheet arrays was rationally designed and fabricated via a facile solvothermal method assisted by the ZIF-67 template. The transformation from the ZIF-67 template to this hollow structure is achieved by a synergistic effect involving the Kirkendall effect and the Ostwald ripening process. The enlarged specific surface area co-occurred with broadened interlayer spacing of LDH nanosheets by finely increasing the Ni concentration, leading to synchronous improvement of electron/ion transfer kinetics. The optimized NiCo-LDH-210 electrode displays a maximum specific capacitance of 2203.6 F g^-1 at 2 A g^-1, excellent rate capability, and satisfactory cycling stability because of the highly exposed active sites and shortened ion transport paths provided by vertically aligned LDH nanosheets together with the cavity. Furthermore, the assembled HSC device achieves a superior energy density of 57.3 Wh kg^-1 with prominent cycling stability. Impressively, the design concept of complex construction derived from metal-organic frameworks (MOF) derivatives shows tremendous potential for use in energy storage systems.

The Microwave Facile Synthesis of NiOx@graphene Nanocomposites for Application in Supercapacitors: Insights into the Formation and Storage Mechanisms

Recently, the strategy of combining carbon-based materials with metal oxides to enhance the electrochemical performance of electrodes has been a topic of great interest, but research focusing on the growth and charge storage mechanisms of such hybrid electrodes has rarely been conducted. In this work, a simple, reproducible, low-cost, and fast microwave heating method was used to synthesize NiOx@graphene nanocomposites. NiOx@graphene nanocomposites were used as a model system for exploring the growth and charge storage mechanisms of the hybrid electrode materials due to their simple preparation process, good stability, low cost, and high specific capacitance. The effects of reaction conditions (the type of metal precursor and feeding ratio between the nickel precursor and graphene) on the formation mechanism of the electrodes were examined, and it was demonstrated that the microstructure and morphology of the electrode materials were metal precursor-dependent, which was directly related to the electrochemical performance of the electrodes. Our work provides a new affordable approach to the synthesis of, and experimental support for designing, hybrid electrode architectures with a high electrochemical performance for next-generation energy storage devices.

Nanoarchitectured two-dimensional layered double hydroxides-based nanocomposites for biomedical applications

Despite the exceptional physicochemical and morphological characteristics, the pristine layered double hydroxides (LDHs), or two-dimensional (2D) hydrotalcite clays, often suffer from various shortcomings in biomedicine, such as deprived thermal and chemical stabilities, acid-prone degradation, as well as lack of targeting ability, hampering their scale-up and subsequent clinical translation. Accordingly, diverse nanocomposites of LDHs have been fabricated by surface coating of organic species, impregnation of inorganic species, and generation of core-shell architectures, resulting in the complex state-of-the-art architectures. In this article, we initially emphasize various bothering limitations and the chemistry of these pristine LDHs, followed by discussions on the engineering strategies of different LDHs-based nanocomposites. Further, we give a detailed note on diverse LDH nanocomposites and their performance efficacy in various biomedical applications, such as drug delivery, bioimaging, biosensing, tissue engineering and cell patterning, deoxyribonucleic acid (DNA) extraction, as well as photoluminescence, highlighting the influence of various properties of installed supramolecular assemblies on their performance efficacy. In summary, we conclude with interesting perspectives concerning the lessons learned to date and the strategies to be followed to further advance their scale-up processing and applicability in medicine.

Sonochemical-Assisted Biogenic Synthesis of Theophrasite β-Ni(OH)2 Nanocluster Using Chia Seeds Extract: Characterization and Anticancer Activity

Theophrasite β-Ni(OH)₂ nanocluster were fabricated via the sonochemical-assisted biogenic method using chia seeds extract as a reducing and stabilizing agent. The optical and morphological feature of the synthesized nanocluster was characterized using UV-Vis, FTIR, FE-SEM-EDS, HR-TEM, DLS, XPS, and XRD analysis. According to FE-SEM and HR-TEM images of the synthesized materials, β-Ni(OH)₂ nanocluster illustrates the hexagonal particle shape with an average size of 5.8 nm, while the EDS results confirm the high purity of the synthesized nanocluster. Moreover, the XRD pattern of the synthesized materials shows typical peaks that match the reference pattern of the Theophrasite form of β-Ni(OH)₂ with a hexagonal crystal system. The XPS analysis illustrates that the prepared samples exhibit both Ni²⁺ and Ni³⁺ with the predominance of Ni²⁺ species. Additionally the in-vitro cytotoxic activity of β-Ni(OH)₂ nanocluster is tested against the MCF7 cell lines (breast cancer cells). The MTT assay results proved that the synthesized β-Ni(OH)₂ nanocluster has potent cytotoxic activity against breast cancer cell lines (IC₅₀: 62.7 μg/mL).

Carbonate doped NiCo-LDH modified with PANI for high performance asymmetric supercapacitors

The as-prepared PANI-NCLDH/CO32− composite has two forms: linear and clustered. The good combination style makes the prepared composite electrode and the assembled device have excellent electrochemical performance.

Sandwich-like NiCo-LDH/rGO with Rich Mesopores and High Charge Transfer Capability for Flexible Supercapacitors

Layered double metal hydroxides (LDHs) have been widely used in the energy storage field due to adjustable composition and interlayer spacing. However, easy to agglomerate, poor electrical conductivity, and large...

In situ growth of corrosion resistant Mg-Fe layered double hydroxide film on Q235 steel

HYPOTHESIS

In situ grown layered double hydroxide (LDH) is commonly used one of the anticorrosion ways for metal materials; Due to the dense growth of LDH on the metal surface, its special layered structure can effectively delay the corrosion rate of metal.

METHODS

In this study, we use a hydrothermal method to successfully grow Mg-Fe LDH film on steel substrates based on self-supplied Fe³⁺ ions. The films were characterized by X-ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectrometry. The potential corrosion resistance of the obtained Mg-Fe LDH film was confirmed using electrochemical impedance spectroscopy and polarization curves.

FINDINGS

After systematic adjustment and parameter optimization, it was found that Mg-Fe LDH film exhibited the best growth morphology and comprehensive performance with an initial pH value of 10, Mg²⁺/urea ratio of 1:4 and reaction time of 12 h. The SEM and electrochemical results further demonstrated that Mg-Fe LDH film play a good protection effect on carbon steel surface. This study provides an important reference for the processing of anticorrosion LDHs film.

Interlayer Spacing Regulation of NiCo-LDH Nanosheets with Ultrahigh Specific Capacity for Battery-Type Supercapacitors

The transition metal-based layered double hydroxides (LDHs) have been extensively studied as promising functional nanomaterials owing to their excellent electrochemical activity and tunable chemical composition. In this work, using acetate anions (Ac^-) as intercalating elements, the NiCo-LDH nanosheets arraying on Ni foam with different amounts of Ac^- anion intercalation or volume of hydrothermal solution were prepared by a simple hydrothermal method. The optimized amount of Ac^- anions expanded the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g^-1 at 1 A g^-1 (690 C g^-1 without Ac^- anions), an outstanding rate capability of 72.5% at 30 A g^-1, and a cycle stability of 79.90% after 4500 cycles were mainly attributed to the higher interlayer spacing of Ac^- anion intercalation. The enlarged interlayer spacing was beneficial for stabilizing the α-phase of LDHs and accelerating the electron transport and electrolyte penetration in the electrochemical reaction. This work sheds light on the mechanisms of the interlayer spacing regulation of NiCo-LDH nanosheets and offers a promising strategy to synthesize functional nanomaterials with excellent electrochemical performance via integrating their unique layered structure and interlayer anion exchange characteristics.

In situ generation of exfoliated graphene layers on recycled graphite rods for enhanced capacitive performance of Ni-Co binary hydroxide

A functionalized exfoliated graphite rod (FEGR), with a high surface area, is produced for use as a promising substrate for supercapacitors, via controlled oxidative treatment of a recycled graphite rod of exhausted zinc–carbon batteries. SEM, EDX, XPS, FT-IR, Raman, and contact angle measurements are carried out to disclose the surface characteristics of the FEGR. The surface of the FEGR is characterized by in situ generated grooves, together with graphene layers which are directly attached to the underlying graphite base. The FEGR electrodes enhance the capacitive performance of Ni(OH)₂ and binary Ni–Co(OH)₂. The Ni–Co(OH)₂/FEGR electrode displays a superb specific capacity value (2552.6 C g⁻¹) at a current density of 5 A g⁻¹ and this value is retained to 70.8% at a high current density of 50 A g⁻¹ indicating the outstanding rate performance of this electrode material. This enhanced behavior is attributed to the facile interaction of electrolyte species, even at high current density, with the active sites of the redox catalyst layer (distributed over a larger fraction of the underlying substrate with enhanced hydrophilicity). Moreover, the excellent electrical conductivity of the in situ surface generated graphene layers is another promoting factor.

A functionalized exfoliated graphite rod (FEGR), with a high surface area, is produced for use as a promising substrate for supercapacitors, via controlled oxidative treatment of a recycled graphite rod of exhausted zinc–carbon batteries.

Efficient degradation of organic dye using Ni-MOF derived NiCo-LDH as peroxymonosulfate activator

Nickel-based metal-organic framework (Ni-MOF) was employed as a sacrificial template for the preparation of nickel-cobalt layered double hydroxide (NiCo-LDH) under different hydrolysis time. The template etching rate varied at different hydrolysis time, resulting in variations of the structural and morphology of NiCo-LDHs. The NiCo-LDH/10 sample showed a large specific surface area and the well-oriented larger dimension of thinner sheets due to the sufficient in-situ etching of the Ni-MOF template. The NiCo-LDH/10 was an excellent heterogeneous catalyst to activate peroxymonosulfate (PMS) for highly efficient Reactive Red-120 dye degradation. The results exhibited that the degradation efficiency of the NiCo-LDH/10-PMS catalyst was 89% for RR-120 dye within 10 min in the presence of the PMS system, which is higher than other NiCo-LDHs. Moreover, the other influencing factors such as PMS concentration, catalyst dosage, initial pH were also investigated towards degradation. The radical quenching measurement proved that the sulfate (SO₄^•-) and hydroxyl (OH^•) had been indicated as the primary radicals. Besides, the NiCo-LDH/10-PMS catalyst showed excellent reusability even after five consecutive cycles (83.6% of the degradation efficiency). This work offer insight study on the construction of controlled morphology NiCo-LDH heterogeneous structure for high-efficiency PMS activation.

Size-controlled Ag quantum dots decorated on binder-free hierarchical NiCoP films by magnetron sputtering to boost electrochemical performance for supercapacitors

This paper reports novel binder-free and self-supported electrodes of hierarchical nickel-cobalt phosphide (NiCoP) films decorated with size-controlled Ag quantum dots by magnetron sputtering (Ag/NiCoP). Ag quantum dots with an average particle size of 7.90 nm uniformly distribute over the nanosheet-assembled architecture of NiCoP films. Benefitting from the good ohmic contact in the interfaces between Ag quantum dots and NiCoP nanosheets, Ag/NiCoP exhibits an ultrahigh specific capacitance of 6150 mF cm-2 (3050 F g-1 at 1 A g-1) higher than the 3445 mF cm-2 (1722 F g-1 at 1 A g-1) of bare NiCoP at 2 mA cm-2. The specific areal capacitance has been increased by 78.5% after introducing Ag quantum dots. 34% capacitance retention rate is achieved while the current density increases from 2 to 30 mA cm-2. The cycling stability displays a remarkable capacitance retention of 73% for 4000 cycles at 30 mA cm-2. These boosted electrochemical performances are mainly attributed to the synergistic effects of enough electroactive sites, high electronic conductivity, and easy electrolyte ion diffusion. An asymmetric supercapacitor is fabricated using hierarchical Ag/NiCoP as the positive electrode and activated carbon as the negative electrode. The supercapacitor delivers an energy density of 0.254 mW h cm-2 (1.81 mW h cm-3) at a power density of 1.88 mW cm-2 (13.4 mW cm-3). At a power density of 18.8 mW cm-2 (134 mW cm-3), an energy density of 0.115 mW h cm-2 (0.82 mW h cm-3) can still be maintained. This study provides an avenue to design a novel generation of supercapacitors for energy storage devices.

Hierarchical Micro-Nanoclusters of Bimetallic Layered Hydroxide Polyhedrons as Advanced Sulfur Reservoir for High-Performance Lithium-Sulfur Batteries

Rational construction of sulfur electrodes is essential in pursuit of practically viable lithium-sulfur (Li-S) batteries. Herein, bimetallic NiCo-layered double hydroxide (NiCo-LDH) with a unique hierarchical micro-nano architecture is developed as an advanced sulfur reservoir for Li-S batteries. Compared with the monometallic Co-layered double hydroxide (Co-LDH) counterpart, the bimetallic configuration realizes much enriched, miniaturized, and vertically aligned LDH nanosheets assembled in hollow polyhedral nanoarchitecture, which geometrically benefits the interface exposure for host-guest interactions. Beyond that, the introduction of secondary metal intensifies the chemical interactions between layered double hydroxide (LDH) and sulfur species, which implements strong sulfur immobilization and catalyzation for rapid and durable sulfur electrochemistry. Furthermore, the favorable NiCo-LDH is architecturally upgraded into closely packed micro-nano clusters with facilitated long-range electron/ion conduction and robust structural integrity. Due to these attributes, the corresponding Li-S cells realize excellent cyclability over 800 cycles with a minimum capacity fading of 0.04% per cycle and good rate capability up to 2 C. Moreover, highly reversible areal capacity of 4.3 mAh cm-2 can be achieved under a raised sulfur loading of 5.5 mg cm-2. This work provides not only an effective architectural design but also a deepened understanding on bimetallic LDH sulfur reservoir for high-performance Li-S batteries.

Phosphatized mild-prepared-NiCo LDHs cabbage-like spheres exhibit excellent performance as a supercapacitor electrode

Phosphating treatment can increase the specific capacitance by 1.88 times without destroying the cabbage-like sphere structure of NiCo LDHs.

Degradation of sulfamethoxazole by cobalt-nickel powder composite catalyst coupled with peroxymonosulfate: Performance, degradation pathways and mechanistic consideration

In this work, cobalt-nickel powder (Co-NP) synthesized through electroless plating was used as a heterogeneous bimetallic catalyst for peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in the aqueous phase. Compared with different oxidation systems and different catalysts, it was proved that Co-NP had excellent catalytic ability, fast electron transfer rate and good stability. The effects of key parameters (initial pH, SMX concentration, catalyst and PMS dosages) on SMX degradation and ion leaching were studied in detail. Furthermore, the sensitivity of inorganic anions and different pollutants towards the Co-NP/PMS system was studied to investigate its application in natural water bodies. Quenching test showed that the main reactive oxygen species generated during the reaction were OH and SO₄^-, of which SO₄^- played a predominating role. Combined with XPS analysis, the activation mechanism was concluded that free radicals were mainly generated through the valence change of Co and Ni. Based on the seven intermediates measured through ultrahigh performance liquid chromatograph-mass spectrometry (UPLC-QTOF-MS/MS), the possible degradation pathways of SMX were proposed. Notably, this study provided a new kind of supporter for advanced oxidation processes and electroless plating technology.

Encapsulation of Porphyrin-Fe/Cu Complexes into Coordination Space for Enhanced Selective Oxidative Dehydrogenation of Aromatic Hydrazides

The encapsulation of specific nanoentities into hollow nanomaterials derived from metal organic frameworks has attracted continuous and growing research attentions owing to their unique structural properties and unusual synergistic functions. Herein, using the phase transformation of uniform rhombi dodecahedron ZIF-67, hollow nano-shell with a well-defined morphology is successfully prepared. Particularly, the iron-oxygen complex, that is formed by the interaction between TCPP-Fe/Cu (TCPP = tetrakis(4-carboxyphenyl)-porphyrin) and oxygen, can be acted as an ideal proton acceptor for practical organic reactions. Considering the unique adaptability of hollow ZIFs (named HZ) to the transformation of encapsulated TCPP-Fe/Cu bimetallic catalytic active sites, a heterogeneous catalyst (defined as HZ@TCPP-Fe/Cu) through morphology-controlled thermal transformation and rear assemble processes is designed and constructed. Under heterogeneous conditions, HZ@TCPP-Fe/Cu serves as a multifunctional molecular selector to promote the oxidative dehydrogenation of different aromatic hydrazide derivatives with high selectivity toward primary carbon among primary, secondary, and tertiary carbons that are unachievable by other traditional homogeneous catalysts. The high catalytic activity, selectivity, and recyclability of the catalyst proposed here are attractive advantages for an alternative route to the environmentally benign transformation of aromatic hydrazides to aromatic azobenzene.

Flower-Like Superstructures: Structural Features, Applications and Future Perspectives

Mimicking natural objects such as flowers, is an objective of scientists not only because of their attractive appearance, but also to understand the natural phenomena that underpin real world applications such as drug delivery, enzymatic reactions, electronics, and catalysis, to name few. This article reviews the types, preparation methods, and structural features of flower-like structures along with their key applications in various fields. We discuss the various types of flower-like structures composed of inorganic, organic-inorganic hybrid, inorganic-protein, inorganic-enzyme and organic compositions. We also discuss recent development in flower-like structures prepared by self-assembly approaches. Finally, we conclude our review with the future prospects of flower-like micro-structures in key fields, being biomedicine, sensing and catalysis.