Metal-organic frameworks-derived layered double hydroxides: From controllable synthesis to various electrochemical energy storage/conversion applications

Localized assembly in biological activity: Origin of life and future of nanoarchitectonics

The concept of nanoarchitectonics has emerged as a post-nanotechnology paradigm in the field of functional materials development. This concept entails the construction of functional material systems at the nanoscale, based on the knowledge acquired from nanotechnology. In biological systems, advanced nanoarchitectonics is achieved through precise structural organization governed by spatial localization, a process facilitated by localized assembly mechanisms. A thorough understanding of the principles of localized assembly is crucial for the creation of complex, asymmetric, hierarchical organizations that are similar in structure and function to living organisms. This review explores the concept of localized assembly, highlighting its biological inspiration, providing representative examples, and discussing its contributions to nanoarchitectonics. Key examples include assemblies using biological materials, those mimicking cellular functions, and those occurring within cells. Additionally, the role of interfacial interactions and liquid-liquid phase separation in localized assembly is emphasized. Particularly, the utilization of liquid-liquid phase separation demonstrates a remarkable capacity for forming intricate compartmentalized structures without discernible membranes, paving the way for multifunctional, localized systems. These localized assemblies are fundamental to essential biological functions and provide valuable insights into the molecular mechanisms underlying the origin of cells and life. Such understanding holds significant promise for advancing materials nanoarchitectonics, particularly in biomedical applications.

Design and Modification of Layered Double Hydroxides-Based Compounds in Electrocatalytic Water Splitting: a Review

Layered double hydroxides (LDHs) exhibit great potential in electrocatalytic water splitting due to the unique 2D feature and an adjustable structure composed of different metal centers. In addition, LDHs have the advantage of being inherently inexpensive compared to other catalysts and have good stability in electrocatalytic water splitting. Up to now, numerous methods have been put forward to improve the activity of LDHs in electrocatalytic water splitting, a comprehensive introduction and comb to the fabrication methods and modification strategies is helpful for the followers to get a clear vein to carry out efficient manipulation to the development of high promising LDHs catalysts. In this review, the basic principles of water electrolysis, and the evaluation indexes are introduced first, and then the basic properties and commonly utilized methods in the fabrication of LDHs are introduced. After that, the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting (OWS) performance of different LDHs-based catalysts and analyze the merits and shortcomings of LDHs in electrocatalytic water splitting is compared. Based on this, the advanced strategies for improving the performance of LDHs is introduced and give a brief prospect for the development of LDHs-based materials in electrocatalysis.

Constructing high-throughput and highly adsorptive lithium-sulfur battery separator coatings based on three-dimensional hexagonal star-shaped MOF derivatives

The electrochemical performance of high-performance lithium-sulfur (Li-S) batteries is affected by many factors such as shuttle effect and lithium dendrites. To effectively solve this problem, a hexagonal star-shaped composite catalyst containing Co-N-C active sites (Co-NC-X) has been rationally developed under the joint action of Zn2+ and Co2+ bimetallic ions. By modifying it to the Li-S battery separator, Co-NC-X can not only act as a physical barrier to effectively prevent the diffusion of lithium polysulfide (LiPS), but also the special morphology can expose more active sites and have a strong chemisorption effect on LiPS, which effectively promotes the redox conversion of LiPS and mitigates the shuttle effect. Li-S battery with Co-NC-X exhibits excellent electrochemical performance. It has a high specific capacity and stable cycling performance, with an initial discharge capacity of 1406.9 mAh·g-1 at 0.2 C and 876.8 mAh·g-1 at 2 C, and a lower capacity decline rate of 0.093 % for 500 cycles.

V-Doping Strategy Induces the Construction of the CoFe-LDHs/NF Electrodes with Higher Conductivity to Achieve Higher Energy Density for Advanced Energy Storage Devices

Doping of metal ions shows promising potential in optimizing and modulating the electrical conductivity of layered double hydroxides (LDHs). However, there is still much room for improvement in common metal ions and conventional doping methods. In contrast to previous methodologies, a hollow triangular nanoflower structure of CoFeV-LDHs is devised, which is enriched with a greater number of oxygen vacancies. This resulted in a significant enhancement in the conductivity of the LDHs, leading to an increase in energy density following the appropriate doping of V. To investigate the impact of V-doping on the energy density of the LDHs, in situ XPS and in situ X-ray spectroscopy is employed. Regarding electrochemical performance, the CoFeV-LDHs/NF electrode with optimal doping ratio exhibited a specific capacitance of 881 F g-1 at a current density of 1 A g-1. The capacitance remained at 90.53% after 3000 cycles. In addition, the constructed battery-type supercapacitor CoFeV-LDHs/NF-2//AC exhibited an impressive energy density of 124.7 Wh kg-1 at a power density of 850 W kg-1 and capacitance remained almost unchanged at 95.2% after 3000 cycles. All the above demonstrates the great potential of V-doped LDHs and brings a new way for the subsequent research of LDHs.

The hierarchical dense structure induced high stability to NiCoB-based electrode for electrochemical energy storage

The construction of stable hierarchical surfaces through structural engineering is the key to improve reactive active sites and cycle stability to achieve high cycle performance of supercapacitors (SCs). In this work, the NiCo-LDH nanoflower as a structure guide agent was used to support NiCoB nanosheets to form a dense and stable hierarchical structure, thereby exposing more active sites and improving cycle stability. Due to the hierarchical stable surface structure, the NiCoB-0.3@NiCo-LDH-30 electrode has an excellent specific capacitance of 2710F g-1 at 1 A/g due to the excellent electrochemical active surface area (1259 mF cm-2), improving the OH- diffusion coefficient (2.4 × 10-9 cm2 s-1) and decreasing ionic diffusion barrier. After 5000 cycles, NiCoB-0.3@NiCo-LDH-30 electrode still has 92.6 % initial specific capacitance. In order to balance the energy density decrease caused by the capacitance imbalance between positive and negative electrodes, the cubed carbon (Co-C) derived from cobalt metal organic frameworks (Co-MOFs) as cathode with a good specific capacitance of 220F g-1 at 1 A/g is prepared. The assembled NiCoB-0.3@NiCo-LDH-30//Co-C hybrid SCs (HSCs), which are assembled with NiCoB-0.3@NiCo-LDH-30 electrode as anode and Co-C electrode as cathode, displays an energy density of 75 Wh kg-1 at a power density of 741 W kg-1.

Layered double hydroxide-based electrode materials derived from metal-organic frameworks: synthesis and applications in supercapacitors

Metal-organic frameworks (MOFs) have emerged as promising electrode materials for supercapacitors (SCs) due to their highly porous structures, tunable chemical compositions, and diverse morphologies. However, their applications are hindered by low conductivity and poor cycling performance. A novel approach for resolving this issue involves the growth of layered double hydroxides (LDHs) using MOFs as efficient templates or precursors for electrode material preparation. This method effectively enhances the stability, electrical conductivity, and mass transport ability of MOFs. The MOF-derived LDH exhibits a well-defined porous micro-/nano-structure, facilitating the dispersion of active sites and preventing the aggregation of LDHs. Firstly, this paper introduces synthesis strategies for converting MOFs into LDHs. Subsequently, recent research progress in MOF-derived LDHs encompassing pristine LDH powders, LDH composites, and LDH-based arrays, along with their applications in SCs, is overviewed. Finally, the challenges associated with MOF-derived LDH electrode materials and potential solutions are discussed.

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

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

Co-Doped Porous Carbon/Carbon Nanotube Heterostructures Derived from ZIF-L@ZIF-67 for Efficient Microwave Absorption

Carbon-based magnetic metal composites derived from metal-organic frameworks (MOFs) are promising materials for the preparation of broadband microwave absorbers. In this work, the leaf-like co-doped porous carbon/carbon nanotube heterostructure was obtained using ZIF-L@ZIF-67 as precursor. The number of carbon nanotubes can be controlled by varying the amount of ZIF-67, thus regulating the dielectric constant of the sample. An optimum reflection loss of -42.2 dB is attained when ZIF-67 is added at 2 mmol. An effective absorption bandwidth (EAB) of 4.8 GHz is achieved with a thickness of 2.2 mm and a filler weight of 12%. The excellent microwave absorption (MA) ability is generated from the mesopore structure, uniform heterogeneous interfaces, and high conduction loss. The work offers useful guidelines to devise and prepare such nanostructured materials for MA materials.

Honeycomb porous heterostructures of NiMo layered double hydroxide nanosheets anchored on CoNi metal-organic framework nano-blocks as electrodes for asymmetric supercapacitors

Supercapacitors (SCs) have the advantages of high power density, long cycle life, and fast charging/discharging rates, but relatively low energy density limits their practical application prospects. The key to improving the energy density of supercapacitors is to develop electrode materials with excellent performance. Metal-organic frameworks (MOFs) used for electrochemical energy storage have emerged as a research hotspot due to their adjustable microstructure, porosity, and high specific surface area. To address the demands of high-performance supercapacitors, composite nanomaterials can be prepared by rationally designing MOFs. Herein, CoNi-MOF nano-blocks are grown on the carbon cloth, and ultrathin NiMo layered double hydroxides (NiMo-LDH) nanosheets are further anchored on its surfaces to form a honeycomb porous heterostructure (NiMo-LDH@CoNi-MOF). The porous heterostructures increase the electrochemically active specific surface area and shorten the charge transfer distance, possessing ultra-high capacitance of 15.6 F/cm2 at 1 mA/cm2. Furthermore, utilizing annealed activated carbon cloth (AAC) as the negative electrode, the assembled NiMo-LDH@CoNi-MOF-2//AAC asymmetric supercapacitor possesses an energy density of 1.10 mWh/cm2 at a power density of 4 mW/cm2, and a capacitance retention of 97.8 % after 10,000 cycles. This material exhibits distinctive nanostructures and favorable electrochemical characteristics, providing a unique idea for preparing supercapacitors with high energy density and power density.