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•The applications of MOFs and MOF composites in electrochemistry were discussed.•The relationship between nanostructures and performances has been summarized.•Developing high ...conductivity MOFs can improve their electrochemical performance.•MOF composites can significantly improve overall performances.
Metal-organic frameworks are a class of functional porous materials. In recent years, metal-organic frameworks have become a hot research topic in the field of electrochemistry because of their controllable morphology, abundant pores, high specific surface area and versatility. Herein, we summarize the latest developments of metal-organic frameworks and metal-organic framework composites as electrode materials or catalysts for electrochemical applications such as batteries, supercapacitors, electrocatalysts and electrochemical sensors. The morphological and electrochemical properties of these promising metal-organic framework materials for their future development are discussed. Finally, based on the reported literature, we propose the future direction of metal-organic frameworks and metal-organic framework composites in the field of electrochemistry.
Abstract
Most metal–organic frameworks (MOFs) hardly maintain their physical and chemical properties after exposure to alkaline aqueous solutions, thus precluding their use as potential electrode ...materials for electrochemical energy storage devices. Here, we present the design and synthesis of a highly alkaline-stable metal oxide@MOF composite, Co3O4 nanocube@Co-MOF (Co3O4@Co-MOF), via a controllable and facile one-pot hydrothermal method under highly alkaline conditions. The obtained composite possesses exceptional alkaline stability, retaining its original structure in 3.0 M KOH for at least 15 days. Benefitting from the exceptional alkaline stability, unique structure, and larger surface area, the Co3O4@Co-MOF composite shows a specific capacitance as high as 1020 F g−1 at 0.5 A g−1 and a high cycling stability with only 3.3% decay after 5000 cycles at 5 A g−1. The as-constructed solid-state flexible device exhibits a maximum energy density of 21.6 mWh cm−3.
As a kind of supercapacitors, pseudocapacitors have attracted wide attention in recent years. The capacitance of the electrochemical capacitors based on pseudocapacitance arises mainly from redox ...reactions between electrolytes and active materials. These materials usually have several oxidation states for oxidation and reduction. Many research teams have focused on the development of an alternative material for electrochemical capacitors. Many transition metal oxides have been shown to be suitable as electrode materials of electrochemical capacitors. Among them, vanadium based materials are being developed for this purpose. Vanadium based materials are known as one of the best active materials for high power/energy density electrochemical capacitors due to its outstanding specific capacitance and long cycle life, high conductivity and good electrochemical reversibility. There are different kinds of synthetic methods such as sol-gel hydrothermal/solvothermal method, template method, electrospinning method, atomic layer deposition, and electrodeposition method that have been successfully applied to prepare vanadium based electrode materials. In our review, we give an overall summary and evaluation of the recent progress in the research of vanadium based materials for electrochemical capacitors that include synthesis methods, the electrochemical performances of the electrode materials and the devices.
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•Vanadium based materials for high performance supercapacitor were reviewed.•The advantages and disadvantages were discussed in details.•Perspectives as to the future directions of vanadium based materials were provided.
•A flexible, superhydrophobic and conductive nanofiber composite was prepared.•The nanofiber composite exhibited excellent durability and corrosion resistance.•The nanofiber composite could be used ...for wearable strain sensors.•The sensing performance could be maintained after cyclic abrasion and stretching.
Conductive polymer composite based strain sensors have promising applications in the fields of artificial skin, wearable health-care device, etc. However, fabrication of strain sensors with good stretchability, anti-corrosion, excellent durability and reliability remains challenging. In this work, a superhydrophobic strain sensor based on conductive thermoplastic polyurethane/carbon nanotubes/polydimethylsiloxane (TPU/CNTs/PDMS) was prepared by ultrasonication induced CNTs decoration onto the electrospun TPU nanofiber surface, followed by the PDMS modification. Uniformly dispersed CNTs on the nanofiber surface with a hierarchical structure construct the conductive network. The PDMS layer with a low surface energy endows the nanofiber composite with superhydrophobicity thus anti-corrosion property. The introduction of CNTs/PDMS improves both the Young's modulus, tensile strength and the elongation at break. The superhydrophobicity and conductivity can be maintained after the cyclic stretching-releasing test, displaying excellent durability. When used as a wearable strain sensor, the nanofiber composite is capable of detecting body motion and could work even under harsh conditions (moisture, acid and alkaline environment), showing promising application in wearable electronics.
Over the past two decades, metal–organic frameworks (MOFs), a type of porous material, have aroused great interest as precursors or templates for the derivation of metal oxides and composites for the ...next generation of electrochemical energy storage applications owing to their high specific surface areas, controllable structures, and adjustable pore sizes. The electrode materials, which affect the performance in practical applications, are pivotal components of batteries and supercapacitors. Metal oxide composites derived from metal–organic frameworks possessing high reversible capacity and superior rate and cycle performance are excellent electrode materials. In this Review, potential applications for MOF‐derived metal oxide composites for lithium‐ion batteries, sodium‐ion batteries, lithium–oxygen batteries, and supercapacitors are studied and summarized. Finally, the challenges and opportunities for future research on MOF‐derived metal oxide composites are proposed on the basis of academic knowledge from the reported literature as well as from experimental experience.
Synthesis strategies, tailored material properties, and different electrochemical performance are prominent features of batteries and supercapacitors. Metal–organic frameworks (MOFs) are a kind of porous materials used as precursors for the derivation of composites. MOF‐derived metal oxide composites possessing high reversible capacity, rate capability, and cycling stability are excellent electrode materials. Here, MOF‐derived metal oxide composites are comprehensively summarized and evaluated.
2D materials are ideal for constructing flexible electrochemical energy storage devices due to their great advantages of flexibility, thinness, and transparency. Here, a simple one‐step hydrothermal ...process is proposed for the synthesis of nickel–cobalt phosphate 2D nanosheets, and the structural influence on the pseudocapacitive performance of the obtained nickel–cobalt phosphate is investigated via electrochemical measurement. It is found that the ultrathin nickel–cobalt phosphate 2D nanosheets with an Ni/Co ratio of 4:5 show the best electrochemical performance for energy storage, and the maximum specific capacitance up to 1132.5 F g−1. More importantly, an aqueous and solid‐state flexible electrochemical energy storage device has been assembled. The aqueous device shows a high energy density of 32.5 Wh kg−1 at a power density of 0.6 kW kg−1, and the solid‐state device shows a high energy density of 35.8 Wh kg−1 at a power density of 0.7 kW kg−1. These excellent performances confirm that the nickel–cobalt phosphate 2D nanosheets are promising materials for applications in electrochemical energy storage devices.
Nickel–cobalt phosphate 2D ultrathin nanosheets are synthesized by a one‐step hydrothermal process. Several reaction conditions are changed to explore the impact of the materials. The structural influence on the pseudocapacitive performance of the obtained sample is investigated via electrochemical measurement. It is found that the sample with an Ni/Co ratio of 4:5 shows the best electrochemical energy storage.
•The recent progress of the use of MOFs as a platform for clean energy, including physical hydrogen and methane storage, chemical hydrogen storage, solar energy conversion, and electrochemical ...conversion and storage, has been reviewed.•The challenges and opportunities towards advanced energy technologies with the MOF-based materials for clean energy applications have been discussed.
Metal–organic frameworks (MOFs), an emerging class of porous materials, have shown intriguing and promising properties in a wide range of applications due to their versatile structures, large surface areas, tunable porosity and tailorable chemistry. In recent years one of the most active research fields is to explore energy applications of MOF-based materials. In this review, we present a critical overview on the recent progress of the use of MOF-based materials for gaseous fuel storage, chemical hydrogen storage, solar and electrochemical energy storage and conversion. The challenges and opportunities towards advanced energy technologies with the MOF-based materials are discussed.
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Ruthenium based materials and their composite nanomaterials comprehensively summarized and evaluations are given in this review.
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•Ruthenium based materials for supercapacitors have ...been aroused the great interest.•This review provides a comprehensive introduction.•Focusing on synthetic methods and their electrochemical performances.
Ruthenium based materials with rapid reversible redox process, a variety of valence options and flexible environmental adaptability have been aroused researcher’s great interest in the development of supercapacitors. This review provides a comprehensive introduction to the application of ruthenium based materials and their composites in supercapacitors, focusing on their synthetic methods, the selection of raw materials, the control of conditions such as temperature, electrolyte, and pH, as well as their electrochemical performances.
Transition‐metal (Fe, Co, Ni) based metal‐organic framework materials with controllable structures, large surface areas and adjustable pore sizes have attracted wide research interest for use in ...next‐generation electrochemical energy‐storage devices. This review introduces the synthesis of transition‐metal (Fe, Co, Ni) based metal‐organic frameworks and their derivatives with the focus on their application in supercapacitors and batteries.
Transition‐metal (Fe, Co, Ni) based metal‐organic frameworks represent one promising kind of power materials for electrochemical energy storage. Synthesis strategies, tailored material properties and different electrochemical performances are prominent features of supercapacitors and batteries. Transition‐metal (Fe, Co, Ni) based metal‐organic frameworks and their derivative nanomaterials are comprehensively summarized and evaluations are given in this review.
Abstract
Most metal-organic frameworks (MOFs) hardly maintain their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, resulting in insufficient ...stability, therefore limiting their applications. Thus, the design and synthesis of stable size/morphology-controlled MOF nanocrystals is critical but challenging. In this study, dual-ligand and hard-soft-acid-base strategies were used to fabricate a variety of 3D pillared-layer Ni(thiophene-2,5-dicarboxylate)(4,4′-bipyridine)n MOF nanocrystals (1D nanofibers, 2D nanosheets and 3D aggregates) with controllable morphology by varying the concentration of 4,4′-bipyridine and thus controlling the crystal growth direction. Owing to the shorter ion diffusion length, enhanced electron/ion transfer and strong interactions between thiophene-2,5-dicarboxylate and 4,4′-bipyridine, the 2D nanosheets showed much larger specific capacitance than 1D nanofibers and 3D aggregates. A single device with an output voltage as high as 3.0 V and exceptional cycling performance (95% of retention after 5000 cycles at 3 mA cm–2) was realized by configuring two aqueous asymmetric supercapacitive devices in series. The excellent cycling property and charge–discharge mechanism are consistent with the hard-soft-acid-base theory.
A unique method combines dual-ligand with hard-soft-acid-base strategies to achieve the morphology-controlled formation of the 3D pillared-layer MOF nanocrystals, which can effectively promote the electrochemical cyclic stability.
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