Search

Among a large variety of energy storage technologies, supercapacitors possess special advantages such as rapid charge/discharge, high power density, safety, and environmental friendliness to meet the requirement of specific applications. The common electrode materials of supercapacitors, including porous carbon, conductive polymers, and metal oxides/hydroxides, have their own benefits and drawbacks in energy density and stability. Owing to the big surface area and controllable porosity, the metal-organic frameworks (MOFs) have been explored as important candidates for supercapacitor applications. This mini-review focuses on the recent advances of MOF-based materials including pristine MOFs, MOFs composite materials, and MOF-derived materials in the development of long cycling life supercapacitors. The devices discussed here mean those with capacitive retention rates of more than 90% after 10,000 cycles and high energy density. In addition, we also describe the fundamental knowledge of supercapacitors, highlight the stabilization mechanism of MOFs, and propose the strategies to enhance the stability of MOF-based supercapacitor electrodes. • The fundamental knowledge of supercapacitor is illustrated. • The fundamental mechanisms of MOFs stabilization are emphasized. • Recent advances of MOF-based long cycling stability supercapacitors are reviewed. • The strategies to enhance the stability of MOF-based supercapacitors are proposed. [ABSTRACT FROM AUTHOR]

A metal porous carbon (Ni@NC) supported nickel/cobalt layered double hydroxide (NiCo-LDH) (Ni@NC@NiCo-LDH) with a cauliflower morphology was synthesized by a successive double template method. At first a nickel metal-organic framework (Ni-MOF) was prepared and used as a sacrifice template to produce metal porous carbon (Ni@NC). Then the prepared conductive porous carbon material was exploited as a substrate for in-situ growing of ZIF-67 on its surface. Lastly the obtained Ni@NC@ZIF-67 was further used as a sacrifice template to prepare the final electrode material Ni@NC@NiCo-LDH by Ni2+ etching and co-precipitation. The cooperation of Ni@NC with excellent conductivity and NiCo-LDH with superior pseudocapacitive property yielded a synergistic effect, which effectively improved the electrochemical performance of the resulted electrode material. And the special flower morphology exposed more redox active sites and provided proper charge transport path for enhanced electrochemical performance. The prepared Ni@NC@NiCo-LDH exhibited a high specific capacitance of 1761.8 F·g−1 at the current density of 1 A·g−1. The assembled Ni@NC@NiCo-LDH//AC asymmetric supercapacitor also displayed an acceptable energy density (39.27 Wh·kg−1 at the power density of 757.21 W·kg−1) and ultrahigh cycling stability (94.74% capacitance retention after 25000 cycles at 10 A g−1). [Display omitted] • Ni@NC@NiCo-LDH was prepared by combination of Ni@NC and NiCo-LDH for the first time. • Ni@NC@NiCo-LDH had a big specific capacitance. • The assembled supercapacitor with Ni@NC@NiCo-LDH and AC had excellent cycle stability. [ABSTRACT FROM AUTHOR]

Nickel-cobalt sulfides (NiCo 2 S 4) with abundant valence states are promising electrode materials for multiple faradaic reactions in hybrid supercapacitors. However, the slow electron transfer kinetics and lack of active sites restrict its electrochemical activity. Herein, an effective synthesis strategy was proposed to synergistically improve the electrochemical performance of NiCo 2 S 4 through one-step in-situ carbonization-vulcanization method of metal-organic frameworks (MOF). Through rational selection and optimization of the Ni:Co ratio, the fibre-assembled urchin-like 3D nanoflowers (denoted as NCSC) possess abundant sulfur vacancies and appropriate porosity. Interestingly, the S vacancies can expose more redox active sites, while the expandable 3D carbon conductive network can accelerate electron transport. Furthermore, the electrical conductivity and interfacial activity is synergistically enhanced by strong electronic coupling effects. Experimental results reveal that the NiCo 2 S 4 /C exhibit excellent electrochemical performance as a battery-type electrode material. The specific capacitance is 1934 F·g−1 (967 C·g−1) at 1 A·g−1 and the capacitance retention is 93.2% after 5000 cycles at 5 A·g−1. The assembled hybrid supercapacitor device (NiCo 2 S 4 /C//AC) exhibits an exceptionally high energy density of 50.24 Wh·kg−1 at power density of 800 W·kg−1. These results have significant implications for the optimization of the transition metal compounds for electrochemical energy-storage devices. [Display omitted] • The sulfur vacancy-rich 3D fibrous nanoflowers is synthesized successfully. • The in situ generated carbon network modulates the intrinsic electronic/surface structure. • One-step vulcanization-carbonization achieves highly dispersive S vacancies-rich NiCo 2 S 4. • Highly graphitized 3D nanostructures shows high specific capacitance of 1934 F·g−1 at 1 A·g−1. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs), as multinuclear metal oxide clusters, possess natural multi-electron redox properties and high electrical conductivity. However, their susceptibility to leaching and agglomeration limits their application in energy storage. MOF materials provide a solution to the limitation of POMs due to their controllable pore sizes, big surface areas and strong adsorption properties. The synergistic effect between the two components greatly improves the electrochemical properties of the composites. In view of this, PMo 12 is encapsulated in ZIF-67 to form PMo 12 @ZIF-67 by in situ self-assembly, and benefitted from this unique precursor, MoSe 2 /(Ni, Co)Se 2 hollow structures assembled by nanoparticles are synthesized though Ni2+ etching and selenization process. At the same time, the PMo 12 content is optimized to get the best performance of 60-MoSe 2 /(Ni, Co)Se 2. In the three-electrode test, the developed 60-MoSe 2 /(Ni, Co)Se 2 electrode material exhibits an excellent specific capacity of 359.9 mA h g−1 at a current density of 1 A g−1, and a capacitance retention rate of 83.7 % after 10,000 cycles. In addition, the asymmetric supercapacitor (ASC) assembled with a positive electrode of 60-MoSe 2 /(Ni, Co)Se 2 and a negative electrode of activated carbon exhibits an excellent energy density of 40.3 W h kg−1 at a power density of 800.9 W kg−1. These superior electrochemical properties are attributed to the unique electronic structure of PMo 12 , which further demonstrates the feasibility of constructing hollow multicomponent selenides as energy storage materials using PMo 12 -ZIF-67 as a precursor. [Display omitted] • Successful construction of hollow MoSe 2 /(Ni, Co)Se 2 nanomaterial by in situ self-assembly. • 60-MoSe 2 /(Ni,Co)Se 2 exhibits a high specific capacitance of 359.9 mA h g−1 at 1 A g−1. • The ASC device displays a high energy density of 40.3 Wh kg−1 at 800.9 W kg−1. • The assembled ASC device keeps 89.6 % of its initial capacity after 10,000 cycles. [ABSTRACT FROM AUTHOR]

The application of MOF materials in supercapacitors has been greatly restricted due to the poor conductivity and structural stability. Given that, this work improves the conductivity and stability of Ni-MOF by self-assembled strategy. We report here the Mo-doped Ni-MOF nanosheets (M-NMN), in which the Mo-based clusters are encapsulated in the holes of the Ni-MOF frame structure by self-assembly. The results show that the M-NMN-1 material with a Mi/Mo molar ratio of 1: 1 exhibits an excellent electrochemical performance. Furthermore, the nanosheet structure of the M-NMN-1 materials acts as a "superhigh way" for charge transport to accelerate charge transfer rate and enhance the conductivity of the electrode materials. As-prepared M-NMN-1 electrode material exhibits high specific capacity of 802 C g−1 at 1 A g−1. Furthermore, assembled battery-supercapacitor hybrid device exhibits an excellent energy density of 59 Wh kg−1 at a power density of 802 W kg−1, and superior cycle retention of 93% after 20,000 cycles. Image 1 • Design and fabrication of self-assembled Mo-doped Ni-MOF nanosheets (M-NMN-1). • The M-NMN-1 material exhibits the improved the conductivity and stability. • The ultrahigh specific capacity of 802 C g-1 at 1 A g-1 in three electrode system. • High energy density of 59 Wh kg-1 at power density of 802 W kg-1 in hybrid device. [ABSTRACT FROM AUTHOR]

As a kind of energy storage device, supercapacitors have attracted the attention of researchers, and the development of high-performance electrode materials is also the focus of attention. In this paper, template synthesis and pyrolysis were combined to prepare high performance porous carbon electrode materials. The carbonized electrode material effectively increased the capacitance storage capacity and charge transfer rate. The results revealed that the derivative had a relatively low charge-transfer resistance and high specific capacitance of 1059 F·g−1 at a current density of 1.0 A·g−1 in a three-electrode system. To further exploring practical application, a device based on the derivative and hemp-activated carbon asymmetric supercapacitor was assembled in 0.1 M Na 2 SO 4 neutral electrolyte, which exhibited an energy density of 20.35 Wh·kg−1 at a power density of 400 W·kg−1. Interestingly, it showed capability retention of nearly of 91.7% and columbic efficiency of 100% even after 10000 charging/discharging cycles in the neutral electrolyte. Image 1 • The aqueous NPCZ-3//HAC ASC is assembled in 0.1 M Na 2 SO 4 neutral electrolyte. • Both cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) curves of ASC display pip symmetric characteristic. • The as-assembled ASC delivers a nearly of 91.7% capability retention after 10000 cycles. • The ASC delivers has a coulomb efficiency of 100% after 10000 cycles in a neutral electrolyte. [ABSTRACT FROM AUTHOR]

We created a simple electrodeposition method of preparing Ni 3 S 2 nanosheets deposited on 3D hemp-activated carbon supported by a Ni foam. We selected three optimized deposition cycles because of high capacitances of 3D hemp-activated carbon/Ni 3 S 2 electrodes (2,797.43 F g−1 at 1 A g−1) in a 6 M KOH solution. Meanwhile, the capacitances' retention rate is 82.13%, indicating an excellent cyclic stability. To evaluate the further performance of 3D hemp-activated carbon/Ni 3 S 2 electrodes materials in a full cell, the self-assembled all-solid-state supercapacitors device 3D hemp-activated carbon//3D hemp-activated carbon-Ni 3 S 2 have the energy density of 55.32 Wh kg−1 at a current density of 1 A g−1, and a great cycle ability (it retain approximately 83.47% of the initial capacitance after 10,000 charge/discharge cycles). Image 1 • Agricultural wastes hemp bast is used to preparation porous activated carbon. • Ni 3 S 2 decorated on 3DHAC supported by binder-free Ni foam has high capacitance performance. • HAC//HAC-Ni 3 S 2 delivers an energy density of 55.32 Wh kg−1 at a power density of 1,053.71 Wkg−1. • Capacitance retention of HAC//HAC-Ni 3 S 2 electrode after 10000 charge-discharge cycles is 83.47%. [ABSTRACT FROM AUTHOR]

In this article, a trimesic acid-mediating control synthesis strategy was proposed for preparing the NiCo-MOF composition structure of microsphere and nanosheet by substituting 1,4-dicarboxybenzene with trimesic acid. Then the pre-synthesized MOF, as a precursor and template, was further vulcanized by a facile hydrothermal method to obtain hollow microsphere and nanosheet interleaved nickel and cobalt bimetallic sulfide materials (NiCo-S) while these microspheres and nanosheets were composed of smaller nanoparticles. This unique structure endowed quick electron/ion transport and electrolyte penetration as well as abundant redox active sites, significantly facilitating electrochemical performance. The obtained NiCo-S-2 showed higher specific capacitance (1790.4 F g−1) than its precursor NiCo-MOF-2 and other molar ratios of counterparts. Using it as an positive electrode and activated carbon (AC) as negative electrode, the assembled asymmetric supercapacitor NiCo-S-2//AC also delivered a high specific capacitance of 114.4 F g−1 and big specific energy of 35.5 Wh kg−1 at 799.99 W kg−1. • A ligand mediated control synthesis strategy was used for NiCo-MOF preparation. • Hollow microsphere and nanosheet interleaved structural NiCo-S had high specific capacitance (1790.4 F g−1). • NiCo-S-2//AC ASC delivered a high energy density of 35.5 Wh kg−1 at at 799.99 W kg−1. [ABSTRACT FROM AUTHOR]

Bimetallic metal-organic frameworks (MOFs) with a controlled morphology are potential materials for boosting the electrochemical performance of supercapacitors owing to their unique structural merits. Herein, a solvent-regulated strategy was proposed to synthesize bimetallic MOFs with various morphologies, such as microflowers, microspheres, and nanosheets, and the possible mechanisms of morphology control during nucleation and crystal growth were analyzed. When employed as electrode materials for supercapacitors, the NiCo-MOF microflowers possessed the biggest specific capacitance, which could achieve 1086 F g−1 at a current density of 1 A g−1. To further improve the electrochemical performance of materials, NiCo-P was prepared via a low-temperature phosphating method using NiCo-MOF microflowers as the precursor. Electrochemical studies displayed that the NiCo-P(6) microflowers exhibited good capacitance and superior rate capability with specific capacitances of 1592 and 1384 F g−1 at 1 and 20 A g−1, respectively. Furthermore, an asymmetric supercapacitor assembled by NiCo-P(6) and active carbon exhibited a high energy density of 51.2 Wh kg−1 at a power density of 749.8 W kg−1 and outstanding cycling stability. This work is easy to operate and can be extended to the preparation of other MOF-based electrode materials. The delivered excellent electrochemical performance suggests the resulted flower-like NiCo-P is a promising electrode material for advanced energy storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering the high electrical conductivity of carbon dots (CDs) and good oxidation-reduction property of polyoxometalates (POMs), a novel CDs coated POMs /metal organic frameworks (POMOFs) composition structure, CDs@PMo 12 /Ni-MOF, was prepared by hydrothermal reaction in this work. PMo 12 was encapsulated in the Ni-MOF framework to form the POMOF composite material, which realized the fixation of water-soluble [PMo 12 O 40 ]3- (PMo 12). A comparison study on the cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) of the resulting CDs@PMo 12 /Ni-MOF with different compositions revealed that 6CDs@PMo 12 /Ni-MOF was better formulation in terms of specific capacity (748.8 C·g−1 at 1 A·g−1) and rate performance (75.93 % at 10 A·g−1). Furthermore, a hybrid supercapacitor device was assembled using 6CDs@PMo 12 /Ni-MOF as positive electrode and activated carbon (AC) as negative electrode, which showed an high energy density of 39.22 Wh·kg−1 under 749.9 W·kg−1 and excellent cyclic stability (98.4 % for 20000 cycles at 5 A·g−1). [Display omitted] • Fixation of water-soluble PMo 12 was realized to form POMOF composite material. • CDs@PMo 12 /Ni-MOF has excellent rate performance and cycle stability. • 6CDs@PMo 12 /Ni-MOF exhibits high specific capacitance and energy density. [ABSTRACT FROM AUTHOR]

As a typical pseudocapacitance material, NiS is considered a promising electrode material due to its high theoretical specific capacitance and abundant reserves. However, the electrical conductivity is poor, resulting in a decrease in cycle stability and rate performance. Here, we introduce cobalt-containing porous nanocarbon (Co-NC) derived from zeolite-imidazolate frameworks (ZIFs) as a supporting base to design a hybrid structure. As an electrode material, NiS@Co-NC nanocomposite has a composite effect of double-layer capacitive porous carbon and pseudo-capacitance NiS nanoparticles and excellent electrochemical performance. Specifically, the specific capacitance of NiS@Co-NC nanocomposite is as high as 1116.6 F·g−1 when the current density is 1 A·g−1, and capacity retention is 90.177% at a very high current density of 10 A·g−1 after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers an energy density of 21.6 Wh·kg−1 at 799.9 W·kg−1 with coulombic efficiency of 90.177%, and 14.22 Wh·kg−1 at a high power density of 7999.9 W·kg−1, along with excellent cyclic stability of 89.85% at 5 A·g−1 after 5000 cycles. All results indicate that NiS@Co-NC nanocomposites have the potential to be applied as electrodes in hybrid supercapacitors and other energy storage devices. ZIF-67 @ZIF-8 was synthesized through hydrothermal reaction and carbonized as a sacrificial template to generate cobalt-containing nano-carbon and carbon nanotubes. [Display omitted] • CNTs interconnected NiS@Co-containing porous carbon nanocomposite was synthesized. • The composite showed a strong synergistic effect of NiS, CNTs and metallic cobalt modified porous carbon. • NiS@Co-NC nanocomposite has a high specific capacitance of 1116.6 F.g-1 1 A.g-1. [ABSTRACT FROM AUTHOR]

Due to the insufficient performance, it is still a challenge to combine conventionally synthesized metal-organic framework (MOF-74) with other materials to fabricate composite electrodes for high-performance supercapacitors. Herein, we synthesized a series of NiCo-MOF-74 composite materials with different amounts of polypyrrole nanotubes (T-PPy) denoted as NiCo-MOF-74/T-PPy-m (m = 2.5, 5, 10, 15 and 20) through in situ growth of the bimetallic MOF around the PPy nanotubes by a simple solvothermal method. By comparison, the NiCo-MOF-74(1)/T-PPy-10 composite, with a Ni/Co molar ratio of 1:1 obtained in the presence of 10 mg of T-PPy, possessed the highest specific capacitance of 849 C·g−1 at 1 A·g−1 and excellent cyclic stability with a capacitance retention rate of 90.0% after 10,000 cycles as well as good rate performance. Moreover, the assembled asymmetric supercapacitor respectively using NiCo-MOF-74(1)/T-PPy-10 and active carbon as positive electrode and negative electrode achieved a superior energy density of 58.4 Wh kg−1 at the power density of 747.6 W kg−1 and high cyclic lifespan (91.4% capacitance retention after 10,000 cycles). The mechanism of capacitance increase was studied in detail, influences of metal molar ratios, morphology and addition amounts of PPy on electrochemical performances of the formed composition materials were systematically discussed, and it was found that the interpenetrating network structure assembled by "string of candied haws"-like T-PPy-interweaved NiCo-MOF-74(1) polyhedrons possessed the best capacitive performance for enhanced conductivity of the resulted composite, improved dispersity of the bimetallic MOF and more exposed active sites. And the interwoven structure alleviated the stress change-induced structure or phase variation caused by repeated volumetric swelling and shrinking during charge/discharge cycle and enhanced the rate capability and cycling stability. Interpenetrating network structure assembled by "string of candied haws"-like T-PPY-interweaved NiCo-MOF-74(1) polyhedrons [Display omitted] • Interpenetrating networks assembled by PPY nanotube-interweaved NiCo-MOF-74 were constructed. • The structure delivered good conductivity, high specific capactitance and long cyclic lifespan as supercapacitor electrode. • NiCo-MOF-74 in situ grown around the PPY tubes was directly used as electrode without carbonization and heteroatom doping. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotube (MWCNT)/Ni-Mn-S composites are derived from MWCNT/Ni/Mn bimetallic metal-organic framework (MOF) for supercapacitor electrodes. Electroconductive MWCNT is introduced into Ni-Mn-S to form a three-dimensional interconnected structure due to the covalent interaction between Ni atoms and C atoms. During energy storage, MWCNT serves as miniature current collector to shorten pathway of electron collection and transmission. In addition, S2- etching agent with Kirkendall effect makes edges and surfaces of the resulted sulfide structures rougher provide more active sites and improves electrochemical performance compared with precursors. By finely adjusting Ni/Mn molar ratio, the prepared MWCNT/Ni-Mn-S composite achieves excellent properties. As-prepared MWCNT/Ni-Mn-S(3:2) exhibits high specific capacitance of 1041 mAh g−1 at 1 A g−1 and good cyclic stability. The capacitance retention reaches 83.3% after 10,000 cycles. The assembled MWCNT/Ni-Mn-S(3:2)//AC hybrid supercapacitor (HSC) also shows high energy density of 25.33 Wh Kg−1 at power density of 829 W Kg−1 and outstanding cycling stability (93.3% after 20,000 cycles), which illustrates MWCNT/Ni-Mn-S(3:2) has important potential in supercapacitor. [Display omitted] • MWCNT/Ni-Mn-S(3:2) is derived from corresponding MWCNT/MOF-Ni/Mn for supercapacitors. • MWCNT/Ni-Mn-S(3:2) electrode shows high specific capacitance of 1041 mAh g−1. • Assembled MWCNT/Ni-Mn-S(3:2)//AC HSC delivers high specific capacitance and excellent cyclic stability. [ABSTRACT FROM AUTHOR]

The caCTF-1 derived from CTF-1 by carbonization is introduced into the multi-step heat treatment carbon repaired pC-C 3 N 4 to form a 3D interconnected nitrogen-rich carbon structure (caC@pC). Through carbon repairing process, the obtained pC-C 3 N 4 has an extended π-conjugate plane and it is closely interconnected with the nitrogen-rich caCTF-1, thereby accelerating charge transfer, improving energy storage, and exhibiting high specific capacitance (535.8 F·g−1 under 1 A·g−1) and good rate performance. In addition, by employing MOF with diphenyl semicarbazide structural unit as a precursor, NiCoTe 2 is prepared by a simple hydrothermal process, which exhibits high redox activity with a high specific capacitance of 2006.0 F·g−1 at 1 A·g−1 and good cycle stability. The hybrid supercapacitor NiCoTe 2 //caC@pC HSC is assembled with caC@pC as the negative electrode and NiCoTe 2 as the positive electrode. When the power density is 790.05 W·kg−1, it exhibits a high energy density of 50.84 Wh·kg−1 and high cycle stability. After 25,000 cycles, the capacitance retention rate is 87.88%. • A three-dimensional cross-linked nitrogen-rich carbon material caCTF-1 @pC-C 3 N 4 was constructed. The 3D cross-linked structure facilitates the rapid penetration of electrolyte ions. The introduction of nitrogen source into the carbon material can enhance the surface charge mobility of carbon. The material exhibits high specific capacitance (535.8 F·g−1 under 1 A·g−1) and good rate performance (the specific capacitance still remains 85.67% at 10 A·g−1) in the three-electrode test. • caCTF-1 is derived from CTF-1. This material has a high nitrogen content and was first used in supercapacitors, showing better application potential. • The carbon self-repairing pC-C 3 N 4 can be combined with ethanol to introduce carbon units into g-C 3 N 4 through the hydrothermal method, which improves the slow charge transfer due to the limitation of bridge nitrogen atoms. Multi-step heat treatment also makes it have more pores. Thereby improving electrochemical performance. • NiCoTe 2 with broccoli structure provides fast Faraday reaction active sites, ensures high utilization of electrode materials, and enables electrode active materials to exhibit ultra-high specific capacitance (2006 F/g at 1 A/g), rate performance and good cycle stability (when assembled into a supercapacitor, the capacitance retention rate after 20,000 cycles is 96.15%). • The assembled asymmetric supercapacitor NiCoTe 2 //caC@pC has a large potential window (0–1.6 V) and high energy density (when the power density is 790.05 W/kg, the energy density is 50.84 Wh/ kg), and good cycle stability. [ABSTRACT FROM AUTHOR]

• Ni-MOF on MXene is vulcanized to sandwiched p-MXene/Ni 3 S 4 /CuS in the presence of copper. • p-MXene/Ni 3 S 4 /CuS show the remarkable specific capacitance. • The p-MXene/Ni 3 S 4 /CuS//AC has a high energy density and ultrahigh cyclic stability. [Display omitted] Metal-organic frameworks (MOFs) have ordered porous structure and intriguing properties for supercapacitors, however, poor conductivity and cycle stability limits their application. To solve these problems, hence, a simple strategy is proposed, by which MOFs are in-situ grown in the porous conductive p-MXene substrate. And then, along with the introduction of CuS, the grown Ni-MOF is derived to Ni 3 S 4 , which is more stable and more electrochemically active. Due to higher contact area, excellent synergistic effect and more exposed active sites, the prepared sandwiched p-MXene@Ni 3 S 4 /CuS nanostructure displays a big specific capacitance (1917 F·g−1) and superior cycling performance (91.2%@30000). What's more, the assembled p-MXene@Ni 3 S 4 /CuS//AC asymmetric device delivers a high energy density of 87.62 Wh·Kg−1 at the power density of 775.02 W·Kg−1, suggesting that this material provides a brilliant candidate for energy storage. [ABSTRACT FROM AUTHOR]

• Design and fabrication of self-assembled Ni-doped ZIF-67 (NiCo-ZIF-67). • Sandwich MXene/NiCoZDHis used for supercapacitor for the first time. • The specific capacitance of MXene/NiCoZDH is greater than that of MXene and ZIF-67. • Excellent cyclic stability of MXene/NiCoZDH (90.9%@30,000). Zeolite-imidazole frameworks (ZIFs) are the promising materials for supercapacitors (SC), however, the shortcomings of easy agglomeration, low conductivity and low stability limit the further improvement of their electrochemical properties. Hence, in order to produce high-performance SC, ZIFs are usually grown directly on some conductive substrates or post-treated. In this paper, MXene was explored as the substrate and Ni-doped ZIF-67 (denoted as NiCo-ZIF-67) was in situ anchored on negatively charged MXene surface via chemical bonds to supply more available active sites for the enhancement of capacitance. At the same time, the surface functional groups in MXene can also enhance the chemical connection between NiCo-ZIF-67 and MXene to attain higher ion diffusion and charge transfer rates. The size of the NiCoZDH (ZIFs-derived double hydroxide denoted as ZDH) obtained by the alkali treatment of NiCo-ZIF-67 is smaller, which is good for increasing specific surface area. The prepared composite MXene/NiCoZDH electrode shows a larger specific capacitance (877 F g-1) than MXene/NiCo-ZIF-67 (460 F·g-1), NiCoZDH (354 F g-1), NiCo-ZIF-67 (130 F g-1) and MXene (15 F g-1), and superior cycling stability with a capacitance retention of 90.9% after 30000 cycles. Additionally, the assembled asymmetric supercapacitor delivers an energy density of 34 Wh kg-1 at the power density of 748 W kg-1 and maintains 93.3% of the initial capacitance after 30,000 cycles. [ABSTRACT FROM AUTHOR]

In this paper, novel hybrid nanomaterials constituting carbonized biomass materials derived from walnut shells and metal-organic framework (MOF) have been researched as a new class of renewable supercapacitor materials for electrochemical energy storage. One synthetic route is employed to grow Ni-MOF in the peripheries and channels of walnut shells derived carbon (WS), which had been carbonized previously by heat treatment in air at 850 °C to produce a highly porous network, and vulcanized polyaniline (SPANI) is used as a dummy plate preventing the agglomeration of MOFs and a wire connecting WS and MOFs, which easily improves the electron transfer and enhances the conductivity of the electrode material. The specific capacitance of the obtained WS@Ni-MOF composite is up to 4 times that of the biochar at the current density of 1 A g-1. The connection of SPANI also obviously accelerates the transfer of electrolyte ions. The resulting specific capacitance could reach 14 times of the biochar and exhibit high cycle stability (retention rate of 90.4% after 20000 cycles). In addition, the assembled asymmetrical supercapacitor (ASC) shows a high energy density of 34.79 Wh kg-1 at the power density of 824 W kg-1. This work provides a brilliant renewable candidate for the excellent energy storage device and a promising route design strategy for preparation of high performance and long life electrode materials. [Display omitted] • Design and fabrication of self-assembled Walnut shell-derived carbon and MOF composites. • WS@Ni-MOF/SPANI, as a new electrode material with sandwich structure, applied for supercapacitors for the first time. • The specific capacitance of WS@Ni-MOF/SPANI is greater than that of WS, Ni-MOF and SPANI. • Excellent cyclic stability of WS@Ni-MOF/SPANI (90.4%@20000). [ABSTRACT FROM AUTHOR]

[Display omitted] • CNT/MOF-74 materials are prepared and their electrochemical properties compared. • CNT/Ni-MOF-74 derived 0.2CNT/NiSe x has excellent electrochemical performance. • 0.2CNT/NiSe x is used for not only supercapacitors but also electrochemical sensors. • CNTs improve specific capacitance and conductivity of the composite simultaneously. Selenides derived from MOFs have attracted attention as the materials with excellent electrochemical properties. CNT/MOF-74 composites are successfully synthesized by a simple hydrothermal method. Then CNT/Ni-MOF-74 materials are selected as the precursors for further selenization to prepare CNT/NiSe x. The results show that 0.2CNT/NiSe x derived from CNT/Ni-MOF-74 prepared in the presence of 0.2 g CNTs has the best electrochemical performance as electrochemical capacitor electrode, which exhibits the highest specific capacitance of 2136 F·g−1 at a current density of 1 A·g−1. In addition, a hybrid electrochemical capacitor (HEC) is assembled with 0.2CNT/NiSe x and activated carbon (AC). The obtained 0.2CNT/NiSe x //AC HEC shows a high energy density of 59 Wh·kg−1 at a power density of 800 W·kg−1. In order to expand the application of the composition material, a 0.2CNT/NiSe x /GCE electrochemical sensor is prepared. The results show that 0.2CNT/NiSe x /GCE electrochemical sensor can be used for simultaneous determination of acetaminophen (AMP) and dopamine (DA). [ABSTRACT FROM AUTHOR]

• A simple ultrasound-assisted method was used to synthesize nitrogen-containing p - π conjugated-organic ligands. • Nitrogen-containing conjugated organic ligands have good conductivity. • Carbon-enriched MOFs and derived porous carbon have excellent electrochemical performance. • The change law of electrochemical performance was explored with gradient temperature. • The MOF-B-600//AC ASC device exhibits a high energy density of 63.62 Wh·kg−1 at power density of 400 W·kg−1. [Display omitted] This article aims to use nitrogen-doped metal p - π conjugated-organic frameworks and derived carbon-rich electrode materials for high-performance electrode materials. Nitrogen-doped contributes to the energy storage performance, and the p-π conjugated-organic ligands of the conjugated system can not only improve the stability of the structure, but increase the conductivity of the material. Gradient carbonization can explore the maximum electrochemical potential of MOF-B, from which the previous 1271.0 increased to 2727.5 F·g−1 at a current density of 1.0 A·g−1. The excellent capacitance retention rate is 86.67% of the initial value at a high current density after 20,000 cycles. Besides, the MOF-B-600//AC also shows a high energy density of 63.62 Wh·kg−1 at a power density of 400 W·kg−1 and good coulomb efficiency of 90.7%. As a result, the excellent electrochemical performance of the nitrogen-doped and carbon-enriched MOF-B-600 has potential application prospects in energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • MoS 2 @Ni-MOF was prepared and alkalized to obtain MoS 2 /Ni(OH) 2. • MoS 2 /Ni(OH) 2 has high specific capacitance and long cycling life for supercapacitor. • MoS 2 /Ni(OH) 2 was used to construct electrochemical sensor for HQ and CC. A nickel-based metal-organic framework (Ni-MOF) layer was in situ grown on the surface of the sheet MoS 2 to synthesize MoS 2 @Ni-MOF as a precursor. In order to improve the properties of the precursor material, the final MoS 2 /Ni(OH) 2 material was obtained by alkalizing the precursor material. Supercapacitors and electrochemical sensors were prepared by MoS 2 /Ni(OH) 2 composite material. The test indicates that alkaline treatment of Ni-MOF materials is helpful to improve electrochemical performance. MoS 2 /Ni(OH) 2 material used as supercapacitor electrode has a high specific capacitance of 2192 F g−1 and excellent cyclic stability (the capacitance retention rate remains 85.19% after 10,000 charge/discharge cycles). The hybrid supercapacitor (HSC) was assembled with MoS 2 /Ni(OH) 2 as the positive electrode and activated carbon as the negative electrode. The MoS 2 /Ni(OH) 2 //AC HSC device shows an excellent energy density of 50.58 Wh kg−1 at the power density of 800 W·Kg−1. In addition, the MoS 2 /Ni(OH) 2 modified GCE electrode is an excellent electrochemical sensor for the simultaneous determination of hydroquinone (HQ) and catechol (CC). The modified electrode provides wide linear ranges of 1 ∼ 500 and 2 ∼ 400 μM and low detection limits of 0.43 and 0.48 μM for HQ and CC, respectively (S/N=3). The MoS 2 /Ni(OH) 2 material can be applied to supercapacitors and electrochemical sensors, indicating that the material has great potential application value in energy storage and biosensing. [ABSTRACT FROM AUTHOR]

The transition metal selenides have aroused wide concern due to their potential characteristics in the energy storage and conversion. The formation of multivariate MOFs attracts much research attention and provides the essential guarantee for multivariate mixed-metal selenides. Herein, a series of isostructural MOF-74 materials with different divalent metals were prepared by changing the molar ratios of nickel to cobalt. After selenizing, CoSe 2 , NiSe 2 and three kinds of mixed-metal selenides were easily obtained, prompting us to systematically research the effect of different metal species and molar ratios on the electrochemical performance of the mixed-metal selenides. It is found that mixed-metal selenides derived from MOF-74 display much better performance than single metal selenides, and NiCoSe-4 with a Ni/Co molar ratio of 4:1 demonstrates a high specific capacity of 211 mAh g−1 at a current density of 1 A g−1. What's more, the assembled asymmetric supercapacitor NiCoSe-4//AC shows a high energy density of 61.24 Wh kg−1 at power density of 800 W kg−1, which suggests that NiCoSe-4 as a promising electrode material possesses further research value and potential for practical applications in energy storage fields. Image 1 • CoSe 2 , NiSe 2 and three kinds of mixed-metal selenides were easily obtained by selenizing different isostructural MOF-74 materials. • Mixed-metal selenides of electrochemical performance derived from MOF-74 display much better than single metal selenides, and NiCoSe-4 demonstrates a high specific capacity of 211 mAh g−1 at a current density of 1 A g−1. • The assembled NiCoSe-4//AC exhibits high energy density of 61.24 Wh kg−1 at power density of 800 W kg−1. The capacitance retention and Faradic efficiency of the NiCoSe-4//AC are 91% and 89% after 12,000 cycles at a current density of 10 A g−1. [ABSTRACT FROM AUTHOR]

A new two-dimensional covalent organic framework (DBT-MA-COF) is designed and synthesized via Carbon–Nitrogen coupling reaction by using 2,5-dibromothiophene (DBT) and melamine (MA) as the monomers. The C−Hˑ N intralayer hydrogen bonding exists in the structure of DBT-MA-COF so that a plane rigid structure can be maintained. The material exhibits a quasi-reversible redox process caused by triazine units and the transformation of the quinone and aromatic structures to make the DBT-MA-COF possess pseudocapacitive characteristics. DBT-MA-COF has high heteroatom content for the existence of triazine and thiophene units, which can accelerate the transfer of electrolyte ions on the surface of DBT-MA-COF electrode and improve the solution conductivity of the material. The assembled asymmetric supercapacitor DBT-MA-COF//C-CTS ASC has a high energy density of 32.1 W h kg−1 with the power density of 800 W kg−1. The cycle life of the device is excellent which can reach 83% even after 30,000 continuous galvanostatic charge-discharge cycles. The strategy in this work provides a line of thinking to design and prepare new COFs used as long life and pseudocapacitive supercapacitor materials. Image 1 • A novel covalent organic framework(DBT-MA-COF) is synthesized via Carbon-Nitrogen coupling reaction. • C-H...N intralayer hydrogen bonding existed in DBT-MA-COF leads to a plane rigid structure. • The COF has pseudocapacitive characteristics for a transformation of quinone and aromatic structures in triazine unit. • The existence of triazine and thiophene units improves the conductivity of the resulting material. • Assembled asymmetric supercapacitor shows a high energy density of 32.1Wh kg-1 and the long life of 83% after 30000 cycles. [ABSTRACT FROM AUTHOR]

• The novel Mn-Ni double hydroxide composite was prepared by alkalizing the Mn/Ni-MOF-74 precursor. • MnNiDH shows high specific capacitance and excellent retention rate. • The assembled aqueous and all-solid-state devices display high energy densities and wide voltage window. MOF-derived hydroxides provide a promising platform for high performance supercapacitors as electrode materials. Herein, a novel manganese-nickel double hydroxide (MnNiDH) composite with special morphology has been successfully prepared by alkalizing the precursor Mn/Ni-MOF-74. Obtaining electrode material inherits the spear-shaped morphology of the precursor well and possesses a smaller particle size by potassium hydroxide treatment. The smaller particle size and rich microporous structure can shorten the ion or proton transport path, thereby improve its electrochemical activity and utilization. Benefiting from these specific properties, the resultant MnNiDH composite demonstrates a high specific capacitance of 2498 F g−1 at a current density of 1A g−1. The assembled aqueous device exhibits high energy density of 58.53Wh kg−1, meanwhile the all-solid-state device also displays energy density of 30.63 Wh kg−1 based on the outstanding voltage window of 0∼2.1 V. These results suggest that as-synthesized MnNiDH hold great potential for practical applications in the energy storage field. [ABSTRACT FROM AUTHOR]

A facile alkaline treatment stripping precursor strategy is developed for preparing MOF derived double hydroxide. The bimetallic MOFs material provides multi-type of redox reaction centres, and the hydroxide nanonanoflower obtained by alkali stripping Ni-MOF@Co-MOF effectively expands the "active area (circumference)" of the redox reaction. The exfoliated sheets expose more active sites, which are more favorable for effective contact with the electrolyte and facilitate the occurrence of redox reactions. The MOF derived double hydroxide maintains the structural and performance advantage of the MOF precursor as well as overcomes the disadvantages of poor conductivity and serious agglomeration of common hydroxide. As-synthesized electrode exhibited high specific capacity of 1088 C g−1 at 1 A g−1 and cycle retention of 94% after 12,000 cycles. Furthermore, assembled battery-supercapacitor hybrid device exhibits a maximum energy density of 66.5 Wh kg−1 at a power density of 825 W kg−1, and superior cycle retention and coulombic efficiency of 86% and 95% after 18,000 cycles, which shows that Ni-MOF@Co-MOF derived double hydroxide has good potential application value. [ABSTRACT FROM AUTHOR]

In this present paper, a novel layered multi-metal sulphide was reported as a positive electrode material with abundant electroactive sites and redox reaction centres. Molybdenum and sulfur elements were introduced into the metal-organic frameworks (M-MOF: M = Ni, Co and Ni/Co) to synthesize layered MMoS x by a hydrothermal method. The electrochemical performance comparison of MOFs and six electrode materials demonstrated that NiCoMoS x electrode materials had the best electrochemical performance and the highest specific capacitance. The highest specific capacitance could reach 2595 F g−1 at a current density of 1 A g−1. The NiCoMoS x electrode material also had an excellent cycle stability with a retention rate of 90.8% after 10,000 charge and discharge cycles. In addition, the as-assembled NiCoMoS x //AC assymmetric supercapacitor (ASC) device exhibited a maximum energy density of 48.2 Wh·kg−1 at a power density of 807.2 W kg−1, and the capacity retention rate after 10,000 charge and discharge cycles was 91.6%. This electrochemical performance indicated that this kind of material had a good market development prospect. • Six kinds of materials were synthesized by hydrothermal method to make working electrodes, and electrochemical properties were tested and compared. • It is proved that cobalt-nickel composite has higher specific capacitance and better electrochemical performance after molybdenum-doped vulcanization with MOF as precursor. • NiCoMoS x electrode material has good electrochemical properties and excellent cycling stability. • The assembled asymmetric supercapacitor has good energy storage and can light up red LED. [ABSTRACT FROM AUTHOR]

Nitrogen sulfur co-doped bimetal nanocomposites (NS-BNs) are prepared through vulcanization and annealing using bimetallic Ni/Co-MOF as a precursor. The nitrogen sulfur co-doped bimetal nanocomposites have abundant electroactive sites and redox reaction centres, which exhibit remarkable electrochemical performance as electrode materials for supercapacitor. The specific capacitance could reach 1529 F g−1 at a current density of 1 A g−1 and excellent cycle stability (retention rate of 89.29% after 10000 cycles). After the current density is expanded ten times, the specific capacitance can still reach 1069 F g−1, indicating superior rate performance. Furthermore, the assembled asymmetric supercapacitor displayed a high energy density of 41.04 Wh kg−1 at power density of 750 W kg−1. As a result, non-metal doped nanocomposites material has promised applications for electrochemical supercapacitors. Image 1 • Advanced asymmetric supercapacitor device assembled by nitrogen sulfur co-doped bimetal nanocomposites. • Outstanding electrochemical behaviour and ultrahigh specific capacitance of 1529 F g−1 at 1 A g−1. • High energy density of 41.04 Wh kg−1 at power density of 750 W kg−1. • Remarkable long term cycle stability with 90% after 10000 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

• The method of synthesizing the composite has been novel and has not been reported so far. • MoS 2 @Ni-MOF shows the remarkable specific capacitance. • The introduction of sulfur has established a bridge for the charge transfer. • The MoS 2 @Ni-MOF//AC ASC device exhibits a high energy density of 72.93 Wh kg−1 at power density of 375 W·kg−1. • The assembled all-solid-state MoS 2 @Ni-MOF//AC can illuminate commercial red LED lamps for up to 30 s. Two-dimensional metal-organic frameworks and nanoflowers of the MoS 2 form a composite structure as an electrode material for high-performance supercapacitor application. MoS 2 expands in the accordion-type Ni-MOF layers, and -S- joins the two materials to form a Ni-MOF coating MoS 2 composite structure. The composite material MoS 2 @Ni-MOF combines the structural characteristics of the Ni-MOF and MoS 2 , and effectively improves the electrochemical performance. The basic skeleton structure of the MoS 2 @Ni-MOF material remains unchanged, showing a remarkable specific capacitance of 1590.24 F·g−1 at a current density of 1.0 A·g−1 and an excellent cycle stability (retention rate of 87.97% after 20,000 cycles at current of 5.0 A·g−1). Due to the special composite structure of MoS 2 @Ni-MOF, the as-assembled MoS 2 @Ni-MOF//AC assymmetric supercapacitor (ASC) device exhibits a maximum energy density of 72.93 Wh·kg−1 at a power density of 375 W·Kg−1. These excellent electrochemical properties indicate that the MoS 2 @Ni-MOF has potential applications in energy storage devices. [ABSTRACT FROM AUTHOR]