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Metal–organic frameworks (MOFs) have found wide applications in the field of supercapacitors due to their highly controllable porous structure, big specific surface area, and abundant chemical functional groups. MOF-on-MOF hybrids not only enhance the composition of MOFs (such as ligands and/or metal centers) but also provide greater structural diversity. By utilizing MOFs as precursors for preparing sulfides, the unique characteristics and inherent structure of MOFs are preserved but their conductivity and capacitance are enhanced. This study successfully synthesized hollow-structured Ni3S4@Co3S4 derived from an Ni-MOF@ZIF-67 hybrid structure, where the Ni-MOF serves as the core and ZIF-67 as the satellite. The Ni3S4@Co3S4 electrode demonstrated a specific capacity as high as 747.3 C g−1 at 1 A g−1, and it could still maintain 77% of its initial capacity at 10 A g−1. Furthermore, the assembled Ni3S4@Co3S4//AC hybrid supercapacitor (HSC) device achieved a maximum energy density of 30.8 W h kg−1 when the power density was 750 W kg−1. The device exhibited remarkable cycling durability, retaining 85.4% of its initial capacitance after 5000 cycles. Therefore, the derived functional materials based on MOF-on-MOF provide a more scalable and promising approach for the preparation of efficient electrode materials. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are battery-type supercapacitor electrode materials with application potential due to their abundant active metal sites and surface functional groups. The traditional LDH structure easily aggregates and collapses. In this work, a stable cobalt zeolite imidazole framework (Co-ZIF) was used as the derived template to grow LDH nanosheets in situ to increase the contact area with the electrolyte, and polyaniline (PANI) acted as a conductive bridge to provide a rapid charge transfer pathway. The fabricated NiCo-LDH@PANI hollow structure demonstrated a specific capacity of 1315 C g−1 at 1 A g−1 and achieved a rate capacity of 951 C g−1 at 20 A g−1. Furthermore, the battery–supercapacitor hybrid device (NiCo-LDH@PANI//AC) exhibited an high energy density of 66.2 W h kg−1 at a power density of 800 W kg−1 with 95.5% capacitance retention after 20 000 cycles. [ABSTRACT FROM AUTHOR]

The application of Ni‐MOF in supercapacitors has received widespread attention, but its poor conductivity and bad stability hinder its application. Therefore, Ni‐MOF derived CMs@Ni(OH)2/NiSe with a core‐shell structure was designed. Here, carbon microspheres (CMs) were explored as the conductive substrate to enhance the stability and in situ prepared Ni‐MOF was anchored on the surface of CMs. Then, alkali‐treatment and selenylation were carried out on CMs@Ni−MOF to improve stability and conductivity. The obtained core‐shell nanostructure material possesses a high contact area, excellent synergistic effect and can provide more reactive active sites. The prepared CMs@Ni(OH)2/NiSe shows a higher specific capacitance (2106 F g−1) and excellent cycling performance with a capacitance retention of 95 % after 30000 cycles. Furthermore, the assembled CMs@Ni(OH)2/NiSe//AC device delivers a high energy density of 70.84 Wh kg−1 at the power density of 756.8 W kg−1 and maintains 100 % of the initial capacitance after 40000 cycles. [ABSTRACT FROM AUTHOR]

MnCo2O4 is derived from a Co/Mn bimetallic metal‐organic framework (MOF). Then Ni‐MOF is directly grown on the surface of the obtained MnCo2O4 to form a nano‐flower structure with small balls. A large surface area, abundant active sites of MnCo2O4 and porosity of Ni‐MOF allow the prepared MnCo2O4/Ni‐MOF composite material to deliver an excellent electrochemical performance. At the same time, an appropriate thermal treatment temperature of the MnCo2O4 precursor is also very important for controlling the morphology of the obtained MnCo2O4 and electrochemical performances of the resulted composite material including electric conductivity, specific capacitance and rate performance. The prepared MnCo2O4‐600/Ni‐MOF shows an ultrahigh rate performance (when the current density increases from 1 to 10 A g−1, the capacitance retention rate is as high as 93.41 %) and good cycle stability (the assembled asymmetric supercapacitor advice delivers a capacitance retention rate of 94.74 % after 20 000 charge and discharge cycles) as well as a relatively high specific capacitance. These excellent electrochemical properties indicate that MnCo2O4/Ni‐MOF has a good application prospect in the market. [ABSTRACT FROM AUTHOR]

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]

Transition metal sulfides derived from metal‐organic frameworks (MOFs) have received increasing attention as a potential energy storage electrode material. Here, a series of NiS2/CoS2/NC‐T (T=temperature) have been successfully constructed by carbonizing and sulfuring the precursor of Ni/Co‐MOF. It is worth emphasizing that N‐doped carbon materials improve the conductivity of the electrode material. Moreover, NiS2/CoS2/NC‐500 maintains the rod‐like structure of the precursor and exhibits a high specific capacitance of 1325 F g−1 at a current density of 1 A g−1. Apart from high capacitance, the NiS2/CoS2/NC‐500 also demonstrated excellent cycling stability with retention rate of 75 % after 5000 cycles at a current density of 5 A g−1. The good performance could be attributed to the unique rod‐like structure and pore‐size distribution of NiS2/CoS2/NC‐500. Moreover, an assembled asymmetric supercapacitor NiS2/CoS2/NC‐500//AC displays a high energy density of 53.93 Wh kg−1 at a power density of 800 W kg−1 and good cycle stability with capacitance retention of 85.71 % after 20,000 cycles at 5 A g−1. In particular, a red LED can be illuminated by the assembled ASC, indicating that as‐synthesized NiS2/CoS2/NC‐500 hold great potential for practical applications. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a new class of porous organic materials, which are constructed with periodic organic units comprised entirely of light elements (typically C, H, O, N and B) and linked by strong covalent bonds. COFs have been applied in extensive fields, owing to their extraordinary properties in areas such as gas storage and separation, heterogeneous catalysis, sensors, semiconductors, drug delivery, and photoconduction. In particular, the ordered micropore or mesopore structures, high surface areas, and designable structures have enabled COFs to become new candidates for supercapacitor electrode materials. This Minireview focuses on the major progress of COFs as electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

A novel tetrahydroxy-anthraquinone zeolitic framework (TZM) with a Viburnum blossom-like structure is synthesized via a simple solvothermal method by using tetrahydroxy-anthraquinone to substitute imidazolate without carbonization at high temperature. Considering the excellent electrochemical performance of the TZM, including a high specific capacitance of 2030 F g−1 at a current density of 1 A g−1, and good cycling stability with a capacitance retention of 94% of the initial capacitance after 1000 cycling charge/discharge measurements, an aqueous TZM//AC asymmetric supercapacitor (ASC) in 1 M KOH electrolyte is successfully fabricated by using the resultant TZM as the positive electrode and activated carbon nanosheets (ACS) as the negative electrode, respectively. The as-assembled aqueous ASC delivers a high energy density of 47.7 W h kg−1 at a power density of 750 W kg−1 with a high potential window of 0–1.5 V. Moreover, for the purpose of exploring the practical application of the active materials, an all-solid-state ASC TZM//ACS device with PVA-KOH gel electrolyte and separator is assembled and connected, which can light up a red light-emitting diode (LED). Its good performance demonstrates that the TZM//ACS ASC is a promising energy-storage system. [ABSTRACT FROM AUTHOR]

Phosphorus-doped three-dimensional hierarchical porous carbons (P-3DHPCs) have been synthesized by direct pyrolysis of mixture containing glucose, manganese nitrate and sodium hypophosphite without any hard templates. Glucose and sodium hypophosphite are used as carbon and phosphorus source in the facile template-free strategy, respectively. The P-3DHPCs not only possess favorable hierarchical pore structure which is beneficial to ion adsorption and transportation, but also acquire effective heteroatoms doping, further improving the capacitive performance. More importantly, the amount of sodium hypophosphite plays a critical role in textural properties and phosphorus content of P-3DHPCs. The results demonstrate that P-3DHPC-0.2 shows the best electrochemical performance compared to the other samples. High specific capacitance (367 F g −1 at 0.3 A g −1 ) is obtained in 6 M KOH, and the capacitance still maintains 319 F g −1 when tested at 20 A g −1 (ca.88% capacitance retention). Moreover, the P-3DHPC-0.2 also possesses good cycling stability with only a loss of 3.5% after 10000 cycles at 3 A g −1 . The facile preparation method and good electrochemical performance render P-3DHPCs to be a promising candidate for supercapacitor application. [ABSTRACT FROM AUTHOR]

This work report the synthesis of porous carbon with hierarchical pore structure and uniform nitrogen-sulfur-oxygen doping. The favorable pore structure (micro-, meso-, and macro-pores) is beneficial to ion adsorption and transportation, and the doping heteroatoms can introduce electrochemical active sites which contribute to additional pseudocapacitance. Therefore, the carbon material shows good electrochemical performance when employed as supercapacitor electrode. High specific capacitance (367 F g −1 at 0.3 A g −1 ), good rate performance and stable cycling characteristics are obtained in 6 M KOH. In addition, when tested in 1 M H 2 SO 4 , a higher specific capacitance (382 F g −1 at 0.3 A g −1 ) is delivered. Furthermore, the assembled symmetric cell yields a maximum specific energy of 35.3 W h kg −1 in 1 M TEABF 4 /AN, significantly improving the specific energy of carbon-based supercapacitors. [ABSTRACT FROM AUTHOR]

The ultrathin porous carbon shell with the thickness of about 10 nm has been fabricated by a facile method using sodium citrate as carbon precursor without any activation. The electric conductivity of the material is as high as 7.12 S/cm, which contributes to a good rate performance for supercapacitor electrode without any conductive additive. When tested in 6 M KOH by three-electrode system, the C-700 sample exhibits specific capacitance of 251 F g −1 at 1 A g −1 , high rate capability with the specific capacitance of 228 F g −1 at 20 A g −1 , only a loss of 3% after 10000 cycles at a current density of 3 A g −1 . Non aqueous performance was tested in 1 M TEA-BF 4 /acetonitrile, the material can deliver an energy density of 12–17 Wh kg −1 in a two-electrode system. Apparently, the porous carbon with ultrathin structure can provide low-resistant pathways and short ion diffusion channels for energy storage. Therefore, the ultrathin porous carbon shell would be a promising material particularly for applications where high power output performances are required. [ABSTRACT FROM AUTHOR]

Nanoflower‐like composites have greater contact area and more redox reactive centers, which have great potential in the application of electrode materials for supercapacitors. A nonconductive polymer binder is usually used in preparation of electrodes, which causes an increase in interface resistance and a decrease in material active sites. Here, polyaniline (PANI) and ZIF‐9 are directly grown on the Ni foam (ZIF‐9@PANI/NF) by a simple solvothermal method without a nonconductive polymer binder. A nanoflower array is grown on the NF, which can be directly used as electrode material of supercapacitor. The attachment of PANI facilitates electron transfer and increases the conductivity of the material. At a current density of 1 A g−1, the specific capacitance is up to 7 times that of the ZIF‐9. The assembled asymmetric supercapacitor has a high energy density of 52 Wh kg−1 at a power density of 800 W kg−1, remaining 90.1% after 50 000 cycles. These great electrochemical properties show the material has good market development prospects for energy storage device. [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]

• Hetero-phase hybridization strengthens internal electric field. • Covalent interaction creates nucleation sites and stabilizes the hybrids. • In-situ growth of MOF on Co 2 (OH) 2 CO 3 eliminates self-aggregation. • Controlled synthesis of the heterostructure with MWCNTs aid produces synergistic effect. • The integrated electrode delivers superior rate performance at high current density. In this work, bimetallic nickel-cobalt based metal organic framework (MOF) is in-situ grown on 2D laminar Co 2 (OH) 2 CO 3 with multi-walled carbon nanotubes (MWCNTs) aid to form nanoflower-like hierarchical porous heterogeneous structure for advanced supercapacitor application. Benefitting from the low crystal surface energy of Co 2 (OH) 2 CO 3 , its intersection and connection with MOF generate convenient electron path and open channel for ionic transmission, and large contact area. The high aromaticity of MWCNTs slows down destruction for MOF structure from water molecule through providing hydrophobic environment, guaranteeing stable presence of the resulting composite in aqueous electrolyte. The synergistic effect of Ni/Co with high redox activity in bimetallic NiCo-MOF provides rapid and multiple redox reactions for enhanced capacitance. Taking full advantage of promising merits of individual components, the optimized NiCo MOF-Co 2 (OH) 2 CO 3 nanosheet-MWCNT 30 (NCM-NS-CNT 30) composite under MWCNT dosage of 30 mg delivers greatly enhanced specific capacitance (1773 F g−1 at 1 A g−1) and obviously improved rate performance (96.5 % retention at 10 A g−1). Based on it, the fabricated hybrid supercapacitor (HSC) NCM-NS-CNT 30 //AC presents comparatively good energy density (30.625 Wh Kg−1), superior to most recently reported Ni, Co-based supercapacitors. [Display omitted] [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]

A new covalent organic framework material (NWNU-COF-1) with hexagonal honeycomb-like structure linked by NH bond was synthesized by the condensation reaction of melamine and 2,4,6-trichloro-1,3,5-triazine and its structure and properties were characterized by Fourier transform infrared spectra (FT-IR), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), N 2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The BET specific surface area of NWNU-COF-1 is 301.149 m 2 g −1 , and the pore size is about 1.41 nm, and the preparation is simple and cheap. This material is expected to be used in the field of electrode materials of supercapacitor and adsorbent materials. [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]

A new approach was proposed to construct a novel 3D hybrid nanocomposite heterostructure GO/MnCo 2 O 4 /Ni-V-Se as a hybrid supercapacitor electrode. Electrons can easily migrate from Mn ions to Ni ions, thereby increasing the electron energy of the metal orbital, and this inductive effect can effectively improve the electron transfer efficiency. In addition, the application of surface/interface control method also enables this electrode material to exhibit unique advantages. In this heterostructure, graphene serves as the extended conductive framework, cube-like MnCo 2 O 4 and flower-like Ni-V-Se spheres derived from MOFs as spacers separate the sheets to avoid the layer-by-layer stacking of graphene. Complemented by Ni-V-Se coating, the formed composite heterostructure exhibits excellent electrochemical performance. The as-prepared GO/MnCo 2 O 4 /Ni-V-Se delivers ultra-high specific capacity (1292.3 C·g−1 at 1 A·g−1), rate capability (94.87%) and cycling stability. Finally, the hybrid supercapacitor assembled by GO/MnCo 2 O 4 /Ni-V-Se and activated carbon also shows good electrochemical performance. [Display omitted] • Loose and porous 3D heteroconductive network had high specific capacity (1292.3 C/g) and excellent rate performance (94.87%). • A flower-like Ni-V-Se nanosphere composite derived from Ni-V-MOFs was designed for the first time. • The ternary composite avoided the stacking of graphene sheets and achieved the best synergistic effect. • GO/MnCo 2 O 4 /Ni-V-Se//AC HSC had high specific capacity, energy density and good cycling stability. [ABSTRACT FROM AUTHOR]

• A hollow structure PZ-20 was prepared by controlling the ligand exchange time. • Hollow structure r-NiCo 2 S 4 with sulfur vacancies for more active sites and redox reactions was synthesized. • The fabricated structure exhibited an ultra-high specific capacitance. • The assembled device presented an high energy density of 43.80 Wh·kg−1 under 800 W·kg−1. Defect and hollow structure on transition metal sulfides can produce abundant active sites and shorten electron/ion diffusion paths, improving the conductivity of electrochemically active materials. In this study, an effective strategy was proposed for preparing r-NiCo 2 S 4 electrode materials with sulfur vacancies and hollow structures and resulted excellent electrochemical performance through ligand exchange followed chemical reduction. Due to the unique structure, the prepared r-NiCo 2 S 4 electrode exhibited excellent specific capacitance (1406.4 F g−1 at 1 A g−1) and rate capacity (90.03%). Additionally, a hybrid supercapacitor r-NiCo 2 S 4 //AC HSC was assembled using r-NiCo 2 S 4 as the positive electrode and AC as the negative electrode. It presented an excellent energy density of 43.8 Wh kg−1 under 800 W kg−1 and cycling performance with 93.93% capacity retention after 10,000 cycles at 5 A g−1. This study provided a simple strategy for design and optimization of electrode materials with a unique hollow structure and sulfur vacancies. [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]

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]

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]

[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]

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]

• 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]