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Transition metal chalcogenides are considered to be the most promising battery-type cathodes to construct hybrid supercapacitors. The rational design and construction of multi-anion-based heterojunctions with multi-interface structures, such as sulfoselenide and oxyselenide, are significant and necessary. In this work, a bimetallic sulfoselenide–selenite heterojunction, (Ni,Co)(Se,S)2/(Ni,Co)SeO3, was facilely synthesized by a simple one-pot hydrothermal method using NiCo–LDH as a template. The rough surface of the nanosheet array provides more active sites and the multi-interface optimizes the electronic structure for electrochemical reactions. As a battery-type cathode for supercapacitors, the optimized (Ni,Co)(Se,S)2/(Ni,Co)SeO3-1 exhibits a high specific capacitance of 7.61 F cm−2 at a current of 2 mA cm−2. In addition, the assembled HSC device provides a high energy density of 0.59 mW h cm−2 at a power density of 1.44 mW cm−2 and displays a capacitance retention rate of 84.38% after 5000 charge/discharge tests. These results demonstrate a green, safe and simple method to prepare bimetallic sulfoselenide–selenite heterojunctions from LDH-based templates as high-capacity battery-type materials for hybrid supercapacitors. [ABSTRACT FROM AUTHOR]

Transition metal sulfides and selenides are common electrode materials in supercapacitors. However, the slow redox kinetics and structural collapse during charge–discharge cycles of single-component materials have impeded their electrochemical performance. In this study, hollow Co9S8 nanotubes were synthesized through a rational morphology design approach. Subsequently, NiSe2 or Co0.85Se was electrodeposited onto the Co9S8 nanotubes, yielding two core–shell heterostructure arrays, namely, NiSe2@Co9S8 and Co0.85Se@Co9S8. By fully leveraging the advantages and synergistic effects of these dual-phase heterostructures, the NiSe2@Co9S8 and Co0.85Se@Co9S8 configurations demonstrated outstanding areal capacitances of 12.54 F cm−2 and 9.61 F cm−2, respectively, at 2 mA cm−2. When integrated with activated carbon in hybrid supercapacitors, the NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC devices exhibited excellent energy storage performance, with energy densities of 0.959 mW h at 1.681 mW and 0.745 mW h at 1.569 mW, respectively. Additionally, these hybrid supercapacitors demonstrated remarkable cycling stability, with capacitance retention of 87.5% and 89.5% after 5000 cycles for NiSe2@Co9S8//AC and Co0.85Se@Co9S8//AC, respectively. This study provides a novel approach to the synthesis of multiphase core–shell heterostructures based on metal sulfides and selenides, opening new avenues for future research. [ABSTRACT FROM AUTHOR]

Transition metal sulfides are promising electrode materials for supercapacitors due to their excellent electrochemical performance and high conductivity. Unfortunately, the low rate performance and poor cycling stability limited their progress towards commercial applications. Herein, the core–shell structure of MoO42−-intercalated LDHs coated on Co9S8 nanotubes was rationally designed and prepared to improve their electrochemical performance and cycling stability by adjusting the composition of LDHs. Compared to NiMo-LDH@Co9S8 and CoMo-LDH@Co9S8, the optimized NiCoMo-LDH@Co9S8 electrode exhibits excellent areal specific capacitance (11 F cm−2 at 3 mA cm−2) and excellent cycling stability (94.4% after 5000 cycles). In addition, asymmetric supercapacitor devices were assembled with NiCoMo-LDH@Co9S8 and activated carbon (AC), which delivered a high energy density of 0.94 mWh cm−2, at a power density of 1.70 mW cm−2, and good cycling stability (89.4% after 5000 cycles). These results indicate that the introduction of MoO42− can enhance the synergistic effect of multiple metals and the synthesized NiCoMo-LDH@Co9S8 core–shell composite has great potential in the development of high-performance electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been extensively applied in supercapacitors. Unfortunately, metal active sites in MOFs are commonly blocked and saturated by organic ligands, leading to insufficient positions available for the electrochemical reaction. To address this issue, we develop a novel strategy to design and prepare a series of hollow metal sulfide/MOF heterostructures, which simultaneously alleviate the large volume expansion, avoid slow kinetics of metal sulfides and expose more electrochemically active sites of the MOF. Consequently, the optimized Co9S8/Co-BDC MOF heterostructure presents outstanding electrochemical performance with a high areal specific capacitance of 15.84 F cm−2 at 2 mA cm−2 and a capacitance retention rate of 87.5% after 5000 charge–discharge cycles. The asymmetric supercapacitors based on the heterostructure deliver a high energy density of 0.87 mW h cm−2 and a power density of 19.84 mW cm−2, as well as long cycling stability. This study provides a new strategy for the rational design and in situ synthesis of metal sulfide/MOF heterostructures for electrochemical applications. [ABSTRACT FROM AUTHOR]

Binary transition metal sulfides are considered to be a promising material for supercapacitors, possessing richer electrochemically active sites and superior electrochemical performance. Metal–organic frameworks (MOFs) are often used as self-sacrificing templates in the preparation of metal sulfides. Usually, direct sulfidation of MOFs tends to cause collapse of the morphological structure and blockage of the ion transport channels, so that the morphology of the original MOF template can be well preserved by using pyrolysis followed by S2− ion exchange. In this paper, we first prepared NiCo–MOF-74 on nickel foam by an in situ transformation method from layered double hydroxides (LDHs) through a ligand exchange reaction. Then, CoNi2S4 was synthesized in two steps involving the pyrolysis of NiCo–MOF-74 and a subsequent S2− ion exchange reaction. Compared with direct sulfidation, this synthetic strategy can well maintain the rod-like morphology of MOF-74 arrays and prevent structural collapse. The surface of CoNi2S4 has a fine nanosheet structure, which exposes more active sites and shows a high specific capacitance of 7.50 F cm−2 at 2 mA cm−2 and an excellent Coulomb efficiency (96.32%). In addition, the hybrid supercapacitor assembled with activated carbon shows a high energy density of 0.64 mW h cm−2 at a power density of 1.64 mW cm−2 and a high capacitance retention of 88.39% after 5000 cycles. These results indicate that rod-shaped CoNi2S4 can be controllably prepared from MOF-74 involving an exchange reaction and has promising application in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Nickel phosphite (Ni11(HPO3)8(OH)6) superstructures assembled by nanotubes are synthesized under mild hydrothermal conditions with the sodium salt of polystyrene sulfonic acid. More importantly, Ni11(HPO3)8(OH)6 superstructures are applied as electrode materials for supercapacitors. Benefitting from their novel superstructures, in a three-electrode system, Ni11(HPO3)8(OH)6 superstructure electrodes show a good specific capacitance (1876 F g−1 at 0.625 A g−1), good rate capability, and excellent cycling properties (95 % of the initial specific capacitance at 6.25 A g−1 after 2000 cycles) in 3.0 M KOH. Additionally, asymmetric Ni11(HPO3)8(OH)6-graphene nanosheet supercapacitors are also designed. The specific energy of a cell in 3.0 M KOH reaches about 28.6 Wh kg−1 at 92.5 W kg−1. [ABSTRACT FROM AUTHOR]

Cobalt pyrophosphate (CoPO) nano/microstructures (oblong plate, microplate, microflower, and hierarchical architectures) have been successfully synthesized through calcination of NHCoPO·HO nano/microstructures. More importantly, supercapacitive performances of CoPO nano/microstructures were studied using cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy methods in 3.0 M KOH solution. These results show that CoPO hierarchical architecture electrodes exhibit high specific capacitance of 367 F g at current density of 0.625 A g in aqueous KOH solution. CoPO hierarchical architecture electrodes remain 96.2 % of the initial specific capacitance after 3,000 charge/discharge cycles. [ABSTRACT FROM AUTHOR]

Designing high-performance electrodes and elucidating their energy storage mechanisms are crucial for supercapacitors. In this study, an in situ conversion method is firstly employed to transform CoCH (Co(CO 3) 0.5 (OH)·0.11 H 2 O) into Co-MOF-74 nanorods, which serves as a self-sacrificial template. Subsequently, the amorphous CoMoS 4 hollow tube arrays with self-assembled nanosheet surfaces are obtained through MoO 4 2- etching and S2- exchange. Benefiting from the nanosheets-coated hollow tubular structure and amorphous characteristics, CoMoS 4 exhibits a high areal capacitance of 7.01 F·cm−2 at 2 mA·cm−2 and 91.81 % retention after 5000 cycles. When further assembled into a hybrid supercapacitor, the CoMoS 4 //AC device exhibits excellent performance with the energy density of 0.684 mWh·cm−2 at 1.876 mW·cm−2 and 91.39 % retention after 10000 cycles. Furthermore, the mechanism study reveals that Mo- and S-doped amorphous CoOOH is a genuine energy storage material. This work provides valuable insights into the preparation of amorphous materials using the self-sacrificial template transformation method and the understand of their energy storage mechanisms. [Display omitted] • Amorphous CoMoS 4 hollow tube array exhibits excellent specific capacitance and cycling stability. • CoMoS 4 exhibits a high areal capacitance of 7.01 F·cm−2 at a current density of 2 mA·cm−2. • CoMoS 4 exhibits high cycling stability with 91.81 % capacity retention after 5000 cycles. • CoMoS 4 //AC device demonstrates remarkable cycling stability with capacitance retentions of 91.39 % after 10000 cycles. [ABSTRACT FROM AUTHOR]

Transition metal sulfides are gaining attention as a new highly capacitive active material for high-performance supercapacitors, however, it is still a challenge that synthesizes a distinctive structure to enhance the electrochemical characteristics and practical applications. In this work, hierarchical structural hybrid metal sulfides (NiCo 2 S 4 /Co 4 S 3) based on nanosheets and nanocages are synthesized by sulfurating the NiCo-LDH/ZIF-67 precursors. The NiCo 2 S 4 /Co 4 S 3 electrode with remarkable layered and porous structure effectively increase the electrochemical active surface area and accelerate the charge transfer, achieving a high specific capacitance of 8.43 F cm−2 at a current density of 2 mA cm−2 and good cyclic stability. An assembled asymmetric supercapacitor with activated carbon delivers a high energy density of 0.50 mWh cm−2 at a power density of 1.69 mW cm−2. These results demonstrate that NiCo 2 S 4 /Co 4 S 3 is an ideal electrode material for high-performance electrochemical energy storage devices. [Display omitted] • NiCo 2 S 4 /Co 4 S 3 displays a hierarchical structure based on nanosheet and nanocage. • NiCo 2 S 4 /Co 4 S 3 achieves a high specific capacitance and good cyclic stability. • An assembled asymmetric supercapacitor delivers a high energy density. • NiCo 2 S 4 /Co 4 S 3 is an ideal electrode material for high-performance supercapacitor. [ABSTRACT FROM AUTHOR]

Abstract: Porous nickel oxide (NiO) microflowers have been successfully synthesized by calcining a coordination microflower without any hard template, seed or using soft template. More importantly, porous NiO microflowers have been applied as effective electrochemical sensor of the tripeptide glutathione (GSH) and electrochemical supercapacitors. The effectively electrochemical GSH sensor of porous NiO microflowers in 0.1M HAc–NaAc (pH 5.0) solution was the first time evaluated. Moreover, the specific capacitance of porous NiO microflower was up to 1678.4Fg−1 at current density of 0.625Ag−1, and maintained about 99.7% at 6.25Ag−1 after 1000 cycles. [Copyright &y& Elsevier]

Bimetal oxides have superior supercapacitive properties because of synergistic effect, but their applications are usually limited because of low conductivity. Metal cations doping has been a promising method to break the restriction. Here, we first selected CuCo 2 O 4 nanowire arrays with high electrochemical activity as mother bimetal oxides and Al3+ with high electric conductivity as the dopant to investigate the influence of doped amounts on the electrochemical behaviors. With the increase of doped Al3+, the specific capacitance increased at first and then decreased, in accord with the analysis results of the conductivity, capacitive and diffusion-controlled contribution. The sample with the optimal doping amount had the highest capacitive behavior (1871 F g−1 at 1 A g−1) and considerable cycling performance (93% after 8000 cycles at 2 A g−1). A full button cell consisting of anode material (AC) and cathode material (the optimal Al-doping CuCo 2 O 4) exhibited satisfied energy density (65 Wh kg−1) and power density (735 W kg−1) as well as favorable cycling performance (95% retention after 4000 cycles). A LED was successfully powered by the constructed full cell suggested the promising application in future industrial green energy-storage devices of the Al-doping CuCo 2 O 4 nanomaterials. Image 1 • Al3+ was doped into CuCo 2 O 4 nanowires to investigate the influence of doped amounts on the electrochemical behaviors. • With the increase of doped Al3+, the specific capacitance increased at first and then decreased. • A full cell device based on AC anode and the optimal Al-doping CuCo 2 O 4 cathode has been constructed. • The full cell device exhibited a high energy density of 65 Wh kg-1 at the power density of 735 W kg-1. [ABSTRACT FROM AUTHOR]