Hierarchical CuCo2O4@nickel-cobalt hydroxides core/shell nanoarchitectures for high-performance hybrid supercapacitors

Hierarchical core-shelled CoMo layered double hydroxide@CuCo2S4 nanowire arrays/nickel foam for advanced hybrid supercapacitors

The development of core-shelled heterostructures with the unique morphology can improve the electrochemical properties of hybrid supercapacitors (HSC). Here, CuCo2S4 nanowire arrays (NWAs) are vertically grown on nickel foam (NF) utilizing hydrothermal synthesis. Then, CoMo-LDH nanosheets are uniformly deposited on the CuCo2S4 NWAs by electrodeposition to obtain the CoMo-LDH@CuCo2S4 NWAs/NF electrode. Due to the superior conductivity of CuCo2S4 (core) and good redox activity of CoMo-LDH (shell), the electrode shows excellent electrochemical properties. The electrode's specific capacity is 1271.4 C g-1 at 1 A g-1, and after 10, 000 cycles, its capacity retention ratio is 92.2 % at 10 A g-1. At a power density of 983.9 W kg-1, the CoMo-LDH@CuCo2S4 NWAs/NF//AC/NF device has an energy density of 52.2 Wh kg-1. This indicates that CoMo-LDH@CuCo2S4/NF has a great potential for supercapacitors.

Construction of Binder-Free, Self-Supported, Hetero-Core-Shell Honeycomb Structured CuCo2 O4 @Ni0.5 Co0.5 (OH)2 with Abundant Mesopores and High Conductivity for High-Performance Energy Storage

Clever and rational design of structural hierarchy, along with precise component adjustment, holds profound significance for the construction of high-performance supercapacitor electrode materials. In this study, a binder-free self-supported CCO@N0.5 C0.5 OH/NF cathode material is constructed with hierarchical hetero-core-shell honeycomb nanostructure by first growing CuCo2 O4 (CCO) nanopin arrays uniformly on highly conductive nickel foam (NF) substrate, and then anchoring Ni0.5 Co0.5 (OH)2 (N0.5 C0.5 OH) bimetallic hydroxide nanosheet arrays on the CCO nanopin arrays by adjusting the molar ratio of Ni(OH)2 and Co(OH)2 . The constructed CCO@N0.5 C0.5 OH/NF electrode material showcases a wealth of multivalent metal ions and mesopores, along with good electrical conductivity, excellent electrochemical reaction rates, and robust long-term performance (capacitance retention rate of 87.2%). The CCO@N0.5 C0.5 OH/NF electrode, benefiting from the hierarchical structure of the material and the exceptional synergy between multiple components, demonstrates an excellent specific capacitance (2553.6 F g-1 at 1 A g-1 ). Furthermore, the assembled asymmetric CCO@N0.5 C0.5 OH/NF//AC/NF supercapacitor demonstrates a high energy density (70.1 Wh kg-1 at 850 W kg-1 ), and maintains robust capacitance cycling stability performance (83.7%) after undergoing 10 000 successive charges and discharges. It is noteworthy that the assembled supercapacitor exhibits an operating voltage (1.7 V) that is well above the theoretical value (1.5 V).

Trimetallic Oxide Foam as an Efficient Catalyst for Fixation of CO2 into Oxazolidinone: An Experimental and Theoretical Approach

The excess anthropogenic CO₂ depletion via the catalytic approach to produce valuable chemicals is an industrially challenging, demanding, and encouraging strategy for CO₂ fixation. Herein, we demonstrate a selective one-pot strategy for CO₂ fixation into "oxazolidinone" by employing stable porous trimetallic oxide foam (PTOF) as a new catalyst. The PTOF catalyst was synthesized by a solution combustion method using transition metals Cu, Co, and Ni and systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), N₂ sorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS) analysis. Due to the distinctive synthesis method and unique combination of metal oxides and their percentage, the PTOF catalyst displayed highly interconnected porous channels along with uniformly distributed active sites on its surface. Well ahead, the PTOF catalyst was screened for the fixation of CO₂ into oxazolidinone. The screened and optimized reaction parameters revealed that the PTOF catalyst showed highly efficient and selective activity with 100% conversion of aniline along with 96% selectivity and yield toward the oxazolidinone product at mild and solvent-free reaction conditions. The superiority of the catalytic performance could be due to the presence of surface active sites and acid-base cooperative synergistic properties of the mixed metal oxides. A doubly synergistic plausible reaction mechanism was proposed for the oxazolidinone synthesis experimentally with the support of DFT calculations along with bond lengths, bond angles, and binding energies. In addition, stepwise intermediate formations with the free energy profile were also proposed. Also, the PTOF catalyst displayed good tolerance toward substituted aromatic amines and terminal epoxides for the fixation of CO₂ into oxazolidinones. Very interestingly, the PTOF catalyst could be significantly reused for up to 15 consecutive cycles with stable activity and retention in physicochemical properties.

Boron nitride decorated poly(vinyl alcohol)/poly(acrylic acid) composite nanofibers: A promising material for biomedical applications

In this study, polyvinyl alcohol (PVA) and polyacrylic acid (PAA) nanofibers loaded with boron nitride nanoparticles (mBN) were fabricated by using electrospinning and crosslinked by heat treatment. The physical, chemical, and mechanical properties, hydrophilic behavior, and degradability of composite nanofibers were evaluated. The mechanical properties such as elastic modulus, elongation percentage at the break, and mechanical strength of PVA/PAA nanofibers improved with mBN loading. The thermal conductivity of composite nanofibers reached 0.12 W/m·K at mBN content of 1.0 wt% due to the continuous heat conduction pathways of mBN. In the meantime, while there was no cytotoxicity recorded for both L929 and HUVEC cell lines for all composite nanofibers, the antimicrobial efficiency improved with the incorporation of mBN compared with PVA/PAA and recorded as 68.8% and 75.1% for Escherichia coli and Staphylococcus aureus, respectively. On this basis, the present work proposes a promising biomaterial for biomedical applications such as dual drug delivery, particularly including both hydrophobic and hydrophilic drugs or wound dressing.

Facile design and synthesis of a nickel disulfide/zeolitic imidazolate framework-67 composite material with a robust cladding structure for high-efficiency supercapacitors

In this paper, a core-shell structure nickel disulfide and ZIF-67 composite electrode material (NiS2/ZIF-67) was synthesized by a two-step method. Firstly, spherical NiS2 was synthesized by a hydrothermal method, dispersed in methanol, then reacted and coated by adding cobalt ions and 2-methylimidazole to obtain the NiS2/ZIF-67 core-shell composite. The NiS2/ZIF-67 composite shows a high specific capacitance (1297.9 F g-1 at 1 A g-1) and excellent cycling durability (retaining 110.0% after 4000 cycles at 5 A g-1). Furthermore, the corresponding hybrid supercapacitor (NiS2/ZIF-67//AC HSC) has an energy density of 9.5 W h kg-1 at 411.1 W kg-1 (6 M KOH) and remarkable cycling stability (maintaining 133.3% after 5000 cycles). Its excellent electrochemical performance may be due to the core-shell structure and the synergistic effect between the transition metal sulfide and metal-organic framework. These results indicate that the NiS2/ZIF-67 composite as an electrode material with a core-shell structure has potential application in high-efficiency supercapacitors.

Hierarchical coral-like MnCo2O4.5@Co-Ni LDH composites on Ni foam as promising electrodes for high-performance supercapacitor

Transition metal oxides are generally designed as hybrid nanostructures with high performance for supercapacitors by enjoying the advantages of various electroactive materials. In this paper, a convenient and efficient route had been proposed to prepare hierarchical coral-like MnCo₂O_4.5@Co-Ni LDH composites on Ni foam, in which MnCo₂O_4.5nanowires were enlaced with ultrathin Co-Ni layered double hydroxides nanosheets to achieve high capacity electrodes for supercapacitors. Due to the synergistic effect of shell Co-Ni LDH and core MnCo₂O_4.5, the outstanding electrochemical performance in three-electrode configuration was triggered (high area capacitance of 5.08 F cm^-2at 3 mA cm^-2and excellent rate capability of maintaining 61.69% at 20 mA cm^-2), which is superior to those of MnCo₂O_4.5, Co-Ni LDH and other metal oxides based composites reported. Meanwhile, the as-prepared hierarchical MnCo₂O_4.5@Co-Ni LDH electrode delivered improved electrical conductivity than that of pristine MnCo₂O_4.5. Furthermore, the as-constructed asymmetric supercapacitor using MnCo₂O_4.5@Co-Ni LDH as positive and activated carbon as negative electrode presented a rather high energy density of 220μWh cm^-2at 2400μW cm^-2and extraordinary cycling durability with the 100.0% capacitance retention over 8000 cycles at 20 mA cm^-2, demonstrating the best electrochemical performance compared to other asymmetric supercapacitors using metal oxides based composites as positive electrode material. It can be expected that the obtained MnCo₂O_4.5@Co-Ni LDH could be used as the high performance and cost-effective electrode in supercapacitors.

Towards advanced aqueous zinc battery by exploiting synergistic effects between crystalline phosphide and amorphous phosphate

High-performance aqueous zinc batteries are expected to be realized, rooting from component synergistic effects of the hierarchical composite electrode materials. Herein, hierarchical crystalline Ni-Co phosphide coated with amorphous phosphate nanoarrays (C-NiCoP@A-NiCoPO₄) self-supporting on the Ni foam are constructed as cathode material of an aqueous zinc battery. In this unique core-shell structure, the hexagonal phosphide with high conductivity offers ultra-fast electronic transmission and amorphous phosphate with high stability, and open-framework provides more favorable ion diffusivity and a stable protective barrier. The synergistic effects of this intriguing core-shell structure endow the electrode material with outstanding reaction kinetics and structural stability, which is theoretically confirmed by density functional theory (DFT) calculations. As a result, the C-NiCoP@A-NiCoPO₄ electrode exhibits a higher specific capacity of 350.6 mA h g^-1 and excellent cyclic stability with 92.6% retention after 10 000 cycles. Moreover, the C-NiCoP@A-NiCoPO₄ is coupled with Zn anode to assemble an aqueous pouch battery that delivers ultra-high energy density (626.33 W h kg^-1 at 1.72 kW kg^-1) with extraordinary rate performance (452.05 W h kg^-1 at 33.56 kW kg^-1). Moreover, the corresponding quasi-solid flexible battery with polyacrylamide hydrogel electrolyte exhibits favorable durability under frequent mechanical strains, which indicates the great promise of crystalline/amorphous hierarchical electrodes in the field of energy storage.

Three-dimensional hierarchical core-shell CuCo2O4@Co(OH)2 nanoflakes as high-performance electrode materials for flexible supercapacitors

Rational design of composite electrode materials with novel nanostructures plays an important role in improving both high energy density and structure stability of flexible and wearable supercapacitors. Herein, numerous peculiar three-dimensional hierarchical core-shell CuCo₂O₄@Co(OH)₂ nanoflakes directly grown on Ni foam are synthesized via a facile hydrothermal method and subsequent electrodeposition technique. Ultrathin Co(OH)₂ nanosheets arrays vertically anchored on CuCo₂O₄ nanoflakes can not only improve the electrical conductivity, but also provide interconnected channels for ion diffusion and enrich electrochemical active sites to boost faradaic redox reaction, leading to the enhanced electrochemical behavior. Excellent electrochemical performance of CuCo₂O₄@Co(OH)₂ electrode can be reflected on a higher specific capacitance of 1558 F/g and lower resistance compared with that of the pristine CuCo₂O₄ electrode. The asymmetric flexible supercapacitor assembled by the optimized CuCo₂O₄@Co(OH)₂ electrode and activated carbon exhibits high energy density of 62.5 Wh/kg at 893 W/kg, outstanding cycle stability of 88.6% capacitance retention after 10,000 cycles and remarkable mechanical flexibility, performing the best electrochemical behavior among various metal oxides based asymmetric supercapacitors. All above results indicate that the resulted hierarchical core-shell CuCo₂O₄@Co(OH)₂ electrode can be a promising candidate for flexible energy storage devices.

Modified Co4N by B-doping for high-performance hybrid supercapacitors

High-performance energy storage systems are becoming essential to cope with the possible energy crisis in the future. Herein, unique hierarchical B-Co₄N have been reasonably designed and synthesized on Ni foam (NF) via a typical chemical reduction strategy. The successful realization of B-doping engineering effectively facilitates ion and electron transport, adding the electrochemically reactive sites, which endow the B-Co₄N-20/NF electrode with high specific capacity (817.9 C g^-1 at 1 A g^-1), excellent rate capability (maintained about 90.9% at 10 A g^-1) and cycling stability (about 93.06% retention of the initial capacity after 5000 cycles). The corresponding hybrid supercapacitor assembled with B-Co₄N-20/NF electrodes has an energy density of 25.85 W h kg^-1 at the power density of 800.2 W kg^-1 and a long cycle life (98.59% retention ratio after 5000 cycles). These remarkable properties indicate that the doping of heteroatom and the construction of hierarchical structure will provide a favorable reference for the performance promotion of next-generation energy storage devices.

DMF stabilized Li3N slurry for manufacturing self-prelithiatable lithium-ion capacitors

Li₃N is an excellent zero-residue positive electrode pre-lithiation additive to offset the initial lithium loss in lithium-ion capacitors. However, Li₃N has an intrinsic problem of poor compatibility with commonly used aprotic polar solvents in electrode manufacture procedure due to its high reactivity with commonly used solvents like N-methy-2-pyrrolidone (NMP) and etc. It is the Valley of Death between research and large-scale commercialization of Li-ion capacitors using Li₃N as prelithiation agent. In this work, Li₃N containing electrode is prepared by a commercially adoptable route for the first time, using N,N-dimethylformamide (DMF) to homogenate the electrode slurry. The DMF molecular stabilizing mechanism is confirmed via experiment analysis and DFT simulation, indicating that the dehydrogenation energy for DMF is obviously larger than other commonly used solvents such as NMP and etc. The soft package lithium-ion capacitors (LIC250) with only 12 wt% Li₃N addition in AC positive electrode exhibits excellent rate capability, cyclic stability and ultrahigh specific energy. Its specific energy is 2.3 times higher than the Li₃N-free devices, with energy retention as high as 90% after 10,000 cycles.

Dual-functional NiCo2S4 polyhedral architecture with superior electrochemical performance for supercapacitors and lithium-ion batteries

Dual-functional NiCo₂S₄ polyhedral architectures with outstanding electrochemical performance for supercapacitors and lithium-ion batteries (LIBs) have been rationally designed and successfully synthesized by a hydrothermal method. The as-synthesized NiCo₂S₄ electrode for supercapacitor exhibits an outstanding specific capacitance of 1298Fg^-1 at 1Ag^-1 and an excellent rate capability of ~80.4% at 20Ag^-1. Besides, capacitance retention of 90.44% is realized after 8000 cycles. In addition, the NiCo₂S₄ as anode in LIBs delivers high initial charge/discharge capacities of 807.6 and 972.8mAhg^-1 at 0.5C as well as good rate capability. In view of these points, this work provides a feasible pathway for assembling electrodes and devices with excellent electrochemical properties in the next generation energy storage applications.

Hierarchically hollow structured NiCo2S4@NiS for high-performance flexible hybrid supercapacitors

Hierarchical nanostructures with outstanding electrochemical properties and mechanical stability are ideal for constructing flexible hybrid supercapacitors. Herein, hierarchically hollow NiCo2S4@NiS nanostructures were designed and synthesized by sulfurizing the hierarchical NiCo double hydroxides (DHs) coated with nickel hydroxide nanostructures on carbon fabrics (NiCo-DHs@Ni(OH)2/CF), which trigger excellent electrochemical performances. The NiCo2S4@NiS/CF exhibits a high specific capacity of 1314.0 C g-1 at a current density of 1 A g-1, and maintains the rate performance at about 79.2% of the initial capacity at 30 A g-1. The hybrid supercapacitors of NiCo2S4@NiS//AC display a high energy density of 62.4 W h kg-1 at a power density of 800 W kg-1 with a remarkable cycling stability (96.2% of initial capacitance after 5000 cycles) and robust mechanical flexibility (no obvious decay of specific capacitance during various deformations). Consequently, NiCo2S4@NiS electrodes are expected to be a promising candidate for new smart energy storage devices with high security, stability and flexibility.

Cu-MOF derived Cu-C nanocomposites towards high performance electrochemical supercapacitors

For the development of asymmetric supercapacitors with higher energy density, the study of new electrode materials with high capacitance is a priority. Herein, the electrochemical behavior of nano copper in alkaline electrolyte is first discovered. It is found that there are two obvious reversible redox symmetric peaks in the range of -0.8-0.2 V in the alkaline electrolyte, corresponding to the conversion of copper into cuprous ions, and then converting cuprous ions into copper ions, indicating that the nanocomposite electrode has the characteristics of a pseudocapacitive reaction. It has a specific capacitance of up to 318 F g-1 at a current density of 1 A g-1, which remains at nearly 100% after 10 000 cycles at the same current density. When assembled with a Ni(OH)2-based electrode into an asymmetric supercapacitor, the device shows excellent capacitive behavior and good reaction reversibility. At 0.4 A g-1, the supercapacitor delivers a reversible capacity of 8.33 F g-1 with an energy density of 13.5 mW h g-1. This study first discovers the electrochemical behavior of nano copper, which can provide a new research idea for further expanding the negative electrodes of supercapacitors with higher energy density.

Designed synthesis of nickel-cobalt-based electrode materials for high-performance solid-state hybrid supercapacitors

Supercapacitors with high security, excellent energy and power densities, and superior long-term cycling performance are becoming increasingly essential for flexible devices. Herein, this study has reported a novel method to synthesize CoNi2S4, which delivered a high specific capacitance of 1836.6 F g-1 at 1 A g-1, with a slight fluctuation in the testing temperature rising up to 50 °C (1855.2 F g-1) or decreasing to 0 °C (1587.6 F g-1). In addition, the corresponding solid-state CoNi2S4//AC HSC could achieve a high energy density of 35.8 W h kg-1 at a power density of 800.0 W kg-1, with nearly no change when tested at 0 °C and 50 °C, and possessed excellent long-term electrochemical cycling stability of 132.3% after 50 000 cycles; the solid-state hybrid supercapacitor using biomass-derived carbon (BC) as the negative electrode (CoNi2S4//BC HSC) could also deliver a high energy density of 38.9 W h kg-1 at a power density of 850.0 W kg-1 and the specific capacitance retention was 101.2% after cycling for 50 000 times. This work has provided a promising method to prepare high-performance electrode materials for solid-state hybrid supercapacitors with superior cycling stability and energy density.

CoNi2S4 nanosheets on nitrogen-doped carbon foam as binder-free and flexible electrodes for high-performance asymmetric supercapacitors

Flexible electrode materials show many advantages and hold great prospects for energy storage application. But, the synthesis processes of these kind of materials are always complicated, are low in efficiency and high in cost. Here, we propose a facile and cost-effective two-step synthesis strategy of a flexible electrode by growing ultrathin and vertical CoNi₂S₄ nanosheets on nitrogen-doped carbon foam (CoNi₂S₄ NSs@NCF). The NCF is obtained by direct carbonization of the melamine foam. When evaluated as binder-free electrode material for supercapacitor in three-electrode system, the CoNi₂S₄ NSs@NCF exhibits an excellent specific capacitance of 1576.8 F g^-1 and a superior cycling stability (91.5% capacitance retention at the 5000th cycle). Then, an asymmetrical supercapacitor was fabricated using the as-synthesized material as the positive electrode and activated carbon as the negative electrode, which delivers a high energy density of 42.8 Wh kg^-1 at a power density of 399.7 W kg^-1, remarkable rate capability and satisfactory cycling stability (85.3% capacitance retention at the 5000th cycle). In brief, our work offers a low-cost and facile approach to prepare promising flexible electrode materials for high-performance supercapacitors.

Crude Oil Sensing using Carbon Nano Structures Synthetized from Phoenix Dactylifera L. Cellulose

This study reports on the crude oil-sensing using carbon nano structures (CNSs). A mixture of CNSs was obtained by a simple method of preparation using palm cellulose ash and nitric acid as precursors, the powder was characterized by x-ray diffraction and infrared spectroscopy. The optical density of crude oil from Rhoud El-Baguel area (Southeast of Algeria) studied using UV-Vis spectroscopy, before and after adding an amount of CNSs powder to view the CNSs crude oil sensing and therefore a new method to determine the quality of crude oils and the comparison between them. Results show that CNSs prepared from palm cellulose ash have a good crystallinity and it is formed mainly from carbon nano dots (CNDs) with 4.32 Å in layers spacing and 7.4 Å in crystallite size, indicate that CNSs can be used as an excellent crude oil sensor.

A water-evaporation-induced self-charging hybrid power unit for application in the Internet of Things

A self-charging hybrid power unit has been developed by integrating a water-evaporation-induced nanogenerator with a flexible nano-patterned supercapacitor. The nanogenerator can harvest environmental thermal energy and mechanical energy through the water evaporation process, and the supercapacitor can be charged simultaneously. The former offers stable electrical power as output, whereas the Ppy-based supercapacitor shows a capacitance of 12.497 mF/cm² with 96.42% retention after 4,000 cycles. After filling the power unit with water as the fuel, it can be fully charged in about 20 min. The power unit can be flexibly integrated with electronic devices such as sensor nodes and wireless transmitters employing the Internet of Things. This new approach can offer new possibilities in continuous future operation of randomly distributed electronic devices incorporated in the Internet of Things.

Self-Assembly of Ultrathin Nanocrystals to Multidimensional Superstructures

The self-assembly of ultrathin nanocrystals (UTNCs) into well-organized multidimensional superstructures is one of the key topics in material chemistry and physics. Highly ordered nanocrystal assemblies also known as superstructures or synthetic structures have remained a focus for researchers over the past few years due to synergy in their properties as compared to their components. Here, we aim to present the recent progress being made in this field with highlights of our research group endeavors in the engineering of self-assembled complex multidimensional superstructures of various inorganic materials, including polyoxometalates. The driving forces for the assembly process and its kinetics along with the potential applications associated with these unique ordered and spatially complex superstructures are also discussed.

Uniform P doped Co-Ni-S nanostructures for asymmetric supercapacitors with ultra-high energy densities

Uniform P doped Co-Ni-S nanosheet arrays were directly grown on Ni foams by an efficient and cost-effective process. The binder-free electrode of P doped Co-Ni-S nanosheet arrays possesses an ultra-high specific capacitance of ∼3677 F g-1 at 1 A g-1 with an excellent rate capability (∼63% capacitance retention at 20 A g-1) and considerable cycling performance (∼84% capacitance retention after 10 000 cycles). Correspondingly, the asymmetric supercapacitors assembled with P doped Co-Ni-S as the positive electrode and AC as the negative electrode display an ultra-high energy density of ∼68.7 W h kg-1 at a power density of ∼0.8 kW kg-1. In view of these features, this work provides a simple and scalable strategy for designing electrodes and devices with superior electrochemical performance in next generation energy storage applications.

A MnCo2 O4 @NiMoO4 Core-Shell Composite Supported on Nickel Foam as a Supercapacitor Electrode for Energy Storage

A MnCo₂ O₄ @NiMoO₄ composite was synthesized on nickel foam by a two-step method. The composite has a core-shell structure in which MnCo₂ O₄ nanoneedles are wrapped by NiMoO₄ nanoflakes. The MnCo₂ O₄ @NiMoO₄ /Ni foam is applied as a binder-free electrode for supercapacitors and it achieves a specific capacitance of up to 1718 F g^-1 at a current density of 1 A g^-1 , and 84 % capacitance retention after 6000 charge-discharge cycles. The capacitance of the MnCo₂ O₄ @NiMoO₄ composite is much higher than MnCo₂ O₄ nanoneedles and NiMoO₄ nanoflakes alone. Moreover, a hybrid supercapacitor is assembled by applying the MnCo₂ O₄ @NiMoO₄ /Ni foam as the positive electrode, activated carbon/Ni foam as the negative electrode. The hybrid supercapacitor reaches an energy density of up to 42.3 W h kg^-1 at a power density of 797 W kg^-1 , a power density of 6256 W kg^-1 at an energy density of 17.4 W h kg^-1 , and 86 % capacitance retention after 2000 charge-discharge cycles. The results suggest that the rational design of electrode materials with such structure and composition is an effective strategy to improve electrochemical performance.

Hedgehog-inspired nanostructures for hydrogel-based all-solid-state hybrid supercapacitors with excellent flexibility and electrochemical performance

High-security deformable energy-storage devices that are mechanically robust, with considerable energy and power densities are becoming desirable for smart wearable electronics. Here, a highly flexible hydrogel-based all-solid-state hybrid supercapacitor was rationally designed and assembled, with unique NiCo2O4@NixCoyMoO4 (x : y = 3 : 1) nanostructures as the electrode, which was bio-inspired by the curling up and relaxation of hedgehogs. The hybrid supercapacitor shows no obvious decay in capacitance during bending to different states, indicating its outstanding flexibility and mechanical stability. The capacitance was still maintained at 92.0% of the initial value, even after continuous bending for 3000 cycles. The highly monodisperse NiCo2O4@NixCoyMoO4 nanostructures releasing stress during bending is responsible for the favorable stability and flexibility. Furthermore, the hybrid supercapacitor displayed outstanding electrochemical performance, with a high specific capacitance of 207 F g-1 at 1 A g-1, a high energy density of 64.7 W h kg-1 at 749.6 W kg-1, and favorable cycling stability (nearly 100% after 10 000 cycles). The flexible hybrid supercapacitor could be charged with a solar cell and served as the power source to light up LEDs. This simple and reliable hybrid supercapacitor, with extraordinary mechanical stability and electrochemical performance, is a promising power source for smart wearable electronics.

Ni-Doped Cobalt Phosphite, Co11(HPO3)8(OH)6, with Different Morphologies Grown on Ni Foam Hydro(solvo)thermally for High-Performance Supercapacitor

Ni-doped Co₁₁(HPO₃)₈(OH)₆ with different morphologies was directly grown on Ni foam hydro(solvo)thermally under different synthetic conditions. The optimum condition is solvothermal reaction for 6 h in an ethanol/water (EW) mixed solution, the molar ratio of NaH₂PO₂/Co(NO₃)₂ being 0.5:0.1, and the obtained S0.5-6 h-EW shows three-dimensional (3D) porous nanowire bundles. Whereas in the water-only solution, microrods are obtained, suggesting that the nanowires in bundles are aggregated together via the lateral (400) direction. Long reaction time and low molar ratio of reactants are all beneficial for the lateral growth of the nanowires, and the possible formation mechanism is proposed. All the obtained Ni-doped Co₁₁(HPO₃)₈(OH)₆/Ni foam samples are directly used as supercapacitor electrodes, and S0.5-6 h-EW shows the best electrochemical performance with a specific capacity of 159 mAh g^-1 at 0.5 A g^-1, which is close to the theoretical value of 212 mAh g^-1 for Co₁₁(HPO₃)₈(OH)₆, and it is the largest reported value so far. The excellent capacitive behavior of S0.5-6 h-EW is ascribed to the 3D porous nanowire bundles directly grown on a Ni foam collector without an additive and a binder, as well as to the doping of Ni into the cobalt phosphite. The S0.5-6 h-EW//activated carbon asymmetrical supercapacitor shows a maximum energy density of 58.7 Wh kg^-1 at a power density of 532 W kg^-1 and good cycling stability with the capacity retention of 90.5% after 10 000 charging-discharging cycles at 5.5 A g^-1.

One-pot synthesis of nickel-cobalt hydroxyfluorides nanowires with ultrahigh energy density for an asymmetric supercapacitor

A novel and unique nickel-cobalt hydroxyfluorides (NiCo-HF) nanowires material is fabricated by one-pot solvothermal synthesis method for asymmetric supercapacitor. The synthesis mechanism and factors that influence the formation of the NiCo-HF nanowires have been further discussed. The as-prepared NiCo-HF electrode exhibits a high specific capacitance of 3,372.6 F g^-1, and the capacitance retention of 94.3% can be achieved at a high current density of 20 A g^-1 after 10,000 cycles. The outstanding electrochemical performance of the electrode can be attributed to the synergistic effect of the nanowires morphology and complicated redox process of active material. Furthermore, an asymmetric supercapacitor assembled with NiCo-HF nanowires as positive electrode and activated carbon as the negative electrode shows an ultrahigh energy density of 83.6 Wh kg^-1 at a power density of 379.4 W kg^-1 and an excellent cycling stability with 86.3% capacitance retention after 10,000 cycles, indicating that this novel material has great promise for potential application in energy storage device.

Aqueous Binder Enhanced High-Performance GeP5 Anode for Lithium-Ion Batteries

GeP5 is a recently reported new anode material for lithium ion batteries (LIBs), it holds a large theoretical capacity about 2300 mAh g-1, and a high rate capability due to its bi-active components and superior conductivity. However, it undergoes a large volume change during its electrochemical alloying and de-alloying with Li, a suitable binder is necessary to stable the electrode integrity for improving cycle performance. In this work, we tried to apply aqueous binders LiPAA and NaCMC to GeP5 anode, and compared the difference in electrochemical performance between them and traditional binder PVDF. As can be seen from the test result, GeP5 can keep stable in both common organic solvents and proton solvents such as water and alcohol solvents, it meets the application requirements of aqueous binders. The electrochemistry results show that the use of LiPAA binder can significantly improve the initial Coulombic efficiency, reversible capacity, and cyclability of GeP5 anode as compared to the electrodes based on NaCMC and PVDF binders. The enhanced electrochemical performance of GeP5 electrode with LiPAA binder can be ascribed to the unique high strength long chain polymer structure of LiPAA, which also provide numerous uniform distributed carboxyl groups to form strong ester groups with active materials and copper current collector. Benefit from that, the GeP5 electrode with LiPAA can also exhibit excellent rate capability, and even at low temperature, it still shows attractive electrochemical performance.

Electrocatalytic oxidation of benzyl alcohol for simultaneously promoting H2 evolution by a Co0.83Ni0.17/activated carbon electrocatalyst

Co_0.83Ni_0.17 alloy nanoparticles on activated carbon were successfully fabricated by a simple thermal-treatment method, as electrocatalyst exhibiting superior HER, OER and electrocatalytic oxidation activity toward benzyl alcohol.

Zn-doped SnO2 nano-urchin-enriched 3D carbonaceous framework for supercapacitor application

Distribution of nano-urchin spheres over the RGO sheets.