Nickel cobalt manganese ternary carbonate hydroxide nanoflakes branched on cobalt carbonate hydroxide nanowire arrays as novel electrode material for supercapacitors with outstanding performance

Dandelion-like VSe2-embellished CuSe-Co3Se4 hollow nanotube clusters as bifunctional catalysts for high-performance alkaline hydrogen evolution and solar cells

Among the various non-precious metal catalysts that drive hydrogen evolution reactions (HERs) and dye-sensitized solar cells (DSSCs), transition metal selenides (TMSs) stand out due to their unique electronic properties and tunable morphology. Herein, the multicomponent selenide CuSe-Co3Se4@VSe2 was successfully synthesized by doping with metal element vanadium and selenization on the copper-cobalt carbonate hydroxide (CuCo-CH) template. CuSe-Co3Se4@VSe2 exhibited the dandelion-like cluster structure composed of hollow nanotubes doped with VSe2 nanoparticles. Due to the unique structure and the synergistic effect of various elements, CuSe-Co3Se4@VSe2 showed excellent alkaline HER and DSSC performances. The DSSC based on CuSe-Co3Se4@VSe2 exhibited an impressive power conversion efficiency (PCE) of 9.64 %, which was much higher than that of Pt (8.39 %). Besides, it possessed a low HER overpotential of 76 mV@10 mA cm-2 and a small Tafel slope of 88.9 mV dec-1 in 1.0 M KOH.

Controlled preparation of cobalt carbonate hydroxide@nickel aluminum layered double hydroxide core-shell heterostructure for advanced supercapacitors

Herein, we report the rational fabrication of unique core-shell nanoclusters composed of cobalt carbonate hydroxide (Co-CH) @ nickel aluminum layered double hydroxide (NiAl-LDH) on a carbon cloth (CC) substrate using a two-step hydrothermal strategy. The one-dimensional (1D) Co-CH nanowires core-shell functions as a framework for the growth of two-dimensional (2D) NiAl-LDH nanosheets, leading to the formation of a hierarchically porous core-shell heterostructure. The presence of abundant heterointerfaces enhances electrical conductivity, reduces charge transfer resistance, and facilitates ion/electron transfer. Taking full advantage of its unique nanostructure and synergistic effect of two components, the as-prepared Co-CH@NiAl-LDH hybrid material illustrates a specific capacity of 1029.4 C/g (2058.9 mC cm-2) at 1 A g-1 and good rate capability with a capacity retention of 68.5% at 20 A g-1. Additionally, the assembled Co-CH@NiAl-LDH//pine pollen-derived porous carbon (PPC) hybrid supercapacitor (HSC) delivers impressive energy and power densities of 66.2 Wh kg-1 (0.27 Wh cm-2) and 17529.7 Wh kg-1 (0.11 Wh cm-2), respectively. This device also achieves a superior capacity retention of 80.3% over 20,000 cycles. These findings prove the importance of engineering heterointerfaces in heterostructure for the promotion of energy storage performance.

Two-Dimensional Synergistic Interfacial Orientation on Tin Oxide-Reinforced Cobalt Carbonate Hydroxide Heterostructures for High-Performance Energy Storage

A hierarchical cobalt carbonate hydroxide (CCH) nanostructure with outstanding electrochemical kinetics and structural stability for energy storage is largely unknown. Herein, we report tin oxide-functionalized CCH surface-enabled unique two-dimensional (2D) interlayered heterostructures that promote high conductivity with more electroactive sites to maximize redox reactions. A simple electrodeposition technique was utilized to construct the hierarchical 2D CCH electrode, while a surface-reinforced method was employed to fabricate the 2D interlayered SnO on CCH. The fabricated SnO@CCH-8 electrode showed a maximum areal capacity of 720 mC cm-2 (specific capacitance of 515 F g-1) at a current density of 1 mA cm-2 in 3 M KOH electrolyte. The obtained results indicate that the synergetic effect of SnO in the CCH network delivers an efficient charge transfer pathway to achieve high-performance energy storage. Moreover, SnO@CCH-8//AC was devised as a hybrid supercapacitor (HSC), ensuring a maximum specific capacitance of 129 F g-1 and maximum specific energy and power of 40.25 W h kg-1 and 9000 W kg-1, respectively, with better capacitance retention (94%) even beyond 10,000 cycles. To highlight the excellent performance in real-time studies, the HSC was constructed using a coin cell and displayed to power 21 light-emitting diodes (LEDs).

Self-templated flower-like NiCoZn-carbonate hydroxide hollow nanospheres for asymmetric supercapacitors with high performance

With the increasing demand for energy resources, it is crucial to explore electrode materials with high specific capacitance and cycling stability for supercapacitors. Herein, flower-like NiCoZn-carbonate hydroxide (NiCoZn-CH) hollow nanospheres are prepared using self-templated NiCoZn-glycerate solid nanospheres through the Kirkendall effect in a solvothermal reaction. Benefiting from a flower-like morphology, NiCoZn-CH not only provides large contact areas on the electrolyte-electrode and an abundant number of active sites but also shortens the ion transportation pathway. Meanwhile, the hollow structure also improves cycling stability by relieving stresses. Furthermore, Zn2+ can accelerate the ion transfer and improve the electrochemical activity. Therefore, the Ni1Co1Zn0.25-CH electrode shows an attractive specific capacitance of 1585.2 F g-1 at 1 A g-1 and excellent cycling stability. Additionally, the asymmetric supercapacitor Ni1Co1Zn0.25-CH//AC delivers a superior cycling stability of 99.9% after 15 000 cycles at 10 A g-1 and an energy density of 33.7 W h kg-1 at a power density of 400 W kg-1. This work provides a simple and efficient route for the fabrication of various carbonate hydroxides.

Morphology Modulation and Phase Transformation of Manganese-Cobalt Carbonate Hydroxide Caused by Fluoride Doping and Its Effect on Boosting the Overall Water Electrolysis

Increasing demands for pollution-free energy resources have stimulated intense research on the design and fabrication of highly efficient, inexpensive, and stable non-noble earth-abundant metal catalysts with remarkable catalytic activity for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Morphology control of the catalysts is widely implemented as an effective strategy to change the surface atomic coordination and increase the catalytic behavior of the catalysts. In this study, we have designed a series of Mn-Co catalyts with different morphologies on the graphite paper substrate to enhance OER and HER activities in alkaline media. The prepared catalysts with different morphologies were successfully obtained by adjusting the amount of ammonium fluoride (NH₄F) in the hydrothermal process. The electrochemical tests display that the cubic-like Mn-Co catalyst with pyramids on the faces at a concentration of 0.21 M NH₄F exhibits the best activity toward both OER and HER. The cubic-like Mn-Co catalyst with pyramids on the faces showed overpotentials of 240 and 82 mV at a current density of 10 mA cm^-2 for OER and HER, respectively. Also, the cubic-like Mn-Co catalyst with pyramids on the faces required overpotentials of 319 and 216 mV to reach the current density of 100 mA cm^-2 for OER and HER, respectively. The current density of this catalyst at η = 0.32 V was 701.05 mA cm^-2 for OER, and for HER, the current density of the catalyst was 422.89 mA cm^-2 at η = 0.23 V. The Tafel slopes of the Mn-Co catalyst with cubic-like structures with pyramids on the faces were 78 and 121 mV dec^-1 for OER and HER, respectively. A two-electrode overall water electrolysis system using this bifunctional Mn-Co catalyst exhibited low cell voltages of 1.60 in the alkaline electrolyte at the standard current density of 10 mA cm^-2 with appropriate stability. These electrochemical merits exhibit the considerable potential of the cubic-like Mn-Co catalyst with pyramids on the faces for bifunctional OER and HER applications.

New nickel-rich ternary carbonate hydroxide two-dimensional porous sheets for high-performance aqueous asymmetric supercapattery

Transition metal carbonate hydroxides (M-CHs) are promising candidates for electrode materials in supercapattery, due to their low-cost preparation and high-energy features. However, they also suffer from ionic kinetics bottlenecks without efficient morphological design. Tailoring the chemical compositions and nanostructures of electrode materials to realize high performance is significant for meeting the current demand for electrical energy storage devices. Therefore, we present a simple hydrothermal method for constructing better electrochemically active M-CHs with ternary metal components and hierarchical nanostructures that are assembled by interwoven nanosheets. Benefiting from higher contents of Ni species and superior two-dimensional/three-dimensional (2D/3D) pore structures, the fabricated cobalt-nickel-zinc carbonate hydroxides with Co/Ni/Zn molar ratios of 2:3:1 (CoNiZn-231) delivered the best specific capacity of 1130.8 C g^-1 at 1 A g^-1, decent rate performance (67.2% in 1-10 A g^-1), and excellent cycling performance (92.6% over 10,000 cycles) in comparison with the majority of mono/bimetallic materials. Then, an alkaline hybrid (CoNiZn-231//activated carbon (AC)) device is developed, which shows a high energy density of 31.62 Wh kg^-1 at a power density of 646 W kg^-1 and an excellent capacity retention of 99.27% after 10,000 cycles. Herein, the rational design of trimetallic compositions and hierarchical structures of carbonate hydroxides is described, which provides good choices for the synthesis of high-performance electrode materials in electrochemical energy storage applications.

Skillful Introduction of Urea during the Synthesis of MOF-Derived FeCoNi-CH/p-rGO with a Spindle-Shaped Substrate for Hybrid Supercapacitors

A composite (FeCoNi-CH/p-rGO) with a spindle-shaped substrate is controllably prepared by combining FeCoNi carbonate hydroxide (FeCoNi-CH) and partially reduced graphite oxide (p-rGO) using a novel chemical strategy. In the synthetic process, urea is introduced as the precipitant and reducing agent. MIL-88A as a self-template is converted into a ternary-metal CH composite, maintaining the original morphology by the metal ion etching and coprecipitation method, and graphite oxide is reduced to rGO with stronger conductivity partially at the same time. The electrochemical performance of the FeCoNi-CH/p-rGO is superior to FeCoNi-CH, with a high specific capacitance (1346 F g^-1 at 0.5 A g^-1) and rate capability (55.5% at 10 A g^-1). The better electrochemical performance of the FeCoNi-CH/p-rGO composite is attributed to the pseudocapacitive energy storage capacity caused by the synergistic action of ternary-metal CH and the high conductivity of p-rGO. Meanwhile, the uniform mixture of FeOOH/activated carbon (AC) is fabricated as an anode to instead of the pure FeOOH or AC, which leads to the balancing energy density and high cycle stability of the hybrid supercapacitor (HSC). The corresponding assembled FeCoNi-CH/p-rGO//FeOOH/AC HSC exhibits a high energy density of 46.93 W h kg^-1 at 400 W kg^-1 power density and a cycle stability of 66.7% after 3000 cycles. In addition, this work also provides a facile method to fabricate metal-organic framework-derived ternary-metal CH/p-rGO composite materials, which could be applied in the fields of supercapacitors and other fields.

1D-on-1D core-shell cobalt iron selenide @ cobalt nickel carbonate hydroxide hybrid nanowire arrays as advanced battery-type supercapacitor electrode

Sluggish kinetics and poor structural stability are two main obstacles hampering the exploration of transition metal selenides (TMSs) for supercapacitor. Developing a reasonable core-shell heterostructure with unique morphology is an effective approach to resolve these issues. Herein, a core-shell cobalt iron selenide (CoFe₂Se₄) @ cobalt nickel carbonate hydroxide (CoNi-CH) heterostructure is directly fabricated on carbon cloth via an electrodeposition method followed by a hydrothermal reaction. In this well-defined heterostructure, one-dimensional (1D) CoFe₂Se₄ nanowires function as the cores and CoNi-CH nanowires as the shells, which combines the merits of highly conductive CoFe₂Se₄ for rapid electron transfer and highly electroactive CoNi-CH for multiple redox reactions. Further, the intimate interaction between CoNi-CH and CoFe₂Se₄ realizes large surface area with hierarchical network and generates rich heterointerfaces with modified the electronic structure. By virtue of its facile 1D-on-1D nanoarchitecture and synergistic effect, the CoFe₂Se₄@CoNi-CH electrode delivers a increased specific capacity of 218.6 mAh g^-1 at 1 A^-1 and enhanced rate capability (65.5% at 20 A g^-1) compared with pure CoFe₂Se₄ and CoNi-CH. Besides, a hybrid supercapacitor is established by coupling CoFe₂Se₄@CoNi-CH cathode and porous carbon anode, which enjoys a maximum energy density of 67.3 Wh kg^-1 at 765.9 W kg^-1 and prominent durability with 85.4% of capacity retention over 20,000 cycles.

Quasi-anisotropic benefits in electrospun nickel–cobalt–manganese oxide nano-octahedron as anode for lithium-ion batteries

A polyhedral Ni–Co–Mn–O nano-octahedron anode for lithium-ion batteries was synthesized, which demonstrated enhanced lithium storage properties as compared to the nanofiber counterpart.

NiAlP@Cobalt substituted nickel carbonate hydroxide heterostructure engineered for enhanced supercapacitor performance

Transitional metal phosphides with high electrical conductivity and superb physicochemical features have been recognized as ideal battery-type electrode materials for outstanding performance supercapacitors. However, their specific capacities and structural stability are needed to be enhanced for large-scale practical applications. To overcome these shortcomings, we fabricated heterostructured NiAlP@cobalt substituted nickel carbonate hydroxide (Co-NiCH) nanosheet arrays by sequential a hydrothermal reaction, a phosphorization treatment, and a second hydrothermal reaction. Profiting from its core-shell porous nanostructure and synergistic effect of NiAlP with high electrical conductivity and Co-NiCH with high redox reactivity, the resultant NiAlP@Co-NiCH electrode delivers a large specific capacity of 825.7C g^-1 at 1 A g^-1, excellent rate capability with 78.9% capacity retention and long lifespan, superior to those of pure NiAlP and Co-NiCH electrodes. Additionally, an aqueous asymmetric supercapacitor device is constructed by NiAlP@Co-NiCH and lotus pollen-derived hierarchical porous carbon, which demonstrates a large energy density of 82.3 Wh kg^-1 at a power density of 739.8 W kg^-1, and wonderful cycle stability with 88.2% capacity retention after 10,000 cycles. This work proposes a feasible strategy on construction of transitional metal phosphide-based heterojunctions for advanced asymmetric supercapacitor devices.

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.

Rational synthesis of CoFeP@nickel-manganese sulfide core-shell nanoarrays for hybrid supercapacitors

Transition metal phosphide electrodes, particularly those with unique morphologies and micro-/nanostructures, have demonstrated desirable capabilities for hybrid supercapacitor applications by virtue of their superior electrical conductivity and high electrochemical activity. Here, three-dimensional hierarchical CoFeP@nickel-manganese sulfide nanoarrays were in situ constructed on a flexible carbon cloth via a hydrothermal method, a phosphorization process, followed by an electrodeposition approach. In this smart nanoarchitecture, CoFeP nanorods grown on carbon cloth act as the conductive core for rapid electron transfer, while the nickel-manganese sulfide nanosheets decorated on the surface of CoFeP serve as the shell for efficient ion diffusion, forming a stable core-shell heterostructure with enhanced electrical conductivity. Benefiting from the synergy of the two components and the generation of a heterointerface with a modified electronic structure, The CoFeP@nickel-manganese sulfide electrodes deliver a high capacity of 260.7 mA h g^-1 at 1 A g^-1, excellent rate capability, and good cycling stability. More importantly, an aqueous hybrid supercapacitor based on CoFeP@nickel-manganese sulfide as a positive electrode and a lotus pollen-derived hierarchical porous carbon as a negative electrode is constructed to display a maximum energy density of 60.1 W h kg^-1 at 371.8 W kg^-1 and a good cycling stability of 85.7% capacitance retention after 10 000 cycles.

Porous Carbon Nanosheets Armoring 3D Current Collectors toward Ultrahigh Mass Loading for High-Energy-Density All-Solid-State Supercapacitors

The in situ growth of active materials on 3D current collectors (such as Ni foams) presents facile and efficient access to high-performance supercapacitors. However, the low surface area of current collectors limits the mass loading, microstructure, and capacitive performance of active materials thereon. Herein, we develop a novel surface modification with hierarchical N-rich carbon nanosheets on Ni foams via a simple sol-gel method. At the same time, its favorable effects on mass loading and utilization are demonstrated using NiCoMn-carbonate hydroxide (NCM) as a model active material. Specifically, the carbon modification greatly boosts the current collector's specific surface area and enables the growth of dense NCM nanoneedles with controllable mass loading ranging from 5.2 to 23.1 mg cm-2. Meanwhile, the correlation between mass loading and utilization is systematically studied, which shows the well-maintained energy storage efficiency due to the conducive surface modification. As a result, excellent performance with the ultrahigh area-specific capacity of 19.36 F cm-2 at 2 mA cm-2 in the three-electrode configuration and remarkable area-specific energy density of 1352 μW h cm-2 in the solid-state asymmetric device can be achieved, demonstrating a prospective pathway toward facile and effective current collector designs for high-energy/power-density supercapacitors.

Dual-electrocatalysis behavior of star-like zinc-cobalt-sulfide decorated with cobalt-molybdenum-phosphide in hydrogen and oxygen evolution reactions

Although important advances have been acquired in the field of electrocatalysis, the design and fabrication of highly efficient and stable non-noble earth-abundant metal catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remain a significant challenge. In this study, we have designed a superior bifunctional catalyst for OER and HER in alkaline media based on the Co-Mo-P/Zn-Co-S multicomponent heterostructure. The as-prepared multicomponent heterostructure was successfully obtained via a simple three-step hydrothermal-sulfidation-electrodeposition process consisting of star-like Co-Zn-S covered with Co-Mo-P. The structure and morphology evaluation of the prepared catalysts were performed via Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and elemental mapping techniques. The electrochemical tests show that Co-Mo-P/Co-Zn-S exhibits outstanding activity toward both OER and HER with OER overpotentials of 273 mV and 312 mV to drive the benchmark current densities of 10 and 50 mA cm^-2, respectively, with a Tafel slope of 41 mV dec^-1. In addition, the HER overpotentials of 120 mV and 165 mV were required to reach the benchmark current densities of 10 and 50 mA cm^-2, respectively, with a Tafel slope of 61.7 mV dec^-1 that outperforms most other state-of-the-art catalysts. In the case of HER, the prepared catalyst required an overpotential of 202 mV to reach the current density of 200 mA cm^-2 that was much lower than the overpotential of Pt/C (286 mV) to achieve the same current density. Co-Mo-P/Co-Zn-S also exhibits a suitable stability length of 10 h for OER and HER during the chronoamperometric tests. The superior performance of the Co-Mo-P/Co-Zn-S multicomponent heterostructure toward OER and HER may be related to the large specific surface area, accelerated mass and electron transport, and synergistic effect of multiple hybrid materials. These merits suggest that Co-Mo-P/Co-Zn-S can be considered as a promising catalyst for bi-functional OER and HER, and can be offered a great promise for future applications.

Controllable Morphology of Sea-Urchin-like Nickel-Cobalt Carbonate Hydroxide as a Supercapacitor Electrode with Battery-like Behavior

Nickel-cobalt carbonate hydroxide with a three-dimensional (3D) sea-urchin-like structure was successfully developed by the hydrothermal process. The obtained structure enables the enhancement of charge/ion diffusion for the high-performance supercapacitor electrodes. The mole ratio of nickel to cobalt plays a vital role in the densely packed sea-urchin-like structure formation and electrochemical properties. At optimized nickel/cobalt mole ratio (1:2), the highest specific capacitance of 950.2 F g^-1 at 1 A g^-1 and the excellent cycling stability of 178.3% after 3000 charging/discharging cycles at 40 mV s^-1 are achieved. This nickel-cobalt carbonate hydroxide electrode yields an energy density in the range of 42.9-15.8 Wh kg^-1, with power density in the range of 285.0-2849.9 W kg^-1. The charge/discharge mechanism at the atomic level as monitored by time-resolved X-ray absorption spectroscopy (TR-XAS) indicates that the high capacitance behavior in a nickel-cobalt carbonate hydroxide is mainly dominated by cobalt carbonate hydroxide.

High-performance asymmetric supercapacitor based on CdCO3/CdO/Co3O4 composite supported on Ni foam

A CdCO₃/CdO/Co₃O₄ composite has been prepared on nickel foam through a combined hydrothermal-annealing method. An asymmetric hybrid supercapacitor (SC) device was assembled with this composite as the positive electrode and activated carbon was the negative electrode. The SC exhibited a high specific capacitance of 84 F g⁻¹ @ 1 mA cm⁻², a maximum energy density of 26.3 W h kg⁻¹, and a power density of 2290 W kg⁻¹, along with a wide potential window of 1.5 V and long cycle life (92% after 6000 cycles). SCs assembled in series powered various light-emitting diodes and moved an electrical mini-motor.

This work presents for the first time a CdCO₃/CdO/Co₃O₄@nickel foam based supercapacitor with high both specific capacitance and energy density, a widespread potential window and a long cycle life.

Design of a Scalable Dendritic Copper@Ni2+, Zn2+ Cation-Substituted Cobalt Carbonate Hydroxide Electrode for Efficient Energy Storage

Design and fabrication of novel electrode materials with excellent specific capacitance and cycle stability are urgent for advanced energy storage devices, and the combinability of multiple modification methods is still insufficient. Herein, Ni²⁺, Zn²⁺ double-cation-substitution Co carbonate hydroxide (NiZnCo-CH) nanosheets arrays were established on 3D copper with controllable morphology (3DCu@NiZnCo-CH). The self-standing scalable dendritic copper offers a large surface area and promotes fast electron transport. The 3DCu@NiZnCo-CH electrode shows a markedly improved electrochemical performance with a high specific capacity of ∼1008 C g^-1 at 1 A g^-1 (3.2, 2.83, and 1.26 times larger than Co-CH, ZnCo-CH, and NiCo-CH, respectively) and outstanding rate capability (828.8 C g^-1 at 20 A g^-1) due to its compositional and structural advantages. Density functional theory (DFT) calculation results illustrate that cation doping adjusts the adsorption process and optimizes the charge transfer kinetics. Moreover, an aqueous hybrid supercapacitor based on 3DCu@NiZnCo-CH and rGO demonstrates a high energy density of 42.29 Wh kg^-1 at a power density of 376.37 W kg^-1, along with superior cycling performance (retained 86.7% of the initial specific capacitance after 10,000 cycles). Impressively, these optimized 3DCu@NiZnCo-CH//rGO devices with ionic liquid can be operated stably in a large potential range of 4 V with greatly enhanced energy density and power capability (110.12 Wh kg^-1 at a power density of 71.69 W kg^-1). These findings may shed some light on the rational design of transition-metal compounds with tunable architectures by multiple modification methods for efficient energy storage.

Synergistic effects of Fe and Mn dual-doping in Co3S4 ultrathin nanosheets for high-performance hybrid supercapacitors

Dopant engineering in nanostructured materials is an effective strategy to enhance electrochemical performances via regulating the electronic structures and achieving more active sites. In this work, a robust electrode based on Fe and Mn co-doped Co₃S₄ (FM-Co₃S₄) ultrathin nanosheet arrays (NSAs) on the Ni foam substrate is prepared through a facile hydrothermal method followed by a subsequent sulfurization reaction. It has been found that the incorporation of Fe ions is beneficial to higher specific capacity of the final electrode and Mn ions contribute to the excellent rate capability in the reversible redox processes. Density functional theory (DFT) calculations further verify that the Mn doping in the Co₃S₄ obviously shorten the energy gap of Co₃S₄, which favors the electrochemical performances. Due to the synergetic effects of different transition metal ions, the as-prepared FM-Co₃S₄ ultrathin NSAs exhibit a high specific capacity of 390 mAh g^-1 at 5 A g^-1, as well as superior rate capability and excellent cycling stability. Moreover, the corresponding quasi-solid-state hybrid supercapacitors constructed with the FM-Co₃S₄ ultrathin NSAs and active carbon exhibit a high energy density of 55 Wh kg^-1 at the power density of 752 W kg^-1. These findings demonstrate a new platform for developing high-performance electrodes for energy storage applications.

A high-performance asymmetric supercapacitor-based (CuCo)Se2/GA cathode and FeSe2/GA anode with enhanced kinetics matching

The performance of asymmetric supercapacitors (ASCs) is limited by the poorly matched electrochemical kinetics of available electrode materials, which generally results in reduced energy density and inadequate voltage utilization. Herein, a porous conductive graphene aerogel (GA) scaffold was decorated with copper cobalt selenide ((CuCo)Se₂) or iron selenide (FeSe₂) to construct positive and negative electrodes, respectively. The (CuCo)Se₂/GA and FeSe₂/GA electrodes exhibited high specific capacitances of 672 and 940 F g^-1, respectively, at 1 A g^-1. The capacitance contributions from the Co³⁺/Co₂⁺ and Fe³⁺/Fe²⁺ redox couple for the positive and negative electrodes were determined to elucidate the energy storage mechanism. Furthermore, the kinetics study of the two electrodes was performed, revealing b values ranging between 0.7 and 1 at various scan rates and demonstrating that the surface-controlled processes played the dominant role, leading to fast charge storage capability for both electrodes. Fabrication of an ASC device with a configuration of (CuCo)Se₂/GA//FeSe₂/GA resulted in a voltage of 1.6 V, a high energy density of 39 W h kg^-1, and a power density of 702 W kg^-1. The excellent electrochemical performances of the (CuCo)Se₂/GA and FeSe₂/GA electrodes demonstrate their potential applications in energy storage devices.

Vertically oriented Ni-MOF@Co(OH)2 flakes towards enhanced hybrid supercapacitior performance

Two dimensional (2D) materials, with ideal interlayer spacing for ion intercalation/de-intercalation, are quite appealing for hybrid supercapacitors (HSCs) in the pursuit of harvesting promising electrochemical performance. Integrating different 2D materials together is one effective strategy to achieve such goals. However, preserving the ion diffusion channel and accelerating electron transfer should be considered during the compositing process. Herein, we propose a two-step strategy to efficiently composite cobalt hydroxide (Co(OH)₂) and Ni-based MOF (Ni-MOF-24), in which a vertically oriented Ni-MOF@Co(OH)₂ array on nickel foam is obtained. The maximum specific capacitance of 1448 Fg^-1 (2 Ag^-1) is delivered by Ni-MOF@Co(OH)₂. Accordingly, a hybrid Ni-MOF@Co(OH)₂//AC HSC is thereof assembled, which outputsa high specific power of 22,400 W kg^-1 and a considerable specific energy of 45.7 Wh kg^-1.

Core-shell nanostructured Zn-Co-O@CoS arrays for high-performance hybrid supercapacitors

Although zinc oxide (ZnO) with wide distribution is one of the most attractive energy storage materials, the low electronic conductivity and insufficient active sites of bulk ZnO increase the internal resistance and reduce the capacity of electrodes for supercapacitors. Herein, CoS nanosheets are coated on the surface of heterostructured ZnO/Co₃O₄ nanowires to synthesize a core-shell Zn-Co-O@CoS electrode by a three-step method. The built-in electric field formed between ZnO and Co₃O₄ can enhance the conductivity of the composite electrode. The coating of amorphous CoS can also provide sufficient active sites and improve the chemical stability of ZnO/Co₃O₄ nanowires. As a result, the as-prepared Zn-Co-O@CoS electrode delivers a high specific capacity of 1190 C g^-1, which is 7 times higher than that of the pristine ZnO electrode. Besides, a hybrid supercapacitor (HSC) with the Zn-Co-O@CoS electrode exhibits a high energy density of 56.8 W h kg^-1 at a power density of 771.6 W kg^-1. Furthermore, we assembled a solar-charging power system by combining the HSC and monocrystalline silicon plates to prove the practicability of the device, which can power a toy electric fan successfully. This study provides an effective idea and strategy for preparing Zn-based supercapacitor electrodes with low cost and deep discharge.

3D hierarchical nanoarrays composed of NiCo–Te multilayer nanoneedles modified with Co1.29Ni1.71O4 for high-performance hybrid supercapacitors

Electrolyte ions can easily complete intercalation and deintercalation due to the multilayer structure of nanoneedles.