Search Results (14)

Supercapacitors (SCs) offer a potential replacement for traditional lithium-based batteries in energy-storage devices thanks to the increased power density and stable charge–discharge cycles, as well as negligible environmental impact. Given this, a vast array of materials has been explored for SCs devices. Among the materials, iron oxyhydroxide (FeOOH) has gained significant attention in SC devices, owing to its superior specific capacitance, stability, eco-friendliness, abundance, and affordability. However, FeOOH has certain limitations that impact its energy storage capabilities and thus implicate the need for optimizing its structural, crystal, electrical, and chemical properties. This review delves into the latest advancements in FeOOH-based materials for SCs, exploring factors that impact their electrochemical performance. To address the limitations of FeOOH’s materials, several strategies have been developed, which enhance the surface area and facilitate rapid electron transfer and ion diffusion. In this review, composite materials are also examined for their synergistic effects on supercapacitive performance. It investigates binary, ternary, and quaternary Fe-based hydroxides, as well as layered double hydroxides (LDHs). Promising results have been achieved with binder-free Fe-based binary LDH composites featuring unique architectures. Furthermore, the analysis of the asymmetric cell performance of FeOOH-based materials is discussed, demonstrating their potential exploitation for high energy-density SCs that could potentially provide an effective pathway in fabricating efficient, cost-effective, and practical energy storage systems for future exploitations in devices. This review provides up-to-date progress studies of novel FeOOH’s based electrodes for SCs applications. Full article

With the flourishing development of the new energy automobile industry, developing novel electrode materials to balance the capacity between cathode and anode is a challenge for hybrid supercapacitors. In comparison to conventional inorganic materials, metal–organic frameworks materials offer higher porosity and greater surface area for use in supercapacitors. Herein, we proposed a facile one–pot solvothermal technique to synthesize an Fe(BPDC) nanosheet array on Ni foam, which we then applied as a binder–free cathode for a supercapacitor. The solvothermal time was adjusted to ensure a desirable morphology of the final product. Benefitting from the impressive nanosheet morphology, to a great extent, Fe(BPDC) has solved the problem of volume expansion of Fe–based electrode materials during cycling, and exhibits brilliant electrochemical performances, i.e., high specific capacitance (17.54 F/cm² at 1 mV/s) and satisfactory cycle performance (129% retention after 10,000 cycles). Furthermore, Fe(BPDC) and activated carbon (AC) have been chosen to assemble a hybrid supercapacitor (namely Fe(BPDC)//AC), delivering an energy density of 45.64 Wh/kg at the power density of 4919.6 W/kg with 87.05% capacitance retention after 10,000 cycles. These brilliant results prove that Fe(BPDC) material has great potential as the cathode of supercapacitors. Full article

The development of battery-type electrode materials with hierarchical nanostructures has recently gained considerable attention in high-rate hybrid supercapacitors. For the first time, in the present study novel hierarchical CuMn₂O₄ nanosheet arrays (NSAs) nanostructures are developed using a one-step hydrothermal route on a nickel foam substrate and utilized as an enhanced battery-type electrode material for supercapacitors without the need of binders or conducting polymer additives. X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques are used to study the phase, structural, and morphological characteristics of the CuMn₂O₄ electrode. SEM and TEM studies show that CuMn₂O₄ exhibits a nanosheet array morphology. According to the electrochemical data, CuMn₂O₄ NSAs give a Faradic battery-type redox activity that differs from the behavior of carbon-related materials (such as activated carbon, reduced graphene oxide, graphene, etc.). The battery-type CuMn₂O₄ NSAs electrode showed an excellent specific capacity of 125.56 mA h g⁻¹ at 1 A g⁻¹ with a remarkable rate capability of 84.1%, superb cycling stability of 92.15% over 5000 cycles, good mechanical stability and flexibility, and low internal resistance at the interface of electrode and electrolyte. Due to their excellent electrochemical properties, high-performance CuMn₂O₄ NSAs-like structures are prospective battery-type electrodes for high-rate supercapacitors. Full article

The development of responsive materials in a predictable manner is high on the list of the material industry’s trends. In this work, responsive Ag@NiCo₂O₄ nanowires were, firstly, anchored on N-doped carbon cloth (NC) and, then, employed as array electrodes for a nonenzymatic glucose-sensing application. The results showed that the highly conductive NiCo₂O₄ nanowires supported Ag nanoparticles and exhibited high conductivity and electrocatalytic properties. The fully exposed crystalline planes of Ag nanoparticles provided more active surface sites. As a result, the assembled Ag@NiCo₂O₄-NC electrodes for the glucose-sensing evaluation delivered a selectivity of 2803 μA mM⁻¹ cm⁻² and a detection limit of 1.065 μM, which outperformed the literature-reported Ag- and NiCo₂O₄-based glucose-sensing catalysts. Full article

Herein, a 3D hierarchical structure is constructed by growing NiCo₂O₄ nanowires on few-layer Ti₃C₂ nanosheets using Ni foam (NF) as substrate via simple vacuum filtration and solvothermal treatment. Ti₃C₂ nanosheets are directly anchored on NF surface without binders or surfactants, and NiCo₂O₄ nanowires composed of about 15 nm nanoparticles uniformly grow on Ti₃C₂/NF skeleton, which can provide abundant active sites and ion diffusion pathways for enhancing electrochemical performance. Benefiting from the unique structure feature and the synergistic effects of active materials, NiCo₂O₄/Ti₃C₂ exhibits a high specific capacitance of 2468 F g⁻¹ at a current density of 0.5 A g⁻¹ and a good rate performance. Based on this, an asymmetric supercapacitor (ASC) based on NiCo₂O₄/Ti₃C₂ as positive electrode and activated carbon (AC)/NF as negative electrode is assembled. The ASC achieves a high specific capacitance of 253 F g⁻¹ at 1 A g⁻¹ along with 91.5% retention over 10,000 cycles at 15 A g⁻¹. Furthermore, the ACS presents an outstanding energy density of 90 Wh kg⁻¹ at the power density of 2880 W kg⁻¹. This work provides promising guidance for the fabrication of binder-free, free-standing and hierarchical composites for energy storage application. Full article

The morphology, microstructure as well as the orientation of cathodic materials are the key issues when preparing high-performance aqueous zinc-ion batteries (ZIBs). In this paper, binder-free electrode Mn(OH)₂ nanowire arrays were facilely synthesized via electrodeposition. The nanowires were aligned vertically on a carbon cloth. The as-prepared Mn(OH)₂ nanowire arrays were used as cathode to fabricate rechargeable ZIBs. The vertically aligned configuration is beneficial to electron transport and the free space between the nanowires can provide more ion-diffusion pathways. As a result, Mn(OH)₂ nanowire arrays yield a high specific capacitance of 146.3 Ma h g⁻¹ at a current density of 0.5 A g⁻¹. They also demonstrates ultra-high diffusion coefficients of 4.5 × 10⁻⁸~1.0 × 10⁻⁹ cm² s⁻¹ during charging and 1.0 × 10⁻⁹~2.7 × 10⁻¹¹ cm⁻² s⁻¹ during discharging processes, which are one or two orders of magnitude higher than what is reported in the studies. Furthermore, the rechargeable Zn//Mn(OH)₂ battery presents a good capacity retention of 61.1% of the initial value after 400 cycles. This study opens a new avenue to boost the electrochemical kinetics for high-performance aqueous ZIBs. Full article

It is of great significance to design electrochemical energy conversion and storage materials with excellent performance to fulfill the growing energy demand. Bimetallic cobalt/nickel-based electrode materials exhibit excellent electrical conductivity compared to mono oxides. However, their potential as electrode materials for high-performance supercapacitors (SCs) is limited because of their poor cycling stability and high-capacity fading. This work demonstrates the synthesis of binder-free bimetallic NiCo₂O₄ nano-needles supported on CC (NCO@CC) via a facile and scalable hydrothermal process. Excellent electrical conductivity and interconnected nanostructure of NCO@CC nano-needles provide the fast transfer of electrons with numerous channels for ion diffusion. Owing to such features, the binder-free NCO@CC electrode for SC discloses excellent specific capacitance (1476 Fg⁻¹ at 1.5 Ag⁻¹) with 94.25% capacitance retention even after 5000 cycles. From these outstanding electrochemical performances, it can be inferred that NCO@CC nano-needle array-structured electrodes may be potential candidates for SC applications. Full article

Vertically aligned Fe, S, and Fe-S doped anatase TiO₂ nanotube arrays are prepared by an electrochemical anodization process using an organic electrolyte in which lactic acid is added as an additive. In the electrolyte, highly ordered TiO₂ nanotube layers with greater thickness of 12 μm, inner diameter of approx. 90 nm and outer diameter of approx. 170 nm are successfully obtained. Doping of Fe, S, and Fe-S via simple wet impregnation method substituted Ti and O sites with Fe and S, which leads to enhance the rate performance at high discharge C-rates. Discharge capacities of TiO₂ tubes increased from 0.13 mAh cm⁻²(bare) to 0.28 mAh cm⁻² for Fe-S doped TiO₂ at 0.5 C after 100 cycles with exceptional capacity retention of 85 % after 100 cycles. Owing to the enhancement of thermodynamic and kinetic properties by doping of Fe-S, Li-diffusion increased resulting in remarkable discharge capacities of 0.27 mAh cm⁻² and 0.16 mAh cm⁻² at 10 C, and 30 C, respectively. Full article

The advantage of low resistivity and inactive binders makes binder-free electrode an excellent candidate for high-performance energy devices. A simple hydrothermal method was used to fabricate M₁₁(HPO₃)₈(OH)₆ (M: Ni and Co) (MHP) arrays combined with activated carbon fabric (ACF) without binder. The structures of MHP can be easily tuned from bouquets to nano-sheets by the concentration of NaH₂PO₂. The MHP/ACF composite materials with different structures showed the typical battery-type characteristic of anodic electrodes. In a three-electrode cell configuration, the MHP nano-sheet arrays/ACF composite has a higher capacity, of 1254 F/g, at a scan rate of 10 mA/cm² and shows better cycling stability: 84.3% remaining specific capacity after 1000 cycles of charge-discharge measurement. The composite is highly flexible, with almost the same electrochemical performance under stretching mode. The MHP/ACF composite@ACF hybrid supercapacitor can deliver the highest energy density, of 34.1 Wh·kg⁻¹, and a power density of 722 W·kg⁻¹ at 1 A·g⁻¹. As indicated by the results, MHP/ACF composite materials are excellent binder-free electrodes, candidates for flexible high-performance hybrid super-capacitor devices. Full article

SnO₂, a typical transition metal oxide, is a promising conversion-type electrode material with an ultrahigh theoretical specific capacity of 1494 mAh g⁻¹. Nevertheless, the electrochemical performance of SnO₂ electrode is limited by large volumetric changes (~300%) during the charge/discharge process, leading to rapid capacity decay, poor cyclic performance, and inferior rate capability. In order to overcome these bottlenecks, we develop highly ordered SnO₂ nanopillar array as binder-free anodes for LIBs, which are realized by anodic aluminum oxide-assisted pulsed laser deposition. The as-synthesized SnO₂ nanopillar exhibit an ultrahigh initial specific capacity of 1082 mAh g⁻¹ and maintain a high specific capacity of 524/313 mAh g⁻¹ after 1100/6500 cycles, outperforming SnO₂ thin film-based anodes and other reported binder-free SnO₂ anodes. Moreover, SnO₂ nanopillar demonstrate excellent rate performance under high current density of 64 C (1 C = 782 mA g⁻¹), delivering a specific capacity of 278 mAh g⁻¹, which can be restored to 670 mAh g⁻¹ after high-rate cycling. The superior electrochemical performance of SnO₂ nanoarray can be attributed to the unique architecture of SnO₂, where highly ordered SnO₂ nanopillar array provided adequate room for volumetric expansion and ensured structural integrity during the lithiation/delithiation process. The current study presents an effective approach to mitigate the inferior cyclic performance of SnO₂-based electrodes, offering a realistic prospect for its applications as next-generation energy storage devices. Full article

Nanoscale engineering of regular structured materials is immensely demanded in various scientific areas. In this work, vertically oriented TiO₂ nanotube arrays were grown by self-organizing electrochemical anodization. The effects of different fluoride ion concentrations (0.2 and 0.5 wt% NH₄F) and different anodization times (2, 5, 10 and 20 h) on the morphology of nanotubes were systematically studied in an organic electrolyte (glycol). The growth mechanisms of amorphous and anatase TiO₂ nanotubes were also studied. Under optimized conditions, we obtained TiO₂ nanotubes with tube diameters of 70–160 nm and tube lengths of 6.5–45 μm. Serving as free-standing and binder-free electrodes, the kinetic, capacity, and stability performances of TiO₂ nanotubes were tested as lithium-ion battery anodes. This work provides a facile strategy for constructing self-organized materials with optimized functionalities for applications. Full article

The novel hierarchical Ni-Co sulfide nanosheet-nanotubes arrays were directly grown on Ni foam, as binder-free electrodes, have been successfully synthesized following a one-step facile hydrothermal method combined with a sulfide treatment. The initial value of the area capacitance achieved 2.28 F cm⁻² at a current density of 1 mA cm⁻². A high areal capacitance retention of 95.2% compared to activation-induced peak value is achieved after 3000 charge-discharge cycles, which is much better than counter Ni-Co oxide electrode (1.75 F cm⁻² at 1 mA cm⁻², 93.2% retention compared to activation induced peak value). The outstanding and excellent super capacitive performance is ascribed to ion-exchange reaction, which induces a flexible hollow nanotube feature and show higher conductivity, compared with Ni-Co oxide NWs. Cyclic voltammetry (CV) and Electrochemical impedance spectra (EIS) results confirmed that the synthesized electrode contains the lowest resistance at high, and at lower frequency, leading to easy penetration of electrolytes and fast transportation of electrons inside the electrode. In this proposed work, a one-step hydrothermal method has been followed, and provided for the sulfide-induced, with a noticeable electrochemical performance of nickel cobaltite compounds and supplying a promising route for high-performance supercapacitor electrodes. Full article

The development of cheap and efficient catalytic electrodes is of great importance, to promote the sluggish overall water-splitting systems associated with the large-scale application of clean and renewable energy technologies. In this work, we report the controlled synthesis of pyrite-type bimetallic Ni-doped CoS₂ nanoneedle (NN) arrays supported on stainless steel (SS) (designated as Ni_xCo_1−xS₂ NN/SS, 0 ≤ x ≤ 1) and the related compositional influence on electrocatalytic efficiencies for the oxygen and hydrogen evolution reaction (OER/HER). Impressively, the Ni_0.33Co_0.67S₂ NN/SS displays superior activity and faster kinetics for catalyzing OER (low overpotential of 286 mV at 50 mA cm⁻²; Tafel value of 55 mV dec⁻¹) and HER (low overpotential of 350 mV at 30 mA cm⁻²; Tafel value of 76 mV dec⁻¹) than those of counterparts with other Ni/Co ratios and also monometallic Ni- or Co-based sulfides, which is attributed to the optimized balance from the improved electron transfer capability, increased exposure of electrocatalytic active sites, and favorable dissipation of gaseous products over the nanoneedle surface. Furthermore, the conductive, flexible SS support and firmly attached in-situ integrated feature, result in the flexibility and remarkable long-term stability of as-prepared binder-free Ni_0.33Co_0.67S₂ NN/SS electrode. These results demonstrate element-doping could be an efficient route at the atomic level to design new materials and further optimize the surface physicochemical properties for enhancing the overall electrochemical water splitting activity. Full article

Hierarchical copper oxide @ ternary nickel cobalt sulfide (CuO/Cu₂O@NiCo₂S₄) core-shell nanowire arrays on Cu foam have been successfully constructed by a facile two-step strategy. Vertically aligned CuO/Cu₂O nanowire arrays are firstly grown on Cu foam by one-step thermal oxidation of Cu foam, followed by electrodeposition of NiCo₂S₄ nanosheets on the surface of CuO/Cu₂O nanowires to form the CuO/Cu₂O@NiCo₂S₄ core-shell nanostructures. Structural and morphological characterizations indicate that the average thickness of the NiCo₂S₄ nanosheets is ~20 nm and the diameter of CuO/Cu₂O core is ~50 nm. Electrochemical properties of the hierarchical composites as integrated binder-free electrodes for supercapacitor were evaluated by various electrochemical methods. The hierarchical composite electrodes could achieve ultrahigh specific capacitance of 3.186 F cm⁻² at 10 mA cm⁻², good rate capability (82.06% capacitance retention at the current density from 2 to 50 mA cm⁻²) and excellent cycling stability, with capacitance retention of 96.73% after 2000 cycles at 10 mA cm⁻². These results demonstrate the significance of optimized design and fabrication of electrode materials with more sufficient electrolyte-electrode interface, robust structural integrity and fast ion/electron transfer. Full article