Unique Core-Shell Nanorod Arrays with Polyaniline Deposited into Mesoporous NiCo2O4 Support for High-Performance Supercapacitor Electrodes

Elucidating the performance of hexamethylene tetra-amine interlinked bimetallic NiCo-MOF for efficient electrochemical hydrogen and oxygen evolution

Bimetallic metal-organic frameworks (MOFs) play a significant role in the electrocatalysis of water due to their large surface area and availability of increased numbers of pores. For the inaugural time, we examine the effectiveness of a hexamethylene tetra-amine (HMT)-induced 3D NiCo-MOF-based nanostructure as a potent bifunctional electrocatalyst with superior performance for overall water splitting in alkaline environments. The structural, morphological, and electrochemical properties of the as-synthesized bifunctional catalyst were examined thoroughly before analyzing its behavior towards electrochemical water splitting. The HMT-based NiCo-MOF demonstrated small overpotential values of 274 mV and 330 mV in reaching a maximum current density of 30 mA cm-2 for hydrogen and oxygen evolution mechanisms, respectively. The Tafel parameter also showed favorable HER/OER reaction kinetics, with slopes of 78 mV dec-1 and 86 mV dec-1 determined during the electrochemical evaluation. Remarkably, the NiCo-HMT electrode exhibited a double-layer capacitance of 4 mF cm-2 for hydrogen evolution and 23 mF cm-2 for oxygen evolution, while maintaining remarkable stability even after continuous operation for 20 hours. This research offers a valuable blueprint for implementing a cost-effective and durable MOF-based bifunctional catalytic system that has proven to be effective for complete water splitting. Decomposition of water under higher current densities is crucial for effective long-term generation and commercial consumption of hydrogen.

Ni0.5Co0.5S nano-chains: a high-performing intercalating pseudocapacitive electrode in asymmetric supercapacitor (ASC) mode for the development of large-scale energy storage devices

Grid-scale energy storage solutions are necessary for using renewable energy sources efficiently. A supercapattery (supercapacitor + battery) has recently been introduced as a new variety of hybrid devices that engage both capacitive and faradaic charge storage processes. Nano-chain architectures of Ni0.5Co0.5S electrode materials consisting of interconnected nano-spheres are rationally constructed by tailoring the surface structure. Nano-chains of the bimetallic sulfide Ni0.5Co0.5S are presented to have a superior charge storage capacity. The Ni0.5Co0.5S nano-chain electrode presents a capacitance of 2001.6 F g-1 at 1 mV s-1, with a specific capacity of 267 mA h g-1 (1920 F g-1) at 1 A g-1 in 4 M KOH aqueous electrolyte through the galvanostatic charge-discharge (GCD) method. The reason behind the high charge storage capacity of the materials is the predominant redox-mediated diffusion-controlled pseudocapacitive mechanism coupled with surface capacitance (electrosorption), as the surface (outer) and intercalative (inner) charges stored by the Ni0.5Co0.5S electrodes are close to 46.0% and 54.0%, respectively. Additionally, a Ni0.5Co0.5S//AC two electrode full cell operating in asymmetric supercapacitor cell (ASCs) mode in 4 M KOH electrolyte exhibits an impressive energy density equivalent to 257 W h kg-1 and a power density of 0.73 kW kg-1 at a current rate of 1 A g-1.

Construction and application of NiCo2O4@MnS composite with hierarchical structure for hybrid supercapacitor

The development of an electrochemical energy storage system with exceptional performance is an important way to address the energy crisis and environmental pollution of the modem world. In this study, an NiCo2O4@MnS composite with a unique hierarchical structure has been successfully synthesized on an NF substrate using the hydrothermal-electrodeposition method. The results indicate that NiCo2O4@MnS possesses superior specific capacitance and excellent cycling stability. At a current density of 2 A g-1, its specific capacitance can reach 2100 F g-1, while the capacitance retention is still 76% after 10 000 cycles at 10 A g-1. Moreover, when the current density is 1 A g-1, the assembled NiCo2O4@MnS//AC device can deliver a specific capacitance of 203 F g-1, and the energy density is up to 55 W h kg-1 at a power density of 697 W kg-1. These outstanding electrochemical properties of NiCo2O4@MnS can be ascribed to the increase in ion diffusion, specific surface area and electronic conductivity due to its unique hierarchical structure and introduction of MnS.

A 3D stacked corrugated pore structure composed of CoNiO2 and polyaniline within the tracheids of wood-derived carbon for high-performance asymmetric supercapacitors

A novel 3D stacked corrugated pore structure of polyaniline (PANI)/CoNiO₂@activated wood-derived carbon (AWC) has been successfully constructed to prepare high-performance electrode materials for supercapacitors. AWC functions as a supporting framework that provides ample attachment sites for the loaded active materials. The CoNiO₂ nanowire substrate, consisting of 3D stacked pores, not only serves as a template for subsequent PANI loading, but also acts as an effective buffer to mitigate the volume expansion of the PANI during ionic intercalation. The distinctive corrugated pore structure of PANI/CoNiO₂@AWC facilitates electrolyte contact and significantly enhances the electrode material properties. The PANI/CoNiO₂@AWC composite materials exhibit excellent performance (14.31F cm^-2 at 5 mA cm^-2) and superior capacitance retention (80% from 5 to 30 mA cm^-2), owing to the synergistic effect among their components. Finally, PANI/CoNiO₂@ AWC//reduced graphene oxide (rGO)@AWC asymmetric supercapacitor is assembled, which has a wide operating voltage (0 ∼ 1.8 V), high energy density (4.95 mWh cm^-3 at 26.44 mW cm^-3) and cycling stability (90.96% after 7000 cycles).

Transferring and Retaining of Different Polyaniline Nanofeatures via Electrophoretic Deposition for Enhanced Sensing Performance

Nanofeatured polyaniline (PANI) electrodes have demonstrated impressive sensing performance due to the enhanced electrolyte diffusion and ion transport. However, the retaining of these nanostructures on substrates via electrophoretic deposition (EPD) faces an insurmountable challenge from the involved dedoping process. Here, camphorsulfonic acid is utilized with high steric effects to dope PANI (PANI-CSA) that can be directly used EPD without involving a dedoping process. Five different nanofeatures (sea cucumber-like, nanofiber, amorphous, nanotube, and nanorod) are synthesized, and they have been all successfully transferred onto indium tin oxide substrate in a formic acid/acetonitrile system, namely a morphology memory effect. The mechanism of retaining these nanofeatures is revealed, which is realized via the processes of dissolution of PANI-CSA, codoping and solvation, and reassembly of basic units into the original nanofeature. The enhanced protonation level by the codoping of formic acid and solvation of acetonitrile plays the key role in retaining these nanofeatures. This method is also applicable to transfer PANI/gold nanorod composites (PANI-CSA/AuNRs). The PANI-CSA/AuNRs electrode as an ascorbic acid sensor has shown an excellent sensing performance with a sensitivity up to 872.7 µA mm^-1 cm^-2 and a detection limit of as low as 0.18 × 10^-6 m.

Facile Synthesis of NiCo2O4 Nanowire Arrays/Few-Layered Ti3C2-MXene Composite as Binder-Free Electrode for High-Performance Supercapacitors

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.

Continuously Reinforced Carbon Nanotube Film Sea-Cucumber-like Polyaniline Nanocomposites for Flexible Self-Supporting Energy-Storage Electrode Materials

The charge storage mechanism and capacity of supercapacitors completely depend on the electrochemical and mechanical properties of electrode materials. Herein, continuously reinforced carbon nanotube film (CNTF), as the flexible support layer and the conductive skeleton, was prepared via the floating catalytic chemical vapor deposition (FCCVD) method. Furthermore, a series of novel flexible self-supporting CNTF/polyaniline (PANI) nanocomposite electrode materials were prepared by cyclic voltammetry electrochemical polymerization (CVEP), with aniline and mixed-acid-treated CNTF film. By controlling the different polymerization cycles, it was found that the growth model, morphology, apparent color, and loading amount of the PANI on the CNTF surface were different. The CNTF/PANI-15C composite electrode, prepared by 15 cycles of electrochemical polymerization, has a unique surface, with a "sea-cucumber-like" 3D nanoprotrusion structure and microporous channels formed via the stacking of the PANI nanowires. A CNTF/PANI-15C flexible electrode exhibited the highest specific capacitance, 903.6 F/g, and the highest energy density, 45.2 Wh/kg, at the current density of 1 A/g and the voltage window of 0 to 0.6 V. It could maintain 73.9% of the initial value at a high current density of 10 A/g. The excellent electrochemical cycle and structural stabilities were confirmed on the condition of the higher capacitance retention of 95.1% after 2000 cycles of galvanostatic charge/discharge, and on the almost unchanged electrochemical performances after 500 cycles of bending. The tensile strength of the composite electrode was 124.5 MPa, and the elongation at break was 18.9%.

Hybrid Structures of Sisal Fiber Derived Interconnected Carbon Nanosheets/MoS2/Polyaniline as Advanced Electrode Materials in Lithium-Ion Batteries

In this work, we designed and successfully synthesized an interconnected carbon nanosheet/MoS₂/polyaniline hybrid (ICN/MoS₂/PANI) by combining the hydrothermal method and in situ chemical oxidative polymerization. The as-synthesized ICNs/MoS₂/PANI hybrid showed a "caramel treat-like" architecture in which the sisal fiber derived ICNs were used as hosts to grow "follower-like" MoS₂ nanostructures, and the PANI film was controllably grown on the surface of ICNs and MoS₂. As a LIBs anode material, the ICN/MoS₂/PANI electrode possesses excellent cycling performance, superior rate capability, and high reversible capacity. The reversible capacity retains 583 mA h/g after 400 cycles at a high current density of 2 A/g. The standout electrochemical performance of the ICN/MoS₂/PANI electrode can be attributed to the synergistic effects of ICNs, MoS₂ nanostructures, and PANI. The ICN framework can buffer the volume change of MoS₂, facilitate electron transfer, and supply more lithium inset sites. The MoS₂ nanostructures provide superior rate capability and reversible capacity, and the PANI coating can further buffer the volume change and facilitate electron transfer.

Electrochemical deposition of highly hydrophobic perfluorinated polyaniline film for biosensor applications

Highly hydrophobic perfluorinated polyaniline thin films with water contact angle of ∼140° and low internal resistance properties are prepared through electrochemical polymerization. UV-visible spectroscopy demonstrates a gradual evolution of the polaron band which indicates the electronic conductive properties of the polymers. Simultaneous possession of the water-repelling property and electron conductivity for superhydrophobic perfluorinated polyaniline leads to a unique polymer that is suitable as a solid contact in ion-selective electrodes for in situ monitoring of pH changes during early stages of inflammation and septic shock. The superhydrophobic properties should suppress interactions with interfering salts and proteins, and the sensitivity towards protons could be monitored by measuring the phase boundary potential, which depends on the H⁺ concentration. The potentiometric measurements demonstrate a fast response with a slope of 44.4 ± 0.2 mV per unit pH. The presence of interfering ions and/or human serum albumin does not have any significant effect on the performance of the perfluorinated film. Moreover, it is demonstrated that the response of the perfluorinated film is reversible within the biomedically relevant pH range from 4.0 to 8.5, and stable over time.

Simultaneous possession of the water-repelling property and electron conductivity for superhydrophobic perfluorinated polyaniline leads to a unique polymer that is suitable for in situ monitoring of pH changes during early stages of inflammation and septic shock.

PANI/MoO3−x shell–core composites with enhanced rate and cycling performance for flexible solid-state supercapacitors and electrochromic applications

PANI/MoO_3−x shell–core composites show enhanced electrochemical and electrochromic performance as a bi-functional electrode material for flexible solid-state supercapacitors, attributed to a synergistic effect from PANI nanorods and MoO_3−x nanobelts.

Morphological Modulation of Conducting Polymer Nanocomposites with Nickel Cobaltite/Reduced Graphene Oxide and Their Subtle Effects on the Capacitive Behaviors

This work reports on the urchin-like architecture-based nickel cobaltite (NiCo₂O₄)/reduced graphene oxide (rGO)/conducting polymer [polyaniline (PANI) or polypyrrole (PPy)] nanocomposites prepared through a hydrothermal synthesis procedure, followed by in situ polymerization techniques. Subsequently, these materials are subjected to electrochemical investigation to search for promising electrode materials for energy storage applications. Interestingly, the morphology of NiCo₂O₄ varies upon the addition of rGO as well as nitrogen-doped rGO (N-rGO). When it is composite with rGO, it forms an urchin-like architecture, and with N-rGO, it forms nanoparticle structures having a diameter of 90 ± 10 nm. Further, these nanostructures are intricately coated by conducting polymers (such as PANI and PPy) as evidenced from the field emission scanning electron microscopy and high-resolution transmission electron microscopy observations, and the overall shape does not alter after the modification. All composites are investigated thoroughly by Fourier transform infrared, Raman, X-ray powder diffraction, and X-ray photoelectron spectroscopies to confer the formation and presence of polymers. The NiCo₂O₄/rGO/PPy nanocomposites exhibit an excellent specific capacitance of 1547 ± 5 F/g at a current density of 0.5 A/g, a better energy density of 34.37 ± 0.11 W h/kg at 0.5 A/g, a notable power density of 99.98 ± 0.31 W/kg at 0.5 A/g, and retains its 94 ± 1% specific capacitance after 5000 charge-discharge cycles. The uniform coating over the urchin-like architecture by conducting polymers constructs a typical morphology, and possibly, it is the key factor behind gaining such superior electrochemical behavior owing to (a) the enhancement of surface area and (b) the combination of double-layer capacitive and pseudocapacitive properties. Furthermore, a symmetric flexible supercapacitor device made of NiCo₂O₄/rGO/PPy nanocomposites provides superior electrochemical behavior.

A multi-interfacial FeOOH@NiCo2O4 heterojunction as a highly efficient bifunctional electrocatalyst for overall water splitting

Electrocatalytic water decomposition is the key to sustainable energy, and the design and synthesis of cost-effective electrocatalysts is the main objective of electrocatalytic water splitting. In this paper, multi-interfacial FeOOH@NiCo2O4 hybrid nanoflowers are prepared through a two-step hydrothermal reaction. In such heterostructures, NiCo2O4 nanoflowers are coated with a layer of FeOOH nanoparticles. In addition, the obtained electrocatalyst could provide abundant electroactive sites and the formation of FeOOH@NiCo2O4 nanointerfaces can also improve the charge transfer rate. As a result, under the HER and OER conditions, the prepared catalysts show an outstanding electrocatalytic performance. Moreover, in a two-electrode water splitting system, the FeOOH@NiCo2O4 heterostructure, as a dual-function electrocatalyst, needs a cell voltage of only 1.58 V at a current density of 10 mA cm-2. This study provides a facile and feasible method to construct different kinds of heterostructures as bifunctional electrocatalysts with multiple interfaces by a simple hydrothermal method.

NiCo Metal-Organic Framework and Porous Carbon Interlayer-Based Supercapacitors Integrated with a Solar Cell for a Stand-Alone Power Supply System

Nickel cobalt-metal-organic framework (NiCo-MOF), with a semihollow spherical morphology composed of rhombic dodecahedron nanostructures, was synthesized using a scalable and facile wet chemical route. Such a structure endowed the material with open pores, which enabled rapid ion ingress and egress, and the high effective surface area of the MOF allowed the uptake and release of a large number of electrolyte ions during charge-discharge. By combining this NiCo-MOF cathode with a highly porous carbon (PC) anode (derived from the naturally grown and abundantly available bio-waste, namely, palm kernel shells), the resulting PC//NiCo-MOF supercapacitor using an aqueous potassium hydroxide (KOH) electrolyte delivered a capacitance of 134 F g^-1, energy and power densities of 24 Wh kg^-1 and 0.8 kW kg^-1 at 1 A g^-1, respectively, over an operational voltage window of 1.6 V. By employing thin interlayers of PC coated over a Whatman filter paper (PC@FP), the modified supercapacitor configuration of PC/PC@FP//PC@FP/NiCo-MOF delivered greatly enhanced performance. This cell delivered a capacitance of 520 F g^-1 and an energy density of 92 Wh kg^-1, improved by nearly 4-fold, compared to the analogous supercapacitor without the interlayers (at the same power and current densities and voltage window), thus evidencing the role of the cost-effective, electrically conducting porous carbon interlayers in amplifying the supercapacitor's energy storage capabilities. Further, illumination of white light-emitting diodes (LEDs) using a three-series configuration and the photocharging of this supercapacitor with a solution-processed solar cell are also demonstrated. The latter confirms its ability to function as a stand-alone power supply system for electronic/computing devices, which can even operate under medium lighting conditions.

One-Dimensional NiSe-Se Hollow Nanotubular Architecture as a Binder-Free Cathode with Enhanced Redox Reactions for High-Performance Hybrid Supercapacitors

Selenium-enriched nickel selenide (NiSe-Se) nanotubes supported on highly conductive nickel foam (NiSe-Se@Ni foam) were synthesized using chemical bath deposition with the aid of lithium chloride as a shape-directing agent. The uniformly grown NiSe-Se@Ni foam, with its large number of electroactive sites, facilitated rapid diffusion and charge transport. The NiSe-Se@Ni foam electrode exhibited a superior specific capacitance value of 2447.46 F g^-1 at a current density value of 1 A g^-1 in 1 M aqueous KOH electrolyte. Furthermore, a high-energy-density pouch-type hybrid supercapacitor (HSC) device was fabricated using the proposed NiSe-Se@Ni foam as the positive electrode, activated carbon on Ni foam as the negative electrode, and a filter paper separator soaked in 1 M KOH electrolyte solution. The HSC delivered a specific capacitance of 84.10 F g^-1 at a current density of 4 mA cm^-2 with an energy density of 29.90 W h kg^-1 at a power density of 594.46 W kg^-1 for an extended operating voltage window of 1.6 V. In addition, the HSC exhibited excellent cycling stability with a capacitance retention of 95.09% after 10,000 cycles, highlighting its excellent potential for use in the hands-on applications. The real-life practicality of the HSC was tested by using it to power a red light-emitting diode.

Core-shell nanowires of NiCo2O4@α-Co(OH)2 on Ni foam with enhanced performances for supercapacitors

The composites of NiCo₂O₄ with unique structures are extensively explored as promising electrodes. In this work, core-shell structured nanowires anchored on nickel foam are synthesized by the hydrothermal synthesis of NiCo₂O₄ as core and subsequent electrodeposition of α-Co(OH)₂ as shell. The core-shell composites exhibit enhanced electrochemical performances ascribing to the synergistic reactions from both materials, showing higher specific capacitance than any single component. By changing the deposition time, the mass loading of α-Co(OH)₂ can be easily controlled. The electrochemical performances of the hybrid electrodes are diverse with the mass loading of Co(OH)₂. The optimized hybrid electrode with 3 mins electrodeposition exhibits the highest specific capacitance (1298 F g^-1 at 1 A g^-1) among all electrodes. The redox reaction is a main contributor to the total specific capacitance through electrochemical kinetics analysis. An asymmetric supercapacitor assembled by the optimized material as positive electrode and activated carbon as negative electrode can achieve a relatively high energy density of 39.7 Wh kg^-1 at a power density of 387.5 W kg^-1 (at 0.5 A g^-1) in a voltage of 1.55 V.

Porous spherical NiO@NiMoO4@PPy nanoarchitectures as advanced electrochemical pseudocapacitor materials

In this work, a rational design and construction of porous spherical NiO@NiMoO₄ wrapped with PPy was reported for the application of high-performance supercapacitor (SC). The results show that the NiMoO₄ modification changes the morphology of NiO, and the hollow internal morphology combined with porous outer shell of NiO@NiMoO₄ and NiO@NiMoO₄@PPy hybrids shows an increased specific surface area (SSA), and then promotes the transfer of ions and electrons. The shell of NiMoO₄ and PPy with high electronic conductivity decreases the charge-transfer reaction resistance of NiO, and then improves the electrochemical kinetics of NiO. At 20Ag^-1, the initial capacitances of NiO, NiMoO₄, NiO@NiMoO₄ and NiO@NiMoO₄@PPy are 456.0, 803.2, 764.4 and 941.6Fg^-1, respectively. After 10,000 cycles, the corresponding capacitances are 346.8, 510.8, 641.2 and 904.8Fg^-1, respectively. Especially, the initial capacitance of NiO@NiMoO₄@PPy is 850.2Fg^-1, and remains 655.2Fg^-1 with a high retention of 77.1% at 30Ag^-1 even after 30,000 cycles. The calculation result based on density function theory shows that the much stronger Mo-O bonds are crucial for stabilizing the NiO@NiMoO₄ composite, resulting in a good cycling stability of these materials.

Facile Synthesis of Bio-Template Tubular MCo2O4 (M = Cr, Mn, Ni) Microstructure and Its Electrochemical Performance in Aqueous Electrolyte

In this project, we present a comparative study of the electrochemical performance for tubular MCo2O4 (M = Cr, Mn, Ni) microstructures prepared using cotton fiber as a bio-template. Crystal structure, surface properties, morphology, and electrochemical properties of MCo2O4 are characterized using X-ray diffraction (XRD), gas adsorption, scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), cyclic voltammetry (CV), and galvanostatic charge-discharge cycling (GCD). The electrochemical performance of the electrode made up of tubular MCo2O4 structures was evaluated in aqueous 3M KOH electrolytes. The as-obtained templated MCo2O4 microstructures inherit the tubular morphology. The large-surface-area of tubular microstructures leads to a noticeable pseudocapacitive property with the excellent electrochemical performance of NiCo2O4 with specific capacitance value exceeding 407.2 F/g at 2 mV/s scan rate. In addition, a Coulombic efficiency ~100%, and excellent cycling stability with 100% capacitance retention for MCo2O4 was noted even after 5000 cycles. These tubular MCo2O4 microstructure display peak power density is exceeding 7000 W/Kg. The superior performance of the tubular MCo2O4 microstructure electrode is attributed to their high surface area, adequate pore volume distribution, and active carbon matrix, which allows effective redox reaction and diffusion of hydrated ions.

Construction of Hierarchical NiCo2O4@Ni-MOF Hybrid Arrays on Carbon Cloth as Superior Battery-Type Electrodes for Flexible Solid-State Hybrid Supercapacitors

Metal-organic frameworks (MOFs) have been considered as a class of promising electrode materials for supercapacitors owing to their large surface area, rich porosity, and variable redox sites; however, direct application of pristine MOFs in energy storage has been largely hindered by their poor electrical conductivity and stability issues. In this work, we demonstrate a facile two-step approach to address the controlled growth of Ni-MOF arrays on the surface of NiCo₂O₄ nanowires by modulating the formation reaction of MOFs. By taking advantage of the intriguing merits from the NiCo₂O₄ core and Ni-MOF shell as well as their synergistic effects, the optimized NiCo₂O₄@Ni-MOF hybrid electrode exhibits boosted electrochemical performance, in terms of high specific capacity (208.8 mA h/g at 2 mA/cm²) and good rate capability. In addition, the assembled flexible solid-state HSC device based on the optimized NiCo₂O₄@Ni-MOF and activated carbon as the cathode and anode achieves a maximum energy density of 32.6 W h/kg at a power density of 348.9 W/kg without sacrificing its outstanding cycling performance (nearly 100% retention over 6000 cycles at 8 mA/cm²) and mechanical stability, outperforming most recently reported MOF-based HSC devices in an aqueous electrolyte. Our work demonstrates the possibility of exploiting novel MOF-based hybrid arrays as battery-type electrodes with enhanced electrochemical properties, which exhibits great potential in flexible energy storage devices.

Facile Synthesis of Novel V0.13Mo0.87O2.935 Nanowires With High-Rate Supercapacitive Performance

Binary metal oxides composed of molybdenum–vanadium oxides are promising candidates for supercapacitors. Here, we report the synthesis of one-dimensional V_0.13Mo_0.87O_2.935 nanowires through a facile one-step hydrothermal method. This nanowire presented a high specific capacitance of 394.6 F g⁻¹ (1 mV s⁻¹) as an electrode applied to the supercapacitor. Importantly, this electrode showed a perfect rate capability of 91.5% (2 to 10 A g⁻¹) and a continuous verified outstanding cyclic voltammetry of 97.6% after 10,000 cycles. These superior electrochemical properties make the synthesized V_0.13Mo_0.87O_2.935 nanowires a prospective candidate for high-performance supercapacitors.

Synthesis and Electrochemical Energy Storage Applications of Micro/Nanostructured Spherical Materials

Micro/nanostructured spherical materials have been widely explored for electrochemical energy storage due to their exceptional properties, which have also been summarized based on electrode type and material composition. The increased complexity of spherical structures has increased the feasibility of modulating their properties, thereby improving their performance compared with simple spherical structures. This paper comprehensively reviews the synthesis and electrochemical energy storage applications of micro/nanostructured spherical materials. After a brief classification, the concepts and syntheses of micro/nanostructured spherical materials are described in detail, which include hollow, core-shelled, yolk-shelled, double-shelled, and multi-shelled spheres. We then introduce strategies classified into hard-, soft-, and self-templating methods for synthesis of these spherical structures, and also include the concepts of synthetic methodologies. Thereafter, we discuss their applications as electrode materials for lithium-ion batteries and supercapacitors, and sulfur hosts for lithium–sulfur batteries. The superiority of multi-shelled hollow micro/nanospheres for electrochemical energy storage applications is particularly summarized. Subsequently, we conclude this review by presenting the challenges, development, highlights, and future directions of the micro/nanostructured spherical materials for electrochemical energy storage.

Core-shell nanomaterials: Applications in energy storage and conversion

Materials with core-shell structures have attracted increasing attention in recent years due to their unique properties and wide applications in energy storage and conversion systems. Through reasonable adjustments of their shells and cores, various types of core-shell structured materials can be fabricated with favorable properties that play significant roles in energy storage and conversion processes. The core-shell material can provide an effective solution to the current energy crisis. Various synthetic strategies used to fabricate core-shell materials, including the atomic layer deposition, chemical vapor deposition and solvothermal method, are briefly mentioned here. A state-of-the -art review of their applications in energy storage and conversion is summarized. The involved energy storage includes supercapacitors, li-ions batteries and hydrogen storage, and the corresponding energy conversion technologies contain quantum dot solar cells, dye-sensitized solar cells, silicon/organic solar cells and fuel cells. In addition, the correlation between the core-shell structures and their performance in energy storage and conversion is introduced, and this finding can provide guidance in designing original core-shell structures with advanced properties.

Application of Polyaniline for Li-Ion Batteries, Lithium-Sulfur Batteries, and Supercapacitors

Conducting polyaniline (PANI) exhibits interesting properties, such as high conductivity, reversible convertibility between redox states, and advantageous structural feature. It therefore receives ever-increasing attention for various applications. This Minireview evaluates recent studies on application of PANI for Li-ion batteries (LIBs), Li-S batteries (LSBs) and supercapacitors (SCPs). The flexible PANI is crucial for cyclability, especially for buffering the volumetric changes of electrode materials, in addition to enhancing the electron/ion transport. Furthermore, PANI can be directly used as an electroactive component in electrode materials for LIBs or SCPs and can be widely applied in LSBs due to its physically and chemically strong affinity for S and polysulfides. The evaluation of studies herein reveals significant improvements of electrochemical performance by physical/chemical modification and incorporation of PANI.