Carbon/MnO(2) double-walled nanotube arrays with fast ion and electron transmission for high-performance supercapacitors

Construction of modified screen-printed graphite electrode for the application in electrochemical detection of sunset yellow in food samples

The current work introduced a novel electrochemical sensor (screen-printed graphite electrode (SPGE) modified with MnO₂ nanorods anchored graphene oxide nanocomposite (MnO₂ NRs/GO) for sensitive determination of sunset yellow. The characterization of MnO₂ NRs/GO nanocomposite synthesized through a simple hydrothermal approach was determined employing varied analytical equipment like Field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Chronoamperometric measurements, differential pulse voltammetry (DPV), cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were recruited to recognize the electrochemical oxidation of sunset yellow on the MnO₂ NRs/GO/SPGE. The results of CV proved that the as-synthesized MnO₂ NRs/GO nanocomposite has a good electrocatalytic activity toward sunset yellow. The MnO₂ NRs/GO/SPGE electrode under optimized conditions using the DPV possessed a linear response for different concentrations of sunset yellow (between 0.01 and 115.0 μM) with a low limit of detection (LOD) (0.008 μM). Finally, the impressive applicability of this sensor was confirmed via real sample analysis with excellent recoveries (between 97.3 and 104.6%).

Structure-engineering of core-shell ZnCo2O4@NiO composites for high-performance asymmetric supercapacitors

The implementation of a structure-designed strategy to construct hierarchical architectures of multicomponent metal oxide-based electrode materials for energy storage devices is in the limelight. Herein, we report NiO nanoflakes impregnated on ZnCo2O4 nanorod arrays as ZnCo2O4@NiO core-shell structures on a flexible stainless-steel mesh substrate, fabricated by a simple, cost-effective and environmentally friendly reflux condensation method. The core-shell structure of ZnCo2O4@NiO is used as an electrode material in a supercapacitor as it provides a high specific surface area (134.79 m2 g-1) offering high electroactive sites for a redox reaction, reduces the electron and ion diffusion path, and promotes an efficient contact between the electroactive material and electrolyte. The binder-free ZnCo2O4@NiO electrode delivers a high specific capacitance of 882 F g-1 at 4 mA cm-2 current density and exhibits remarkable cycling stability (∼85% initial capacitance retention after 5000 charge-discharge cycles at 10 mA cm-2). The asymmetric supercapacitor device ZnCo2O4@NiO//rGO delivered a maximum energy density of 46.66 W h kg-1 at a power density of 800 W kg-1. The device exhibited 90.20% capacitance retention after 4000 cycles. These results indicate that the ZnCo2O4@NiO architecture electrode is a promising functional material for energy storage devices.

Carbon dots conjugated nanocomposite for the enhanced electrochemical performance of supercapacitor electrodes

Naturally, a combination of metal oxides and carbon materials enhances the electrochemical performance of supercapacitor (SC) electrodes. We report on two different materials with highly conductive carbon dots (CDs) and a Co0.5Ni0.5Fe2O4/SiO2/TiO2 nanocomposite with a high power density, a high specific surface area, and a nanoporous structure to improve power and energy density in energy storage devices. A simple and low-cost process for synthesizing the hybrid SC electrode material Co0.5Ni0.5Fe2O4/SiO2/TiO2/CDs, known as CDs-nanocomposite, was performed via a layer-by-layer method; then, the CDs-nanocomposite was loaded on a nickel foam substrate for SC electrochemical measurements. A comparative study of the surface and morphology of CDs, the Co0.5Ni0.5Fe2O4/SiO2/TiO2 nanocomposite and CDs-nanocomposite was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), BET surface area, and Raman spectroscopy. The synthesized CDs-nanocomposite electrode material displayed enhanced electrochemical performance, having a high specific capacitance of 913.7 F g-1 at a scan rate of 5 mV s-1 and capacitance retention of 72.2%, as well as remarkable long-life cyclic stability over 3000 cycles in the three-electrode setup and 1 M KOH electrolyte. It also demonstrated a superior energy density of 130.7 W h kg-1. The improved electrochemical behavior of the CDs-nanocomposite for SC electrodes, together with its fast and simple synthesis method, provides a suitable point of reference. Other kinds of metal oxide nanocomposites can be synthesized for use in energy storage devices.

Neatly arranged mesoporous MnO2 nanotubes with oxygen vacancies for electrochemical energy storage

Intrinsically poor conductivity, sluggish ion transfer kinetics, and limited specific area are the three main obstacles that confine the electrochemical performance of manganese dioxide in supercapacitors. Herein, one-dimensional mesoporous MnO2 nanotubes were prepared using a polycarbonate film as a template and a large number of oxygen vacancies were introduced by calcination under a N2 atmosphere. The effects of calcination temperature on the crystal structure, micro-morphology and electrochemical performance of MnO2 nanotubes were studied. The presence of oxygen vacancies increases the redox capacity of ov-MnO2-300 nanotubes, and the unique one-dimensional mesoporous structure also provides an effective channel for ion transport. Therefore, the ov-MnO2-300 nanotube has an excellent specific capacitance of 459.0 F g-1 at a current density of 1 A g-1 and also has outstanding rate performance and cycle performance. An asymmetric supercapacitor assembled with ov-MnO2-300 nanotubes as the positive electrode and graphene@MoS2 as the negative electrode delivered an energy density of 40.2 W h kg-1 at a power density of 1024 W kg-1. The excellent capacitance performance is mostly attributed to the introduction of oxygen vacancies to increase the intrinsic conductivity of MnO2, and the unique one-dimensional mesoporous nanotube structure increases the active sites of redox reactions.

A Review on Nano-/Microstructured Materials Constructed by Electrochemical Technologies for Supercapacitors

The article reviews the recent progress of electrochemical techniques on synthesizing nano-/microstructures as supercapacitor electrodes. With a history of more than a century, electrochemical techniques have evolved from metal plating since their inception to versatile synthesis tools for electrochemically active materials of diverse morphologies, compositions, and functions. The review begins with tutorials on the operating mechanisms of five commonly used electrochemical techniques, including cyclic voltammetry, potentiostatic deposition, galvanostatic deposition, pulse deposition, and electrophoretic deposition, followed by thorough surveys of the nano-/microstructured materials synthesized electrochemically. Specifically, representative synthesis mechanisms and the state-of-the-art electrochemical performances of exfoliated graphene, conducting polymers, metal oxides, metal sulfides, and their composites are surveyed. The article concludes with summaries of the unique merits, potential challenges, and associated opportunities of electrochemical synthesis techniques for electrode materials in supercapacitors.

Wearable biosensors for healthcare monitoring

Wearable biosensors are garnering substantial interest due to their potential to provide continuous, real-time physiological information via dynamic, noninvasive measurements of biochemical markers in biofluids, such as sweat, tears, saliva and interstitial fluid. Recent developments have focused on electrochemical and optical biosensors, together with advances in the noninvasive monitoring of biomarkers including metabolites, bacteria and hormones. A combination of multiplexed biosensing, microfluidic sampling and transport systems have been integrated, miniaturized and combined with flexible materials for improved wearability and ease of operation. Although wearable biosensors hold promise, a better understanding of the correlations between analyte concentrations in the blood and noninvasive biofluids is needed to improve reliability. An expanded set of on-body bioaffinity assays and more sensing strategies are needed to make more biomarkers accessible to monitoring. Large-cohort validation studies of wearable biosensor performance will be needed to underpin clinical acceptance. Accurate and reliable real-time sensing of physiological information using wearable biosensor technologies would have a broad impact on our daily lives.

Synthesis of NiGa2S4-rGO on nickel foam as advanced electrode for flexible solid-state supercapacitor with superior energy density

Pseudocapacitive electrode materials employed in supercapacitors may bring in high energy density (ED) and specific capacitance (C_sc), which are critical for their practical applications. Accordingly, logical design of advanced electrode materials is highly demanded to progress high-performance supercapacitors. Here, for the first time, we suggest a straightforward route for the synthesis of NiGa₂S₄-rGO as an advanced cathode material supported on nickel foam (NF) for employed in flexible solid-state asymmetric supercapacitors (FSASCs). Due to an abundant ratio of active sites and large surface area of the NiGa₂S₄-rGO advanced material, the as-prepared NiGa₂S₄-rGO/NF electrode illustrates considerable electrochemical properties including remarkable specific capacitance (C_sc) of 2124.34 F g^-1 with excellent rate capability of 73%, and exceptional durability, which are better than NiGa₂S₄/NF and previously reported transition metal sulfides (TMSs). Furthermore, for the first time a pseudocapacitive advanced anode material of FeSe₂-rGO have been successfully fabricated on a nickel foam (NF) substrate by a facile strategy. Element Selenium as the favorable element was offered into the Fe for enhancement and adjustment of the anode material electrochemical performance. The FeSe₂-rGO/NF advanced anode electrode presents satisfactory electrochemical properties containing an exceptional specific capacitance (C_sc) of 432.40 F g^-1, significant rate performance of 57.84% and superior durability, which are better than FeSe₂/NF electrode and previously studied Fe-based anode material. Considering the remarkable electrochemical performance of the as-prepared pseudocapacitive advanced electrode materials, a FSASC based on the NiGa₂S₄-rGO/NF as the cathode electrode and FeSe₂-rGO/NF as the anode electrode was assembled. The FSASC device delivers superior C_sc of 341.20 F g^-1, outstanding energy density (ED) of 121.31 W h kg^-1, remarkable cycle stability (only 7.30% damage after 5000 charge/discharge (CD) cycles).

Morphologically Tunable MnO2 Nanoparticles Fabrication, Modelling and Their Influences on Electrochemical Sensing Performance toward Dopamine

The morphology or shape of nanomaterials plays an important role in functional applications, especially in the electrochemical sensing performance of nanocomposites modified electrodes. Herein, the morphology-dependent electrochemical sensing properties of MnO2-reduced graphene oxide/glass carbon electrode (MnO2-RGO/GCE) toward dopamine detection were investigated. Firstly, various morphologies of nanoscale MnO2, including MnO2 nanowires (MnO2 NWs), MnO2 nanorods (MnO2 NRs), and MnO2 nanotubes (MnO2 NTs), were synthesized under different hydrothermal conditions. Then the corresponding MnO2-RGO/GCEs were fabricated via drop-casting and the subsequent electrochemical reduction method. The oxidation peak currents increase with the electrochemical activity area following the order of MnO2 NWs-RGO/GCE, MnO2 NTs-RGO/GCE, and MnO2 NRs-RGO/GCE. The spatial models for MnO2 NWs, MnO2 NTs, and MnO2 NRs are established and accordingly compared by their specific surface area, explaining well the evident difference in electrochemical responses. Therefore, the MnO2 NWs-RGO/GCE is selected for dopamine detection due to its better electrochemical sensing performance. The response peak current is found to be linear with dopamine concentration in the range of 8.0 × 10−8 mol/L–1.0 × 10−6 mol/L and 1.0 × 10−6 mol/L–8.0 × 10−5 mol/L with a lower detection limit of 1 × 10−9 mol/L (S/N = 3). Finally, MnO2 NWs-RGO/GCE is successfully used for the determination of dopamine injection samples, with a recovery of 99.6–103%. These findings are of great significance for understanding the relationship between unlimited nanoparticle structure manipulation and performance improvement.

Amorphous Carbon Nanotubes-Nickel Oxide Nanoflower Hybrids: A Low Cost Energy Storage Material

Amorphous carbon nanotubes (a-CNTs) have been synthesized by a simple low-temperature process and have been grafted with chemically synthesized nickel oxide microflowers with different concentrations. The phase and morphology of the as-prepared pure and hybrid samples were characterized by X-ray diffraction and field emission scanning and transmission electron microscopes. Thermal properties of the samples were estimated by using thermal gravimetric and differential thermal analysis. The optical properties of the sample were characterized by UV-vis spectroscopic, Raman spectroscopic, and Fourier-transformed infrared spectroscopic analysis. The electrochemical performance of all hybrid samples has been done in detail for different scan rates as well as from charge-discharge analysis. It has been seen that because of the nickel oxide grafting, the electrochemical performance of pure a-CNTs gets enhanced significantly. The value of the specific capacitance of the hybrid comes out to be around 120 F/g for the best sample, which is almost 12 times higher compared to that of the pure a-CNTs. The result has been explained in terms of change in effective surface area as well as change in conductivity of the hybrid samples.

Nucleation and Growth of Porous MnO₂ Coatings Prepared on Nickel Foam and Evaluation of Their Electrochemical Performance

Porous MnO₂ was uniformly electrodeposited on nickel foam in MnSO₄ solution, which was applied as the electrode of supercapacitors. The nucleation/growth mechanisms of porous MnO₂ were investigated firstly. Then two kinds of electrochemical measuring technologies, corresponding to the cycle voltammetry (CV) and galvanostatic charge-discharge, were adopted to assess the electrochemical performance of MnO₂ electrodes. The results demonstrated that the deposition of MnO₂ on nickel foam included four stages. Prior to the deposition, an extremely short incubation period of about 2 s was observed (the first stage). Then the exposed nickel foam was instantly covered by a large number of MnO₂ crystal nuclei and crystal nuclei connected with each other in a very short time of about 3 s (the second stage). Nucleation predominated in the second stage. The sharply rise of current was caused by the increase in substrate surface area which due to nucleation of MnO₂. Grain boundaries grew preferentially due to their high energy, accompanied with a honeycomb-like structure with the higher surface area was formed. However, accompanied with the electrochemical reactions gradually diffusion-controlled, the current presented the decline trend with increasing the time (the third stage). When the electrochemical reactions were completely diffusion-controlled, the porous MnO₂ coating with an approximately constant surface area was formed (the fourth stage). MnO₂ coatings deposited for different time (30, 60, 120, 300 s) exhibited a similar specific capacitance (CV: about 224 F/g; galvanostatic charge-discharge: about 264 F/g). Comparatively speaking, the value of MnO₂ deposited for 600 s was highest (CV: 270 F/g; galvanostatic charge-discharge: 400 F/g).

Recent Advances in Designing and Fabricating Self-Supported Nanoelectrodes for Supercapacitors

Owing to the outstanding advantages as electrical energy storage system, supercapacitors have attracted tremendous research interests over the past decade. Current research efforts are being devoted to improve the energy storage capabilities of supercapacitors through either discovering novel electroactive materials or nanostructuring existing electroactive materials. From the device point of view, the energy storage performance of supercapacitor not only depends on the electroactive materials themselves, but importantly, relies on the structure of electrode whether it allows the electroactive materials to reach their full potentials for energy storage. With respect to utilizing nanostructured electroactive materials, the key issue is to retain all advantages of the nanoscale features for supercapacitors when being assembled into electrodes and the following devices. Rational design and fabrication of self-supported nanoelectrodes is therefore considered as the most promising strategy to address this challenge. In this review, we summarize the recent advances in designing and fabricating self-supported nanoelectrodes for supercapacitors towards high energy storage capability. Self-supported homogeneous and heterogeneous nanoelectrodes in the forms of one-dimensional (1D) nanoarrays, two-dimensional (2D) nanoarrays, and three-dimensional (3D) nanoporous architectures are introduced with their representative results presented. The challenges and perspectives in this field are also discussed.

Supercharging a MnO2 Nanowire: An Amine-Altered Morphology Retains Capacity at High Rates and Mass Loadings

The influence of hexamethylenetetraamine (HMTA) on the morphology of δ-MnO₂ and its properties for electrical energy storage are investigated-specifically for ultrathick δ-MnO₂ layers in the micron scale. Planar arrays of gold@δ-MnO₂, core@shell nanowires, were prepared by electrodeposition with and without the HMTA and their electrochemical properties were evaluated. HMTA alters the MnO₂ in three ways: First, it creates a more open morphology for the MnO₂ coating, characterized by "petals" with a thickness of 6 to 9 nm, rather than much thinner δ-MnO₂ sheets seen in the absence of HMTA. Second, the electronic conductivity of the δ-MnO₂ is increased by an order of magnitude. Third, δ-MnO₂ prepared in HMTA shows a (001) interlayer spacing that is expanded by ≈30% possibly accelerating Li transport. The net effect of "HTMA doping" is to dramatically improve high rate performance, culminating in an increase in the specific capacity for the thickest MnO₂ shells examined here by a factor of 15 at 100 mV/s.

Peptide-templated synthesis of branched MnO2 nanowires with improved electrochemical performances

Self-assembled peptide nanofibers can template the formation of branched MnO₂ nanowires, which show improved electrochemical properties.

Yolk-Shell Sn@C Eggette-like Nanostructure: Application in Lithium-Ion and Sodium-Ion Batteries

Yolk-shell carbon encapsulated tin (Sn@C) eggette-like compounds (SCE) have been synthesized by a facile method. The SCE structures consist of tin cores covered by carbon membrane networks with extra voids between the carbon shell and tin cores. The novel nanoarchitectures exhibit high electrochemical performance in both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). As anodes for LIBs, the SCE electrodes exhibit a specific capacity of ∼850 mA h g(-1) at 0.1 C (100 mA g(-1)) and high rate capability (∼450 mA h g(-1) remains) at high current densities up to 5 C (5000 mA g(-1)). For SIBs, the SCE electrodes show a specific capacity of ∼400 mA h g(-1) at 0.1 C and high rate capacity (∼150 mA h g(-1) remains) at high current densities up to 5 C (5000 mA g(-1)).

High Pseudocapacitive Performance of MnO2 Nanowires on Recyclable Electrodes

Manganese oxides are promising pseudocapacitve materials for achieving both high power and energy densities in pseudocapacitors. However, it remains a great challenge to develop MnO2 -based high-performance electrodes due to their low electrical conductance and poor stability. Here we show that MnO2 nanowires anchored on electrochemically modified graphite foil (EMGF) have a high areal capacitance of 167 mF cm(-2) at a discharge current density of 0.2 mA cm(-2) and a high capacitance retention after 5000 charge/discharge cycles (115 %), which are among the best values reported for any MnO2 -based hybrid structures. The EMGF support can also be recycled and the newly deposited MnO2 -based hybrids retain similarly high performance. These results demonstrate the successful preparation of pseudocapacitors with high capacity and cycling stability, which may open a new opportunity towards a sustainable and environmentally friendly method of utilizing electrochemical energy storage devices.

Hierarchical MnO2 Spheres Decorated by Carbon-Coated Cobalt Nanobeads: Low-Cost and High-Performance Electrode Materials for Supercapacitors

MnO2 is a promising electrode material for supercapacitors, because it exhibits high theoretical specific capacitance (1380 F g(-1)) for electrical charge while also being inexpensive and environmentally benign. However, owing to its low electrical conductivity, the intrinsic pseudocapacity of MnO2 is not fully utilized. In this work, hierarchically structured spheres composed of MnO2 nanoplatelets and carbon coated cobalt nanobeads (MnO2-NPs@Co/C) are chosen as electrode materials for supercapacitor. With a Co/C mass loading of 19 wt %, the electrical conductivity of the hybrid is 122-fold larger than that of pristine MnO2, showing a specific capacitance of the constituent MnO2 as high as 1240 F g(-1), being close to the theoretical value. Such improved specific capacitance of MnO2-NPs@Co/C electrode is largely contributed from the enhanced double-layer charging and Faradaic pseudocapacity of MnO2. Moreover, the fabricated symmetrical supercapacitor also exhibits excellent cycling stability with 89.1% capacitance retention over 10000 cycles, as well as high energy densities in both aqueous and organic electrolyte (24 Wh kg(-1) and 33 W kg(-1), respectively). Compared with frequently used noble metals to enhance the electrochemical performance of MnO2, the utilization of low cost Co/C nanobeads is proven to be more efficient and thus showing great potential for commercial application.

MnO2 nanomaterials for flexible supercapacitors: performance enhancement via intrinsic and extrinsic modification

Increasing power and energy demands for next-generation portable and flexible electronics have raised critical requirements (flexibility, stretch-ability, environmental friendliness, lightweight, etc.) for the energy storage devices. Flexible supercapacitors (SCs), as one of the most promising next-generation energy storage devices, have stimulated intensive interest owing to their outstanding features including small size, low weight, ease of handling, excellent reliability, and high power density. Manganese oxide (MnO₂), has attracted much interest in the development of flexible SCs with high electrochemical performance. Yet, the poor electronic and ionic transport in MnO₂ electrodes still limits its promotion in practical applications. This review aims to describe the recent progress in the application of MnO₂ materials in the development of flexible SCs and summarizes the intrinsic modification of MnO₂via crystallinity, crystal structure, and oxygen vacancy introduction and the extrinsic modification of MnO₂via non-three-dimensional (3D) and 3D flexible conductive scaffolds for high performance flexible SCs. Moreover, we also discuss briefly on the current challenges, future directions, and opportunities for the development of high-performance MnO₂ based flexible SCs.

Solid-State Thin-Film Supercapacitors with Ultrafast Charge/Discharge Based on N-Doped-Carbon-Tubes/Au-Nanoparticles-Doped-MnO2 Nanocomposites

Although carbonaceous materials possess long cycle stability and high power density, their low-energy density greatly limits their applications. On the contrary, metal oxides are promising pseudocapacitive electrode materials for supercapacitors due to their high-energy density. Nevertheless, poor electrical conductivity of metal oxides constitutes a primary challenge that significantly limits their energy storage capacity. Here, an advanced integrated electrode for high-performance pseudocapacitors has been designed by growing N-doped-carbon-tubes/Au-nanoparticles-doped-MnO2 (NCTs/ANPDM) nanocomposite on carbon fabric. The excellent electrical conductivity and well-ordered tunnels of NCTs together with Au nanoparticles of the electrode cause low internal resistance, good ionic contact, and thus enhance redox reactions for high specific capacitance of pure MnO2 in aqueous electrolyte, even at high scan rates. A prototype solid-state thin-film symmetric supercapacitor (SSC) device based on NCTs/ANPDM exhibits large energy density (51 Wh/kg) and superior cycling performance (93% after 5000 cycles). In addition, the asymmetric supercapacitor (ASC) device assembled from NCTs/ANPDM and Fe2O3 nanorods demonstrates ultrafast charge/discharge (10 V/s), which is among the best reported for solid-state thin-film supercapacitors with both electrodes made of metal oxide electroactive materials. Moreover, its superior charge/discharge behavior is comparable to electrical double layer type supercapacitors. The ASC device also shows superior cycling performance (97% after 5000 cycles). The NCTs/ANPDM nanomaterial demonstrates great potential as a power source for energy storage devices.

Electrosynthesis and electrochemical capacitive behavior of a new nitrogen PEDOT analogue-based polymer electrode

As a supercapacitor electrode, a new nitrogen PEDOT analogue (PMDTO) exhibited some outstanding electrochemical performances but still suffered some drawbacks.

Importance of polypyrrole in constructing 3D hierarchical carbon nanotube@MnO2 perfect core-shell nanostructures for high-performance flexible supercapacitors

This study reports the preparation of 3D hierarchical carbon nanotube (CNT) @MnO2 core-shell nanostructures under the assistance of polypyrrole (PPy). The as-prepared CNT@PPy@MnO2 core-shell structures show a perfect coating of MnO2 on each CNT and, more importantly, a robust bush-like pseudocapacitive shell to effectively increase the specific surface area and enhance the ion accessibility. As expected, a high specific capacity of 490-530 F g(-1) has been achieved from CNT@PPy@MnO2 single electrodes. And about 98.5% of the capacity is retained after 1000 charge/discharge cycles at a current density of 5 A g(-1). Furthermore, the assembled asymmetric CNT@PPy@MnO2//AC capacitors show the maximum energy density of 38.42 W h kg(-1) (2.24 mW h cm(-3)) at a power density of 100 W kg(-1) (5.83 mW cm(-3)), and they maintain 59.52% of the initial value at 10,000 W kg(-1) (0.583 W cm(-3)). In addition, the assembled devices show high cycling stabilities (89.7% after 2000 cycles for asymmetric and 87.2% for symmetric), and a high bending stability (64.74% after 200 bending tests). This ability to obtain high energy densities at high power rates while maintaining high cycling stability demonstrates that this well-designed structure could be a promising electrode material for high-performance supercapacitors.

Designing 3D highly ordered nanoporous CuO electrodes for high-performance asymmetric supercapacitors

The increasing demand for energy has triggered tremendous research efforts for the development of lightweight and durable energy storage devices. Herein, we report a simple, yet effective, strategy for high-performance supercapacitors by building three-dimensional pseudocapacitive CuO frameworks with highly ordered and interconnected bimodal nanopores, nanosized walls (∼4 nm) and large specific surface area of 149 m(2) g(-1). This interesting electrode structure plays a key role in providing facilitated ion transport, short ion and electron diffusion pathways and more active sites for electrochemical reactions. This electrode demonstrates excellent electrochemical performance with a specific capacitance of 431 F g(-1) (1.51 F cm(-2)) at 3.5 mA cm(-2) and retains over 70% of this capacitance when operated at an ultrafast rate of 70 mA cm(-2). When this highly ordered CuO electrode is assembled in an asymmetric cell with an activated carbon electrode, the as-fabricated device demonstrates remarkable performance with an energy density of 19.7 W h kg(-1), power density of 7 kW kg(-1), and excellent cycle life. This work presents a new platform for high-performance asymmetric supercapacitors for the next generation of portable electronics and electric vehicles.

Flexible and ultralong-life cuprous oxide microsphere-nanosheets with superior pseudocapacitive properties

A facile electrochemical two-step strategy was adopted to fabricate Cu₂O microsphere-nanosheets on flexible Cu foil with superior pseudocapacitive properties.

Structural and electrochemical analysis of a novel co-electrodeposited Mn2O3–Au nanocomposite thin film

In this work we report the fabrication of both pristine Mn₂O₃ and Mn₂O₃–Au composite thin films on an indium tin oxide (ITO) substrate by a one-step novel co-electrodeposition technique.

In situ anchoring uniform MnO2 nanosheets on three-dimensional macroporous graphene thin-films for supercapacitor electrodes

A three-dimensional macroporous rGO/MnO₂ thin-film is developed through template method and the redox reaction between KMnO₄ and amorphous carbon. The hybrid film shows improved electrochemical performances for supercapacitor electrode application.

Influence of imidazolium-based ionic liquid electrolytes on the performance of nano-structured MnO2 hollow spheres as electrochemical supercapacitor

Activated carbon//MnO₂ hollow sphere asymmetric supercapacitor shows an energy density of 163 W h kg⁻¹ in EMIMBF₄ ionic liquid as electrolyte.

A perfectly aligned 63helical tubular cuprous bromide single crystal for selective photo-catalysis, luminescence and sensing of nitro-explosives

A perfectly aligned 6₃helical tubular cuprous bromide single crystal stabilized by organic template cations has been synthesized, which could be a multifunctional material for highly selective degradation, luminescence and sensing of nitro-explosives at the ppm level.

Synthesis and characterization of solvent-free waterborne polyurethane dispersion with both sulfonic and carboxylic hydrophilic chain-extending agents for matt coating applications

Self-extinction and solvent-free waterborne polyurethane resin without the addition of extra matting agents.

Shape-controlled synthesis of MnCO3 nanostructures and their applications in supercapacitors

A one step co-precipitation method has been developed for synthesizing shape-controlled monodispersed MnCO₃ nanostructures for supercapacitor application.

Interconnected network of MnO2 nanowires with a "cocoonlike" morphology: redox couple-mediated performance enhancement in symmetric aqueous supercapacitor

Low electronic conductivity and slow faradic processes limit the performance of MnO2 as an electrochemical pseudocapacitor with respect to cycling and power density. Herein, we report preparation of single-phase α-MnO2, composed of an interconnected nanowire network with "cocoonlike" morphology, and its application as electrode in a symmetric aqueous supercapacitor. Increased "effective" surface area, coexistence of micropores and mesopores, and enhanced electron transport in these nanowire networks result in a specific pseudocapacitance (CS) of 775 F·g(-1) in 3 M KOH, derived from cyclic voltammetry in the potential window of -1 to +1 V at a scan rate of 2 mV·s(-1), the highest reported for two-electrode symmetric configuration. Furthermore, introduction of K4Fe(CN)6 as a redox-active additive to KOH results in ∼7 times increase in energy density at a power density of ∼6000 W·kg(-1). The presence of the Fe(CN)6(4-)/Fe(CN)6(3-) redox couple provides an electron buffer source compensating for the slow faradic reactions. The results demonstrate that this simple approach might be an effective way to enhance the redox kinetics and reversibility of transition metal oxide-based pseudocapacitors.

Preparation and performance of β-MnO2 nanorod @ nanoflake (Ni, Co, Mn) oxides with hierarchical mesoporous structure

Nanoflake (Ni, Co, Mn) oxides were successfully grown on the surface of β-MnO₂ nanorods via a simple redox reaction.