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In this work, N, P dual-doped molybdenum carbide/porous carbon fiber composites were simply fabricated through electrospinning technology, followed by pyrolysis. The obtained samples were composed ...

As a conductive polymer with great potential, poly(3,4-ethylenedioxythiophene) (PEDOT) has been developed as a high-rate supercapacitor electrode but stores less energy due to its limited theoretic...

By employing a carbon nanotube (CNT) sponge with a 3D porous network as a compressible substrate and NiCo2S4 nanoparticles as active materials, a NiCo2S4/CNT sponge electrode with high compression ...

Molybdenum sulfide (MoS2) is a representative transition-metal chalcogenide holding great potential in electrochemical energy devices. However, poor conductivity and limited stability hinder practi...

Integration of conductive polymers with flexible substrate to construct an electronically conductive and mechanically flexible electrode is of great significance for a flexible energy storage devic...

This work describes the successful growth of electroactive KNb3O8 nanorods on the flexible and conductive activated textile carbon cloth (aTC) for supercapacitor application. The KNb3O8 nanorods on...

By using Ti3C2Tx quantum dots as interlayer spacers, Ti3C2Tx nanosheets/Ti3C2Tx quantum dots/RGO (reduced graphene oxide) fiber (M6M3RG1) is prepared by a wet-spinning method; it shows good capacit...

Sodium-ion capacitors (SICs) have gained great interest for mid- to large-scale energy storage applications because of their high energy and high power densities as well as long cycle life and low cost. Herein, a T-Nb2O5 nanoparticles/N-doped graphene hybrid anode (T-Nb2O5/NG) was prepared by solvothermal treating a mixed ethanol solution of graphene oxide (GO), urea, and NbCl5 at 180 °C for 12 h, followed by calcining at 700 °C for 2 h, in which T-Nb2O5 nanoparticles with average size of 17 nm were uniformly anchored on the surface of the nitrogen-doped reduced GO because their growth and aggregation were hindered, and also, the electronic conductivity and the active sites of T-Nb2O5/NG were improved by doping nitrogen. The T-Nb2O5/NG anode showed superior rate capability (68 mA h g–1 even at 2 A g–1) and good cycling life (106 mA h g–1 at 0.2 A g–1 for 200 cycles and 83 mA h g–1 at 1 A g–1 for 1000 cycles) and also showed high-rate pseudocapacitive behavior from kinetics analysis. A novel SIC system had been constructed by using the T-Nb2O5/NG as anode and commercially activated carbon as the cathode; it delivered an energy density of 40.5 W h kg–1 at a power density of 100 W kg–1 and a long-term cycling stability (capacity retention of 63% after 5000 consecutive cycles at a current density of 1 A g–1) and showed a promising application for highly efficient energy storage systems.

Recently, interest in the use of carbonaceous materials derived from sustainable biomass wastes for supercapacitors (SCs) has grown. The sustainable sunflower stalk is selected as the raw material for preparing activated carbon (AC), using a simple hydrothermal carbonization (HTC) combining an effective activation method. The as-prepared AC sample possesses a unique mesoporous layer-stacking structure which has an unexpected surface area up to 1505 m2 g–1 as well as a pore size of 3.6 nm on average. As an electrode material for SCs, the AC demonstrates high electrochemical storage capacity, with the excellent capacitances of 365 and 263 F g–1 measured by three-electrode and symmetrical SCs systems, respectively. An outstanding capacitance retention rate and a good stability value maintained after 15 000 cycles are close to 81 and 95%, respectively, which are obtained at a current density of 20 A g–1. Further, the symmetrical SCs exhibits an energy density as high as 35.7 Wh kg–1 under the condition of a p...

Graphitic carbon nitride (g-C3N4) has been believed to be a promising photocatalyst for water splitting due to its right band gap and band edges. However, the kinetics of hydrogen evolution on g-C3N4 is very slow. Cocatalysts are usually needed to improve the catalytic kinetics. Herein, palladium-doped graphitic carbon nitride (g-C3N4–Pd) is designed by virtue of the tenacious coordination of Pd atoms with the pyridinic nitrogen atoms of six-fold cavities in g-C3N4. The introduction of Pd does not affect the structure and morphology of g-C3N4. Palladium is found to exist as Pd ions in g-C3N4–Pd catalysts. g-C3N4–Pd catalysts exhibit clearly higher hydrogen evolution activities than g-C3N4. The highest hydrogen evolution activity on g-C3N4–Pd is 15.3 times that of g-C3N4. The improvement of hydrogen evolution activity is found to arise from both the alternation of the electron excitation manner and the acceleration of hydrogen evolution kinetics induced by Pd doping. Our findings provide a promising way to...

Molybdenum ditelluride (MoTe2), which is stabilized in both semiconducting hexagonal (2H) and metallic distorted octahedral (1T’) phases, has attracted increasing attention owing to their attractive properties for promising wide applications. Exploring the full potential of this emerging material requires a reliable synthesis approach to precisely control its phase structure. Here, we report on the growth of high crystallinity MoTe2 nanosheets with a controlled phase via the tellurization of chemical vapor deposition-grown MoO2 nanosheets. The single crystal MoO2 nanosheets with rhombus shape were converted into MoTe2 single crystal nanosheets with morphology maintained well through the tellurization process. The phase structure of as-grown MoTe2 is determined by the synergetic effect of thermodynamics and kinetics in the crystal growth process, which is based on the difference in the thermodynamic stability and the lattice strain between 2H and 1T’ phases. Low growth temperature combined with a slow tell...

A series of multiheteroatom porous carbon frameworks (MPCFs) is prepared successfully from the trimerization of cyano groups of our designed and synthesized 4,4′-(4-oxophthalazine-1,3(4H)-diyl)dibenzonitrile monomers and subsequent ionothermal synthesis. Benefiting from the molecular engineering strategy, the obtained MPCFs framework show a homogeneous distribution of nitrogen and oxygen heteroatoms at the atomic level, confirmed by the transmission electron microscopy mapping intuitively, thereby ensuring the stability of electrical properties. The supercapacitor with the obtained MPCFs@700 as the electrode exhibits a high energy density of 65 Wh kg–1 at 0.1 A g–1, with excellent long cycle life and cycle stability (98% capacitance retention for 10 000 cycles in 1-butyl-3-methylimidazolium tetrafluoroborate). Another two electrolyte systems employed also demonstrate the delightful results, showing a 112% capacitance retention for 30 000 cycles in 1 M H2SO4 and a 95% capacitance retention for 30 000 cycle...

Fe2O3 is one of the promising negative electrodes for asymmetric supercapacitors. But the rather low conductivity and poor cycling stability hinder its practical application. Herein, we report a facile electrochemical deposition technique to prepare porous Fe2O3 nanosheets on carbon fabric (CF-Fe2O3). The obtained Fe2O3 displays highly porous nanosheet structure with reduced ion diffusion length and significantly enhanced conductivity. As a flexible supercapacitor electrode, the CF-Fe2O3 hybrid electrode delivers a large areal capacitance of 1.56 F cm–2, good rate capability, and excellent cycling stability without capacitance decay after 5000 cycles. A packaged solid-state supercapacitor device based on the flexible CF-Fe2O3 electrode exhibits an areal capacitance of 842 mF cm–2 and a volumetric energy density of 6.75 mWh cm–3, together with superior cycling performance which remains 93% capacitance after 4000 cycles. Moreover, the device performance is well retained under various bending and twisting st...

A flexible carbon fiber aerogel with a very high surface area for supercapacitor application is reported by carbonization and chemical activation of low-cost natural cotton with KOH. The carbon fibers in the aerogel present as a twisted and tubular structure. Depending on the amount of KOH used in the activation process, the specific surface area of aerogels ranges from 1536 to 2436 m2 g–1, while their electrical conductivity remains ∼860 S m–1. In spite of pore size in the range of 1.0–4.0 nm and pore volume mainly contributed by micropores, the carbon aerogel exhibits a high specific capacitance of 283 F g–1 (1 A g–1) in 6 M KOH aqueous electrolyte and retains a high capacitance retention of 224 F g–1 at current density up to 100 A g–1. Importantly, a symmetric capacitor built with the aerogel electrodes exhibits a rather small time constant (0.56 s). The superior capacitive performance of a CF electrode is closely related to its distinct structural advantage. The tubular carbon fibers that are several ...

The birnessite-type layered manganese oxide nanoplates with good dispersity and regular hexagonal morphology were obtained by topochemical oxidizing precursor Mn(OH)2 in NaClO solution for 24 h at room temperature, and its formation process was systematically investigated on the basis of the XRD pattern, FESEM and TEM images, XPS, Raman spectra, and TG-DTA analysis. The research results showed that the obtained birnessite-type layered manganese oxide nanoplates inherited the layered structure and regular hexagonal morphology from their Mn(OH)2 precursor. The regular hexagonal nanoplates were about 150 nm in each lateral edge with a thickness of 120 nm, which were self-assembled from MnO2 particles. The dispersity and regular morphology of the obtained materials were affected by the precursor Mn(OH)2 and the oxidation reaction times. This intermediate-mediated topochemical oxidation method could contribute to the design of new kinds of metal oxide materials with novel morphology and potential application.

Hierarchical graphene-based composite consisting of graphene sheets intercalated by MnO(2)-coated carbon nanotubes (MnC) was prepared for high-performance supercapacitor electrode. The highly negatively charged graphene oxides reduced by urea (RGO) and the positively charged MnC functionalized with poly(diallyldimethylammonium chloride) created a strong electrostatic interaction, forming a hierarchical nanostructure. The elelctrocapacitive behaviors of MnC/RGO (MnC-G) were systematically investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. A maximum specific capacitance of 193 F/g was achieved for the MnC-G composite with 37% RGO, which was almost 3-fold higher than 69 F/g of carbon nanotubes/RGO and 2-fold higher than 89 F/g of MnO(2)/RGO composite. Moreover, an excellent rate performance, a good capacitance retention (~70%) and a superior Coulombic efficiency (94-96%) were also observed during the continuous 1300 cycles of galvanostatic charge-discharge.

Hollow carbon spheres (HCS) with specific surface areas as high as 2239 m2/g were prepared by chemical vapor deposition with ferrocene as the carbon precursor and colloidal silica spheres as the template. Chemical oxidative polymerization of aniline in the presence of the HCS yielded composite materials with a layer of polyaniline (PANI) deposited on the external surface of the HCS. The electrocapacitive properties of the composite materials (HCS-PANI) with different PANI contents were evaluated using cyclic voltammetry, galvanostatic charge−discharge, and electrochemical impedance spectroscopy techniques. Results showed that the specific capacitances of the HCS before and after PANI coating were, respectively, 268 and 525 F/g in an aqueous H2SO4 electrolyte, which is almost doubly enhanced. A maximum energy density of 17.2 Wh/kg was achieved for the HCS-PANI electrode at a discharge current density of 0.1 A/g. However, the energy density of the HCS-PANI electrodes with higher PANI contents (>65 wt %) dec...

A novel and effective method was described in this work to prepare two-dimensional hexagonally ordered mesoporous CMK-5 carbon materials. This method is based on the chemical vapor deposition (CVD) of ferrocene in the mesopores of SBA-15 at 500 °C, followed by graphitization at different temperatures. Both the silica/carbon composite and the resulting CMK-5 were characterized by N2 adsorption, powder X-ray diffraction, Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis. It was found that the ferrocene could be used as a new precursor to prepare CMK-5 nanopipes, with pipe thicknesses varying from 0.8 to 2.6 nm, by increasing the CVD time from 20 to 120 min. The resulting CMK-5 exhibits high Brunauer−Emmett−Teller (BET) surface area (1044−2449 m2/g) and large pore volume (1.13−2.20 cm3/g). The graphitization degree of the resulting CMK-5 was investigated by pyrolyzing the corresponding silica/carbon composite at diff...