Search

Abstract: Graphene, graphene–ZnO and graphene–SnO2 films were successfully synthesized and used as electrode materials for electrochemical supercapacitors, respectively. The screen-printing approach was employed to fabricate graphene film on graphite substrate while the ZnO and SnO2 were deposited on graphene films by ultrasonic spray pyrolysis. The electrochemical performances of these electrodes were comparatively analyzed through electrochemical impedance spectrometry, cyclic voltammetry and chronopotentiometry tests. The results showed that the incorporation of ZnO or SnO2 improved the capacitive performance of graphene electrode. Graphene–ZnO composite electrode exhibited higher capacitance value (61.7F/g) and maximum power density (4.8kW/kg) as compared with graphene–SnO2 and pure graphene electrodes. [Copyright &y& Elsevier]

In this work, sulfur-doped carbon spheres with hierarchical micro/mesopores (denoted as S-MCSs) were fabricated via a sol-gel method combined with surfactant-directing assembly strategy and subsequent sulfuration process. When used as anode materials of sodium-ion batteries (SIBs), S-MCSs show excellent electrochemical performance with a high maximum reversible capacity of 443.4 mA h g −1 after 50 cycles at 50 mA g −1 , and even at a high current density of 1 A g −1 , a reversible capacity of 238.2 mA h g −1 is obtained after 600 cycles, mainly due to their hierarchical micro/mesoporous structure with high specific surface area, large pore volume and high sulfur content. The excellent cycling performance and high capacity enable the S-MCSs to be a promising candidate for SIBs. [ABSTRACT FROM AUTHOR]

Nitrogen-doped porous carbon spheres (NPCSs) were prepared through a fast microwave-assisted approach using sucrose as the precursor in a microwave system and subsequent thermal treatment in ammonia atmosphere at different temperatures. The morphology, structure and electrochemical performance of the NPCSs were characterized by scanning electron microscopy, nitrogen adsorption-desorption, X-ray photoelectron spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy, and their electrosorption performance in NaCl solution was studied. The results show that NPCSs treated at 1000 °C exhibit an extremely high electrosorption capacity of 14.91 m g g −1 when the initial NaCl concentration is 1000 mg l −1 , which shows great improvement compared with their undoped counterpart. The nitrogen doping is suggested to be a very effective method to improve the electrosorption performance, and the NPCSs should be a very promising candidate as electrode material for CDI application. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) films have been successfully fabricated by electrophoretic deposition (EPD) technique and used as counter electrodes of dye-sensitized solar cells (DSSCs). The CNTs counter electrodes consisting of a large number of bamboo-like structures with defect-rich edge planes exhibit a highly interconnected network structure with high electrical conductivity and good catalytic activity. A high photovoltaic conversion efficiency of 7.03% is achieved for DSSCs based on the CNTs counter electrodes, which is comparable to the cell based on conventional Pt counter electrode at one sun (AM 1.5G, 100mWcm−2). The results suggest that the present synthetic strategy provides a potential feasibility for the fabrication of low-cost flexible counter electrodes of DSSCs using a facile deposition technique from an environmentally “friendly” solution at low temperature. [Copyright &y& Elsevier]

Abstract Hollow nanostructures are favorable for electrode materials to enhance their energy storage performance due to their unique structural features. In this work, hollow bimetallic phosphide (Ni x Co 1-x P) was fabricated via etching treatment of ZIF-67 and further phosphorization. The as-obtained Ni x Co 1-x P composites display a high specific capacity of 548 C g−1 at 1 A g−1 in 2 M KOH aqueous solution, excellent rate capability (83.7%, 77.6%, 71.7% and 66.2% capacity retention at 10, 20, 30 and 40 A g−1), and remarkable cycling stability (86% capacity retention at 7 A g−1 after 3000 cycles). Furthermore, a hybrid supercapacitor, constructed by Ni x Co 1-x P as anode and active carbon as cathode, exhibits excellent specific capacitance (115.8 F g−1 at 1 A g−1), high gravimetric energy/power density (31.52 Wh kg−1 at 700 W kg−1), and outstanding long-term cycling stability (98.3% capacitance retention even after 10000 cycles). The excellent electrochemical performance should be attributed to the good interfacial contact between electrode and electrolyte, unique hollow structure with suitable surface area and good electrical conductivity of Ni x Co 1-x P. The results suggest a great potential of Ni x Co 1-x P composites in electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

The main challenge of using TiO 2 as anode for sodium-ion batteries (SIBs) is its inherent low electrical conductivity, which leads to its unsatisfied capacity, short cycle life and low initial Coulombic efficiency. Herein, we report that synergistically doped anatase TiO 2 nanotubes with Ni and N via a simple sol-gel process, subsequent alkali-thermal reaction, and final thermal treatment in NH 3 can optimize the relationship among the phase structure, electrical conductivity and sodium-ion diffusion kinetic performance of anatase TiO 2 to enhance its sodium-ion storage and transport performances. The resultant Ni and N co-doped anatase TiO 2 nanotubes (Ni-N/TNTs) exhibit a high charge capacity of 303 mA h g −1 after 500 cycles at a current density of 50 mA g −1 with an initial Coulombic efficiency of 65% and even at a high current density of 5 A g −1 , a capacity of 143 mA h g −1 is maintained after 8000 cycles with a capacity retention of ≥100%. The bandgap estimation, phase structure evolution, and electrochemical impedance spectroscopy analysis combined with the electrochemical test results indicate that the significantly improved sodium-ion storage and transport performances of Ni-N/TNTs should be mainly ascribed to the increased electrical conductivity, stable phase structure during the electrochemical processes, lower charge transfer resistance, and enhanced sodium-ion diffusion coefficient after Ni and N co-doping. The high capacity, improved Coulombic efficiency, excellent rate performance and long cycle life enable Ni-N/TNTs to be an applicable anode material for SIBs. [ABSTRACT FROM AUTHOR]

Cobalt disulfide (CoS 2) is regarded as a low cost and abundant non-noble electrocatalyst, but some drawbacks limit its application due to its sluggish intrinsic electrocatalytic kinetics and high hydrogen evolution overpotential. In this work, carbon-wrapped Fe-doped CoS 2 nanocages (C/Fe–CoS 2) were synthesized via gradual sulfurization of cobalt hexacyanoferrate and evaluated as electrocatalysts for hydrogen evolution reaction (HER). The nanocage architecture exposes more electrochemically active site, and carbon wrapping reduces the agglomeration of C/Fe–CoS 2 and optimizes the electronic structure, while the Fe doping decreases the hydrogen adsorption free energy of CoS 2. Therefore, C/Fe–CoS 2 demonstrates a superior HER performance, showing a benchmark current density of 10 mA cm−2 at the low overpotential of 151 mV in acidic electrolyte and a remarkable stability (cyclic voltammetry cycling for 3000 cycles and continuous electrolysis at the overpotential of 180 mV for 25,000 s). The as-designed C/Fe–CoS 2 should be one of the most promising catalysts for HER application. This strategy highlights the construction of high performance electrocatalysts via structure designing and heteroatom doping for efficient and stable hydrogen generation. [ABSTRACT FROM AUTHOR]

Novel Sb 2 S 3 @multiwalledcarbonnanotubes(MWCNTs) (SM) composites were synthesized via a facile and green method which included an in-situ growth of Sb 2 S 3 nanoparticles on the surface of MWCNTs through precipitation and subsequent thermal treatment. The morphologies and structures of SM composites were tested by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and nitrogen adsorption and desorption isotherms. Finally, their application as anode materials for sodium-ion batteries (SIBs) was investigated through corresponding electrochemical measurements such as galvanostatic charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the SM composites display higher capacity, better cycling stability and superior rate performance than pure Sb 2 S 3 , and a capacity of 412.3 mAh g −1 after 50 cycles at 50 mA g −1 is obtained for SM composites with 30 wt.% MWCNTs loading. The enhanced performance is ascribed to an increase in the specific surface area, an improvement in the charge transfer and effective buffering of the volume change offered by the porous conductive network structure of the composite with the introduction of MWCNTs. [ABSTRACT FROM AUTHOR]

Capacitive neutralization deionization with flow electrodes (FCND) was proposed by combining neutralization dialysis (ND) and flow-electrode capacitive deionization (FCDI). Its key property is that by employing flow electrodes, capacitive adsorption of salt ions occurs simultaneously during the neutralization dialysis process. To compare the desalination performance between FCND and FCDI, a series of experiments were conducted by changing salt concentration and applied electrical voltage. The hybrid exhibits a promising average salt adsorption rate (ASAR) and salt removal efficiency (SRE) compared to either ND or FCDI process. The ASAR and SRE of FCND are 203.27 mmol m −2 min −1 and 72.20% in 0.1 mM NaCl solution at 1.2 V after 120 min, whereas the values of FCDI are 120.86 mmol m −2 min −1 and 42.92%, respectively. In order to facilitate the understanding of the ion transportation in this complex system, a theory was also set up based on simplified Nernst-Planck equation and Donnan equilibrium, which helps to understand the experimental data. [ABSTRACT FROM AUTHOR]

One of the most challenging issues in developing supercapacitor and capacitive deionization (CDI) technologies is the rational design and synthesis of active electrode materials, with favorable morphologies, reasonable porous structure and high surface area. Recently, three-dimensional (3D) graphene frameworks (3DGF)-based hybrids have been considered as one of the most promising candidates for supercapacitor and CDI applications. By incorporating functional nanomaterials into 3DGF, the obtained 3DGF-based hybrids exhibited enhanced properties or unique character compared to 3DGF. Here we report novel hierarchical hybrids with microporous carbon spheres (MCS) decorated 3DGF (3DGF-MCS), which not only possesses a hierarchical porous structure, but also maintains favorable features for supercapacitor and CDI applications, such as a large surface area and good electrical conductivity. The results indicate that 3DGF-MCS with 10 wt% MCS exhibits excellent electrochemical performances, including a superior specific capacitance of 288.77 F g −1 , and an ultrahigh electrosorption capacity of 19.8 mg g −1 . The 3DGF-MCS should be promising electrode materials for highly efficient supercapacitor and CDI applications. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon microspheres (NCSs) derived from oatmeal are employed as anodes for sodium ion batteries (SIBs). Their morphology, structure and electrochemical performance are characterized by field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption isotherms, galvanostatic charge/discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy, respectively. The results show that NCSs treated at 500 °C exhibit a high maximum charge capacity of 336 mA h g −1 after 50 cycles at a current density of 50 mA g −1 and even at a high current density of 10 A g −1 within 70 s charging time, a capacity of 104 mA h g −1 is maintained after 12500 cycles without obvious decay. The high capacity, excellent rate performance, long life cycling and ultrafast rechargeable ability enable the NCSs to be a promising candidate for practical SIBs. [ABSTRACT FROM AUTHOR]

Here a facile strategy was proposed to prepare graphene (GE) sheets with unique mesoporous morphology (denoted as mGE) via a simple carbothermal reaction by using KMnO 4 as the etching agent. The morphology, structure and electrochemical properties of mGE were investigated by scanning electron microscopy, transmission electron microscopy, Raman spectra, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy. The electrosorption performance of mGE in NaCl solution was studied and compared with GE. The results show that mGE electrode exhibits a high electrosorption capacity of 6.38 mg g −1 when the initial NaCl concentration is ∼75 mg L −1 and applied voltage is 1.2 V, which is about 2.3 and 1.5 times of those of GE (2.76 mg g −1 ) and recently reported microporous GE (∼4 mg g −1 ), respectively, and also higher than those of other carbon materials in the literatures, due to short ion diffusion path, large accessible surface area and low charge transfer resistance offered by its novel mesoporous structure. Therefore, it is believed that mGE is a promising candidate for practical capacitive deionization applications. [ABSTRACT FROM AUTHOR]

Porous carbon spheres (PCSs) were fabricated through a fast microwave-assisted approach using sucrose as the precursor in a microwave system and subsequent thermal treatment at 600, 800 and 1000 °C. The morphology, structure and electrochemical performance of the PCSs were characterized by scanning electron microscopy, Raman spectroscopy, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy. Their electrosorption performance in NaCl solution was studied and compared with activated carbon, carbon nanotubes, reduced graphene and carbon aerogels. The results show that due to their high specific surface area and low charge transfer resistance, PCSs treated at 1000 °C exhibit high electrosorption capacity of 5.81 m g g −1 when the initial solution concentration is 500 mg l −1 , which is higher than those of other carbon materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] A modified membrane capacitive deionization device was proposed. [•] The electrodes consisted of ion exchange polymers and carbon nanotubes. [•] The polymers improved the contact adhesion and reduced the co-ion expulsion effect. [•] The device exhibited a high NaCl removal with a good regeneration ability. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs)–polyacrylic acid (PAA) composite film has been successfully fabricated by electrophoretic deposition method in PAA aqueous solution containing CNTs and used as electrodes for capacitive deionization (CDI). The PAA serves as the cation-exchange polymer and the matrix to incorporate the CNTs. The CDI unit cell based on CNTs–PAA composite film electrode exhibits a high NaCl removal of 83%, 51% higher than that of the cell based on pure CNTs electrode, with a good regeneration ability. [Copyright &y& Elsevier]

Layered double hydroxides (LDHs) have shown remarkable potentials in supercapacitors for their highly-redox capacitance. However, the poor contact with substrate, slow charge transfer and ion diffusion, and low electrical conductivity limit their capacitor performance. In this work, a flexible free-standing supercapacitor was designed, with in-situ grown hollow-structured NiCo layered double hydroxide (H–NiCo LDH) as the active material based on a partial Ni ion substitution of Co ion in ZIF-67, and flexible carbon material as the substrate. Systematical investigation has been conducted in terms of nanostructures of the active material NiCo LDH (hollow or laminar structure) and flexible carbon substrates (acidified carbon cloth or acidified carbon fibers). A hollow-structured NiCo LDH@acidified carbon cloth (H–NiCo LDH@ACC) sample showed a promising capacity of 1377 mC/cm2 (3060 mF/cm2) at 1 mA/cm2, a low charge transfer resistance of 0.15 Ω, a capacity retention of 70% and a coulombic efficiency retention of 99% upon 10,000 cycles at 80 mA/cm2. PDMS-sealed solid-state H–NiCo LDH@ACC//AC devices were fabricated with an energy density of 0.0708 mWh/cm2 at a power density of 0.7 mW/cm2, with no obvious capacity decrease upon bending angles from 0° to 180°. SEM, EDS, XPS, and XRD analyses indicated the H–NiCo LDH has been in-situ grown on flexible carbon substrates. Hollow-structured LDH accelerated charge transfer and ion diffusion compared with a laminar-structured LDH. Acidified carbon cloth (ACC) showed better electrical conductivity compared with the biomass-derived acidified carbon fibers. Thus, a H–NiCo LDH@ACC is proposed as a promising candidate of a flexible supercapacitor. Image 1 • Hollow-structured NiCo layered double hydroxide (LDH) was in-situ grown on flexible carbon substrate for supercapacitor. • Hollow-structured LDH accelerated charge transfer and ion diffusion compared with a laminar-structured LDH. • Acidified carbon cloth showed better electrical conductivity compared with the acidified carbon fibers as substrate. [ABSTRACT FROM AUTHOR]