Effective Electrode Material Research Articles

Enhanced electrochemical performance of CoAl-layered double hydroxide nanosheet arrays coated by platinum films

Abstract Three-dimensional network of cobalt and aluminum layered double hydroxide (LDH) nanosheets was synthesized on nickel foam by a simple hydrothermal method. The CoAl-LDH nonosheets were subsequently coated by ion sputtering with thin layers of Pt films to facilitate fast electron transport between current collector and the CoAl-LDH active materials. The optimal thickness of the Pt film acquiring the best performance was identified by applying various sputtering time in controlled experiments. The supercapacitor built by the CoAl-LDH nanosheets coated with Pt film sputtered for 5 min has a high specific capacitance (734.4 F g −1 at 3 A g −1 ), excellent rate capability as well as cycling stability. Moreover, it showed a long life of 77% retention after 6000 cycles and its general morphology was preserved after the test. The synergetic affect of conductive layer of Pt films and CoAl-LDH on the improvement of electrochemical properties was discussed and this would provide a useful clue in designing novel and effective electrode materials for supercapacitors.

Reduced graphene oxide/nickel cobaltite nanoflake composites for high specific capacitance supercapacitors

Reduced graphene oxide (RGO)/nickel cobaltite (NiCo2O4) nanoflake composites were prepared by combining in situ assembling and subsequent thermal treatment. The RGO/NiCo2O4 composites were characterized by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption isotherms and thermogravimetric analysis. Cyclic voltammetry and chronopotentiometry measurements were performed to investigate the electrochemical properties of the composites. Superior performances were achieved with high specific capacitance of 1693Fg−1 at 1Ag−1, good rate capability (67.6% capacity retention at 16Ag−1) and long-term cyclability (only 9.2% loss after 2000 cycles). The binary redox couples of Ni2+/Ni3+ and Co2+/Co3+, ultrathin nanoflake structure, together with the high electrical conductivity of RGO to the outside current collectors are responsible for the excellent electrochemical performances of the RGO/NiCo2O4 composite, thus suggesting its potential application as an effective electrode material for supercapacitors.

Three‐Dimensional Graphene/Metal Oxide Nanoparticle Hybrids for High‐Performance Capacitive Deionization of Saline Water

A novel and general method is proposed to construct three-dimensional graphene/metal oxide nanoparticle hybrids. For the first time, it is demonstrated that this graphene-based composite with open pore structures can be used as the high-performance capacitive deionization (CDI) electrode materials, which outperform currently reported materials. This work will offer a promising way to develop highly effective CDI electrode materials.

Facile fabrication of Bi2S3–ZnS nanohybrids on graphene sheets with enhanced electrochemical performances

Graphene nanosheets (GNs) coated with Bi2S3–ZnS (Bi2S3–ZnS/GNs) hybrid materials were synthesized via a facile solvothermal method. The obtained material was characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) measurements. It was revealed that the GNs were in a gauze-like morphology, and the Bi2S3–ZnS nanorods assembled into an echinus structure and attached onto the GNs. The electrochemical performances of the nanohybrids were investigated by cyclic voltammetry (CV) and charge/discharge techniques. It showed that the Bi2S3–ZnS/GNs nanocomposite had a high electrocatalytic activity, durability, and stability. Bi2S3–ZnS/GNs were expected to be an effective electrode material for formic acid oxidation.

Nickel Phosphite Superstructures Assembled by Nanotubes: Original Application for Effective Electrode Materials of Supercapacitors

AbstractNickel phosphite (Ni11(HPO3)8(OH)6) superstructures assembled by nanotubes are synthesized under mild hydrothermal conditions with the sodium salt of polystyrene sulfonic acid. More importantly, Ni11(HPO3)8(OH)6 superstructures are applied as electrode materials for supercapacitors. Benefitting from their novel superstructures, in a three‐electrode system, Ni11(HPO3)8(OH)6 superstructure electrodes show a good specific capacitance (1876 F g−1 at 0.625 A g−1), good rate capability, and excellent cycling properties (95 % of the initial specific capacitance at 6.25 A g−1 after 2000 cycles) in 3.0 M KOH. Additionally, asymmetric Ni11(HPO3)8(OH)6–graphene nanosheet supercapacitors are also designed. The specific energy of a cell in 3.0 M KOH reaches about 28.6 Wh kg−1 at 92.5 W kg−1.

Template-Free Synthesis of Renewable Macroporous Carbon via Yeast Cells for High-Performance Supercapacitor Electrode Materials

The urgent need for sustainable development has forced material scientists to explore novel materials for next-generation energy storage devices through a green and facile strategy. In this context, yeast, which is a large group of single cell fungi widely distributed in nature environments, will be an ideal candidate for developing effective electrode materials with fascinating structures for high-performance supercapacitors. With this in mind, herein, we present the first example of creating three-dimensional (3D) interpenetrating macroporous carbon materials via a template-free method, using the green, renewable, and widespread yeast cells as the precursors. Remarkably, when the as-prepared materials are used as the electrode materials for supercapacitors, they exhibit outstanding performance with high specific capacitance of 330 F g(-1) at a current density of 1 A g(-1), and good stability, even after 1000 charge/discharge cycles. The approach developed in this work provides a new view of making full use of sustainable resources endowed by nature, opening the avenue to designing and producing robust materials with great promising applications in high-performance energy-storage devices.

Cobalt phosphite microarchitectures assembled by ultralong nanoribbons and their application as effective electrochemical capacitor electrode materials

Cobalt phosphite (Co(11)(HPO(3))(8)(OH)(6)) microarchitectures assembled by ultralong nanoribbons are successfully synthesized by a mild hydrothermal condition without any additives. The uniform ultralong nanoribbon has a width of 100 nm and length of 20-30 μm. More importantly, Co(11)(HPO(3))(8)(OH)(6) microarchitectures are also successfully applied as an electrochemical supercapacitor with a good specific capacitance (312 F g(-1) at 1.25 A g(-1)), good rate capability and excellent cycling property (maintaining about 89.4% at 1.25 A g(-1) after 3000 cycles).

Mesoporous carbon decorated graphene as an efficient electrode material for supercapacitors

A novel mesoporous carbon decorated graphene (MCG) material was fabricated as an effective electrode material for supercapacitors through the rational design of the nanostructure. The mesoporous carbon layer served as an effective inhibitor of the aggregation of the graphene sheets and a place of charge accumulation, while the graphene sheets acted as a highly conductive carbon frame. Compared to the pure graphene, the as-obtained MCG electrode materials exhibited higher surface area and more favorable pore size distribution. The electrochemical measurements of CV, galvanostatic charge–discharge and the impedance spectrum were used to investigate the electrochemical performance of the as-fabricated MCG electrodes. In particular, the results showed that the MCG-20 electrode could deliver a specific capacitance as high as 213.3 F g−1 at a current density of 0.5 A g−1. The other electrochemical observations revealed that the as-fabricated electrodes offered reduced ESR and excellent cycling stability. Such results demonstrate that this graphene based composite material is a promising candidate for the electrode material for high-performance supercapacitors.

Design and demonstration of a novel micro-Coulter counter utilizing liquid metal electrodes

This paper describes the design and demonstration of a novel, easily fabricated micro-Coulter counter utilizing liquid metal electrodes. Fluid and electrode channels were fabricated simultaneously in a single lithographic patterning step. Eutectic gallium–indium (EGaIn) was injected into the device to form functional electrodes in a cross-channel parallel configuration. Functionality of the device was demonstrated at an ac excitation frequency of 5 kHz using a polymer microsphere suspension and simple post-processing techniques. The device successfully detected particles, exhibiting an output response proportional to particle size. EGaIn was demonstrated to be an effective micro-fluidic electrode material and provided a novel approach for the fabrication of a functional micro-Coulter counter.

Fabrication of Pd/TiO2-multiwall carbon nanotubes catalyst and investigation of its electrocatalytic activity for formic acid oxidation

In this study, a novel Pd/TiO2-MWNTs catalyst is synthesized by a unique chemical method. The pretreated TiO2 nanoparticles are applied as support materials between Pd nanoparticles and functional multiwall carbon nanotubes (MWNTs) template. The morphology and physicochemical properties of the catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It is observed that the functional MWNTs are partially covered by TiO2 nanoparticles, and that the metallic Pd nanoparticles are homogeneously deposited onto the TiO2 nanoparticles with smaller sizes compared with those of Pd/MWNTs. The electrocatalytic activity of the Pd/TiO2-MWNTs is investigated by cyclic voltammetry and chronoamperometry measurements in 0.5 M H2SO4 and 1 M HCOOH acidic solution, respectively. Results indicate that the introduction of pretreated TiO2 into the nanocomposite highly improves its electrocatalytic activity, durability, and stability. Thus, the Pd/TiO2-MWNTs catalyst is expected to be an effective electrode material for formic acid oxidation.

Cu2ZnSnS4 Hierarchical Microspheres as an Effective Counter Electrode Material for Quantum Dot Sensitized Solar Cells

We explore the application of Cu2ZnSnS4 (CZTS) microspheres as an effective counter electrode material for low-cost and high-efficiency quantum dot sensitized solar cells (QDSSCs). Nearly monodisperse Cu2ZnSnS4 (CZTS) hierarchical microspheres with diameters of ∼2 μm built from nanoflakes have been synthesized via a facile solvothermal approach. The nanoflakes are assembled from CZTS quantum dots with 3–5 nm, showing a three-tiered organization of hierarchical microspheres. The morphology, crystal structure, composition, and optical properties of the CZTS microspheres are characterized by SEM, HRTEM, XRD, XPS, EDS, EELS, Raman, and UV–vis analysis. Chemical conversion and phase transformation from hexagonal CuS to tetragonal CZTS have been systematically investigated to reveal formation mechanism of the CZTS microspheres. These CZTS microspheres are used as an effective counter electrode material in QDSSCs for the first time to show high electrocatalytic activity for catalyzing reduction of polysulfide (S...

Carbon nanowalls thin films as nanostructured electrode materials in vanadium redox flow batteries

Three carbon nanowalls (CNWs) thin films, synthesized by Radiofrequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) using different processing parameters, are studied as electrode materials in the positive half-cell of a Vanadium Redox Flow Battery (VRFB). These 2D-networks of interconnected graphenes exhibit an excellent electrochemical performance towards the V(IV)/V(V) redox couple in terms of a low overpotential and fast electron transfer kinetics. This can be attributed to certain specific features of CNWs such as the arrangement of the graphene planes perpendicular to the substrate, thus facilitating the electron transfer from the substrate and resulting in a large amount of exposed reactive graphitic edge planes. Repetitive cyclic voltammetry measurements, at various scan rates, together with SEM images evidence the long term stability of these materials. The obtained results represent a significant step forward in the development of highly effective VRFB electrode materials.

Graphene Aerogels as a Highly Effective Counter Electrode Material for Dye- Sensitized Solar Cells

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A minimally coloured dioxypyrrole polymer as a counter electrode material in polymeric electrochromic window devices

As the colour palette of solution processable electrochromic conjugated polymers has extended from hues of purple and blue to vibrant colours such as yellow, orange, red, green, and cyan, the need for a counter electrode material that provides charge balance in electrochromic devices, but lends minimal colour, has become increasingly necessary. Nowhere is this more true than in absorptive/transmissive window-type devices where a high level of transparency and near colourlessness is needed in the device bleached state. This argument can also be extended to absorptive/reflective display-type devices where an “on” (coloured) and “off” (bleached or white) state is desired. Here, we report the development of a highly electroactive, low colouration efficiency propylenedioxypyrrole-based polymer that exhibits a low redox potential and minimal colour saturation in both fully neutralised and fully oxidised states. Thin films of the polymer, spray-cast onto transparent electrodes exhibited relatively low composite colouration efficiencies at 555 nm of 35 cm2C−1, contrasted with the the high colouration efficiency ECP-Magenta that exhibits 633 cm2C−1. We further demonstrate the utilisation of this polymer as an effective charge balancing counter electrode material in an absorptive/transmissive window-type device wherein the vibrantly coloured state and highly transmissive, near colourless bleached state of ECP-Magenta is maintained giving an overall device contrast of 61% at 540 nm.

Large-scale synthesis of Cu2SnS3 and Cu1.8S hierarchical microspheres as efficient counter electrode materials for quantum dot sensitized solar cells

Exploration of new catalytic semiconductors with novel structures as counter electrode materials is a promising approach to improve performances of quantum dot sensitized solar cells (QDSSCs). In this work, nearly mono-disperse tetragonal Cu(2)SnS(3) (CTS) and rhombohedral Cu(1.8)S hierarchical microspheres with nanometer-to-micrometer dimensions have been synthesized respectively via a simple solvothermal approach. These microspheres are also demonstrated as efficient counter electrode materials in solar cells using ZnO/ZnSe/CdSe nanocables as photoanode and polysulfide (S(n)(2-)/S(2-)) solution as electrolyte. While copper sulfide is regarded as one of the most effective counter electrode materials in QDSSCs, we demonstrate the CTS microspheres to show higher electrocatalytic activity for the reduction of polysulfide electrolyte than the Cu(1.8)S microspheres. This contributes to obvious enhancement of photocurrent density (J(SC)) and fill factor (FF). Power conversion efficiency (PCE) is significantly enhanced from 0.25% for the cell using a pure FTO (SnO(2):F) glass as counter electrode, to 3.65 and 4.06% for the cells using counter electrodes of FTO glasses coated respectively with Cu(1.8)S and CTS microspheres.

Thermally reduced graphite oxide as positive electrode in Vanadium Redox Flow Batteries

Two graphene-like materials, obtained by thermal exfoliation and reduction of a graphite oxide at 700 and 1000 °C, were studied as active electrodes in the positive half-cell of a Vanadium Redox Flow Battery (VRFB). In particular, that obtained at 1000 °C exhibited an outstanding electrochemical performance in terms of peak current densities (30.54 and 30.05 mA cm −2 for the anodic and cathodic peaks at 1 mV s −1, respectively) and reversibility (Δ E p = 0.07 V). This excellent behavior is attributed to the restoration of sp 2 domains after thermal treatment, which implies the production of a graphene-like material with a high electrical conductivity and accessible surface area. Moreover, the residual functional groups, –OH, act as active sites towards the vanadium redox reactions. This represents a significant step forward in the development of highly effective VRFB electrode materials.

Electrochemical Impedance Spectroscopic Study of Polythiophenes on Carbon Materials

This review article focuses on electrochemical impedance spectroscopic study of thiophenes on carbon materials, the importance of which has been realized by recent progress in literature. The review article has 3 separate sections. In the first part, most of the thiophene derivatives (thiophene, 3-methylthiphene, 3-hexylthiophene, 3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, bithiophene, octylthiophene, 3-dodecylthiophene, 3-terthiophene, 3-phenylthiophene, 3-methoxythiophene) and copolymers of thiophenes have been reviewed. In the second part, carbon surfaces (carbon fiber microelectrode, glassy carbon, carbon nanotubes, etc.) were used as effective electrode materials. In the third part, the electrochemical impedance spectroscopy (EIS) of thiophenes was explained with supercapacitors and many different circuit modeling evaluations.

Fabrication and characterization of buckypaper-based nanostructured electrodes as a novel material for biofuel cell applications

The fabrication process of buckypapers (BPs) made from stable suspensions of as-received or functionalized multi-walled carbon nanotubes (MWCNTs) with high purity (97.5 wt%, Baytubes), their characterization and their utilization towards novel biofuel cell electrode applications are reported. The BPs can vary in thickness between 1 μm and 200 μm, are mechanically robust, flexible, stable in solvents, possess high meso-porosities as well as high apparent electrical conductivities of up to 2500 S m(-1). Potentiodynamic measurements of biocathodes based on bilirubin oxidase (BOD)-decorated BPs for the oxygen reduction reaction (ORR) in neutral media (phosphate buffer solution) containing glucose indicate that BP electrodes based on functionalized MWCNTs (fBPs) perform better than BP electrodes of as-received MWCNTs and have high potential as an effective electrode material in biofuel cells and biosensors.

Flexible graphene/MnO2 composite papers for supercapacitor electrodes

Graphene/manganese dioxide (MnO2) composite papers (GMCP) are fabricated via a simple three-step route: preparation of graphene oxide/MnO2 composite (GOMC) dispersion, subsequent vacuum filtration of GOMC dispersion to achieve graphene oxide/MnO2 composite paper (GOMCP), and finally thermal reduction of GOMCP to generate GMCP. The morphology and microstructure of the prepared samples are characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transformation infrared spectroscopy, thermal gravimetric analysis and X-ray photoelectron spectroscopy. Moreover, as a binder-free and flexible electrode material for supercapacitors, the electrochemical properties of the prepared GMCP are evaluated by cyclic voltammetry and galvanostatic charge/discharge tests. As a result, the specific capacitance of the GMCP with the MnO2 weight ratio of 24% (GMCP-24) reaches 256 F g−1 at a current density of 500 mA g−1 and also shows good cycle stability, indicating a promising potential application as an effective electrode material for supercapacitors.

Towards intelligent engineering of SOFC electrodes: a review of advanced microstructural characterisation techniques

<title/>Solid oxide fuel cells (SOFCs) are high temperature electrochemical devices with the potential for clean and efficient power generation. The electrodes, which support the electrochemical reactions, play a vital role in determining the performance and durability of these devices. Effective electrode materials must balance a spectrum of criteria, including cost, thermal and chemical stability, electronic conductivity and catalytic activity. A number of successful electrode materials have been identified; the most widely adopted materials are composite structures providing electronic, ionic and gas phase percolation, which promotes electrochemical activity throughout the bulk of the electrode. The contiguous contact of electronic, ionic and gas phases at so called triple phase boundaries provides a direct indication of the electrochemical activity of the electrode. Improvements in tomography techniques have allowed SOFC electrode microstructures to be characterised in three dimensions, giving unprecedented access to a wealth of microstructural information on the nature of triple phase contact and percolation. With improved availability of advanced tomographic techniques, fuel cell developers are increasingly equipped to link processing routes to electrode microstructure and in turn electrochemical performance, such that the intelligent engineering of SOFC electrodes is becoming a reality. Here we review the development and application of these advanced microstructural characterisation techniques.